rf planning guide

CDMA/CDMA2000 1X RFPlanning Guide

CDMA/CDMA2000 1X

English

Mar 200268P09248A69–A

NoticeWhile reasonable efforts have been made to assure the accuracy of this document, Motorola, Inc. assumes no liability resulting from anyinaccuracies or omissions in this document, or from use of the information obtained herein. The information in this document has beencarefully checked and is believed to be entirely reliable. However, no responsibility is assumed for inaccuracies or omissions. Motorola,Inc. reserves the right to make changes to any products described herein and reserves the right to revise this document and to makechanges from time to time in content hereof with no obligation to notify any person of revisions or changes. Motorola, Inc. does notassume any liability arising out of the application or use of any product, software, or circuit described herein; neither does it conveylicense under its patent rights or the rights of others.It is possible that this publication may contain references to, or information about Motorola products (machines and programs),programming, or services that are not announced in your country. Such references or information must not be construed to meanthat Motorola intends to announce such Motorola products, programming, or services in your country.

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iCDMA/CDMA2000 1X RF Planning GuideMar 2002

Table of Contents

CDMA/CDMA2000 1X RF Planning Guide

1 How to Use This Guide

1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 - 3

1.2 Quick Guide to Contents of Each Section . . . . . . . . . . . . . . . . . . . . . . . 1 - 4

2 Basic CDMA Spectrum Planning

2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 3

2.2 North American and International Frequency Blocks . . . . . . . . . . . . . 2 - 3

2.3 CDMA Channel Spacing - General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 52.3.1 Minimum Spacing Between CDMA Carriers . . . . . . . . . . . . . . . 2 - 52.3.2 Maximum Spacing Between CDMA Carriers . . . . . . . . . . . . . . . 2 - 82.3.3 Multiple Market Spectrum Planning Considerations. . . . . . . . . . 2 - 112.3.4 Multiple Carrier Overlay Guidelines . . . . . . . . . . . . . . . . . . . . . . 2 - 11

2.3.4.1 IS-2000 1X New Carrier Overlay . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 142.3.4.2 IS-2000 1X Shared Carrier Overlay . . . . . . . . . . . . . . . . . . . . . . . . 2 - 15

2.3.5 Guard Band Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 152.3.5.1 AMPS Guard Band Recommendation . . . . . . . . . . . . . . . . . . . . . . 2 - 172.3.5.2 2nd CDMA Carrier with AMPS Guard Band. . . . . . . . . . . . . . . . . 2 - 172.3.5.3 Greater Than Two CDMA Carriers with AMPS Guard Band . . . . 2 - 18

2.4 Channel Spacing and Designation - 800 MHz . . . . . . . . . . . . . . . . . . . . 2 - 192.4.1 Segregated Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 20

2.5 Channel Spacing and Designation - 1900 MHz . . . . . . . . . . . . . . . . . . . 2 - 23

2.6 Dual-Mode vs. Dual-Band . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 25

2.7 Spectrum Clearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 25

2.8 Background Noise Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 262.8.1 Suggested Measurement Method . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 27

2.8.1.1 Test System Functional Description . . . . . . . . . . . . . . . . . . . . . . . . 2 - 272.8.1.2 Test System Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 28

2.8.2 Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 292.8.3 Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 30

2.9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 30

ii CDMA/CDMA2000 1X RF Planning Guide Mar 2002

Table of Contents - continued

3 CDMA Capacity

3.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 5

3.2 Reverse Link Pole Capacity Estimation . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 53.2.1 Data Rates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 113.2.2 Median Eb/(No+Io) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 123.2.3 Voice or Data Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 133.2.4 Cell Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 143.2.5 Sectorization Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 153.2.6 Power Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 17

3.3 Reverse Link Soft Blocking Capacity Estimation . . . . . . . . . . . . . . . . . 3 - 183.3.1 Conventional Blocking Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 183.3.2 CDMA Soft Blocking Capacity Estimation . . . . . . . . . . . . . . . . . 3 - 18

3.3.2.1 Assumptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 193.3.2.2 Theoretical Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 193.3.2.3 Single Cell Case. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 223.3.2.4 Multiple Cell System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 23

3.4 Reverse Link Noise Rise Capacity Estimation . . . . . . . . . . . . . . . . . . . . 3 - 323.4.1 Reverse Link Noise Rise Capacity Limit . . . . . . . . . . . . . . . . . . . 3 - 323.4.2 Reverse Noise Rise Capacity Estimation . . . . . . . . . . . . . . . . . . . 3 - 333.4.3 Probability Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 353.4.4 Reverse Link Noise Rise Capacity Estimation Examples . . . . . . 3 - 37

3.4.4.1 Example #1: Voice Only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 373.4.4.2 Example #2: Voice and Data Users . . . . . . . . . . . . . . . . . . . . . . . . 3 - 38

3.4.5 Reverse Link Noise Rise Capacity Estimates for IS-2000 1X. . . 3 - 413.4.5.1 Noise Rise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 413.4.5.2 F-factor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 423.4.5.3 Average Eb/No . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 433.4.5.4 Eb/No Standard Deviation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 433.4.5.5 Processing Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 443.4.5.6 Activity Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 443.4.5.7 Traffic Mix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 453.4.5.8 Throughput Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 453.4.5.9 IS-2000 1X Reverse Noise Rise Capacity Analysis Results . . . . . 3 - 46

3.5 Forward Link Pole Capacity Estimation . . . . . . . . . . . . . . . . . . . . . . . . 3 - 523.5.1 Forward Link Load Factor Estimation . . . . . . . . . . . . . . . . . . . . . 3 - 523.5.2 Forward Link Pole Capacity Estimation . . . . . . . . . . . . . . . . . . . 3 - 53

3.6 Forward Link Fractional Power Capacity Estimation . . . . . . . . . . . . . 3 - 54

iiiCDMA/CDMA2000 1X RF Planning GuideMar 2002


3.7 Forward Link Noise Rise Capacity Estimation . . . . . . . . . . . . . . . . . . . 3 - 573.7.1 Forward Link Noise Rise Capacity Limit . . . . . . . . . . . . . . . . . . 3 - 583.7.2 Forward Noise Rise Capacity Estimation. . . . . . . . . . . . . . . . . . . 3 - 593.7.3 Forward Link Noise Rise Capacity Estimation Examples . . . . . . 3 - 60

3.7.3.1 Example #1: Voice Only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 613.7.3.2 Example #2: Voice and Data Users . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 62

3.7.4 Forward Link Noise Rise Capacity Estimates for IS-2000 1X . . 3 - 653.7.4.1 Noise Rise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 653.7.4.2 I-factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 663.7.4.3 Average Eb/No . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 663.7.4.4 Eb/No Standard Deviation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 673.7.4.5 Processing Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 673.7.4.6 Activity Factor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 683.7.4.7 Orthogonality Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 693.7.4.8 Traffic Mix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 693.7.4.9 Throughput Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 693.7.4.10 IS-2000 1X Forward Noise Rise Capacity Analysis Results . . . . . 3 - 70

3.8 Forward vs. Reverse Link Capacity Comparison . . . . . . . . . . . . . . . . . 3 - 76

3.9 EIA/TIA Specifications and RF Air Interface Limitations. . . . . . . . . . 3 - 803.9.1 IS-95 Forward Channel Structure. . . . . . . . . . . . . . . . . . . . . . . . . 3 - 803.9.2 IS-95 Reverse Channel Structure . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 813.9.3 IS-2000 1X Forward Channel Structure. . . . . . . . . . . . . . . . . . . . 3 - 82

3.9.3.1 IS-2000 Forward Channels (Motorola Implementation) . . . . . . . . . 3 - 833.9.3.2 IS-2000 Forward Link Radio Configurations . . . . . . . . . . . . . . . . . 3 - 863.9.3.3 IS-2000 Walsh Code Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 88

3.9.4 IS-2000 Reverse Channel Structure . . . . . . . . . . . . . . . . . . . . . . . 3 - 913.9.4.1 IS-2000 Reverse Channels (Motorola Implementation) . . . . . . . . . 3 - 913.9.4.2 IS-2000 Reverse Link Radio Configurations . . . . . . . . . . . . . . . . . 3 - 92

3.10 Handoffs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 943.10.1 Soft Handoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 943.10.2 Inter-CBSC Soft Handoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 953.10.3 Hard Handoffs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 95

3.10.3.1 Anchor Handoff. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 953.10.3.2 IS-95 to IS-2000 Hand-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 953.10.3.3 IS-2000 to IS-95 Hand-down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 963.10.3.4 Packet Data Handoffs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 963.10.3.5 Inter-Carrier Hand-across . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 96

3.11 Budgetary Estimate of Sites for Capacity (Voice Only) . . . . . . . . . . . . 3 - 963.11.1 Required Parameters for Initial System Design . . . . . . . . . . . . . . 3 - 97

3.11.1.1 Busy Hour Call Attempts and Completions . . . . . . . . . . . . . . . . . . 3 - 973.11.1.2 Average Holding Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 973.11.1.3 Erlangs per Subscriber. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 97

iv CDMA/CDMA2000 1X RF Planning Guide Mar 2002


3.12 IS-95 and IS-2000 Simulations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 102

3.13 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 104

4 Link Budgets and Coverage

4.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 3

4.2 Radio Frequency Link Budget. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 44.2.1 Propagation Related Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 6

4.2.1.1 Building Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 64.2.1.2 Vehicle Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 94.2.1.3 Body Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 94.2.1.4 Ambient Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 94.2.1.5 RF Feeder Losses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 94.2.1.6 Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 12

4.2.2 CDMA Specific Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 144.2.2.1 Interference Noise Rise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 144.2.2.2 Soft Handoff Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 184.2.2.3 Eb/No . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 19

4.2.3 Product Specific Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 204.2.3.1 Product Transmit Power. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 204.2.3.2 Product Receiver Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 24

4.2.4 Reliability (Shadow Fade Margin) . . . . . . . . . . . . . . . . . . . . . . . . 4 - 294.2.5 Example Reverse (Uplink - Subscriber to Base) Link Budget. . . 4 - 364.2.6 RF Link Budget Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 40

4.3 Propagation Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 414.3.1 Free Space Propagation Model. . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 414.3.2 Hata Propagation Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 434.3.3 COST-231-Hata Propagation Model . . . . . . . . . . . . . . . . . . . . . . 4 - 444.3.4 Additional Propagation Models . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 45

4.4 Forward Link Coverage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 464.4.1 BTS Equipment Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 474.4.2 CDMA Signal Power Distribution Characteristics and PA Sizing 4 - 514.4.3 General Power Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 514.4.4 Design Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 53

4.4.4.1 Comparison to Average Rated Power . . . . . . . . . . . . . . . . . . . . . . 4 - 534.4.4.2 Comparison to High Power Alarm Rating. . . . . . . . . . . . . . . . . . . 4 - 544.4.4.3 Comparison to Walsh Code Limit . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 54

4.4.5 General Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 544.4.5.1 Minimum ARP Based on LT-AVG Estimate . . . . . . . . . . . . . . . . . 4 - 554.4.5.2 Minimum HPA Based on VST-AVG Estimate . . . . . . . . . . . . . . . 4 - 564.4.5.3 Exceeding the High Power Alarm Rating . . . . . . . . . . . . . . . . . . . 4 - 564.4.5.4 Carrier Load Management Overview . . . . . . . . . . . . . . . . . . . . . . 4 - 57

vCDMA/CDMA2000 1X RF Planning GuideMar 2002


4.4.6 Power Allocation in Mixed Mode Systems . . . . . . . . . . . . . . . . . 4 - 584.4.7 Government Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 65

4.5 CDMA Repeaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 654.5.1 CDMA Repeater Design Considerations . . . . . . . . . . . . . . . . . . . 4 - 66

4.5.1.1 Coverage Impact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 664.5.1.2 Cascaded Noise Figure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 694.5.1.3 Interference and Capacity Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 734.5.1.4 Filtering Issues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 73

4.5.2 CDMA Repeater Installation Considerations . . . . . . . . . . . . . . . . 4 - 744.5.2.1 Antenna Isolation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 744.5.2.2 Repeater Antenna Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 774.5.2.3 Repeater Gain Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 78

4.5.3 CDMA Repeater Optimization Considerations . . . . . . . . . . . . . . 4 - 794.5.3.1 Timing Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 794.5.3.2 Optimization Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 81

4.5.4 CDMA Repeater Maintenance Considerations . . . . . . . . . . . . . . 4 - 814.5.4.1 Future Expansion Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 824.5.4.2 Environmental Changes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 834.5.4.3 Operations and Maintenance Considerations . . . . . . . . . . . . . . . . . 4 - 83

4.6 Theoretical vs. Simulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 83

4.7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 85

5 PN Offset Planning and Search Windows

5.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 3

5.2 Number of Pilot Offsets per CDMA Frequency. . . . . . . . . . . . . . . . . . . 5 - 3

5.3 PN Offset Planning - General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 35.3.1 Consequences and Sources of Offset Interference . . . . . . . . . . . . 5 - 35.3.2 PN Offset Planning - Parameters and Terms . . . . . . . . . . . . . . . . 5 - 55.3.3 Converting Between Chips and Time or Distance . . . . . . . . . . . . 5 - 85.3.4 Search Windows and Geography . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 95.3.5 Search Windows and Scan Intervals . . . . . . . . . . . . . . . . . . . . . . 5 - 11

5.4 PN Offset Planning - Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 125.4.1 Mitigating Adjacent Offset Interference - General . . . . . . . . . . . 5 - 12

5.4.1.1 Adjacent Offset Interference Protection Based on Timing . . . . . . . 5 - 125.4.1.2 Adjacent Offset Interference Protection Based on Signal Strength 5 - 14

5.4.2 Protection Against Co-Offset Interference . . . . . . . . . . . . . . . . . . 5 - 155.4.3 Incorrect Identification of an Offset by the Base Station . . . . . . . 5 - 185.4.4 PILOT_INC and the Scan Rate of Remaining Set Pilots . . . . . . . 5 - 195.4.5 Summary of Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 20

vi CDMA/CDMA2000 1X RF Planning Guide Mar 2002


5.4.6 Guidelines for Assigning Offsets . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 225.4.7 Guidelines for Changing PILOT_INC

at Inter-CBSC Boundaries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 25

5.5 Reuse Patterns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 26

5.6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 27

6 RF Antenna Systems

6.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 3

6.2 CDMA Cell Site Antenna Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 36.2.1 Antenna Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 36.2.2 Antenna Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 46.2.3 Antenna Beamwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 66.2.4 Voltage Standing Wave Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 66.2.5 Return Loss. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 66.2.6 Power Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 76.2.7 Front to Back Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 76.2.8 Side Lobes & Back Lobes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 76.2.9 Antenna Downtilting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 86.2.10 Antenna Height. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 8

6.3 CDMA Antenna Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 96.3.1 Antenna Isolation Considerations. . . . . . . . . . . . . . . . . . . . . . . . . 6 - 9

6.3.1.1 CDMA/AMPS Transmit/Receive Antenna Isolation Requirements 6 - 106.3.1.2 Measuring Port-to-Port Antenna Isolation. . . . . . . . . . . . . . . . . . . 6 - 136.3.1.3 Reducing the Required Antenna Isolation . . . . . . . . . . . . . . . . . . . 6 - 136.3.1.4 Typical Antenna Isolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 146.3.1.5 CDMA Antenna Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 14

6.3.2 Antenna Diversity (Spacial) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 156.3.2.1 Horizontal Antenna Diversity and Recommended Separation . . . 6 - 166.3.2.2 Vertical Antenna Diversity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 16

6.4 CDMA Antenna Sharing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 176.4.1 Multiple Frame Antenna Sharing with 800 MHz BTS Products . 6 - 176.4.2 Multiple Carrier Cavity Combining

With 1900 MHz BTS Products. . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 206.4.2.1 Output Power Without Combining . . . . . . . . . . . . . . . . . . . . . . . . 6 - 206.4.2.2 Type of Combining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 206.4.2.3 Multiple Carrier Scenarios. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 21

6.4.3 Duplexing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 226.4.3.1 Pre-Engineered Kits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 236.4.3.2 Duplexers and Intermodulation . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 236.4.3.3 Proper Installation and Maintenance of Duplexed Antennas . . . . 6 - 24

viiCDMA/CDMA2000 1X RF Planning GuideMar 2002


6.5 CDMA Antenna Sharing With Other Technologies . . . . . . . . . . . . . . . 6 - 286.5.1 SC9600 BTS/HDII Shared Facilities . . . . . . . . . . . . . . . . . . . . . . 6 - 28

6.5.1.1 Common Transmit Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 296.5.1.2 Common Receive Antenna(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 32

6.5.2 Duplexed AMPS/CDMA Antennas . . . . . . . . . . . . . . . . . . . . . . . 6 - 39

6.6 GPS Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 41

6.7 Ancillary Antenna System Components . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 416.7.1 Directional Couplers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 416.7.2 Surge (Lightning) Protectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 416.7.3 Transmission Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 42

6.7.3.1 RF Performance of Transmission Lines . . . . . . . . . . . . . . . . . . . . . 6 - 426.7.3.2 Physical Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 426.7.3.3 Choice of Transmission Line. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 43

6.7.4 Transition Feeder Cables (Jumper Cables). . . . . . . . . . . . . . . . . . 6 - 43

6.8 RF Diagnostic System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 44

7 RF Antenna Systems - Advanced Topics

7.1 Dual Polarized Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 37.1.1 Fundamental Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 3

7.1.1.1 Dual Polarization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 37.1.1.2 Diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 47.1.1.3 Diversity Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 57.1.1.4 Cross-Correlation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 7

7.1.2 Isolation Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 117.1.3 Performance Impacts - Industry and Motorola Findings . . . . . . . 7 - 127.1.4 Antenna Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 14

7.1.4.1 Dual Polarized Antennas versus Singularly Polarized Antennas . . 7 - 147.1.4.2 Antenna Selection Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 15

7.1.5 Transmission at 45° . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 157.1.6 Incorporation of Dual Polarized Antennas into a Link Budget . . 7 - 167.1.7 Dual Polarized Antenna Summary . . . . . . . . . . . . . . . . . . . . . . . . 7 - 17

7.2 In-Building Distributed Antenna Systems . . . . . . . . . . . . . . . . . . . . . . . 7 - 187.2.1 In-Building System Architecture Overview. . . . . . . . . . . . . . . . . 7 - 197.2.2 Coaxial Cable System Design Using A Link Budget. . . . . . . . . . 7 - 20

7.2.2.1 Design Procedure Flow Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 207.2.2.2 Gathering Building Information . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 217.2.2.3 Determining the Base Station Location. . . . . . . . . . . . . . . . . . . . . . 7 - 237.2.2.4 Estimating the Antenna Placement within the Building . . . . . . . . . 7 - 247.2.2.5 Selecting the Antenna Type: Omni vs. Directional . . . . . . . . . . . . . 7 - 247.2.2.6 Choosing the Base Station Type . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 25

viii CDMA/CDMA2000 1X RF Planning Guide Mar 2002


7.2.2.7 Choosing the Cable Topology: Splitters, Couplers, and Taps . . . . 7 - 257.2.2.8 Estimating Cable Lengths from the Base Station to the Antennas 7 - 307.2.2.9 Selecting the Coaxial Cable Type . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 307.2.2.10 Link Budgets For In-Building Design . . . . . . . . . . . . . . . . . . . . . . 7 - 327.2.2.11 Evaluating the First Pass and Iterating the Design . . . . . . . . . . . . 7 - 38

7.2.3 Active Coaxial Cable System Design. . . . . . . . . . . . . . . . . . . . . . 7 - 387.2.3.1 Downlink Amplifier Design Considerations . . . . . . . . . . . . . . . . . 7 - 397.2.3.2 Uplink Amplifier Design Considerations . . . . . . . . . . . . . . . . . . . 7 - 407.2.3.3 Optimizing Amplifier Placement. . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 45

7.2.4 Fiber Optics for In-Building Systems. . . . . . . . . . . . . . . . . . . . . . 7 - 477.2.4.1 Fiber Optic Distribution System Architecture . . . . . . . . . . . . . . . . 7 - 477.2.4.2 When To Use Fiber Optics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 477.2.4.3 Fiber Optic System Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 48

7.2.5 In-Building Antenna Systems Summary . . . . . . . . . . . . . . . . . . . 7 - 49

7.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 50

8 Synchronization of the CDMA System

8.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 3

8.2 Base Station Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 3

8.3 Synchronization Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 58.3.1 Global Positioning System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 58.3.2 Low Frequency Receiver (LFR). . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 68.3.3 High Stability Oscillator (HSO) . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 7

8.4 Synchronization Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 7

8.5 Synchronization Source Antenna Planning and Installation . . . . . . . . 8 - 88.5.1 GPS Antenna/Preamplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 9

8.5.1.1 Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 98.5.1.2 Cabling Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 108.5.1.3 Multiple Frame GPS Cabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 10

8.5.2 Remote GPS Antenna/Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 118.5.2.1 RGPS Receiver Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 138.5.2.2 Cabling Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 148.5.2.3 Multiple Frame RGPS Cabling . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 15

8.5.3 LFR Antenna / Preamplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 168.5.3.1 Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 178.5.3.2 Cabling Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 17

ixCDMA/CDMA2000 1X RF Planning GuideMar 2002


9 Inter-System Interference (ISI)

9.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 3

9.2 Cellular/PCS Inter-System Interference. . . . . . . . . . . . . . . . . . . . . . . . . 9 - 39.2.1 Intra-Band Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 4

9.2.1.1 AMPS Cells to CDMA Subscribers . . . . . . . . . . . . . . . . . . . . . . . . 9 - 69.2.1.2 AMPS Subscribers to CDMA Cells . . . . . . . . . . . . . . . . . . . . . . . . 9 - 99.2.1.3 CDMA Cells to AMPS Subscribers . . . . . . . . . . . . . . . . . . . . . . . . 9 - 99.2.1.4 CDMA Subscribers to AMPS Cells . . . . . . . . . . . . . . . . . . . . . . . . 9 - 9

9.2.2 Inter-Band Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 109.2.2.1 Preventative Measures: BS-to-BS Interference. . . . . . . . . . . . . . . . 9 - 139.2.2.2 Preventative Measures: Subscriber-to-Subscriber Interference . . . 9 - 27

9.3 PCS and Microwave Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 289.3.1 PCS to Microwave Interference . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 28

9.3.1.1 Coordination Distances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 299.3.1.2 Propagation Models. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 309.3.1.3 Power Aggregation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 349.3.1.4 Microwave Receiver Interference Criteria . . . . . . . . . . . . . . . . . . . 9 - 359.3.1.5 PCS to Microwave Interference Summary . . . . . . . . . . . . . . . . . . . 9 - 37

9.3.2 Microwave to PCS Interference . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 389.3.2.1 General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 389.3.2.2 Calculation of Nominal Noise Floor . . . . . . . . . . . . . . . . . . . . . . . . 9 - 389.3.2.3 Calculation of Effective Interference Power . . . . . . . . . . . . . . . . . . 9 - 399.3.2.4 Calculation of Effective Noise Figure . . . . . . . . . . . . . . . . . . . . . . . 9 - 399.3.2.5 Microwave to PCS Interference Summary . . . . . . . . . . . . . . . . . . . 9 - 40

9.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 40

APPENDICES:

I Terms and Acronyms

I.1 Terms and Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I - 3

II Glossary

II.1 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II - 3

III Watts to dBm Conversion Table

III.1 Watts to dBm Conversion Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III - 3

IV Complementary Error Function Table

IV.1 Complementary Error Function Table . . . . . . . . . . . . . . . . . . . . . . . . . . IV - 3

x CDMA/CDMA2000 1X RF Planning Guide Mar 2002


NOTES

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xiCDMA/CDMA2000 1X RF Planning GuideMar 2002

List of Figures


Figure 1-1: Radio Sub-System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 - 3Figure 2-1: 3G Spectrum Allocations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 5Figure 2-2: Minimum Spacing Between 800 MHz CDMA Channels . . . . . . . 2 - 6Figure 2-3: Minimum Spacing Between 1900 MHz CDMA Channels . . . . . . 2 - 6Figure 2-4: Adjacent Channel Interference Reverse Rise Estimates . . . . . . . . 2 - 7Figure 2-5: Total Channel Numbers Available . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 9Figure 2-6: Assign Guard Band. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 9Figure 2-7: Assign 1st and Last CDMA Carries . . . . . . . . . . . . . . . . . . . . . . . . 2 - 10Figure 2-8: Equally Distribute Remaining CDMA Carriers . . . . . . . . . . . . . . . 2 - 10Figure 2-9: 1-to-1 Overlay Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 12Figure 2-10: Non 1-to-1 Overlay Examples (NOT Recommended). . . . . . . . . . 2 - 12Figure 2-11: Service Acquisition Issues Due To Uneven Carrier Coverage . . . 2 - 13Figure 2-12: New IS-2000 1X Carrier Deployment . . . . . . . . . . . . . . . . . . . . . . 2 - 14Figure 2-13: Second IS-2000 1X Carrier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 14Figure 2-14: IS-2000 1X Shared Carrier Overlay . . . . . . . . . . . . . . . . . . . . . . . . 2 - 15Figure 2-15: Calculation of Spectrum Required for a CDMA Carrier . . . . . . . . 2 - 17Figure 2-16: Calculation of Minimum Spectrum Required

for Two CDMA Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 17Figure 2-17: 2nd CDMA Carrier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 18Figure 2-18: 3rd CDMA Carrier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 18Figure 2-19: AMPS Frequency Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 20Figure 2-20: Segregated Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 22Figure 2-21: Suggested CDMA Noise Floor Measurement System . . . . . . . . . . 2 - 28Figure 3-1: Impact of Eb/(No+Io) on the Number of Users. . . . . . . . . . . . . . . . 3 - 12Figure 3-2: Impact of Voice or Data Activity on the Number of Users . . . . . . 3 - 13Figure 3-3: Impact of Other Cell Interference on the Number of Users . . . . . . 3 - 14Figure 3-4: Impact of Sectorization Gain on the Number of Users (3 Sector) . 3 - 16Figure 3-5: Impact of Imperfect Power Control on the Number of Users . . . . 3 - 17Figure 3-6: Values of the Integral and

with Various Path Loss Slope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 26Figure 3-7: Probability of Blocking vs. Erlangs per CDMA Sector with

Various Path Loss Slope Values with Rate Set 1 Vocoder . . . . . . 3 - 28Figure 3-8: Probability of Blocking vs. Erlangs per CDMA Sector with Various

Power Control Standard Deviations with Rate Set 1 Vocoder. . . . 3 - 29Figure 3-9: Probability of Blocking vs. Erlangs per CDMA Sector with

Various Path Loss Slope Values with Rate Set 2 Vocoder . . . . . . 3 - 30

I α δ,( ) I 2α δ,( )

xii CDMA/CDMA2000 1X RF Planning Guide Mar 2002

List of Figures - continued

Figure 3-10: Probability of Blocking vs. Erlangs per CDMA Sector with VariousPower Control Standard Deviations with Rate Set 2 Vocoder . . . . 3 - 31

Figure 3-11: Rise versus Percent of Pole Capacity . . . . . . . . . . . . . . . . . . . . . . . 3 - 33Figure 3-12: Standard Normal Distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 35Figure 3-13: Rise and Radius versus Loading Example . . . . . . . . . . . . . . . . . . . 3 - 36Figure 3-14: Reverse Link Rise vs. Throughput . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 49Figure 3-15: Reverse Link Rise vs. Erlangs for Different Data Rates . . . . . . . . 3 - 50Figure 3-16: Reverse Link Total Erlangs & Throughput vs.

Data Activity Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 51Figure 3-17: Forward Link Rise vs. Throughput. . . . . . . . . . . . . . . . . . . . . . . . . 3 - 73Figure 3-18: Forward Link Rise vs. Erlangs for Different Data Rates . . . . . . . . 3 - 74Figure 3-19: Forward Link Total Erlangs & Throughput vs.

Data Activity Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 75Figure 3-20: Forward and Reverse Link Rise vs.

Throughput - 95% Probability Factor . . . . . . . . . . . . . . . . . . . . . . . 3 - 76Figure 3-21: Forward and Reverse Link Rise vs.

Erlangs for Different Data Rates . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 77Figure 3-22: Forward and Reverse Link Erlangs & Thruput vs.

Data Activity Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 78Figure 3-23: Alternate Forward and Reverse Link Erlangs & Thruput vs.

Data Activity Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 79Figure 3-24: Example of IS-95 Forward CDMA Channels. . . . . . . . . . . . . . . . . 3 - 80Figure 3-25: Example of IS-95 Reverse CDMA Channels . . . . . . . . . . . . . . . . . 3 - 82Figure 3-26: Example of IS-2000 Forward CDMA Channels. . . . . . . . . . . . . . . 3 - 83Figure 3-27: QPCH to PCH Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 85Figure 3-28: IS-2000 Walsh Code Tree. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 89Figure 3-29: Walsh Code Allocation Tree. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 90Figure 3-30: Walsh Code Allocation Tree. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 90Figure 3-31: Example of IS-2000 Reverse CDMA Channels . . . . . . . . . . . . . . . 3 - 91Figure 3-32: Subscriber Distribution of Chicago Metropolitan Area . . . . . . . . . 3 - 98Figure 4-1: Percentage of Cells Based on dB Changes to the Link Budget . . . 4 - 4Figure 4-2: RF Link Budget Gains & Losses . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 5Figure 4-3: In-Building Propagation Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 6Figure 4-4: Preferred FWT Locations Without External Antennas. . . . . . . . . . 4 - 8Figure 4-5: Typical Components in the RF Feeder Run . . . . . . . . . . . . . . . . . . 4 - 11Figure 4-6: Rise (dB) at the cell of interest versus

X (% load) at the cell of interest . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 18Figure 4-7: Example of Two Different Receive Path Configurations . . . . . . . 4 - 27Figure 4-8: Impact of Fade Margin on Reliability. . . . . . . . . . . . . . . . . . . . . . . 4 - 30Figure 4-9: Edge Reliability vs. Fade Margin . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 32Figure 4-10: Area Reliability vs. Fade Margin . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 33Figure 4-11: Area Reliability as a Function of Shadow Fade Margin. . . . . . . . . 4 - 35Figure 4-12: Edge Reliability as a Function of Shadow Fade Margin . . . . . . . . 4 - 36Figure 4-13: Impact of dB Trade-off to Number of Sites . . . . . . . . . . . . . . . . . . 4 - 41

xiiiCDMA/CDMA2000 1X RF Planning GuideMar 2002


Figure 4-14: Typical Repeater Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 66Figure 4-15: Repeater Range Analysis Results . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 67Figure 4-16: Alternate Repeater Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 68Figure 4-17: Cabled Cascaded Noise Figure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 69Figure 4-18: Base Station & Repeater Diagram . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 70Figure 4-19: Repeater Cascaded Noise Figure . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 71Figure 4-20: Multiple Repeater Cascaded Noise Figure . . . . . . . . . . . . . . . . . . . 4 - 72Figure 4-21: Alternate Repeater Antenna Configuration . . . . . . . . . . . . . . . . . . 4 - 75Figure 4-22: Horizontal Separation Using a Barrier . . . . . . . . . . . . . . . . . . . . . . 4 - 75Figure 4-23: Micro-wave Linked Repeater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 76Figure 4-24: Fiber Linked Repeater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 76Figure 4-25: Potential Range Reduction Due to Repeaters . . . . . . . . . . . . . . . . . 4 - 78Figure 5-1: PN Offset Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 5Figure 5-2: Short PN Sequence w/PILOT_INC = 2 . . . . . . . . . . . . . . . . . . . . . 5 - 5Figure 5-3: Subscriber Location Relative to Search Window . . . . . . . . . . . . . . 5 - 9Figure 5-4: Search Windows in Space. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 10Figure 5-5: Minimum Distance for Adjacent Offset Interference . . . . . . . . . . . 5 - 13Figure 5-6: Active Window Interference Timing Criteria. . . . . . . . . . . . . . . . . 5 - 15Figure 5-7: Neighbor Window Interference Timing Criteria . . . . . . . . . . . . . . 5 - 16Figure 5-8: Active and Neighbor Areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 17Figure 5-9: Phase Measurement Translations . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 18Figure 5-10: Adjacent Sector and Adjacent Site

Offset Assignment Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 22Figure 5-11: Inter-CBSC PILOT_INC Boundary . . . . . . . . . . . . . . . . . . . . . . . . 5 - 25Figure 6-1: dBd vs. dBi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 5Figure 6-2: The Relationship of Antenna Height to Number of Cell Sites. . . . 6 - 9Figure 6-3: Antenna Placement - Shared Platform . . . . . . . . . . . . . . . . . . . . . . 6 - 14Figure 6-4: Antenna Placement - Separate Platforms . . . . . . . . . . . . . . . . . . . . 6 - 15Figure 6-5: SC4812T to SC4812T Expansion Frame . . . . . . . . . . . . . . . . . . . . 6 - 17Figure 6-6: SC2450 to SC4812T Expansion Frame . . . . . . . . . . . . . . . . . . . . . 6 - 18Figure 6-7: SC2400 ELPA to SC4812T Expansion Frame . . . . . . . . . . . . . . . . 6 - 19Figure 6-8: SC9600 SIF to SC4812T Expansion Frame . . . . . . . . . . . . . . . . . . 6 - 19Figure 6-9: SC9600 SIF & LPA with SC4812T Modem Frame . . . . . . . . . . . . 6 - 20Figure 6-10: 2 Carrier Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 21Figure 6-11: 8 Carrier Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 22Figure 6-12: Duplexer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 22Figure 6-13: Two Tone IM Test Set Up (800 MHz) . . . . . . . . . . . . . . . . . . . . . . 6 - 27Figure 6-14: SC9600 LPA Used by HDII Carriers . . . . . . . . . . . . . . . . . . . . . . . 6 - 29Figure 6-15: HDII LPA Used by SC9600 CDMA Carriers . . . . . . . . . . . . . . . . 6 - 30Figure 6-16: HDII LPA Used by SC9600-D CDMA Carriers . . . . . . . . . . . . . . 6 - 31Figure 6-17: SC9600-D CDMA-AMPS Configuration,

Shared Sector HDII Multicoupler. . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 33Figure 6-18: SC9600-D CDMA-AMPS Configuration,

Shared Omni HDII Multicoupler . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 34

xiv CDMA/CDMA2000 1X RF Planning Guide Mar 2002


Figure 6-19: SC9600 CDMA-AMPS Configuration, Shared Sector HDII Multicoupler. . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 35

Figure 6-20: SC9600 CDMA-AMPS Configuration, Shared Omni HDII Multicoupler . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 35

Figure 6-21: SC2400 CDMA-AMPS Configuration, Shared Sector HDII Multicoupler. . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 36

Figure 6-22: SC2400 CDMA-AMPS Configuration, Shared Omni HDII Multicoupler . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 36

Figure 6-23: SC4812T CDMA-AMPS Configuration, Shared Omni HDII Multicoupler . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 37

Figure 6-24: SC4812T CDMA-AMPS Configuration, Shared Sector HDII Multicoupler. . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 37

Figure 6-25: CDMA-AMPS Config., Shared SC9600 SIF frame, AMPS/NAMPS Sector Rx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 38

Figure 6-26: CDMA-AMPS Config., Shared SC9600 SIF Frame, AMPS/NAMPS Omni Rx. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 38

Figure 6-27: CDMA Duplexing Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 39Figure 7-1: Dual Polarization Antenna Element Configurations . . . . . . . . . . . 7 - 4Figure 7-2: Probability Distribution SNR for

M-branch Selection Diversity System . . . . . . . . . . . . . . . . . . . . . . 7 - 7Figure 7-3: Rayleigh Probability Density Function. . . . . . . . . . . . . . . . . . . . . . 7 - 8Figure 7-4: Reception of Highly Correlated Signals . . . . . . . . . . . . . . . . . . . . . 7 - 8Figure 7-5: Reception of Uncorrelated Signals . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 9Figure 7-6: Correlated Signal Diversity Gain . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 10Figure 7-7: Uncorrelated Signal Diversity Gain . . . . . . . . . . . . . . . . . . . . . . . . 7 - 10Figure 7-8: Uncorrelated Signal Diversity Gain . . . . . . . . . . . . . . . . . . . . . . . . 7 - 11Figure 7-9: Theoretical Model for Base Station Polarization Diversity . . . . . . 7 - 11Figure 7-10: Tx, Rx and Diversity Rx Antenna Configurations . . . . . . . . . . . . . 7 - 16Figure 7-11: Coaxial Cable Design Approach. . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 19Figure 7-12: Fiber Optic Design Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 20Figure 7-13: Coax Design Flow Chart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 21Figure 7-14: "Bow Tie" Antenna. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 25Figure 7-15: Schematic Diagram of a Power Tap . . . . . . . . . . . . . . . . . . . . . . . . 7 - 26Figure 7-16: Typical Tap Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 27Figure 7-17: Diagram of a Power Splitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 27Figure 7-18: Schematic of a Directional Coupler . . . . . . . . . . . . . . . . . . . . . . . . 7 - 28Figure 7-19: Parallel Power Distribution Using a Power Splitter . . . . . . . . . . . . 7 - 29Figure 7-20: Series Power Distribution Using Directional Couplers . . . . . . . . . 7 - 29Figure 7-21: Radiating Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 31Figure 7-22: Radiating Cable Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 31Figure 7-23: Radiating Cable Coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 32Figure 7-24: Link Budget Block Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 33Figure 7-25: Maximum Coverage Distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 34Figure 7-26: Multiple Floor Coverage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 34

xvCDMA/CDMA2000 1X RF Planning GuideMar 2002


Figure 7-27: Logarithmic Path Loss Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 35Figure 7-28: Linear Path Loss Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 36Figure 7-29: Measurement System Test Setup . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 37Figure 7-30: Bi-Directional Amplifier. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 38Figure 7-31: Uni-Directional Uplink Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 39Figure 7-32: Downlink Amplifier Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 40Figure 7-33: Effect of a 10 dB Noise Figure Amplifier . . . . . . . . . . . . . . . . . . . 7 - 41Figure 7-34: Noise Figure of a Lossy Device . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 41Figure 7-35: Cascaded System Noise Figure. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 42Figure 7-36: Uplink Amplifier Gain Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 43Figure 7-37: Noise Summing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 44Figure 7-38: Amplifier Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 45Figure 7-39: Amplifier Performance vs. Location . . . . . . . . . . . . . . . . . . . . . . . 7 - 46Figure 7-40: Fiber Optic Star Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 47Figure 7-41: Fiber Uplink Noise Summing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 49Figure 8-1: CDMA Cell site Synchronization Architecture . . . . . . . . . . . . . . . 8 - 5Figure 8-2: Single and Multi-Frame RF GPS Configurations. . . . . . . . . . . . . . 8 - 11Figure 8-3: Single and Multi-Frame Remote GPS Configurations . . . . . . . . . . 8 - 13Figure 8-4: BTS to RGPS Cable Connector Diagram . . . . . . . . . . . . . . . . . . . . 8 - 15Figure 8-5: Remote GPS Distribution Box Diagram. . . . . . . . . . . . . . . . . . . . . 8 - 16Figure 9-1: Intra-Band Interference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 4Figure 9-2: Example of a (1:3) Overlay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 5Figure 9-3: AMPS System with a Larger CDMA Site Overlay . . . . . . . . . . . . 9 - 7Figure 9-4: Required CDMA Signal Strength vs.

Interfering AMPS Signal Strength . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 8Figure 9-5: Inter-Band Interference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 10Figure 9-6: AMPS/TACS/GSM Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 11Figure 9-7: DCS 1800 and PCS 1900 Spectrum . . . . . . . . . . . . . . . . . . . . . . . . 9 - 12Figure 9-8: Transmitter Spectral Mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 16Figure 9-9: Interfering Transmit Carrier and Sideband Emission Spectrum. . . 9 - 16Figure 9-10: Transmitter IM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 19Figure 9-11: Interfering Transmit Carriers and Intermodulation Spectrum . . . . 9 - 20Figure 9-12: Receiver IM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 21Figure 9-13: Victim Receiver Out-of-Band Intermodulation . . . . . . . . . . . . . . . 9 - 22Figure 9-14: External IM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 23Figure 9-15: Victim Receiver Out-of-Band Desensitization . . . . . . . . . . . . . . . . 9 - 24Figure 9-16: The PCS Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 28Figure 9-17: Example Coordination Distances . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 30Figure 9-18: Propagation Curves for High PCS Antennas . . . . . . . . . . . . . . . . . 9 - 33Figure 9-19: Propagation Curves for Low PCS Antennas. . . . . . . . . . . . . . . . . . 9 - 33Figure 9-20: Example Aggregated Service Area. . . . . . . . . . . . . . . . . . . . . . . . . 9 - 34Figure 9-21: Example C/I Curves for a 10 MHz Microwave Receiver. . . . . . . . 9 - 35

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xviiCDMA/CDMA2000 1X RF Planning GuideMar 2002

List of Tables


Table 1-1: Quick Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 - 4Table 2-1: Some Common World-Wide Frequency Bands

for Cellular and PCS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 3Table 2-2: CDMA Channel Spacing and Designation. . . . . . . . . . . . . . . . . . . 2 - 19Table 2-3: Channel Numbers and Frequencies for Band Class 0

and Spreading Rate 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 19Table 2-4: CDMA Channel Number to

CDMA Frequency Assignment Correspondence . . . . . . . . . . . . . . 2 - 20Table 2-5: 7 Cell (120°), 21 Channel Spacing, "B" Band . . . . . . . . . . . . . . . . 2 - 21Table 2-6: Band Class 1 System Frequency Correspondence . . . . . . . . . . . . . 2 - 23Table 2-7: CDMA Channel Number to CDMA Frequency Assignment. . . . . 2 - 23Table 2-8: Channel Numbers and Frequencies for Band Class 1

and Spreading Rate 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 24Table 2-9: Preferred Set of Frequency Assignments for Band Class 1

and Spreading Rate 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 24Table 3-1: Samples of Various f Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 14Table 3-2: Propagation Path Loss in Different Areas . . . . . . . . . . . . . . . . . . . 3 - 24Table 3-3: Probability Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 36Table 3-4: Interference Rise Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 41Table 3-5: F-factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 42Table 3-6: IS-2000 1X Average Eb/No Values . . . . . . . . . . . . . . . . . . . . . . . . 3 - 44Table 3-7: Traffic Mix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 45Table 3-8: Reverse Capacity per Sector

for Various Probabilities of Rise - Pedestrian . . . . . . . . . . . . . . . . 3 - 47Table 3-9: Reverse Capacity per Sector

for Various Probabilities of Rise - Vehicle . . . . . . . . . . . . . . . . . . 3 - 48Table 3-10: Example of Parameter Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 55Table 3-11: Interference Rise Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 65Table 3-12: I-factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 66Table 3-13: IS-2000 1X Average Eb/No Values . . . . . . . . . . . . . . . . . . . . . . . . 3 - 68Table 3-14: Traffic Mix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 69Table 3-15: Forward Capacity per Sector

for Various Probabilities of Rise - Pedestrian . . . . . . . . . . . . . . . . 3 - 71Table 3-16: Forward Capacity per Sector

for Various Probabilities of Rise - Vehicle . . . . . . . . . . . . . . . . . . 3 - 72Table 3-17: IS-2000 Forward Link Radio Configurations. . . . . . . . . . . . . . . . . 3 - 86Table 3-18: Forward Link Radio Configuration Support for CBSC Release 16 3 - 87

xviii CDMA/CDMA2000 1X RF Planning Guide Mar 2002

List of Tables - continued

Table 3-19: Forward Link Channel Element Resource Requirement . . . . . . . . 3 - 88Table 3-20: IS-2000 Reverse Link Radio Configurations . . . . . . . . . . . . . . . . . 3 - 93Table 3-21: Reverse Link Radio Configuration Support for CBSC Release 16 3 - 93Table 3-22: Reverse Link Channel Element Resource Requirement. . . . . . . . . 3 - 94Table 3-23: Subscriber Distribution of Chicago Metropolitan Area . . . . . . . . . 3 - 99Table 3-24: Chicago Metropolitan Area Summary . . . . . . . . . . . . . . . . . . . . . . 3 - 101Table 4-1: Example Building Penetration Losses (800 & 1900 MHz) . . . . . . 4 - 7Table 4-2: Example of Main Transmission Line Losses . . . . . . . . . . . . . . . . . 4 - 10Table 4-3: Processing Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 24Table 4-4: Receive Path Noise Figures and Gains . . . . . . . . . . . . . . . . . . . . . . 4 - 27Table 4-5: Link Budget Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 28Table 4-6: Example of an IS-95 CDMA Reverse RF Link Budget . . . . . . . . . 4 - 37Table 4-7: Example of an IS-2000 1X CDMA RF Link Budget . . . . . . . . . . . 4 - 39Table 4-8: PA Ratings for Some BTS Products . . . . . . . . . . . . . . . . . . . . . . . . 4 - 47Table 4-9: BTS Pilot Power Adjustment Range . . . . . . . . . . . . . . . . . . . . . . . 4 - 49Table 4-10: Relative Tx & Rx Link Difference Example . . . . . . . . . . . . . . . . . 4 - 79Table 5-1: Search Window Size vs. Neighbor Separation . . . . . . . . . . . . . . . . 5 - 11Table 5-2: Distance/Timing Restriction on Adjacent Interference . . . . . . . . . 5 - 13Table 5-3: Pilot Sequence Offset Index Assignment . . . . . . . . . . . . . . . . . . . . 5 - 14Table 5-4: Estimates of Reuse Distance and Cluster Size Based on Timing . . 5 - 16Table 5-5: Calculation of Reuse Distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 18Table 5-6: Summary of PN Offset Planning Guidelines . . . . . . . . . . . . . . . . . 5 - 20Table 5-7: Offset Groupings for PILOT_INC = 2 (also 4, 6, 8, and 12) . . . . . 5 - 23Table 5-8: Offset Groupings for PILOT_INC = 3 (also 6 and 12). . . . . . . . . . 5 - 23Table 5-9: Reuse Pattern Coordinates, i & j, and Cluster Size, N, and D/R . . 5 - 26Table 6-1: CDMA Carrier Frequency Range . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 4Table 6-2: PCS Carrier Frequency Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 4Table 6-3: Degradation to Sensitivity Based on Noise Level Below kTBF . . 6 - 11Table 6-4: Antenna Isolation Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 13Table 6-5: Duplexer Frequency Response Characteristics. . . . . . . . . . . . . . . . 6 - 23Table 6-6: Minimum IM Orders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 24Table 6-7: Possible Duplexed Configurations . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 39Table 6-8: Transmission Line Performance. . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 43Table 6-9: Transition Cable Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 44Table 7-1: Motorola Data Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 14Table 7-2: Building Topology Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 23Table 7-3: Estimated Coverage Radius . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 24Table 7-4: Typical Values for Power Splitters . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 28Table 7-5: Path Loss Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 35Table 7-6: Average Floor Loss Attenuation Factors . . . . . . . . . . . . . . . . . . . . 7 - 36Table 8-1: BTS to RGPS Cable Wiring Definitions . . . . . . . . . . . . . . . . . . . . 8 - 15Table 9-1: Cellular Spectrum Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 11Table 9-2: Inter-Band Interference Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 12Table 9-3: Example IM Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 18

xixCDMA/CDMA2000 1X RF Planning GuideMar 2002


Table 9-4: Partial Example of Base Station Transmitter Specifications . . . . . 9 - 25Table 9-5: DCS 1800 Base Station Transmitter Specifications (GSM 05.05). 9 - 25Table 9-6: Partial Example of Base Station Receiver Specifications . . . . . . . 9 - 26Table 9-7: In-Band GSM Base Station Receiver Blocking

Specifications (GSM 05.05) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 26Table 9-8: Out-of-Band GSM Base Station Receiver Blocking

Specifications (GSM 05.05) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 26Table 9-9: Inter-Band Interference Comparison . . . . . . . . . . . . . . . . . . . . . . . 9 - 27Table III-1: Watts to dBm Conversion Table. . . . . . . . . . . . . . . . . . . . . . . . . . . III - 3Table IV-1: Complementary Error Function, Q(x) . . . . . . . . . . . . . . . . . . . . . . IV - 3

xx CDMA/CDMA2000 1X RF Planning Guide Mar 2002


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Foreword

Mar 2002 xxiCDMA/CDMA2000 1X RF Planning Guide

Scope of manual

This manual is intended for use by cellular telephone systemcraftspersons in the day-to-day operation of Motorola cellular systemequipment and ancillary devices. It is assumed that the user of thisinformation has a general understanding of telephony, as used in theoperation of the Public Switched Telephone Network (PSTN), and isfamiliar with these concepts as they are applied in the cellularmobile/portable radiotelephone environment. The user, however, is notexpected to have any detailed technical knowledge of the internaloperation of the equipment.

This manual is not intended to replace the system and equipmenttraining offered by Motorola, although it can be used to supplement orenhance the knowledge gained through such training.

Text conventions

The following special paragraphs are used in this manual to point outinformation that must be read. This information may be set-off from thesurrounding text, but is always preceded by a bold title in capital letters.The four categories of these special paragraphs are:

Presents additional, helpful, non-critical information thatyou can use.

NOTE

Presents information to help you avoid an undesirablesituation or provides additional information to help youunderstand a topic or concept.

IMPORTANT

*

Presents information to identify a situation in whichequipment damage could occur, thus avoiding damage toequipment.

CAUTION

Presents information to warn you of a potentiallyhazardous situation in which there is a possibility ofpersonal injury.

WARNING

Foreword – continued

CDMA/CDMA2000 1X RF Planning Guide Mar 2002xxii

The following typographical conventions are used for the presentation ofsoftware information:

In text, sans serif BOLDFACE CAPITAL characters (a type stylewithout angular strokes: i.e., SERIF versus SANS SERIF) are usedto name a command.

In text, typewriter style characters represent prompts and thesystem output as displayed on an operator terminal or printer.

In command definitions, sans serif boldface characters representthose parts of the command string that must be entered exactly asshown and typewriter style characters represent command outputresponses as displayed on an operator terminal or printer.

In the command format of the command definition, typewriterstyle characters represent the command parameters.

Changes to manual

Changes that occur after the printing date are incorporated into yourmanual by Cellular Manual Revisions (CMRs). The information in thismanual is updated, as required, by a CMR when new options andprocedures become available for general use or when engineeringchanges occur. The cover sheet(s) that accompany each CMR should beretained for future reference. Refer to the Revision History page for a listof all applicable CMRs contained in this manual.

Receiving updates

Technical Education & Documentation (TED) maintains a customerdatabase that reflects the type and number of manuals ordered or shippedsince the original delivery of your Motorola equipment. Also identifiedin this database is a “key” individual (such as DocumentationCoordinator or Facility Librarian) designated to receive manual updatesfrom TED as they are released.

To ensure that your facility receives updates to your manuals, it isimportant that the information in our database is correct and up-to-date.Therefore, if you have corrections or wish to make changes to theinformation in our database (i.e., to assign a new “key” individual),please contact Technical Education & Documentation at:

MOTOROLA, INC.Technical Education & Documentation1 Nelson C. White ParkwayMundelein, Illinois 60060U.S.A.

Phone: Within U.S.A. and Canada 800-872-8225. . . . . Outside of U.S.A. and Canada +1-847-435–5700. . FAX: +1-847-435–5541. . . . . . . . . . . . . . . . . . . . . .

Foreword – continued

Mar 2002 xxiiiCDMA/CDMA2000 1X RF Planning Guide

Reporting manual errors

In the event that you locate an error or identify a deficiency in yourmanual, please take time to write to us at the address above. Be sure toinclude your name and address, the complete manual title and partnumber (located on the manual spine, cover, or title page), the pagenumber (found at the bottom of each page) where the error is located,and any comments you may have regarding what you have found. Weappreciate any comments from the users of our manuals.

24-hour support service

If you have any questions or concerns regarding the operation of yourequipment, please contact the Customer Network Resolution Center forimmediate assistance. The 24 hour telephone numbers are:

Arlington Heights, IL 800-433-5202. . . . . . . . . . Arlington Heights, International +1–847-632-5390. . Cork, Ireland 44–1793–565444. . . . . . . . . . . . . . . . . Swindon, England 44–1793–565444. . . . . . . . . . . . .

General Safety

CDMA/CDMA2000 1X RF Planning Guide Mar 2002xxiv

Remember! . . . Safetydepends on you!!

The following general safety precautions must be observed during allphases of operation, service, and repair of the equipment described inthis manual. Failure to comply with these precautions or with specificwarnings elsewhere in this manual violates safety standards of design,manufacture, and intended use of the equipment. Motorola, Inc. assumesno liability for the customer’s failure to comply with these requirements.The safety precautions listed below represent warnings of certain dangersof which we are aware. You, as the user of this product, should followthese warnings and all other safety precautions necessary for the safeoperation of the equipment in your operating environment.

Ground the instrument

To minimize shock hazard, the equipment chassis and enclosure must beconnected to an electrical ground. If the equipment is supplied with athree-conductor ac power cable, the power cable must be either pluggedinto an approved three-contact electrical outlet or used with athree-contact to two-contact adapter. The three-contact to two-contactadapter must have the grounding wire (green) firmly connected to anelectrical ground (safety ground) at the power outlet. The power jack andmating plug of the power cable must meet International ElectrotechnicalCommission (IEC) safety standards.

Do not operate in an explosiveatmosphere

Do not operate the equipment in the presence of flammable gases orfumes. Operation of any electrical equipment in such an environmentconstitutes a definite safety hazard.

Keep away from live circuits

Operating personnel must:

not remove equipment covers. Only Factory Authorized ServicePersonnel or other qualified maintenance personnel may removeequipment covers for internal subassembly, or componentreplacement, or any internal adjustment.

not replace components with power cable connected. Under certainconditions, dangerous voltages may exist even with the power cableremoved.

always disconnect power and discharge circuits before touching them.

Do not service or adjust alone

Do not attempt internal service or adjustment, unless another person,capable of rendering first aid and resuscitation, is present.

General Safety – continued

Mar 2002 xxvCDMA/CDMA2000 1X RF Planning Guide

Use caution when exposing orhandling the CRT

Breakage of the Cathode–Ray Tube (CRT) causes a high-velocityscattering of glass fragments (implosion). To prevent CRT implosion,avoid rough handling or jarring of the equipment. The CRT should behandled only by qualified maintenance personnel, using approved safetymask and gloves.

Do not substitute parts ormodify equipment

Because of the danger of introducing additional hazards, do not installsubstitute parts or perform any unauthorized modification of equipment.Contact Motorola Warranty and Repair for service and repair to ensurethat safety features are maintained.

Dangerous procedurewarnings

Warnings, such as the example below, precede potentially dangerousprocedures throughout this manual. Instructions contained in thewarnings must be followed. You should also employ all other safetyprecautions that you deem necessary for the operation of the equipmentin your operating environment.

Dangerous voltages, capable of causing death, are present in thisequipment. Use extreme caution when handling, testing, andadjusting.

WARNING

Revision History

CDMA/CDMA2000 1X RF Planning Guide Mar 2002xxvi

Manual Number

68P09248A69–A

Manual Title


Version Information

The following table lists the manual version, date of version, andremarks on the version.

VersionLevel

Date of Issue Remarks

O December 1998 CDMA RF Planning Guide GA Release

A March 2002 CDMA/CDMA2000 1X RF Planning Guide

Cellular Manual RevisionInformation

The following table lists Cellular Manual Revision (CMR) number, dateof CMR, and remarks on the CMR.

RevisionLevel

Date of Issue Remarks

CMR No. NOV 2000

Patent Notification

Mar 2002 xxviiCDMA/CDMA2000 1X RF Planning Guide

Patent numbers

This product is manufactured and/or operated under one or more of thefollowing patents and other patents pending:

4128740 4661790 4860281 5036515 5119508 5204876 5247544 53013534193036 4667172 4866710 5036531 5121414 5204977 5251233 53013654237534 4672657 4870686 5038399 5123014 5207491 5255292 53032404268722 4694484 4872204 5040127 5127040 5210771 5257398 53032894282493 4696027 4873683 5041699 5127100 5212815 5259021 53034074301531 4704734 4876740 5047762 5128959 5212826 5261119 53054684302845 4709344 4881082 5048116 5130663 5214675 5263047 53070224312074 4710724 4885553 5055800 5133010 5214774 5263052 53075124350958 4726050 4887050 5055802 5140286 5216692 5263055 53094434354248 4729531 4887265 5058136 5142551 5218630 5265122 53095034367443 4737978 4893327 5060227 5142696 5220936 5268933 53111434369516 4742514 4896361 5060265 5144644 5222078 5271042 53111764369520 4751725 4910470 5065408 5146609 5222123 5274844 53115714369522 4754450 4914696 5067139 5146610 5222141 5274845 53134894375622 4764737 4918732 5068625 5152007 5222251 5276685 53197124485486 4764849 4941203 5070310 5155448 5224121 5276707 53217054491972 4775998 4945570 5073909 5157693 5224122 5276906 53217374517561 4775999 4956854 5073971 5159283 5226058 5276907 53233914519096 4797947 4970475 5075651 5159593 5228029 5276911 53253944549311 4799253 4972355 5077532 5159608 5230007 5276913 53275754550426 4802236 4972432 5077741 5170392 5233633 5276915 53295474564821 4803726 4979207 5077757 5170485 5235612 5278871 53296354573017 4811377 4984219 5081641 5170492 5235614 5280630 53393374581602 4811380 4984290 5083304 5182749 5239294 5285447 D3373284590473 4811404 4992753 5090051 5184349 5239675 5287544 D3422494591851 4817157 4998289 5093632 5185739 5241545 5287556 D3422504616314 4827507 5020076 5095500 5187809 5241548 5289505 D3470044636791 4829543 5021801 5105435 5187811 5241650 5291475 D3496894644351 4833701 5022054 5111454 5193102 5241688 5295136 RE318144646038 4837800 5023900 5111478 5195108 5243653 52971614649543 4843633 5028885 5113400 5200655 5245611 52992284654655 4847869 5030793 5117441 5203010 5245629 53010564654867 4852090 5031193 5119040 5204874 5245634 5301188

Patent Notification – continued

CDMA/CDMA2000 1X RF Planning Guide Mar 2002xxviii

Notes

1 - 1Mar 2002


Table of Contents


1.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 - 3

1.2 Quick Guide to Contents of Each Section . . . . . . . . . . . . . . . . . . . . . . . 1 - 4

Chapter

1 How to Use This Guide

1 - 2 CDMA/CDMA2000 1X RF Planning Guide Mar 2002

1

CDMA/CDMA2000 1X RF Planning GuideChapter 1: How to Use This Guide

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1 - 3CDMA/CDMA2000 1X RF Planning GuideMar 2002

1


1.1 Introduction

The purpose of this document is to provide systems engineers/planners with a basic set ofguidelines required to properly design a high quality Code Division Multiple Access (CDMA) RFSystem. The demarcation point for this guide is primarily at the antenna connectors of the BaseTransceiver Station (BTS) equipment. The CDMA RF Planning Guide (RFPG) commences atthese antenna connectors and incorporates the RF antenna system as well as the RF link. In general,most of the content provided in this planning guide can be applied to any CDMA system design.In some instances, specific RF planning information unique to Motorola’s CDMA BTS product isalso provided. The following figure pictorially represents the area within a wireless network thatthis document is focused.

Figure 1-1: Radio Sub-System

Most of the information in this planning guide can be applied to both the IS-95 and IS-2000 CDMAair interface specifications. Where it is appropriate, IS-95 specific and/or IS-2000 specificinformation will be provided.

General RF considerations for CDMA system designs are addressed as well as 800 MHz and 1900MHz specific considerations. Some basic spectrum planning guidelines including channelassignments and designations for both 800 MHz and 1900 MHz are located in Chapter 2. Chapter6 addresses some RF antenna system issues that differ between 800 MHz and 1900 MHz.Throughout this document the terms 800 MHz and cellular may be used interchangeably, as wellas 1900 MHz and PCS may also be used interchangeably.

Terms and acronyms are located in Appendix I. Appendix II is a glossary of terms which arereferred to in Chapter 5. An understanding of these terms and acronyms is recommended prior toreading this document.

Radio Sub-System

BTS

CDMA AirInterface

FixedPortable

Mobile

Core Network


1


1.2 Quick Guide to Contents of Each Section

The CDMA RF Planning Guide is a collection of fairly independent chapters covering variousaspects of CDMA system RF design and implementation.

The table below outlines the key features of each Chapter.

Table 1-1: Quick Guide

Chapter Number

Chapter title Use it to

1 How to Use this Guide Understand the contents of this document.2 Basic CDMA Spectrum

PlanningLearn how to allocate spectrum for multiple CDMA carriersincluding channel spacing and guard band considerations,which bands are used for different technologies (world-wide),and the importance of performing background noisemeasurements, spectrum clearing, and following FederalRules and Regulations.

3 CDMA Capacity Learn several different approaches on how to estimate themaximum capacity of a CDMA carrier for the forward orreverse link as a function of system parameters. Understandthe importance of performing system simulations. Identifysome of the limitations of the air interface. Determine anestimate of the number of CDMA cells required to support agiven traffic load.

4 Link Budgets and Coverage

Understand the parameters that comprise the CDMA RF LinkBudget. Learn about some of the basic propagation models.Understand some of the power amplifier considerations asthey pertain to forward link coverage. Learn some of theissues and considerations of CDMA repeater usage.

5 PN Offset Planning and Search Windows

Understand how to perform PN offset planning and how toproperly set the search window parameters.

6 RF Antenna Systems Learn some of the basic antenna parameters. Discuss some ofthe issues involved with antenna placement. Understand howto share antennas with other CDMA equipment as well aswith AMPS equipment. Establish guidelines for theinstallation of CDMA systems antennas.

7 RF Antenna Systems - Advanced Topics

Discuss some of the issues surrounding the usage of dualpolarized antennas. Learn some useful information in the areaof in-building antenna system design.

8 Synchronization of the CDMA System

Learn about the strength and weakness of varioussynchronization strategies. Determine the requirements toprovide adequate signals to synchronize the CDMA system.

9 Inter-System Interference

Study interference issues with co-location of CDMA withother technologies.


1


I Terms and Acronyms Learn some of the various terms and acronyms.II Glossary Understand some of the various terms used.III Watts to dBm

Conversion TableConvert from watts to dBm and from dBm to watts.

IV Complimentary Error Function Table

Determine the complimentary error function.

Table 1-1: Quick Guide

Chapter Number

Chapter title Use it to


1


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Table of Contents

2.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 3

2.2 North American and International Frequency Blocks . . . . . . . . . . . . . 2 - 3

2.3 CDMA Channel Spacing - General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 52.3.1 Minimum Spacing Between CDMA Carriers . . . . . . . . . . . . . . . 2 - 52.3.2 Maximum Spacing Between CDMA Carriers . . . . . . . . . . . . . . . 2 - 82.3.3 Multiple Market Spectrum Planning Considerations . . . . . . . . . . 2 - 112.3.4 Multiple Carrier Overlay Guidelines . . . . . . . . . . . . . . . . . . . . . . 2 - 11

2.3.4.1 IS-2000 1X New Carrier Overlay . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 142.3.4.2 IS-2000 1X Shared Carrier Overlay . . . . . . . . . . . . . . . . . . . . . . . . 2 - 15

2.3.5 Guard Band Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 152.3.5.1 AMPS Guard Band Recommendation. . . . . . . . . . . . . . . . . . . . . . . 2 - 172.3.5.2 2nd CDMA Carrier with AMPS Guard Band . . . . . . . . . . . . . . . . . 2 - 172.3.5.3 Greater Than Two CDMA Carriers with AMPS Guard Band . . . . 2 - 18

2.4 Channel Spacing and Designation - 800 MHz . . . . . . . . . . . . . . . . . . . . 2 - 192.4.1 Segregated Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 20

2.5 Channel Spacing and Designation - 1900 MHz . . . . . . . . . . . . . . . . . . . 2 - 23

2.6 Dual-Mode vs. Dual-Band . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 25

2.7 Spectrum Clearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 25

2.8 Background Noise Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 262.8.1 Suggested Measurement Method . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 27

2.8.1.1 Test System Functional Description . . . . . . . . . . . . . . . . . . . . . . . . 2 - 272.8.1.2 Test System Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 28

2.8.2 Test Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 292.8.3 Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 30

2.9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 - 30

Basic CDMA SpectrumPlanning

Chapter

2

2

CDMA/CDMA2000 1X RF Planning GuideChapter 2: Basic CDMA Spectrum Planning


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2


2.1 Introduction

This chapter provides a set of general guidelines that can be used to properly allocate spectrum for1.23 MHz CDMA systems (IS-95A/B and IS-2000 Spreading Rate 1), including issues relating tothe co-location of CDMA and AMPS systems. Spectrum planning information for IS-2000Spreading Rate 3 and for Wideband Code Division Multiple Access (WCDMA) for UniversalMobile Telecommunication System (UMTS) will not be covered in this document. Unlessotherwise noted, all references to IS-2000 in this document will imply a Spreading Rate of 1. Theinformation is specific to spectrum allocation based on U.S. and International Standards. Issuesregarding technological impacts to capacity will be addressed in Chapter 3. In this chapter,"channels" refer to frequency allocation and not conversation channels. As a result, a CDMAchannel reference is the same as a CDMA carrier and the two terms can be interchanged for thischapter.

To design a system adequately, RF system engineers will need to work closely with the customerand carefully follow government codes. To optimize CDMA, the signal to noise ratio must bebalanced. The goal is to minimize the noise which will maximize the capacity.

Common world-wide frequency bands for cellular, PCS, and 3G are introduced in the chapteralong with a general discussion on CDMA channel spacing, multiple carrier guidelines, and guardband considerations. Specifics are given on CMDA channel designations (North American) for800 MHz and how to segregate the spectrum with existing 800 MHz technologies. PCS (NorthAmerican) channel designations are listed, followed by a short discussion of dual-mode and dual-band. The topic of spectrum clearing and background noise measurements appears last; however,it is perhaps one of the most important and challenging aspects to the CDMA system designengineer. References include standards and FCC web page locations.

2.2 North American and International Frequency Blocks

The manner in which the frequency spectrum is allocated in some countries imposes somelimitations on where CDMA may be implemented. It is difficult to predict the amount of availablespectrum or the frequency band which international operators might be considering for theirCDMA systems. With this in mind, prior to designing a CDMA system, the CDMA system designengineer should obtain the frequency spectrum information from the operator and then determinethe appropriate BTS products to use based on the desired application and the operating frequency.The table below highlights some of the more common frequency bands which are currently beingutilized for cellular, PCS, and other technologies in adjacent spectrum throughout the world.

Table 2-1: Some Common World-Wide Frequency Bands for Cellular and PCS

Block DesignatorTransmit Frequency Band (MHz)

Personal Station Base Station

SMR (US) 816-821 861-866

AMPS / EAMPS 824-849 869-894

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The technology evolution of wireless communication systems are migrating from the 1stgeneration (1G) voice only services, to the 2nd generation (2 or 2.5G) voice and low to mediumspeed data services, and then to the 3rd generation (3G) voice and multimedia, high speed dataservices. To accommodate the evolution to 3G, the International Telecommunications Union -Radio Communication (ITU-R) standardization sector developed specifications for InternationalMobile Telecommunications - 2000 (IMT-2000). As an output of the standardization effort, severalcountries throughout the world have agreed to allocate new spectrum for 3G deployments. Thechart in Figure 2-1 highlights some of the common world-wide 3G spectrum allocations.

TACS / ETACS 872-915 917-960

DCS 1800 1710-1785 1805-1880

GSM 890-915 935-960

PCS (Korea) 1750-1780 1840-1870

ARDIS (Pan America) 806-824 851-869

RAM Mobitex(Pan America)

896-901 935-940

PCS(U.S. / Pan America)

1850-1910 1930-1990

FPLMTS 1885-2025 2110-2200

FPLMTS (satellite) 1980-2010 2170-2200

PDC 900 940-956 810-826

PDC 1500(Malaysia / Moscow)

1477-1501 1429-1453

Japan Marinet 887-889 832-834

Japan Analog 898-901, 915-925 843-846, 860-870

DECT (TDD Systems) 1880-1900 1880-1900

PHS (TDD Systems) 1895-1918 1895-1918

Table 2-1: Some Common World-Wide Frequency Bands for Cellular and PCS




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Figure 2-1: 3G Spectrum Allocations

2.3 CDMA Channel Spacing - General

CDMA (IS-95A/B and IS-2000 Spreading Rate 1) is a broadband technology which utilizes 1.2288MHz bandwidth per CDMA Channel (this is often rounded off to 1.23 MHz). In order to deployan initial CDMA channel, spectrum must be allocated for the CDMA channel and the guard bandsthat are required on each side of the channel. In order to deploy a second CDMA channel, thechannel spacing between the CDMA channels must be determined. Prior to deploying the firstCDMA channel, long term spectrum planning should be performed in order to maximize thecapacity of a multiple carrier CDMA block of spectrum. This section provides information onCDMA channel spacing, multiple carrier guidelines, and guard band considerations.

In this section, "channel" is defined as each 1.2288 MHz carrier and not as a conversation path. ForAMPS, each frequency (carrier) corresponds to one conversation path. Therefore, a channel couldbe used to discuss conversational paths or the number of carriers. For CDMA, each carrier cansupport many conversation paths and therefore the term "channel" can take on different meaningsbased upon the context in which it is used.

2.3.1 Minimum Spacing Between CDMA Carriers

As the number of the CDMA subscribers increases, there may be a need to add additional CDMAcarrier frequencies to the system. If the first and second carrier frequencies are to be adjacent toone another, then the channel spacing between CDMA carriers (center to center) needs to bedetermined. For 800 MHz IS-95A/B and IS-2000 based systems with a 30 kHz channel increment,the minimum recommended channel spacing separation between CDMA channels is 1.23 MHz(see Figure 2-2).

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Figure 2-2: Minimum Spacing Between 800 MHz CDMA Channels

Note: For the example in Figure 2-2, the second CDMA channel (whether it is ubiquitous ornon-ubiquitous) must be co-located with the first CDMA channel in a 1-to-1 overlayapproach throughout the second CDMA channel deployment area (see Section 2.3.4).

For 1900 MHz IS-95A/B and IS-2000 based systems with a 50 kHz channel increment, theminimum recommended channel spacing separation between CDMA channels is 1.25 MHz (seeFigure 2-3).

Figure 2-3: Minimum Spacing Between 1900 MHz CDMA Channels

Note: For the example in Figure 2-3, the second CDMA channel (whether it is ubiquitous ornon-ubiquitous) must be co-located with the first CDMA channel in a 1-to-1 overlayapproach throughout the second CDMA channel deployment area (see Section 2.3.4).

The minimum channel spacing places the broadband carriers adjacent to one another and allowsthe sidebands of each to intrude into the band of the other. The adjacent channel interference forthis minimum channel separation will slightly reduce the capacity of both CDMA carriers. ACDMA channel with adjacent CDMA channels on both sides will have an even greater reductionin capacity. If system noise, non-linearities, or other imperfections increase the energy in the skirtsof the carriers, then an increased capacity reduction may be experienced.

A reverse link adjacent channel interference analysis was performed in an attempt to estimate andcompare the capacity impact of a 1.26 MHz and a 1.23 MHz channel spacing. The analysisestimates the noise rise for a single carrier configuration (i.e. no adjacent carriers), for the center

1.23 MHz

1st CDMA Channel1.23 MHz

2nd CDMA Channel1.23 MHz

Guard BandGuard Band

1.25 MHz



Guard BandGuard Band


2


carrier of a three carrier configuration with a 1.26 MHz channel separation, and for the centercarrier of a three carrier configuration with a 1.23 MHz channel separation. The results of thisanalysis where all of the carriers are loaded equally is shown in Figure 2-4. (Note: The capacityresults shown in Figure 2-4 should not be used to estimate the actual capacity of a CDMA carrier.They are for comparison purposes only.)

Figure 2-4: Adjacent Channel Interference Reverse Rise Estimates

One method of analyzing the impact is to compare the number of users at a fixed maximum noiserise level. Choosing 6 dB to be the maximum noise rise level, the following results can beextrapolated from the chart in Figure 2-4.

• 23.5 Users with 0 Adjacent Carriers• 22.6 Users with 2 Adjacent Carriers @ 1.26 MHz• 21.8 Users with 2 Adjacent Carriers @ 1.23 MHz

The capacity loss from 0 Adjacent Carriers to 2 Adjacent Carriers with 1.26 MHz spacing isapproximately 0.9 users. The capacity loss from 2 Adjacent Carriers with 1.26 MHz spacing to 2Adjacent Carriers with 1.23 MHz spacing is approximately 0.8 users.

Another method of analyzing the impact is to compare the noise rise increase at a fixed maximumnumber of users. Choosing 23 users to be the maximum number of users, the following noise riseresults can be extrapolated from the chart in Figure 2-4.

0

2

4

6

8

10

12

14

0 5 10 15 20 25 30

# of Users

Ris

e -d

B

0 Adjacent Carriers

2 Adjacent Carriers @ 1.23 MHz

2 Adjacent Carriers @ 1.26 MHz

2



• 5.7 dB noise rise with 0 Adjacent Carriers• 6.2 dB noise rise with 2 Adjacent Carriers @ 1.26 MHz• 6.7 dB noise rise with 2 Adjacent Carriers @ 1.23 MHz

The noise rise increase from 0 Adjacent Carriers to 2 Adjacent Carriers with 1.26 MHz spacing isapproximately 0.5 dB. The noise rise increase from 2 Adjacent Carriers with 1.26 MHz spacing to2 Adjacent Carriers with 1.23 MHz spacing is approximately 0.5 dB.

The results of this analysis show a minimal impact going from 1.26 to 1.23 MHz channel spacing.Ultimately, the system operator must decide whether the modest capacity impact of using theminimum channel spacing is worth the marginal gain in frequency spectrum.

2.3.2 Maximum Spacing Between CDMA Carriers

With the allocations of new spectrum for 3G applications through-out the world, a new opportunityfor deploying CDMA systems has been created. There are many different considerations that mayimpact the spectrum planning for a CDMA system (total spectrum available, government rules andregulations, adjacent spectrum guard band requirements, amount of spectrum that is clear andavailable for use, etc.). For certain applications, there may be some capacity benefits in reducingthe adjacent spectrum guard band requirements in order to increase the guard band between theCDMA carriers. This approach will typically be applied towards the deployment of new spectrumallocations (i.e. 3G deployments). An appropriate adjacent spectrum guard band analysis must beperformed to justify an adjacent spectrum guard band reduction in order to increase the guard bandbetween the CDMA carriers.

Since the minimum channel spacing recommendation does have some impact on capacity, theoptimal channel spacing may not always be the minimum channel spacing recommendation statedin Section 2.3.1. The optimal channel spacing from a CDMA capacity perspective is to maximizethe channel spacing within the total contiguous bandwidth available for the CDMA channels (afterall of the spectrum planning considerations for guard band and other requirements have been takeninto account). For those applications where there is flexibility in performing spectrum planning,the following spectrum planning example of an entire block of spectrum (including guard bandrequirements) can be performed in order to determine the maximum channel spacing whichmaximizes capacity. The following multiple carrier, maximum channel spacing example can beapplied from a general perspective towards both IS-95A/B and/or IS-2000 1X carrier systems.

Example Assumptions:• 5 MHz "D" block of 1900 MHz full duplexed spectrum (5 MHz for Tx, 5 MHz for Rx)• Channel increment is 50 kHz• Guard band requirements for each end of the spectrum is 290 kHz per side

(Note: The 290 kHz guard band value was arbitrarily chosen for this example. It does notrepresent an actual guard band recommendation. See Section 2.3.5 for more informationregarding a guard band analysis and considerations.)

• Government rules and regulations allow the following spectrum planning assignments


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1. Determine the total number of channel numbers (i.e. 30 kHz channel increments for 800MHz systems, or 50 kHz channel increments for 1900 MHz systems) that are availablewithin the allocated bandwidth.

Example: 5 MHz / 0.05 MHz = 100 "D" block channel numbers (see Figure 2-5).

Figure 2-5: Total Channel Numbers Available

2. Allocate and assign the guard band channels to each end of the spectrum. Calculate theminimum number of channel numbers to satisfy the guard band requirements bydividing the guard band by the channel increment and rounding up to the nearest integer.

Example: 290 kHz / 50 kHz = 5.8 = 6 channel numbers per side. See Figure 2-6.6 channels x 50 kHz = 300 kHz per side300 kHz x 2 = 600 kHz = 0.6 MHz total guard band

Figure 2-6: Assign Guard Band

3. Use the following equation to calculate the total number of 1.23 MHz CDMA channels(Nc) for the allocated bandwidth.

Nc = [EQ 2-1]

Where:represents the integer value of X (or floor value of X)

BW is the total bandwidth allocated for CDMA channelsGB is the total guard band requirementsFS is the minimum frequency spacing (1.23 for 800 MHz, 1.25 for 1900 MHz)

Example: BW = 5 MHz, GB = 0.6 MHz, FS = 1.25 MHz

Nc = = 3 CDMA channels

100 Channel Increments x 50 kHz = 5 MHz

300-399

Guard

300-305 394-399

BandGuardBand


306-393

BW GB–( ) FS⁄

X

5 0.6–( ) 1.25⁄

2



4. Determine the minimum number of channel numbers to allocate for each CDMAchannel.

• For 30 kHz channel spacing systems (800 MHz systems) use 41 channel numbers1.23 MHz / 0.03 MHz = 41 channel numbers

• For 50 kHz channel spacing systems (1900 MHz systems) use 25 channel numbers 1.25 MHz / 0.05 MHz = 25 channel numbers

Example: 25 channel numbers for each carrier

5. Assign the minimum number of channels for the 1st and last CDMA carriers next toeach of the adjacent spectrum guard bands.

Example: Assign 25 channel numbers for the F1 and F3 CDMA carriers next to eachadjacent spectrum guard band. See Figure 2-7.

Figure 2-7: Assign 1st and Last CDMA Carries

6. Equally distribute the remaining CDMA carriers while maximizing the spacing betweeneach carrier.

Example: Assign 25 channel numbers for the single remaining CDMA carrier (F2) asclose to the center of the remaining spectrum as possible. See Figure 2-8.

Figure 2-8: Equally Distribute Remaining CDMA Carriers

Note: For the "D" block example shown above, channels 318 and 381 are conditionally validchannel numbers according to the IS-95/IS-2000 standards (see Table 2-8). As statedpreviously, an appropriate guard band analysis must have been performed to justify aguard band reduction in order to utilize these conditional channel numbers.

Guard

CDMA Carrier F1

300-305 306-330 331-368 369-393 394-399

Band

Center Freq. Channel = 318CDMA Carrier F3

Center Freq. Channel = 381

GuardBand


Guard

CDMA Carrier F1

300-305 306-330 331-337 338-362 363-368 369-393 394-399

Band



Center Freq. Channel = 381

GuardBand

ExcessBand

ExcessBand



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2.3.3 Multiple Market Spectrum Planning Considerations

Prior to finalizing a spectrum planning design for an individual market, there are various inter-systemoperation aspects between multiple markets which may need to be considered. Inter-systemreferences in this section can be applied towards different systems (or markets) under the control of asingle operator (or corporation) or under the control of different operators (or corporations). In eithercase, a multiple market spectrum planning perspective may need to be considered. There are twomajor categories of inter-system operation services that will be considered; inter-system handoffs andinter-system automatic roaming.

An inter-system handoff refers to the general provisions by which a call in progress on a trafficchannel under the control of one system may be automatically transferred to another traffic channelunder the control of a different system without interruption to the ongoing communication. Inter-system handoffs can be inter-vendor (i.e. via IS-41 or GSM MAP) or intra-vendor handoffs. The inter-system intra-vendor handoffs can take the form of soft or hard handoffs. If adjacent markets will needto perform inter-system handoffs to each other, the channel numbers selected between the adjacentmarkets may need to be coordinated. For example, if inter-system soft handoffs are to beimplemented, then the channel numbers between the inter-system handoff boundaries must be thesame.

Inter-system automatic roaming refers to the general provisions for automatically providing cellularservices to the subscribers which are operating outside their home service area, but within theaggregate service area of all participating systems. Inter-system roaming can be inter-vendor (i.e. viaIS-41 or GSM MAP) or intra-vendor automatic roaming. If different systems will need to performinter-system automatic roaming to each other, the channel numbers selected between the differentsystems may need to be coordinated. For example, the channel numbers on a preferred roaming listmust be coordinated to accommodate all of the roaming markets.

As a result, a spectrum planning design for an individual market may need to be considered from amultiple market spectrum planning perspective depending upon the inter-system services that will besupported.

2.3.4 Multiple Carrier Overlay Guidelines

As the capacity demand of a system increases, the deployment of additional CDMA carriers willeventually be necessary. The capacity demand may or may not require a ubiquitous deployment of anew carrier throughout the underlying carrier region. When a new carrier is deployed (eitherubiquitous or non-ubiquitous), the new carrier should be deployed with a 1-to-1 co-location overlaywith the underlying carriers (refer to Figure 2-9 for overlay examples) and should also be deployedwith the same coverage area as the underlying carrier.

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Figure 2-9: 1-to-1 Overlay Examples

For the examples in Figure 2-9, an F2 carrier must be co-located with every F1 site within the newcarrier region. It is important to note that F1 micro-cells located in the new carrier region shouldalso be co-located with F2 micro-cells.

Examples of non 1-to-1 overlays are provided in Figure 2-10. These examples are similar to thoseprovided in Figure 2-9, but are NOT recommended.

Figure 2-10: Non 1-to-1 Overlay Examples (NOT Recommended)

There are two main reasons for requiring a 1-to-1 co-location overlay of a new carrier with thesame coverage area.

• To overcome adjacent channel interference causing a near/far interference effect• To overcome a potential service acquisition issue created by uneven coverage between

CDMA carriers

If a 1-to-1 co-location overlay deployment is NOT implemented, a near/far interference effect iscreated from the adjacent CDMA carriers. This will create coverage holes near the sites that arenot co-located with the underlying carriers. See Section 2.3.5 for more details regarding the near/far effect.

F1 & F2 SitesF1 Only Sites

Non-Ubiquitous 1-to-1 Overlay Ubiquitous 1-to-1 Overlay

All Sites have F1 & F2


Non-Ubiquitous Non 1-to-1 Overlay Ubiquitous Non 1-to-1 Overlay



2


If a 1-to-1 co-location overlay deployment is NOT implemented, a service acquisition issue maybe created by the uneven coverage between the CDMA carriers. A diagram to help explain theservice acquisition issue is shown in Figure 2-11.

Figure 2-11: Service Acquisition Issues Due To Uneven Carrier Coverage

There are two different types of service acquisition issues which can be created as a result ofuneven carrier coverage as shown in Figure 2-11.

• At point A, the primary carrier (F1) of Cell 1 is transmitting the channel list messagecontaining channel numbers for both F1 and F2. With 2 channels input into the hashingalgorithm, half of the subscribers at point A should hash to F2. Since the coverage of F2is too weak to acquire service, those same subscribers will fall back to the primarycarrier and attempt to reread the channel list message. These same subscribers will againtry to hash to F2 and again fail to acquire service. This cycle will repeat itself until thosesubscribers move to a location where both F1 and F2 coverage from Cell 1 is acceptable.

• At point B, the primary carrier (F1) of Cell 1 is transmitting the channel list messagecontaining channel numbers for both F1 and F2. With 2 channels input into the hashingalgorithm, half of the subscribers at point B should hash to F2. Since the coverage of F2is provided by Cell 2 which uses a different PN offset, those subscribers will not be ableto decode the synchronization and paging channels and the service acquisition attemptwill fail. As a result, those same subscribers will fall back to the primary carrier andattempt to reread the channel list message. These same subscribers will again try to hashto F2 and again fail to acquire service. This cycle will repeat itself until thosesubscribers move to a location where both F1 and F2 coverage is provided by the samecell.

As a result, a new carrier should always be deployed with a 1-to-1 co-location overlay with theunderlying carriers and should also be deployed with the same coverage area as the underlyingcarriers. Also, if a new cell site is deployed into an existing multiple carrier region, then all of thecarriers in this region should be implemented at the new cell site and the coverage area for eachcarrier should be made the same.

Cell 1

Cell 2B

A

F1&F2

F2

Cell 1 F1Cell 1 - F1 & F2 Coverage

Cell 2 - F2 Coverage

Cell 1 - F1 Coverage

F1 is primary carrier

2



2.3.4.1 IS-2000 1X New Carrier Overlay

The multiple carrier overlay guidelines described in Section 2.3.4 apply to both IS-95A/B and IS-2000 1X CDMA carriers. Figure 2-12 shows an example of a new IS-2000 1X carrier beingdeployed in a system with existing IS-95A/B carriers.

Figure 2-12: New IS-2000 1X Carrier Deployment

A new IS-2000 1X overlay carrier being deployed into an existing IS-95A/B system would haveto be implemented in a 1-to-1 co-location overlay with the underlying IS-95A/B carriers andshould also be deployed with the same coverage area as the underlying IS-95A/B carriers. Forsome applications, a new IS-2000 1X carrier may be deployed to support 1X data applicationsonly. Without the burden of the co-existing voice capacity, an IS-2000 1X data only carrier cansupport higher data rates with improved data capacity. From an overall data performanceperspective, a dedicated 1X data only carrier should provide the best data performance results.

With IS-2000 1X, higher data rates can be achieved with smaller radius cell sites. The link budgetimprovements from a smaller radius cell site can be applied towards producing higher average datarates. As a result, one option is to cell split an area (i.e. deploying more cells in the same area) inorder to improve the chances of achieving higher data rates. In a mixed IS-95A/B and IS-2000system, a new cell site being deployed to improve 1X data performance must also deploy theexisting IS-95A/B carriers at the new cell site.

Another method to improve 1X data performance is to deploy a second IS-2000 1X carrier to anarea that already has 1X deployed (see Figure 2-13).

Figure 2-13: Second IS-2000 1X Carrier

This is an effective approach to alleviate system loading and also increase end user 1X data

F1 F2 F3 F4

IS-95A/B IS-2000

F1 F2 F3 F4

IS-95A/B IS-2000

F5


2


performance. This approach also offers a simple and cost effective solution to improve 1X dataperformance, since an additional 1X carrier can be easily implemented by adding extra 1X MCCand BBX cards to the existing 1X cell sites (assuming the existing 1X cell sites are not populatedto their maximum carrier capacity).

2.3.4.2 IS-2000 1X Shared Carrier Overlay

As an alternate approach to deploying a new CDMA channel frequency, the Walsh codeorthogonality between the IS-95A/B and IS-2000 air interfaces will allow a new IS-2000 1X carrierto share the carrier frequency with an existing IS-95A/B carrier (see Figure 2-14).

Figure 2-14: IS-2000 1X Shared Carrier Overlay

For initial 1X deployments with low 1X subscriber penetration rates, this may be a viable optionto choose, but it is not recommended if the existing IS-95A/B carrier capacity is already near itsmaximum limit. With the burden of the co-existing IS-95A/B traffic capacity, an IS-2000 1Xcarrier will be limited in its data performance. High data rate 1X usage will introduce load that mayresult in bursty performance degradation of the underlying IS-95A/B voice. On the other hand, theIS-95A/B voice users may end up restricting the high data rate 1X users. To protect the IS-95A/Bvoice users, it is recommended to limit the high data rate application usage on the 1X carrier for ashared carrier overlay type of deployment. Since one of the main reasons for deploying a 1X carrieris to provide high data rate service, limiting the high data rate usage on the 1X carrier may actuallydefeat the purpose of deploying the 1X carrier in the first place. As a result, the benefit of usingthis type of deployment may be somewhat limited.

2.3.5 Guard Band Considerations

General spectrum planning guidelines require the use of a guard band between adjacent spectrumbeing used for different operator systems or for different air interface technologies. The guard bandis required to minimize the intra-band and inter-band interference to and from the adjacentspectrum. The determination of a proper guard band involves a detailed analysis of the forward andreverse links for both systems being analyzed. Guard band planning may need to take into accountthe adjacent spectrum, which is geographically along the border of the system, as well as that whichis geographically co-located with the system. Cooperation between neighboring system operatorsis essential to minimize interference problems. All of the possible interference scenarios from bothsystems perspectives must be considered in the analysis. The more common interference scenarios

F1 F2 F3

IS-95A/B IS-2000

2



between two systems are listed below.

• System A subscriber(s) interfering with System B base station• System A base station interfering with System B subscriber(s)• System B subscriber(s) interfering with System A base station• System B base station interfering with System A subscriber(s)

Depending upon the particular interference scenario, there are four predominant interferencemechanisms that may need to be analyzed.

• Transmitter sideband emissions interfering with the adjacent band receiver• Transmitter intermodulation (IM) products interfering with the adjacent band receiver• Receiver desensitization from an interfering transmit carrier• Receiver intermodulation from two or more interfering transmit carriers

Additional details regarding the above interference scenarios and interference mechanisms areprovided in Chapter 9. A detailed analysis of the guard band requirements may need to take intoaccount the following factors:

Interference Geometries• geographic and/or geometric properties of the interference location• antenna orientation (height, azimuth, downtilt)• total path loss (propagation loss, antenna discrimination, and obstruction losses)

Interference Characteristics (for desired and interference signals)• air interface technologies being used• antenna gain and feeder line losses• transmit power, duty cycle, and power spectral density• transmit and receive frequencies being used• transmit and receive filter characteristics• receiver noise threshold and other receiver performance characteristics

A potential interference problem, known as the near/far effect, is created by the geometricrelationship between a subscriber and base station. This effect is produced when a subscriber islocated far from its serving base station, but near an interfering base station. Under thesecircumstances, the strength of the desired signal is low while the strength of the interfering signalis high. A guard band analysis may need to take into account any near/far effects that may bepresent.

The guard band analysis utilizes all of the relevant parameters from the subscriber/base stationgeometries and characteristics to calculate the desired signal strength, receiver noise, and thereceived interfering signal strength. The net value should include all of the relevant effects oftransmit powers, transmit power spectral densities, path loss, filtering, duty cycles, and summationover multiple interferers. Depending upon the air interface technology that is being analyzed, adegradation metric is selected (i.e. C/I, noise floor rise, receiver sensitivity, Eb/No, BER, FER,etc.) to determine how these net values will impact the performance of the receiver, and whether


2


this impact is acceptable or not. Ultimately, the guard band that is selected should provide anacceptable performance value from the degradation metric. Interference improvement mechanisms(i.e. adjustments to base station transmit powers, adding extra filtering, increasing isolation, etc.)should also be considered in the guard band analysis determination.

2.3.5.1 AMPS Guard Band Recommendation

For an 800 MHz system with a 30 kHz channel spacing, it has been determined through a guardband analysis that the minimum recommended guard band between a CDMA channel and anAMPS channel is 0.27 MHz. The initial introduction of CDMA will require a band segment of 1.77MHz. The band segment consists of the 1.23 MHz required for the CDMA carrier bandwidth plus0.27 MHz of AMPS guard band on both sides of the CDMA carrier. The minimum frequencyseparation required between any CDMA carrier and the nearest AMPS carrier is 900 kHz (centerto center).

The CDMA carrier width (1.23 MHz) is the result of the chip rate chosen for the PseudorandomNoise (PN) spreading sequence. The guard band between CDMA and analog systems is defined asthe minimum frequency separation required such that the level of interference caused by one FMsubscriber is less than a predetermined threshold. The threshold is taken to be the thermal noiselevel in each receiver.

Figure 2-15: Calculation of Spectrum Required for a CDMA Carrier

2.3.5.2 2nd CDMA Carrier with AMPS Guard Band

The following figure summarizes the additional and total number of AMPS channels removed tofree up spectrum for the second CDMA channel for an 800 MHz system with a 30 kHz channelspacing.

Figure 2-16: Calculation of Minimum Spectrum Required for Two CDMA Channels

CDMA Channel = 1.23 MHz = 1.23MHz / 30kHza = 41 AMPS Channels

CDMA Guard = 0.27 MHz/side = 0.54MHz / 30kHza = 18 AMPS Channels

Totals 1.77 MHz 59 AMPS Channels

a. One AMPS Channel = 30 kHz

CDMA Spacing= 1.23 MHz = 1.23MHz / 30kHza = 41 AMPS Channels

CDMA Channel = 1.23 MHz = 1.23MHz / 30kHza = 41 AMPS Channels

CDMA Guard = 0.27 MHz/side = 0.54MHz / 30kHza = 18 AMPS Channels

Totals 3.00 MHz 101 AMPS Channels

a. One AMPS Channel = 30 kHz

2



The difference between the 1st CDMA carrier and the 2nd CDMA carrier is equal to the channelspacing. Minimal channel spacing is 1.23 MHz (41 AMPS channels). The following figurerepresents the frequency requirements for 2nd carrier implementation.

Figure 2-17: 2nd CDMA Carrier

2.3.5.3 Greater Than Two CDMA Carriers with AMPS Guard Band

Additional carriers can be added as outlined in Section 2.3.4. See Figure 2-18 for a 3-carrierexample for an 800 MHz system with a 30 kHz channel spacing. CDMA carriers must be at least1.23 MHz apart with guard bands on each end. The governing body controlling the frequencyallocations will dictate the amount of spectrum available for each operator. This spectrum will limitthe number of carriers allowed per block.

Figure 2-18: 3rd CDMA Carrier

1.23 MHz



AMPS GuardAMPS Guard0.27 MHz0.27 MHz

1.23 MHz



AMPS GuardAMPS Guard

1.23 MHz

3rd CDMA Channel1.23 MHz 0.27 MHz0.27 MHz


2


2.4 Channel Spacing and Designation - 800 MHz

The Primary and Secondary CDMA Channel will be assigned as indicated in Table 2-2. Theinformation presented in Table 2-3 is taken directly from the IS-95A/B and IS-2000 standards thatoutline the channel allocations shared by CDMA and AMPS technologies (Note: informationprovided applies only to Spreading Rate 1 for IS-2000).

Table 2-2: CDMA Channel Spacing and Designation

Table 2-3: Channel Numbers and Frequencies for Band Class 0 and Spreading Rate 1

a. The valid channel numbers provided in this table were taken directly from the IS-95 standard.Before using a valid channel number that is near the band edge, an analysis is required to verifyproper guard band and FCC emission compliance with the adjacent band.b. The spectrum allocated to the A’ band is not sufficient for a CDMA carrier.

“A” Band “B” Band

Primary 283 384

Secondary 691 777a

a. In the United States due to proximity of 800 MHz Air-Ground Radiotelephone Service,channel 777 has interference considerations associated with it. Use of this channel shouldrequire determination of sufficient isolation prior to implementation.

SystemDesignator

CDMA Channel Validity

Analog ChannelCount

CDMA Channel Number

Transmitter Frequency Band (MHz) Subscriber Base

A"(1 MHz)

Not Valid 22 991 - 1012 824.040-824.670 869.040-869.670

Valid a 11 1013 - 1023 824.700-825.000 869.700-870.000

A(10 MHz)

Valid a 311 1 - 311 825.030-834.330 870.030-879.330

Not Valid 22 312 - 333 834.360-834.990 879.360-879.990

B(10 MHz)

Not Valid 22 334 - 355 835.020-835.650 880.020-880.650

Valid a 289 356 - 644 835.680-844.320 880.680-889.320

Not Valid 22 645 - 666 844.350-844.980 889.350-889.980

A’(1.5 MHz)

Not Valid 22 667 - 688 845.010-845.640 890.010-890.640

Valid b 6 689 - 694 845.670-845.820 890.670-890.820

Not Valid 22 695 - 716 845.850-846.480 890.850-891.480

B’(2.5 MHz)

Not Valid 22 717 - 738 846.510-847.140 891.510-892.140

Valid a 39 739 - 777 847.170-848.310 892.170-893.310

Not Valid 22 778 - 799 848.340-848.970 893.340-893.970

2



In Table 2-3, the center frequency (in MHz) corresponding to the channel number is calculated asshown in Table 2-4, where N represents the channel number.

Table 2-4: CDMA Channel Number to CDMA Frequency Assignment Correspondence

A visual depiction of the CDMA frequencies is shown in Figure 2-19.

Figure 2-19: AMPS Frequency Allocation

2.4.1 Segregated Spectrum

When the CDMA carrier is deployed where another technology already exists, the system spectrummust be split into two frequency bands. One band is for the existing technology and the other bandis for digital frequency bands. This concept is shown in the following “B” band frequency chart(see Table 2-5). Note that the digital band includes a single primary CDMA carrier.

Transmitter CDMA Channel Number Center Frequency (MHz)

Subscriber Station 1 < N < 799 0.030 * N + 825.000

991 < N < 1023 0.030 * (N-1023) + 825.000

Base Station 1 < N < 799 0.030 * N + 870.000

991 < N < 1023 0.030 * (N-1023) + 870.000

A’A

WirelineNon-Wireline

AMPSA”

EAMPSB’

EAMPS

691

777384

2831st A Band CDMA

BAMPS

2nd ary A Band CDMA

1st B Band CDMA 2ndary B Band CDMA

666

667

716

717

333

334

991

1023

1 799

EAMPS

1st refers to the primary channel.2nd ary refers to the secondary channel. Not to be confused with a second carrier.


2


Any advanced technology (NAMPS, TDMA or CDMA) that must co-exist with AMPS/EAMPSin the available spectrum requires implementation of segregated spectrum. Transition from AMPSto CDMA consists of effectively replacing AMPS channels with CDMA channels. In such a mixedsystem, co-channel interference is minimized by dividing the available cellular spectrum into twoparts as depicted in Figure 2-20. The segregated spectrum approach also requires the system to bepartitioned into three distinct geographic areas. This technique ensures the physical separationneeded to permit reuse of AMPS channels from the CDMA band.

There are two benefits to segregated spectrum planning. First, spectrum division reduces concernover introducing interference as each CDMA carrier is implemented. Second, it will allow forindependent AMPS and CDMA planning.

The three distinct geographic areas created are identified as follows:

Core Zone - The region in which CDMA carriers are deployed. The core will operate CDMAchannels in the CDMA band and AMPS channels in the AMPS band. The existing AMPSfrequency plan is modified to delete AMPS channels in the CDMA band.

Table 2-5: 7 Cell (120°), 21 Channel Spacing, "B" BandA1 B1 C1 D1 E1 F1 G1 A2 B2 C2 D2 E2 F2 G2 A3 B3 C3 D3 E3 F3 G3

334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375

376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417

418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438

439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459

460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480

481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501

502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522

523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543

544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564

565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585

586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606

607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627

628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648

649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 - - -

- - - - - 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732

733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753

754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774

775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795

796 797 798 799

cyan CDMA Channel (364 through 404)yellow CDMA Guard Band (355 through 363 and 405 through 413)

2



Perimeter Zone - The outermost area contains those cells that are located at an adequate distancefrom the CDMA core such that it is acceptable to assign AMPS channels that are in the CDMAband. This physical separation serves to maintain acceptable interference levels.

Transition Zone - The transition zone (also known as the guard zone) is located between the coreand the perimeter. AMPS channels in the CDMA band should not be assigned in the transitionzone. This zone should not be confused with the transition cell hand-down capability.

Figure 2-20: Segregated Spectrum

The grade-of-service (blocking) should be checked for all cells to make sure it is acceptable,particularly in the transition zone. In the event that the grade of service is unacceptable and allchannels have been assigned, certain design options can be exercised to resolve this problem. Thefirst option that may be considered is to replace the AMPS channels with CDMA channels. Thecell would then become a core cell. A second option would be to sectorize or cell split the AMPScell. A third option would be to reduce the size of the CDMA core to the point that this cell wouldthen be considered a perimeter zone cell.

Segregated spectrum may be implemented in various configurations: uniform, non-uniform andhomogenous. Uniform deployment consists of a single core area surrounded by a single transitionand perimeter zone. Non-uniform implementation may establish multiple CDMA core andtransition zones. A homogeneous implementation occurs when the entire system consists ofCDMA and there are no transitions or perimeter zones. Homogeneous system composition may beconsidered by isolated systems or systems adjacent to another CDMA system operating in the samefrequency spectrum.

Perimeter Zone

Core

Transition

CoreCORE

CORE

Option # 3 - Homogeneous

Option # 1 - Uniform Option # 2 - Non-Uniform

Requires Isolated system or adjacent CDMA systems

Zone


2


2.5 Channel Spacing and Designation - 1900 MHz

The block designators for the personal and base station frequencies are as specified in Table 2-6.

Table 2-6: Band Class 1 System Frequency Correspondence

The channel spacing, CDMA channel designations and transmit center frequencies are specified inTable 2-7.

Table 2-7: CDMA Channel Number to CDMA Frequency Assignment

Transmission on conditionally valid channels is permissible if the adjacent block is allocated to thelicensee or if other valid authorization has been obtained. Valid CDMA Channels Numbers areidentified in Table 2-8.



A 1850-1865 1930-1945

D 1865-1870 1945-1950

B 1870-1885 1950-1965

E 1885-1890 1965-1970

F 1890-1895 1970-1975

C 1895-1910 1975-1990

Transmitter CDMA Channel Number Center Frequency (MHz)

Personal Station 0 < N < 1199 1850.000 + 0.050 * N

Base Station 0 < N < 1199 1930.000 + 0.050 * N

2



Table 2-8: Channel Numbers and Frequencies for Band Class 1 and Spreading Rate 1

Table 2-9: Preferred Set of Frequency Assignments for Band Class 1 and Spreading Rate 1

Block Designator

Valid CDMA Frequency

Assignments

CDMA Channel Number

Transmit Frequency Band (MHz)


A(15 MHz)

Not ValidValid

Cond. Valid

0 - 2425 - 275276 - 299

1850.000 - 1851.2001851.250 - 1863.7501863.800 - 1864.950

1930.000 - 1931.2001931.250 - 1943.7501943.800 - 1944.950

D(5 MHz)

Cond. ValidValid

Cond. Valid

300 - 324325 - 375376 - 399

1865.000 - 1866.2001866.250 - 1868.7501868.800 - 1869.950

1945.000 - 1946.2001946.250 - 1948.7501948.800 - 1949.950

B(15 MHz)

Cond. ValidValid

Cond. Valid

400 - 424425 - 675676 - 699

1870.000 - 1871.2001871.250 - 1883.7501883.800 - 1884.950

1950.000 - 1951.2001951.250 - 1963.7501963.800 - 1964.950

E(5 MHz)

Cond. ValidValid

Cond. Valid

700 - 724725 - 775776 - 799

1885.000 - 1886.2001886.250 - 1888.7501888.800 - 1889.950

1965.000 - 1966.2001966.250 - 1968.7501968.800 - 1969.950

F(5 MHz)

Cond. ValidValid

Cond. Valid

800 - 824825 - 875876 - 899

1890.000 - 1891.2001891.250 - 1893.7501893.800 - 1894.950

1970.000 - 1971.2001971.250 - 1973.7501973.800 - 1974.950

C(15 MHz)

Cond. ValidValid

Not Valid

900 - 924925 - 11751176 - 1199

1895.000 - 1896.2001896.250 - 1908.7501908.800 - 1909.950

1975.000 - 1976.2001976.250 - 1988.7501988.800 - 1989.950

Block Designator

Preferred Set Channel Numbers

A 25, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275

D 325, 350, 375

B 425, 450, 475, 500, 525, 550, 575, 600, 625, 650, 675

E 725, 750, 775

F 825, 850, 875

C 925, 950, 975, 1000, 1025, 1050, 1075, 1100, 1125, 1150, 1175


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2.6 Dual-Mode vs. Dual-Band

Dual-mode subscriber units can support two air-interfaces using a common frequency band (i.e.CDMA and analog at 800 MHz). In a mixed digital and analog system, normally the registrationrequest will be attempted first to the digital service then to the analog service. Dual-mode allowsthe digital service provider the option to redirect traffic to a different air-interface where resourcesare available, for capacity control or emergency hand down. Dual-mode phones also allow thesubscriber unit to roam outside of its home network (assuming service is provided).

Dual-band subscriber units are designed to allow a subscriber to utilize two frequency spectrums,such as PCS frequency spectrum and the cellular bands. Handoffs are supported between CDMAproviders of different bands (much like dual-mode) and also supported between CDMA, NAMPSand AMPS. With dual-mode phones, the service provider has the option to redirect the subscriberunit to a different air interface; however, dual-band providers redirect the subscriber unit to adifferent part of the frequency spectrum. An example for dual-mode would be a subscriber unit thatis capable of operating on a CDMA 800 MHz system or could be redirected to an AMPS 800 MHzsystem, assuming resources are available. An example for dual-band operation would be asubscriber unit that is capable of operating on a CDMA PCS (1900 MHz) system and also beingable to operate on an AMPS 800 MHz system.

The goal in developing dual-mode and dual-band subscriber units is to ease transition from onetechnology to a second (such as 800 MHz AMPS to 800 MHz CDMA), allow a single subscriberunit to roam outside of the provider’s service area, and eventually to have a subscriber unit whichwill work everywhere (domestic and international) thus providing "seamless" coverage."Seamless" coverage does not necessarily imply a single service provider.

2.7 Spectrum Clearing

Spectrum clearing is a topic which is especially important to CDMA systems. The CDMAtechnology bases its capacity on a signal to noise balance (uplink and downlink). Adequatespectrum must be cleared to optimize a system to its greatest capacity. Although there are manyapproaches to testing the airways for clearance, it is advised that drive tests are performed (i.e. witha spectrum analyzer) to verify that the spectrum is clear, and/or locate possible spectrum violators.

For new spectrum allocations or for spectrum that is being reallocated for telecommunicationsystems (i.e. 3G spectrum allocations), spectrum measurements may be necessary to verify that thespectrum is clear of any previous users of the spectrum (see Section 2.8 for more information).

In the cellular bands, CDMA bandwidth is created by removing the appropriate number of AMPSchannels. This should be done in cells within the core and transition zones. For the 1st CDMAcarrier, 59 AMPS (30 kHz) channels would need to be cleared.

Cells for the transition (or guard) zone can be identified either by predictive RF propagation oractual noise floor measurements. The coverage area needing spectrum clearing will varydepending upon transmission signal strength, base station height, terrain variation, foliage, andreflection from buildings, hills or the atmosphere. The zone or area of cells to be cleared is related

2



to the reuse distance needed to achieve acceptable C/I levels. The area needing clearing for CDMAmay be reduced by controlling interference. Examples of how to control interference include:utilizing directional antennas, increasing or decreasing antenna heights and downtilts, carefuladjustment of power applied to pilot and voice channels, or by using geographic elements forisolation.

Because all transmission equipment has the capacity to block or disrupt signalling, each countryhas laws governing transmission of signals. Many countries have adopted the United States FederalCommunications Commission (FCC) standards. However, do NOT assume these standards areinternational. In the United States, Codes of Federal Regulations must be strictly adhered to. TheU.S. government divides these codes into what are called "Titles". Each Title covers a specifictopic. For instance, Title 7 covers Agriculture codes, Title 15 covers Commerce and Foreign Trade.The Telecommunication Code of Federal Regulations is listed in Title 47. Title 47 is subdividedinto "Volumes" which contain "Parts" or chapters explicitly defining each code. The FCC World-Wide Web Page contains a search engine which can locate specific regulations. For example,regulations governing licensing and use of frequencies in the 806-824, 851-869, 896-901, and 935-940 MHz bands are located under CFR 47, Part 90.

Specific codes for PCS exist under CFR 47, Part 24. Great detail is given to rules and restrictionswithin CFR 47, Part 24. One rule for example, under paragraph 24.236 gives the field strengthlimits: "The predicted or measured median field strength at any location on the border of the PCSservice area shall not exceed 47 dBuV/m unless the parties agree to a higher field strength."

Rules can be very specific. For instance, regulations are given for items such as antenna mastheights, antenna location, what maximum radiated power is allowed at each frequency, how todivide spectrum, who is responsible for clearing spectrum and what is the allotted time frame. It isimportant to clearly understand the regulations of the government for which the system will bedeployed. Large fines can be assessed to the customer and/or Motorola.

Although Federal Regulations take priority, each state and town/city may have additional codes orzoning regulations.

For non-U.S. regulations, please contact the governing agency of that country.

2.8 Background Noise Measurements

Capacity and coverage in CDMA systems (IS-95 & IS-2000) are, in part, a function of thebackground thermal and man-made interference noise levels. For the 1.23 MHz CDMA channel,the background thermal noise is approximately -113 dBm. Man-made interference includesautomobile ignition noise and spurious emissions from radio and other electronic equipment.

The background man-made noise will vary from site to site depending on the number ofinterference sources and their proximity to the cell. In order to insure the optimal operation of eachof the CDMA cell sites, Motorola recommends that noise floor measurements are considered as apart of the site selection process for CDMA systems. These noise floor measurements can also beused to make adjustments to the noise margin parameter for a particular link budget analysis (seesection 4.2.1.4).


2


It is anticipated that CDMA systems may be deployed in the same geographical areas whereanother technology once occupied the current CDMA system’s spectrum. It is also possible foradjacent band signals from other systems that are in the same geographical areas with the CDMAsystem to cause interference with the CDMA system. As a result, noise floor measurements arealso recommended to be used to identify any in-band or out-of-band interference sources. Once aninterference source has been identified, an evaluation of the interference source can be performedto determine the impact to the CDMA system. If the impact is determined to be significant, thenproper actions can be taken to reduce the source of interference to an appropriate level.

2.8.1 Suggested Measurement Method

Interference is random in nature, with amplitude and frequency varying over time. Some of theinterference sources are thermal noise, environmental noise, and noise from other systems (i.e.AMPS/EAMPS, CDMA, GSM, iDEN, ANSI-136, point-to-point microwave, public safety, landmobile, private mobile, air-to-ground airphone service, etc.). Out of band sources can createinterference through intermodulation (IM).

Due to the random nature of the background noise, Motorola suggests that a data logging systembe employed to measure the noise floor over some period of time. Statistical analysis of thecollected data can then be performed to determine an average and cumulative distribution functionof the noise floor rise. The cumulative distribution function indicates the amount of time thebackground noise rise exceeds some specified limit.

2.8.1.1 Test System Functional Description

A possible configuration of a noise floor test system is shown in Figure 9-1. The test measurementcalibration point (cal point) is at the feedline entrance of a separate antenna or an unused port ofthe receiver multicoupler. The band-pass filter is used to attenuate out-of-band signals, whichotherwise could create in-band intermodulation products. The low noise amplifiers are used toimprove the system noise figure and provide enough gain to allow for the measurement of very lowlevel signals. The step attenuator between the amplifiers is used to limit the system gain, again, toreduce the level of possible intermodulation products. The output of the final amplifier is then splitusing a two-way splitter. The two equal outputs of the splitter are used as inputs to two spectrumanalyzers. Spectrum analyzer 1 operates in the manual mode. This spectrum analyzer is equippedwith a tracking generator which is used for the system gain calibration. This spectrum analyzer isalso used to make noise floor plots and to investigate the nature of interference as it appears on thescreen. Spectrum analyzer 2 is under computer control. Measurement traces are collected with thisspectrum analyzer and are stored to disk for later processing. Up to two spectrum analyzer tracesper second can be recorded for the described system. The noise source is used to measure thesystem noise figure. The measured system noise figure is used when processing the collected datainto the desired cumulative distribution plots.

2



Figure 2-21: Suggested CDMA Noise Floor Measurement System

2.8.1.2 Test System Calibration

The test system gain and noise figure must be measured before data collection begins. Themeasured gain and noise figure are used to make adjustments to the collected data during the dataanalysis operation. The system gain is measured using the tracking generator provided in spectrumanalyzer 1. The system noise figure is determined by first measuring the noise floor with the systemCalibration Point (input) terminated in 50 ohms and then measuring the noise floor with the systemCalibration Point connected to the calibrated noise source. The noise figure is then calculated asfollows:

[EQ 2-2]

Where:ENR Equivalent noise ratio of the calibrated noise source (linear ratio)

Pon Noise floor measurement with the noise source connected to the system input(Watts)

xCalPoint

BandpassFilter

Plotter

Amplifier

NF = 1 dBG = 15 dBIPi = 4 dBm

Amplifier

NF = 2 dBG = 25 dBIPi = 0 dBm

+28 vdc

+28 vdc +28 vdc

StepAtten.

SpectrumAnalyzer 1

NF = 26 dBIP=16 dBm

w/tracker

SpectrumAnalyzer 2

NF = 26 dBIP = 21 dBm

PC

50 ohmtermination

NoiseSource

ENR = 15 dB

IEEE 488

NF 10ENR

PonPoff 1–--------------------

-------------------------

log=


2


Poff Noise floor measurement with the system input terminated in 50 ohms (Watts)

NF System noise figure (dB)

2.8.2 Test Procedures

If the CDMA system is deployed in an area where another technology currently exists, there aretwo proposed methods of co-existence. One method is to clear all co-channels from the othersystem within the CDMA band on a system wide basis. Another possibility is to only clear the co-channels from cells which are near the CDMA cells. Co-channels to the CDMA band are thenreused at distant cells. Before noise floor testing can begin, co-channel clearing, per the chosenimplementation plan, must be completed. This is necessary because co-channels within the CDMAband will appear as interference in the collected data.

After clearing the spectrum, preliminary tests should be run without band select filtering to identifyuncleared channels, out of band large signals, and spurious emissions, and to measure any co-located technology antenna isolation. It is best to perform these tests during the busy hour as moreuplink and downlink channels will be in use, and recorded by the tests.

Plot the system downlink band to identify possible uncleared co-channels, external sources ofdownlink interference, and to verify Tx-Rx isolation with any co-located cell sites.

Plot the uplink band to identify receive isolation with any co-located cell sites and to identify anypossible sources of uplink interference.

Examine the plot of the adjacent system frequencies for out of band or spurious emissions from theother systems in the adjacent bands.

With a co-located cell site configuration, transmitter IM can be a source of interference with aduplexed antenna. If this configuration exists, all of the channels from the co-located site shouldbe keyed up in the sector, and the spectrum should be scanned for IM and cross modulationproducts. This can effectively raise the noise floor 10 to 20 dB. It can be caused by connectorbreakdown in the RF path, and decreased isolation due to the duplexed configuration.

It may also be prudent to perform spot checks to identify possible interference causing conditions.If available, make a call on the competitors system and note the subscriber power level at theCDMA cell site. A maximum subscriber power level near the CDMA cell site may createinterference issues.

Once the system has been cleared of analog co-channels, noise floor testing can proceed. For bestresults, the data should be logged at various times of the day and night at each cell site. This isnecessary because varying traffic patterns throughout the day will effect the noise levels present atthe cell site. It is recommended that at least 2000 traces be collected in each site.

2



2.8.3 Data Analysis

The collected data must be scaled to account for the measurement system gain, noise figure, andbandwidth before the statistical analysis is performed. Once the data is properly scaled, a statisticssoftware package can be used to calculate the average noise floor rise and cumulative distributionfunctions. The noise floor rise cumulative distribution plots can then be used to make a judgementon the effect of background interference to CDMA performance at each cell site. Plots can also beproduced which show the amplitude and frequency of interferers as a function of time. These plotscan be used to help identify the source of interferers, which can lead to methods of interferencereduction.

2.9 References

1 TIA/EIA/IS-95-A, Mobile Station - Base Station Compatibility Standard for Dual-ModeWideband Spread Spectrum Cellular Systems, 1995, Sections 2.1.1.1, 2.2.1.1, 3.1.1.1,3.2.1.1, 6.1.1.1, 6.2.1.1, 7.1.1.1, Tables 2.1.1.1-1, 6.1.1.1-1, 6.1.1.1-2.

2. ANSI J-STD-008, Personal Station-Base Station Compatibility Requirements for 1.8 to2.0 GHz Code Division Multiple Access Personal Communications, March 24, 1995,Section 2.1.1.1, Tables 2.1.1.1-1, 2.1.1.1-2, 2.1.1.1-3 and 2.1.1.1-4.

3. CFR 47 (Telecommunications), Office of the Federal Register National Archives andRecords Administration, October 1, 1997.

4. FCC Web Page (Wireless Telecommunications Bureau): http://www.fcc.gov/wtb/National Archives and Records Administration (CFR Search Engine): http://www.access.gpo.gov/nara/cfr/index.html

5. TIA/EIA/IS-2000-2, Physical Layer Standard for cdma2000 Spread Spectrum Systems

6. TIA/EIA TSB-84A, Licensed PCS to PCS Interference, Version 1.7, June 9, 1998

7. Dennis Schaeffer (Motorola), "Adjacent Channel Interference Impact In CDMASystems", August 20, 1999

8. Asia Pacific Telecom Carrier Solutions Group (Motorola), "cdma2000 1X SystemPlanning Guide", Version 0.1, November 7, 2000

9. Motorola, CDMA Uplink Noise Survey Procedure, Version 0.4.

10. Motorola, RF Logger User Guide, January 2000



Table of Contents

3.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 5

3.2 Reverse Link Pole Capacity Estimation . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 53.2.1 Data Rates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 113.2.2 Median Eb/(No+Io) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 123.2.3 Voice or Data Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 133.2.4 Cell Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 143.2.5 Sectorization Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 153.2.6 Power Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 17

3.3 Reverse Link Soft Blocking Capacity Estimation . . . . . . . . . . . . . . . . . 3 - 183.3.1 Conventional Blocking Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 183.3.2 CDMA Soft Blocking Capacity Estimation . . . . . . . . . . . . . . . . . 3 - 18

3.3.2.1 Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 193.3.2.2 Theoretical Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 193.3.2.3 Single Cell Case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 223.3.2.4 Multiple Cell System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 23

3.4 Reverse Link Noise Rise Capacity Estimation . . . . . . . . . . . . . . . . . . . . 3 - 323.4.1 Reverse Link Noise Rise Capacity Limit . . . . . . . . . . . . . . . . . . . 3 - 323.4.2 Reverse Noise Rise Capacity Estimation . . . . . . . . . . . . . . . . . . . 3 - 333.4.3 Probability Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 353.4.4 Reverse Link Noise Rise Capacity Estimation Examples . . . . . . 3 - 37

3.4.4.1 Example #1: Voice Only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 373.4.4.2 Example #2: Voice and Data Users . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 38

3.4.5 Reverse Link Noise Rise Capacity Estimates for IS-2000 1X. . . 3 - 413.4.5.1 Noise Rise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 413.4.5.2 F-factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 423.4.5.3 Average Eb/No . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 433.4.5.4 Eb/No Standard Deviation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 433.4.5.5 Processing Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 443.4.5.6 Activity Factor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 443.4.5.7 Traffic Mix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 453.4.5.8 Throughput Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 453.4.5.9 IS-2000 1X Reverse Noise Rise Capacity Analysis Results . . . . . . 3 - 46

Chapter

CDMA Capacity3


3

CDMA/CDMA2000 1X RF Planning GuideChapter 3: CDMA Capacity

3.5 Forward Link Pole Capacity Estimation . . . . . . . . . . . . . . . . . . . . . . . . 3 - 523.5.1 Forward Link Load Factor Estimation . . . . . . . . . . . . . . . . . . . . . 3 - 523.5.2 Forward Link Pole Capacity Estimation . . . . . . . . . . . . . . . . . . . 3 - 53

3.6 Forward Link Fractional Power Capacity Estimation . . . . . . . . . . . . . 3 - 54

3.7 Forward Link Noise Rise Capacity Estimation . . . . . . . . . . . . . . . . . . . 3 - 573.7.1 Forward Link Noise Rise Capacity Limit . . . . . . . . . . . . . . . . . . 3 - 583.7.2 Forward Noise Rise Capacity Estimation. . . . . . . . . . . . . . . . . . . 3 - 593.7.3 Forward Link Noise Rise Capacity Estimation Examples . . . . . . 3 - 60

3.7.3.1 Example #1: Voice Only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 613.7.3.2 Example #2: Voice and Data Users . . . . . . . . . . . . . . . . . . . . . . . . 3 - 62

3.7.4 Forward Link Noise Rise Capacity Estimates for IS-2000 1X . . 3 - 653.7.4.1 Noise Rise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 653.7.4.2 I-factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 663.7.4.3 Average Eb/No . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 663.7.4.4 Eb/No Standard Deviation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 673.7.4.5 Processing Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 673.7.4.6 Activity Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 683.7.4.7 Orthogonality Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 693.7.4.8 Traffic Mix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 693.7.4.9 Throughput Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 693.7.4.10 IS-2000 1X Forward Noise Rise Capacity Analysis Results. . . . . 3 - 70

3.8 Forward vs. Reverse Link Capacity Comparison . . . . . . . . . . . . . . . . . 3 - 76

3.9 EIA/TIA Specifications and RF Air Interface Limitations. . . . . . . . . . 3 - 803.9.1 IS-95 Forward Channel Structure. . . . . . . . . . . . . . . . . . . . . . . . . 3 - 803.9.2 IS-95 Reverse Channel Structure . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 813.9.3 IS-2000 1X Forward Channel Structure. . . . . . . . . . . . . . . . . . . . 3 - 82

3.9.3.1 IS-2000 Forward Channels (Motorola Implementation) . . . . . . . . 3 - 833.9.3.2 IS-2000 Forward Link Radio Configurations . . . . . . . . . . . . . . . . 3 - 863.9.3.3 IS-2000 Walsh Code Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 88

3.9.4 IS-2000 Reverse Channel Structure . . . . . . . . . . . . . . . . . . . . . . . 3 - 913.9.4.1 IS-2000 Reverse Channels (Motorola Implementation) . . . . . . . . 3 - 913.9.4.2 IS-2000 Reverse Link Radio Configurations. . . . . . . . . . . . . . . . . 3 - 92

3.10 Handoffs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 943.10.1 Soft Handoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 943.10.2 Inter-CBSC Soft Handoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 953.10.3 Hard Handoffs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 95

3.10.3.1 Anchor Handoff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 953.10.3.2 IS-95 to IS-2000 Hand-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 953.10.3.3 IS-2000 to IS-95 Hand-down. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 963.10.3.4 Packet Data Handoffs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 963.10.3.5 Inter-Carrier Hand-across . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 96


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3.11 Budgetary Estimate of Sites for Capacity (Voice Only) . . . . . . . . . . . . 3 - 963.11.1 Required Parameters for Initial System Design . . . . . . . . . . . . . . 3 - 97

3.11.1.1 Busy Hour Call Attempts and Completions . . . . . . . . . . . . . . . . . . 3 - 973.11.1.2 Average Holding Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 973.11.1.3 Erlangs per Subscriber. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 97

3.12 IS-95 and IS-2000 Simulations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 102

3.13 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 104


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3.1 Introduction

Capacity of a wireless network (for mobile or fixed subscribers) is defined as the number of usersthat a given cell site can support while maintaining a certain QoS/GOS criteria. With theintroduction of various data related services (facilitated by IS-95B or IS-2000), the capacity of agiven cell site can also be represented by the number of users along with the associated datathroughput and a QoS criteria. The amount of RF spectrum available has a direct relationship onthe capacity that can be provided. The air interfaces which make efficient use of the allocatedspectrum will offer greater capacity. In AMPS or TDMA systems, blocking occurs when all voicefrequencies or time slots are fully occupied by other users in the system. In Code Division MultipleAccess (CDMA) systems, all users in the system share a common wideband spectrum over the timethey are active.

Capacity of a CDMA system depends upon the amount of interference in the system. Additionalusers accessing the system will increase the system interference level. In order to maximize thecapacity, steps need to be taken to minimize the total power transmitted so as to reduce the totalinterference in the system. An adjustment to this power will also make an adjustment to thecapacity. Blocking in CDMA is defined to occur when the total interference density reaches apredetermined level above the background noise density. This is a soft blocking condition. Theblocking probability can be relaxed by allowing the maximum tolerable interference level toincrease.

In this chapter, several different capacity equations are provided which can be used to estimate theaverage cell site capacity under various conditions and assumptions. The capacity of a CDMAsystem is dependent upon the RF environment (i.e. path loss, delay spread, cell site layout, etc.).There is no single capacity number but a range of values over an environment. With theintroduction of various data related services, the capacity will also depend upon the mixture ofvoice and data traffic models. A capacity equation analysis is a simplistic approach as it assumesuniform loading across all cells. However, in a live network, such a scenario would be rare. Thus,there is no simple formula that can calculate the actual capacity that a live CDMA cell site will beable to support. Though some equations will be provided to allow the approximation of the numberof users and data throughput that could be supported, these equations will demonstrate that thecapacity of a CDMA carrier varies with many factors. As a result, the capacity equations providedin this chapter should be used for budgetary purposes only. A more sophisticated CDMAsimulation program, such as Motorola’s NetPlan tool, should be used for a live CDMA system tomodel the forward and reverse links for thousands of subscribers in a realistic system environmentwith different voice and data traffic mixes. The NetPlan tool provides detailed simulations of boththe forward and reverse links which produces a more accurate and realistic system capacity andcoverage prediction.

3.2 Reverse Link Pole Capacity Estimation

In digital systems (i.e. IS-95A/B or IS-2000) the energy per bit needs to be a certain level abovethe total interference density in order to detect the transmitted bit. (Note: the following section canbe applied towards both IS-95 and IS-2000 systems.) This is referred to as Eb/Io. Energy isequivalent to power times time or to power divided by the rate. Therefore, the energy per bit can


3


be expressed as the received power divided by the maximum bit rate:

[EQ 3-1]

Assuming:

• P denotes the received power from each subscriber at the base station antenna

• R denotes the data rate (9600 bps for Rate Set 1, 14400 bps for Rate Set 2)

• Power control is perfect

• Subscribers are transmitting just enough power to be received

• Uniform subscriber distribution

The total interference power density assuming N users, can be expressed as

[EQ 3-2]

Where:Bandwidth of the channel

Using Equation 3-1 and Equation 3-2, the energy per bit to the total interference density can bedetermined.

[EQ 3-3]

Solving for N yields:

[EQ 3-4]

It should be pointed out that some papers approximate N-1 with N.

The above equation is an ideal case or can be referred to as a first order capacity estimate. Thecapacity (N) can additionally be impacted by interference from other cell sites, the voice or dataactivity associated with the users, and the effect of thermal noise. Including these other factors intoEquation 3-2 will yield:

[EQ 3-5]

EbPR---=

IoN 1–( )P

W---------------------=

W

Eb

Io------ P R⁄

N 1–( )PW

------------------------------------------- W R⁄

N 1–-------------= =

N 1–W R⁄Eb Io⁄-------------- N≈=

Io No+ρ N 1–( )P 1 f+( )

W----------------------------------------- No+=


3


Where:Interference power density impacted by other cells, and the number of users with

an average voice or data activity rate

Ratio of out of cell (inter-cell) interference power to in cell (intra-cell)interference power. This factor is used to adjust the capacity of a single cell toaccount for the interference generated by other users in a multiple cell system.

Average voice or data activity factor

Thermal noise

Using this new value of Io, Equation 3-3 can be rewritten as follows:

[EQ 3-6]

The pole capacity is defined as the maximum capacity that can be achieved under a given set ofconditions. At pole capacity, the rise over the thermal noise will approach infinity. This can becalculated from the power rise over thermal rise.

[EQ 3-7]

[EQ 3-8]

As the denominator in Equation 3-8 approaches zero, the power rise over thermal rise willapproach infinity. Solving the denominator to be equal to zero will result in the maximum polecapacity.

[EQ 3-9]

Solving for the number of users (N) yields:

Io

f

ρ

No

Eb

N( o Io )+----------------------- P R⁄

ρ N 1–( )P 1 f+( )W

----------------------------------------- No+------------------------------------------------------ W

R-----

PNoW-----------

ρ N 1–( ) 1 f+( )PNoW

----------------------------------------- 1+---------------------------------------------------⋅= =

PNoW-----------

Eb

N( o Io )+----------------------- R

W----- ρ N 1–( ) 1 f+( )P

NoW----------------------------------------- 1+⋅ ⋅=

PNoW-----------

Eb

N( o Io )+----------------------- R

W-----⋅

1Eb

N( o Io )+-----------------------–

RW----- ρ N 1–( ) 1 f+( )⋅ ⋅

-----------------------------------------------------------------------------------------=

Eb

N( o Io )+----------------------- R

W----- ρ N 1–( ) 1 f+( )⋅ ⋅ 1=


3


[EQ 3-10]

As mentioned previously, sometimes N-1 is approximated to be only N.

Two additional items can be taken into account to further refine the number of users that can besupported. They are a reduction factor due to imperfect power control and a factor to account forsectorization. In Equation 3-10, the f factor accounts for interference coming from other cell sites.The sectorization factor will account for the impact of interference leakage between sectors.

To approximate the reverse pole capacity point for CDMA (which can be applied to both IS-95 andIS-2000), the following equation can be used.

[EQ 3-11]

Where:Total received signal and noise power spectral density

Thermal noise power spectral density

Energy per bit

Ratio of Signal energy per bit to the sum of interference and noise adjusted for

imperfect power control

Bandwidth of the channel

Data rate

Processing gain

Ratio of out of cell (inter-cell) interference power to in cell (intra-cell)interference power. This factor is used to adjust the capacity of a single cell toaccount for the interference generated by other users in a multiple cell system.

Average voice or data activity factor

Sectorization gain

N 1–W R⁄

ρ 1 f+( )Eb

N( o Io )+-----------------------⋅

----------------------------------------------- N≈=

ReversePoleCapacity NW R⁄

Eb

No Io+-----------------

adjust

----------------------------------- 11 f+-----------

1ρ---

Gs⋅ ⋅ ⋅= =

Io

No

Eb

EbN

oIo

+--------------------

adjust

W

R

W R⁄

f

ρ

Gs


3


The adjusted Eb/(No+Io) requirement to account for imperfect power control (power controldeviation) can be determined by:

[EQ 3-12]

Where:

Signal / (Interference plus noise) ratio requirement under perfect power control

Standard deviation in imperfect power control

Constant value equal to ln(10)/10

Some reverse link pole equations may use the term F, where F is defined as the ratio of in cell(intra-cell) interference power to the sum of out of cell (inter-cell) interference power and in cell(intra-cell) interference power. F is related to f by the following equation.

[EQ 3-13]

Substituting F into Equation 3-11 results in the following equation (which also can be applied toboth IS-95 and IS-2000).

[EQ 3-14]

Assuming the following values for the various parameters, the reverse link pole capacity for an IS-95 Rate Set 2 site would be 19 users or roughly 12.3 Erlangs per sector (assuming an Erlang Bmodel with 2% grade of service) for a three sector site (57 users per site). This value represents thepole capacity or the point at which no more users can be added without seriously degrading thequality of the system.

Bandwidth of the channel (only one CDMA Channel) 1228800 Hz

Data rate 14400 bps

Ratio of out of cell (inter-cell) interference power to in cell 0.7

Average voice or data activity factor 0.4

Eb

No Io+-----------------

adjust

Eb

No Io+----------------- e

βσe( )2 2⁄⋅=

Eb

N0 I0+-----------------

σe

β

FInCell

InCell OutCell+-------------------------------------------- 1

1OutCellInCell

---------------------+------------------------------ 1

1 f+-----------= = =

ReversePoleCapacity NW R⁄

Eb

No Io+-----------------

adjust

----------------------------------- F1ρ---

Gs⋅ ⋅ ⋅= =

W

R

f

ρ


3


Sectorization gain per sector for a three sector site 2.4/3

Signal / (Interference plus noise) ratio requirement under

perfect power control 6.5 dB

Standard deviation in imperfect power control 2.5

Constant value ln(10)/10

[EQ 3-15]

[EQ 3-16]

Several variations of a reverse link capacity equation exist. The various equations may not beexactly the same as Equation 3-11 or Equation 3-14, but many, if not all, of the items within theequations will be represented: processing gain, Eb/(No+Io) (may also include a factor to accountfor imperfect power control or power control impact may be its own term), other cell interference,voice or data activity factor, and impact of sectorization. When discussing capacity, it is importantto mention all of the factors which are being considered and the assumed value for each factor. Forinstance, 19 users shown above can easily turn into 32 users, if the calculation does not account forany inter-cell interference (f=0). The capacity results are also highly dependent upon the values thatare used for the capacity equation. Even if the equations are similar, the values used may bedifferent which leads to different capacity claims from different sources. Some values are moreoptimistic, thus leading to more users.

The Eb/(No+Io) performance parameter, used as an input to the equations provided above(Equation 3-11 or Equation 3-14), is usually specified for a particular data rate (along with otherassumptions; i.e. flat fading, mobile environment with a 30 kmph worst case speed, 1% FER,diversity, and perfect decorrelation). Although the reverse pole capacity equations can be appliedtowards both IS-95 and IS-2000 systems, they are typically applied towards analyzing a systemutilizing a single data rate. As such, they may be more appropriate in estimating the capacity of anIS-95 system, where it is common to support a single data rate (i.e. Rate Set 1 or Rate Set 2). ForIS-2000 systems which utilize multiple data rates, the reverse pole capacity equations can be usedto analyze the capacity of each individual data rate. They are not recommended to analyze amixture of data rates, unless an appropriate average Eb/(No+Io) performance parameter can beproduced to correlate with an associated average data rate.

Another point to be made is that these equations are for pole capacity. In designing a CDMAsystem, the system designer should not assume that the system pole capacity will be achieved. Thesystem designer should plan that the reverse link capacity will not exceed 75% of the pole capacity.From the above example, this would correspond to about 14 users or 8.2 Erlangs. Note that this is

Gs

Eb

No Io+-----------------

σe

β

Eb

No Io+-----------------

adjust10

6.5 10⁄( )e

0.23 2.5⋅( )2 2⁄5.27 7.22dB==⋅=

ReversePoleCapacity N1228800( ) 14400⁄

107.22 10⁄( )

-------------------------------------------- 11 0.7+----------------

10.4-------

2.43

------- 19≈⋅ ⋅ ⋅= =


3


for the reverse link, the forward link may actually not allow this amount of Erlangs to be provided.

In analyzing Equation 3-11, the following relationships can be observed:

• The reverse pole capacity value is greater for the lower data rate vocoder (i.e. Rate Set 1at 9600 bps will provide greater reverse link capacity than Rate Set 2 at 14400 bps).

• The reverse pole capacity value is increased if the Eb/(No+Io) requirement is reduced.

• The reverse pole capacity value is increased if the average voice or data activity isreduced.

• The reverse pole capacity value is increased if the inter-cell to intra-cell interferenceratio is reduced.

• The reverse pole capacity value is increased if the sectorization gain can be increased(i.e. choosing antennas with better front to back ratios and also antennas that have aquick rolloff from their half power point to the back of the antenna).

• The reverse pole capacity value is increased if the power control standard deviation isreduced.

The following set of graphs demonstrates the six points just made. Only one of the parametervalues was varied for each graph with the other parameter values being left to the values given inEquation 3-16. The intent of the graphs is to demonstrate the sensitivity a parameter value has onthe capacity of site or system.

3.2.1 Data Rates

The capacity of a CDMA carrier is dependent upon the data rate being used. Referring toEquation 3-11, it can be seen that R (the data rate) has an inverse relationship to the reverse polecapacity. Figure 3-1 through Figure 3-5 will show curves for both Rate Set 1 at 9.6 kbps (which isthe air interface data rate used for the 8 kbps vocoder) and Rate Set 2 at 14.4 kbps (which is the airinterface data rate used for the 13 kbps vocoder).


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3.2.2 Median Eb/(No+Io)

Figure 3-1 shows that lower values for Eb/(No+Io) result in more users being supported. BTSinfrastructure enhancements that decrease the required Eb/(No+Io) value is one area Motorola isresearching to improve the capacity of the reverse link.

Figure 3-1: Impact of Eb/(No+Io) on the Number of Users

For a mobile environment, a 7 to 7.5 dB Eb/(No+Io) value is deemed acceptable. For a fixed system,the Eb/(No+Io) requirement can be as low as 3 to 4 dB for some situations. Fixed units installedindoors with a whip antenna will require Eb/(No+Io) values similar to the mobile environment,whereas fixed units installed with outdoor directional antennas will require lower Eb/(No+Io)values. Further advancements in chipsets and the algorithms employed in those chipset may reducethe Eb/(No+Io) requirement and thus smaller values than these previously listed will be acceptable.For example, the values above are reasonable for an IS-95 site, but new chipsets are being used (i.eIS-95 Motorola EMAXX chipset and IS-2000 chipset) which improve upon the Eb/(No+Io)requirement. From the graph above, a 3 dB advantage of a fixed system over a mobile system willyield a pole capacity of approximately twice the number of users (considering just the impact ofEb/(No+Io)).


3


3.2.3 Voice or Data ActivityAs a means to minimize interference, the transmission rate and power can be reduced when thevoice or data activity is absent or lessened. This reduction in transmission rate or power reducesthe average signal power of all users and thereby reduces the interference seen by each user. Thisfollowing figure depicts that as the voice or data activity increases, fewer users can be supported.

Figure 3-2: Impact of Voice or Data Activity on the Number of Users

The typical voice activity factor is 40%.

For some IS-2000 data services applications, a higher data rate coupled with a higher data activityfactor may be required. From the results in Figure 3-2, it can be seen that both of these factors willreduce the capacity that can be supported by a CDMA carrier.


3


3.2.4 Cell InterferenceThe capacity of a cell depends on the total interference it receives from other cells. The level ofpower that is received at the base station from different sources is dependent upon the laws ofpropagation. The following figure shows that when the out of cell interference is increased withrespect to the in cell interference that the capacity will degrade.

[EQ 3-17]

Figure 3-3: Impact of Other Cell Interference on the Number of Users

The following table shows several f values that were obtained from simulations assuming aspecific propagation model (path loss slope, standard deviation, and correlation).

Table 3-1: Samples of Various f Factors

Note: path loss slope converts to path loss dB/decade bymultiplying the slope by a factor of 10

Path loss slope

Standard Deviation Correlation f Factor

4.0 6.5 0.9 0.434.0 8.0 0.5 0.553.5 6.5 0.5 0.693.5 8.0 0.5 0.763.5 10 0.1 1.68

fOutCellInCell

---------------------=


3


The terms of the propagation model correspond to the path loss slope, the shadowing standarddeviation and the site to site correlation value. As shown by the above table, higher propagationexponents (the path loss slope) will reduce the f factor and lower exponents will increase the valueof f.

For a system that is only comprised of a single cell (for example a fixed system in a remote area),there will be no out of cell interference and therefore the pole capacity will be higher. Similarly,cell sites positioned along a highway to provide only highway coverage will not see muchinterference from other sites and therefore the f value will be lower for these sites than for a site inthe middle of a cluster of sites. In addition the f value will be lower for systems that are onlycomprised of a few sites than for a system with many sites. As the number of sites increases thereis a greater occurrence of interference from other cells which will increase the f value as shown byEquation 3-17.

3.2.5 Sectorization Gain

Sectorization gain can be somewhat of a misleading term. The sectorization gain is actually moreof a reduction factor. For an omni site, the sectorization gain is one. For a sector site, one approachmay be to multiply the resulting capacity of an omni site (or single sector) by the number of sectorsfor the sector site (i.e. a three sector site would support three times the number of users than anomni site and a six sector site would support six times the number of users than an omni site). Thisis not the case though. The additional sectors are considered to be other locations generatinginterference to the desired sector. The other cell interference factor accounts for just that,interference generated by other sites. The sectorization gain is the adjustment for the other sectorsat the local site causing increased levels of interference. The reason it is referred to as asectorization gain is that for a given physical site location, this site location is able to support manymore users when it is sectorized than if it stayed omni.

The sectorization gain can be improved by selecting antennas which have a good front to back ratioand which also exhibit a quick rolloff past the half power points (3 dB down from main lobe). Forinstance, using a 90° antenna in place of a 120° antenna for a three sector site would decrease theamount of energy (interference) going into adjacent sectors, thus increasing the sectorization gainand thereby improving upon the number of users which could be supported. It is important to notethat decreasing the horizontal beamwidth too much can also have a negative impact on thecoverage (signal strength) within the cell site’s coverage area. As the sectorization gain increases,the number of users will increase (as seen from the graph in Figure 3-4).

The sectorization gain value which is commonly used is 0.8 per sector or 2.4 for a three sector site(0.8 time 3). This 0.8 sectorization gain can be thought of as a 1 dB impact to the capacity of thesite due to other sectors interference.


3


Figure 3-4: Impact of Sectorization Gain on the Number of Users (3 Sector)

The above figure would apply only to a three sector site. The sectorization gain shown is for anentire site. For instance, a sectorization gain of 2.4 corresponds to 0.8 per each sector (= 2.4/3). Foran omni site the sectorization gain would be 1. If the sectorization per sector for a six sector site isconsidered to be similar to that of a three sector site, then the sectorization gain for the site wouldbe 6 times the per sector value (for instance, 6 * 0.8 = 4.8).


3


3.2.6 Power Control

Traffic capacity of CDMA systems is increased by implementing an appropriate power controlscheme to equalize the performance of all subscribers in the system. The appropriate power controlscheme reduces the interference to the other adjacent cells. The less interference generated in thespectrum, the more users the CDMA system can support. As previously mentioned, the inaccuracyin power control is roughly a log-normal distributed function. Under different path loss situations,the average required Eb/(No+Io) tends to fluctuate around the mean to maintain a desirable FrameErasure Rate. The power control standard deviation varies according to the extent of fluctuations.

Figure 3-5: Impact of Imperfect Power Control on the Number of Users

This graph shows that improving the accuracy of power control can provide some increase to thenumber of users.

At relatively slow speeds or in static conditions (fixed), power control is effective in counteractingslow fades, whereas at high speeds, power control is not as effective in counteracting fast fading.At higher speeds, the effects of interleaving become increasingly beneficial.


3


3.3 Reverse Link Soft Blocking Capacity Estimation

3.3.1 Conventional Blocking Analysis

In AMPS and TDMA systems, voice/traffic channels are assigned to users as long as they areavailable. Given the required offered traffic, the Erlang B model is used to determine the numberof traffic channels required to provide a predetermined grade of service. The Erlang B model isbased upon a model of serving without queuing. In other words, all blocked calls are cleared.Traffic load is the product of call rate and call holding time. It is a dimensionless quantity measuredin Erlangs. One Erlang is the traffic intensity of a traffic channel which is continuously occupied.Grade of service is a term used to quantify the extent to which congestion occurs in any trunkingsystem and is typically expressed as the probability of finding blocking. Blocking in AMPS andTDMA is defined to occur when all voice frequencies (for AMPS) or time slots (for TDMA) havebeen assigned to other subscriber stations.

The values quoted for traffic load and grade of service for cellular systems are usually taken duringthe busy hour. Busy hour is defined as the continuous one-hour period in the day during which thehighest average traffic density is experienced by the system. The Erlang B formula is given by:

[EQ 3-18]

Where:A is the offered traffic

C is the number of available servers

Assumptions of the Erlang “B” Model:

1. The number of potential users is infinite

2. Intervals between originations are random

3. Call set up time is negligible

3.3.2 CDMA Soft Blocking Capacity Estimation

Unlike the traditional analog design, balanced uplink and downlink cannot be achieved in CDMAbecause of the differences in waveform design on both links. Originally it was considered that thereverse link (subscriber to base) would usually be the capacity limiting path. However with theRate Set 2 vocoder and other real world situations, the forward link (base to subscriber) may be thelimiting path. With new higher data rate services being introduced (via IS-95B or IS-2000), it is

PBlocking

AC

C!------

AK

K!------

K 0=

C

∑------------------=


3


expected that the forward link will require higher data downloads than the reverse link. As a result,the forward link is also expected to be the limiting path from a capacity perspective. Even thoughthe forward link may be the limiting factor of capacity for some systems, the reverse link capacityestimates provided in this document can still be used to approximate the capacity under the givenassumptions and conditions. In many instances, the capacity analysis results of the reverse link cansometimes provide an adequate estimate. Simulations should be used (i.e. using NetPlan) to obtainmore accurate capacity estimations. For more detailed results, simulations can take into accountmany variable elements for which a general reverse or forward link capacity equation cannotadequately model (i.e. non uniform traffic and speed distributions, non uniform cell site layouts,propagation characteristics for a specific area, multiple subscriber classes with various call models,combined forward and reverse link analysis, etc.).

Soft blocking in CDMA systems is defined to occur when the total collection of users both withinthe serving cell/sector and in other neighbor cells introduce an amount of interference density sogreat that it exceeds the background noise spectral density by a predefined amount. Under theassumption that the system is not hardware limited, the following analysis applies this softblocking concept to calculate the Erlang capacity of a CDMA system. The concept of soft blockingwill be explained in details in the following paragraphs.

3.3.2.1 Assumptions

1. The number of active calls is a Poisson random variable with mean ( )

2. Each user is active with probability and inactive with probability (1- )

3. Each user’s required energy per bit-to-interference density ratio (Eb/Io) is variedaccording to propagation conditions to achieve the specified Frame Erasure Rate (FER).The FER is usually taken as 1% (0.01) to provide satisfactory transmission.

4. All the sectors have the same number of users.

5. The users are uniformly distributed over each sector.

3.3.2.2 Theoretical Analysis

In mathematical form, the definition of blocking can be restated as follows:

Interference from the + Interference from + Thermal Noise = Total Interference serving cell other cells

Blocking occurs when

[EQ 3-19]

λµ---

ρ ρ

νi

i 1=

k

∑ EbiR vi j( )Ebi j( )R N0W I0W>+

i 1=

k

∑j

othercells

∑+


3


Where:k is the number of simultaneous users per sector. By assumption [1], k is a Poisson

random variable with mean which is the offered traffic

W is the spread spectrum bandwidth allocated to a CDMA channel

R is the data rate

Eb is energy per bit

No is the background thermal noise density

Io is the total allowable interference density

is the voice or data activity and is a binomial random variable with = Pr ( =1),which is the gate on probability.

The voice or data activity factor ( ) is defined as:

= Probability ( =1) [EQ 3-20]

Defining = Eb/Io, which is known as the Bit Energy to Interference Density Ratio, and dividingby IoR, the inequality [Equation 3-19] can be written as follows:

[EQ 3-21]

Where:W/R is known as the processing gain

is the predefined threshold

Hence, the probability of blocking for CDMA is defined as the probability that the above conditionholds true.

Pblocking = Probability Z = [EQ 3-22]

Notice that the blocking probability for CDMA is determined by the system Eb/Io performance,voice or data activity factor, the spread spectrum bandwidth, the data rate, and the maximum

λµ---

ν ρ ν

ρ

ρ ν

ε

νi

i 1=

k

∑ εi vi j( )εi j( )i 1=

k

∑j

othercells

∑+ 1 η–( )> WR-----⋅

ηNo

Io------=

νi

i 1=

k

∑ εi vi j( )εi j( )i 1=

k

∑j

othercells

∑+ 1 η–( )> WR-----⋅


3


allowable interference level. The probability of blocking can be relaxed by allowing the maximumtolerable interference level (Io/No) to increase. In this case, the system is forced to accommodatemore simultaneous users by degrading its service quality. This phenomenon is called “softblocking”. The threshold value for the maximum allowable interference shall be defined in the callprocessing software by the operator.

To evaluate the blocking probability, the distribution of Z has to be determined which, in turn,depends on the following random variables: voice or data activity ( ), bit energy to interferenceratio ( ), the total number of users in the sector (Ns), and the number of active users per sector (k).

The voice or data activity ( ), is a binomial random variable with = Pr ( =1), which is the gateon probability. The distribution is given by:

P( =k) = [EQ 3-23]

The distribution of k is Poisson and is given by:

Pk = [EQ 3-24]

Where:

and are the arrival and service rates and is the offered traffic

The distribution of Eb/No depends on the power control mechanism in the system. Power controlallows the system to equalize the transmit power of all subscribers within the system. In a trial test,the Eb/No performance was measured with a fixed system Frame Erasure Rate (FER) for a fullyloaded CDMA cell. The data showed the overall Eb/No was a log-normal distribution. Hence thedistribution of can be written as:

[EQ 3-25]

Where:x is a Gaussian Random Variable with mean m and standard deviation

The first and second moment of are given by:

E( ) = E[ ] = [EQ 3-26]

νε

ν ρ ν

νNs 1–

k ρk

1 ρ–( )Ns k– 1–⋅ ⋅

λµ---

k

k!----------- exp

λ–µ------

⋅

λ µ λµ---

ε

ε 10x 10⁄

=

σ

ε

ε exp βx( ) expβσ( )2

2-------------- exp βm( )⋅


3


E( ) = E[ ] = [EQ 3-27]

Where:

β =

3.3.2.3 Single Cell Case

For the single cell case, the second summation term in Equation 3-22 is zero (i.e. no interferencefor other cells). Since Z is the sum of k random variables, where k is the number of simultaneoususers in the system, the Central Limit Theorem can be applied for the approximation for Z. Thecentral limit theorem states that the probability density function for the sum of a number ofindependent random variables with arbitrary one-dimensional probability density functionapproaches a Gaussian Distribution. Hence the probability of blocking can be rewritten as:

Probability of Blocking = [EQ 3-28]

Where:E( ) is the expected value

STD( ) is the standard deviation

A = and Q(x) =

The expected value and standard deviation of can be computed as follows. Since Z is the sumof k random variables and k is a Poisson random variable;

Let =

E( )= E(k) E( ) = [EQ 3-29]

ε2 exp 2βx( ) exp 2 βσ( )2[ ] exp 2βm( )⋅

ln 10( )10

----------------

QA E Z( )–

STD Z( )----------------------

ZZ

exp βm( )----------------------=

W R⁄exp βm( )---------------------- 1 η–( )⋅ 1

2π---------- e

x

∞

∫ xpλ2–2

-------- λd⋅

Z

ε εexp βm( )---------------------------

Z γελµ---

ρ expβσ( )2

2--------------

⋅ ⋅


3


VAR( ) = E(k) VAR ( ) + VAR(k) [E( )] 2

= VAR(k) [E( )] 2

= E(k) [E( )] 2

= [E( )] E[ ]

VAR( ) = [EQ 3-30]

STD( ) = [EQ 3-31]

Thus, the probability of blocking for a CDMA single cell system can be formulated as inEquation 3-32.


Although the Single Cell Probability of Blocking equation (Equation 3-32) can be applied towardsboth IS-95 and IS-2000 systems, it is typically applied towards analyzing a system utilizing a singledata rate. As such, it may be more appropriate in estimating the capacity of an IS-95 system, whereit is common to support a single data rate (i.e. Rate Set 1 or Rate Set 2). For IS-2000 systems whichutilize multiple data rates, the Single Cell Probability of Blocking equation can be used to analyzethe capacity of an individual data rate. It is not recommended to analyze a mixture of data rates.Section 3.4 will introduce an analytical approach more suitable for systems serving multiple datarates.

3.3.2.4 Multiple Cell System

In a multiple-cell system the interference created by users in the serving cell and cells other thanthe serving cell needs to be considered. The path loss characteristics and the overhead capacity forsoft handoffs need to be taken into account.

3.3.2.4.1 Path Loss Characteristics

Power control is crucial to CDMA system performance. Assuming that the path loss depends onlyon the subscriber-to-base distance, the subscribers will be power controlled by the nearest cell. Thegenerally accepted theoretical path loss model is to introduce an attenuation which is the productof, the subscriber-to-base distance to the power , and, a log-normal random variable with zeromean and dB standard deviation.

Z γε γε

γε

γε

λµ--- γ2 ε

2

Zλµ---

ρ exp 2 βσ( )2[ ]⋅ ⋅

Zλµ---

ρ exp 2 βσ( )2[ ]⋅ ⋅

Q

W R⁄exp βm( )---------------------- 1 η–( )⋅ λ

µ---

ρ expβσ( )2

2--------------

⋅ ⋅ –

λµ---

ρ exp 2 βσ( )2[ ]⋅ ⋅

-----------------------------------------------------------------------------------------------------------

αδ


3


In Mathematical form, the path loss between the subscriber and the cell site is proportional to

[EQ 3-33]

Where:r is distance from subscriber to cell site

is a Gaussian random variable with standard deviation and zero mean

The path loss can be expressed as

[EQ 3-34]

Where:r and are the base-subscriber distance and the reference distance respectively

When plotting the signal strengths at a given radio path distance, the deviation from the local meanvalues is approximately 8 dB. This standard deviation of 8 dB is roughly true in many differentareas. The path loss curves can be obtained by collecting data from different drive runs in differentenvironments. As long as the subscriber-to-base distance for each run is the same, the signalstrength data measured at that particular subscriber-to-base distance can be used for determiningthe local mean values for the path loss at that distance.

Measurements of path loss have been made in several major cities. Some of the typical values aretabulated as shown in Table 3-2.

Table 3-2: Propagation Path Loss in Different Areasa

a. William C. Y. Lee, "Mobile Cellular Telecommunications Systems", McGraw-Hill Book Company, Sec-ond Edition 1995, figure 4.3, p. 110.

Propagation Area1 Mile Intercept Point (Po)

in dBmPath Loss Slope (γ)

dB/decade

Free Space -45.0 20.0

Open Area -49.0 43.5

Suburban -61.7 38.4

Philadelphia -70.0 36.8

Newark -64.0 43.1

New York City -77.0 48.0

Tokyo, Japan -84.0 30.5

10

ξ10------

rα–⋅

ξ δ

PL α rr0----

log⋅=

r0


3


Since the main concern about propagation at far distances is for coverage purposes, path lossmeasurements typically use a 1 mile (or 1 km) intercept point as a starting point for path losscurves. This also tends to eliminate some of the near-field effects of near-by surroundings andvertical beam width shadowing. Although different areas may have different path loss slopes,Table 3-2 also shows that an area-to-area prediction is represented by two parameters, the 1 mileintercept point (Po, the power received at a distance of 1 mile from the transmitter) and the pathloss slope (γ). Differences in area-to-area prediction curves are primarily due to the differences inman-made structures. When the base station is located in a city environment, then the 1 mileintercept signal level could be very low, but the slope is flattened out, as shown by the Tokyo data.When the base station is located outside the city, the intercept signal level could be much higher,but the slope is larger, as shown by the Newark data. Due to differences in structure density(average separation between buildings), the 1 mile intercept could be high or low, with the pathloss slope still at a typical level of about 40 dB/dec (i.e. compare data of open area to Newark).

3.3.2.4.2 Interference from Other Cells

The normalized interference density from other cells can be written as:

Jo = Ioc / Io = Total Interference from other cells / IoW

Jo = [EQ 3-35]

Where:rm Distance from any subscriber to its own cell not power controlled by the serving

cell

r0 Distance from any subscriber to the serving cell not power controlled by theserving cell

Path loss exponent

Voice or data activity

Ioc Other cells interference density

Io Total allowable interference density

W Spread bandwidth

Eb*R Bit energy * data rate, which is the received power at the base station for any user,assuming power control is applied

Defines the path loss characteristics and is Gaussian random variables with zeromeans and standard deviation of

User density = 2 * users per sector / *sectorization gain

rm

r0-----

γ10

ξ10------

∅ ξr0

rm-----,

EbRνκIoW

-----------------

dAallcells∫∫

γ

ν

ξσ

κ 3


3


= 1, if

= 0, otherwise

By calculating the expected value and standard deviation Jo and , the probability of blocking fora CDMA multiple cell system can be formulated as follows.

E(J0) =

E(J0) = [EQ 3-36]

VAR(J0) =

VAR(J0) = [EQ 3-37]

The following figure provides the values of the numerical integration of the integral and versus various log-normal path loss slopes with a standard deviation of 8 dB.

Figure 3-6: Values of the Integral and with Various Path Loss Slope

∅ ξr0

rm-----,

rm

r0-----

γ10

ξ10------

1≤

z

E ε( ) λµ---

ρrm

r0-----

αexp βδ( )2[ ] 1 Q

10α

2δ2-------------

r0

rm-----

β 2δ2– log–

dA

allcell

∫∫

E ε( ) λµ---

ρ I α δ,( )[ ]⋅

E ε2( ) λµ---

ρrm

r0-----

2αexp βδ( )2[ ] 1 Q

20α

2δ2-------------

r0

rm-----

β 2δ2– log–

dA

allcell

∫∫

E ε2( ) λµ---

ρ I 2α δ,( )[ ]⋅

I α δ,( )I 2α δ,( )

I α δ,( ) I 2α δ,( )

50454035300.0

0.5

1.0

1.5

I(alpha,sigma=8dB)I(2alpha,sigma=8dB)

Path Loss (dB/dec)

Val

ues

of

the

Inte

gra

ls


3


Combining [EQ 3-36]and [EQ 3-37] with [EQ 3-29] and [EQ 3-30], the moments of the totalnormalized interference variable including the interference from outer cells is obtained.

[EQ 3-38]

[EQ 3-39]

Pblocking with outer cell interference = [EQ 3-40]

Where:

[EQ 3-41]

[EQ 3-42]


Note: A Complementary Error Function Q(x) table is provided in Appendix IV.

Z

E Z( ) λµ---

ρ expβσ( )2

2--------------

1 I α δ r, ,( )+[ ]⋅=

STD Z( ) λµ---

ρ exp 2 βσ( )2[ ] 1 I 2α δ r, ,( )+[ ]⋅=

QA E Z( )–

STD Z( )----------------------

AW R⁄

exp βm( )----------------------= 1 η–( )⋅

Q x( ) 1

2π----------= e

x

∞

∫ xpλ2–2

-------- λd⋅

Q

W R⁄exp βm( )---------------------- 1 η–( )⋅ λ

µ---

ρ expβσ( )2

2--------------

1 I α δ r, ,( )+[ ]⋅ –

λµ---

ρ exp 2 βσ( )2[ ] 1 I 2α δ r, ,( )+[ ]⋅

-------------------------------------------------------------------------------------------------------------------------------------------


3


Using Equation 3-32 and Equation 3-43, the probability of blocking is plotted against the Erlangcapacity per CDMA sector in different situations. A list of parameters is included at the bottom ofeach plot.

Figure 3-7: Probability of Blocking vs. Erlangs per CDMA Sector with Various Path Loss Slope Values with Rate Set 1 Vocoder

Note: The figure above is for demonstration purposes, as it is only valid for the assumptionsapplied and for the following parameters:

Parameters:• Mean Eb/No = 7 dB

• Pwr Ctrl Std Dev = 2.5 dB

• Voice or Data Activity Factor = 0.4

• Spread Bandwidth = 1.23 MHz

• Data Rate = 9600 bps (Rate Set 1)

• Total Interference Density to Background Noise Level (Io/No) = 10 dB

• Shadowing Standard Dev = 8 dB


3


Figure 3-8: Probability of Blocking vs. Erlangs per CDMA Sector with Various Power Control Standard Deviations with Rate Set 1 Vocoder







• Path Loss Slope = 40 dB/dec

• Shadowing Std Dev = 8 dB


3


Figure 3-9: Probability of Blocking vs. Erlangs per CDMA Sector with Various Path Loss Slope Values with Rate Set 2 Vocoder



• Pwr Ctrl Std Dev = 2.5 dB





• Shadowing Standard Dev = 8 dB


3


Figure 3-10: Probability of Blocking vs. Erlangs per CDMA Sector with Various Power Control Standard Deviations with Rate Set 2 Vocoder







• Path Loss Slope = 40 dB/dec

• Shadowing Std Dev = 8 dB

The Multiple Cell Probability of Blocking equation shown in Equation 3-43 can be applied towardsboth IS-95 and IS-2000 systems. Since, it is typically applied towards analyzing a system utilizinga single data rate, it may be more appropriate in estimating the capacity of an IS-95 system, whereit is common to support a single data rate (i.e. Rate Set 1 or Rate Set 2). For IS-2000 systems whichutilize multiple data rates, the Multiple Cell Probability of Blocking equation can be used toanalyze the capacity of an individual data rate. It is not recommended in analyzing a mixture ofdata rates. Section 3.4 provides an approach more suitable for systems serving multiple data rates.


3


3.4 Reverse Link Noise Rise Capacity Estimation

The amount of noise rise (interference) that can be tolerated by the CDMA base station will placea limit upon how many users can be supported by the reverse link. As the number of users servedby the reverse link is increased, the level of noise rise seen by the base station will also beincreased. The cell capacity is determined by calculating the number of users required to producea maximum accepted noise rise.

This section provides a method of estimating the noise rise for a particular user type. Theestimating approach will also allow the calculation of the total noise rise for multiple user types.As a result, the noise rise estimation approach provided in this section is better suited to estimatethe capacity of a system which utilizes multiple user types (i.e. multiple data rates). Although thiscapacity estimation approach can be applied towards both IS-95 and IS-2000 systems, it may bemore appropriate in estimating the capacity of an IS-2000 system, where it is more common tosupport different user type profiles utilizing different data rates.

For IS-2000 systems, it is important to note that the capacity estimation calculation provided in thissection does not account for the dynamic resource allocation capabilities of an IS-2000 1X packetdata user. Within the IS-2000 1X infrastructure, the subscriber will be assigned supplementalchannel resources based upon several criteria (e.g. the demand requirements for the amount of datato be transmitted, RF capacity availability, Walsh code resource availability, etc.). The allocationof these IS-2000 1X supplemental channel resources are also dynamically adjusted throughout theduration of the packet data call. The capacity estimation calculation provided in this section treatsa packet data user more like a circuit data user. The capacity formulas provided imply a fixedresource allocation where there are X users at 9.6 kbps, Y users at 19.2 kbps, Z users at 38.4 kbps,etc. As a result, the capacity obtained from the capacity estimation approach will differ from thatof an actual IS-2000 1X system. For a more accurate estimation of packet data services, it isrecommended to utilize a simulation tool which simulates the dynamic resource allocationcapabilities of an IS-2000 1X system. The time-sliced simulation function of the NetPlan tool canbe used for this purpose. See Section 3.12 for more information on the simulation capabilities ofthe NetPlan tool.

3.4.1 Reverse Link Noise Rise Capacity Limit

The reverse link pole capacity is considered to be the point where an additional user will cause thenoise rise within the cell to increase exponentially. This will create an unstable situation where userconnections may be lost and the network grade of service will be severely degraded. The reverselink noise rise pole capacity can be represented by the following equation:

[EQ 3-44]

Where:X Percent of reverse link pole capacity, traffic loading factor

Z Noise Rise (dB)

Z 10 Log10× 11 X–------------

10– Log10× 1 X–( )==


3


Refer to Section 4.2.2.1 for a derivation of Equation 3-44. A graph of the reverse noise rise polecapacity equation (Equation 3-44) is shown in Figure 3-11.

Figure 3-11: Rise versus Percent of Pole Capacity

In order to estimate the capacity from a number of users perspective, a reverse noise rise capacitylimit must be selected. For CDMA RF system designs (for both IS-95A/B and IS-2000), a peaknoise rise of 10 dB is recommended to be the maximum that a system should tolerate. The averagenoise rise would be several dB below this peak value. It is important to note that the 10 dB noiserise limit is a peak value which is associated with a certain probability factor (see Equation 3-48and Section 3.4.3). The recommended probability factors associated with the 10 dB peak noise riserecommendation are as follows.

• 10 dB noise rise with a 90% probability factor (for aggressive capacity results)• 10 dB noise rise with a 95% probability factor (for moderate capacity results)• 10 dB noise rise with a 98% probability factor (for conservative capacity results)

Although the above recommendation provides some flexibility in selecting a probability factor, the10 dB noise rise with a 95% probability factor is the typical limit that is normally recommended.

3.4.2 Reverse Noise Rise Capacity Estimation

To approximate the number of users that could be supported by a site while staying below a desirednoise rise limit, the following reverse link capacity equations can be utilized.

A multi-service traffic loading factor, X, can be expressed as follows:

0

5

10

15

20

0% 25% 50% 75% 100%

Loading Factor, X

Inte

rfer

ence

Ris

e, Z

(d

B)


3


[EQ 3-45]

The mean value for the multi-service traffic loading factor, X, is expressed as:

[EQ 3-46]

The variance for the multi-service traffic loading factor, X, is expressed as:

[EQ 3-47]

The following equation provides the distribution of the noise rise, Z, for the multi-service traffic loading factor, X:

[EQ 3-48]

Where:M Number of different service-types

Traffic load of the mth service-type (in Erlangs)

The energy-per-bit to total-interference-density target of the mth service-type

LN(10)/10

Average Eb/No (dB) of the mth service-type

Eb/No standard deviation, in dB of the mth service-type (to account for

inaccuracies in power control)

Activity Factor of the mth service-type

Mean Square of Activity Factor of the mth service-type (variance = 0.1)

F A measure of the in-cell to total interference density (own cell plus other cell)

Processing gain (Bandwidth/Information rate) of the mth service

X L m( )

m 1=

M

∑ν m( )

F PG m( )×------------------------×

Eb m( )NT

-------------×=

E X[ ] L m( )

m 1=

M

∑ν m( )

F PG m( )×------------------------× βε m( )

βσ m( )( )2

2---------------------+exp×=

Var X( ) L m( )

m 1=

M

∑ψ m( ) ν m( )( )+

2

F PG m( )( )2×-----------------------------------× 2βε m( ) 2 βσ m( )( )2

+[ ]exp×=

Z 10– Log10× 1 Pa Var X( ) E X[ ]–×–( )=

L m( )

Eb m( )NT

-------------

β

ε m( )

σ m( )

ν m( )

ψ m( )

PG m( )


3


Z Interference rise (expressed in dB)

Pa Probability factor (inverse of the standard normal cumulative distribution) with adistribution having a mean of 0 and a standard deviation of 1 (see Figure 3-12)

Briefly looking at Equation 3-46 and Equation 3-47, the average and variance of the loading factorwill increase as the number of users increases. Additionally, as the average and variance valuesincrease, so does Z, as reflected by Equation 3-48.

In a scenario with multiple services, the equations are a bit more complex than for a single service.Basically, an average and variance needs to be determined for each service offered. The net rise,Z, will need to account for all of the users being handled by each service.

3.4.3 Probability Factor

The probability factor (Pa) in Equation 3-48 is used to calculate a percentile noise rise. Thepercentile noise rise is used as the interference margin within the RF link budget calculation of cellrange. Therefore, scenarios with different traffic mixes and rise probabilities but with a constantpercentile noise rise will all maintain the same cell range. However, the mean noise rise and cellcapacity (throughput and Erlangs) will vary depending upon the mix of the different services forthe given scenario.

The probability factor is calculated as the inverse of the standard normal cumulative distributionwith a mean of 0 and a standard deviation of 1. Figure 3-12 shows the relationship of theprobability factor with the Probability Density Function (PDF) and the Cumulative DistributionFunction (CDF) for a standard normal distribution with a mean of 0 and a standard deviation of 1.

Figure 3-12: Standard Normal Distribution

0

0.2

0.4

0.6

0.8

1

-3 -2 -1 0 1 2 3

Probability Factor (Pa)

Dis

trib

uti

on

50%ile

75%il

85%ile95%ile

98%ile

CDFPDF


3


Table 3-3 provides the probability factor values for some common percentile probabilitypercentages.

The rise curves in Figure 3-13 show the 50th (average) and 95th percentile noise rise against cellloading in terms of the number of users. It can be seen that the 95th percentile noise rise curve risesfaster than the 50th percentile (average) noise rise curve and at the 95th percentile noise rise of 10dB for the example provided in Figure 3-13 below, the 50th percentile (average) noise rise isapproximately 5 dB. The relationship between a given percentile rise curve and the average risecurve will be dependent upon what percentile is being represented and also upon the particular callmodel traffic mix.

Figure 3-13: Rise and Radius versus Loading Example

Note: The figure above is for demonstration purposes, as it is only valid for the assumptionsapplied for the scenario portrayed (i.e. 30 kmph, 100% voice, etc.).

Figure 3-13 also shows how the relative cell range decreases with the increasing number of users.

Table 3-3: Probability Factors

PercentileProbability

ProbabilityFactor (Pa)

50% 075% 0.674585% 1.036490% 1.281695% 1.644898% 2.0537

0

5

10

15

20

25

0 5 10 15 20 25 30 35

Users

Ris

e (d

B)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1R

elat

ive

Rad

ius

% of Radius

95%ile Rise

50%ile (Avg.) Rise


3


A relative range impact of 50% corresponding to a 10 dB 95th percentile noise rise can be observedfrom this figure.

3.4.4 Reverse Link Noise Rise Capacity Estimation Examples

The following section provides two examples of how to use the reverse link noise rise capacityestimation equations provided in Section 3.4.2. The first example estimates the noise rise for asingle service type of traffic load of voice users only. The second example provides the calculationsrequired to estimate the noise rise for a multiple service type of traffic load with a mixture of voiceand data users.

3.4.4.1 Example #1: Voice Only

The following example calculates the noise rise for, on average, 20 IS-2000 1X voice users at 9600bps, in a 3-sectored system with a 95% probability factor. Additional assumptions are providedbelow.

Traffic Load:20 Voice users (average) at 9600 bps

General Assumptions:• 0.45 = F-factor (3 sector cell site assumed)• 1.64 = probability factor for 95% (Pa)• 0.23 = Beta value LN(10)/10 ( )

Traffic Load Assumptions: Voice @ 9600 bps• 20 = number of average users at 9600 bps ( )• 21.1 dB = Processing gain ( ) or 1228800/9600 = 128 linear• 3.6 dB = average Eb/No for 1% FER with vehicular fading at 30 kmph ( )• 2.5 dB = Eb/No standard deviation ( )• 0.713 = voice activity factor ( )• 0.1 = mean square of activity factor ( )

The first step is to calculate the mean value of the traffic loading factor, X, for the 20 average voiceusers by using Equation 3-46 (repeated below for reference).

Using the input variables from the assumptions above, E[X] is calculated as follows:

β

L m( )PG m( )

ε m( )σ m( )

ν m( )ψ m( )

E X[ ] L m( )

m 1=

M

∑ν m( )

F PG m( )×------------------------× βε m( )

βσ m( )( )2

2---------------------+exp×=

E X[ ] 200.713

0.45 128×-------------------------× 0.230259( ) 3.6( )⋅ 0.230259( ) 2.5( )⋅( )2

2---------------------------------------------------+exp×=


3


The next step is to calculate the variance for the traffic loading factor, X, for the 20 average voiceusers by using Equation 3-47 (repeated below for reference).

The final step is to calculate the noise rise, Z, for the 20 average voice users by using Equation 3-48 (repeated below for reference).

dB

3.4.4.2 Example #2: Voice and Data Users

The following example calculates the noise rise for a multiple service type traffic load environmentconsisting of, on average, 6 IS-2000 1X voice users at 9600 bps, 3 IS-2000 1X data users at 19200bps, and 1 data user at 38400 bps. Additional assumptions are provided below.

Traffic Load:6 Voice users (average) at 9600 bps3 Data users (average) at 19200 bps1 Data user (average) at 38400 bps

General Assumptions:• 0.45 = F-factor (3 sector cell site assumed)• 1.64 = probability factor for 95% (Pa)• 0.23 = Beta value LN(10)/10 ( )

E X[ ] 0.247569 0.994617[ ]exp× 0.247569 2.703690 0.669351=×==

Var X( ) L m( )

m 1=

M

∑ψ m( ) ν m( )( )+

2

F PG m( )( )2×-----------------------------------× 2βε m( ) 2 βσ m( )( )2

+[ ]exp×=

Var X( ) 200.1 0.713( )+

2

0.45 128( )2×----------------------------------× 2 0.230259( ) 3.6( )⋅ 2 0.230259( ) 2.5( )⋅( )⋅ 2

+[ ]exp×=

Var X( ) 0.001650 2.320605[ ]exp× 0.001650 10.181831× 0.016803===

Z 10– Log10× 1 Pa Var X( ) E X[ ]–×–( )=

Z 10– Log10× 1 1.644848 0.016803 0.669351–×–( )=

Z 10– Log10× 0.117432( ) 9.30==

β


3


Traffic Load Assumptions: Voice @ 9600 bps• 6 = number of average users at 9600 bps ( )• 21.1 dB = Processing gain ( ) or 1228800/9600 = 128 linear• 3.6 dB = average Eb/No for 1% FER with vehicular fading at 30 kmph ( )• 2.5 dB = Eb/No standard deviation ( )• 0.713 = voice activity factor ( )• 0.1 = mean square of activity factor ( )

Traffic Load Assumptions: Data @ 19200 bps• 3 = number of average users at 19200 bps ( )• 18.1 dB = Processing gain ( ) or 1228800/19200 = 64 linear• 3.0 dB = average Eb/No for 5% FER with vehicular fading at 30 kmph ( )• 2.5 dB = Eb/No standard deviation ( )• 1.0 = data activity factor ( )• 0.1 = mean square of activity factor ( )

Traffic Load Assumptions: Data @ 38400 bps• 1 = number of average users at 38400 bps ( )• 15.1 dB = Processing gain ( ) or 1228800/38400 = 32 linear• 2.4 dB = average Eb/No for 5% FER with vehicular fading at 30 kmph ( )• 2.5 dB = Eb/No standard deviation ( )• 1.0 = data activity factor ( )• 0.1 = mean square of activity factor ( )

The first step is to calculate the mean value of the traffic loading factor for the 6 average voice usersat 9600 bps by using Equation 3-46. Using the input variables from the assumptions above,E[X]9600 is calculated as follows:

Now, calculate the mean value of the traffic loading factor for the 3 average data users at 19200bps by using Equation 3-46. Using the input variables from the assumptions above, E[X]19200 iscalculated as follows:

Now, calculate the mean value of the traffic loading factor for the 1 average data user at 38400 bps

L m( )PG m( )

ε m( )σ m( )

ν m( )ψ m( )

L m( )PG m( )

ε m( )σ m( )

ν m( )ψ m( )

L m( )PG m( )

ε m( )σ m( )

ν m( )ψ m( )

E X[ ] 9600 60.713

0.45 128×-------------------------× 0.230259( ) 3.6( )⋅ 0.230259( ) 2.5( )⋅( )2

2---------------------------------------------------+exp×=

E X[ ] 9600 0.074271 0.994617[ ]exp× 0.074271 2.703690 0.200805=×==

E X[ ] 19200 31

0.45 64×----------------------× 0.230259( ) 3.0( )⋅ 0.230259( ) 2.5( )⋅( )2

2---------------------------------------------------+exp×=

E X[ ] 19200 0.104167 0.856462[ ]exp× 0.104167 2.354815 0.245293=×==


3


by using Equation 3-46. Using the input variables from the assumptions above, E[X]38400 iscalculated as follows:

Finally, calculate the total loading factor E[X]Total for all user types by summing together all of theindividual results.

The next step is to calculate the variance for the traffic loading factor for the 6 average voice usersat 9600 bps by using Equation 3-47. Using the input variables from the assumptions above,Var(X)9600 is calculated as follows:

Now, calculate the variance for the traffic loading factor for the 3 average data users at 19200 bpsby using Equation 3-47. Using the input variables from the assumptions above, Var(X)19200 iscalculated as follows:

Now, calculate the variance for the traffic loading factor for the 1 average data user at 38400 bpsby using Equation 3-47. Using the input variables from the assumptions above, Var(X)38400 iscalculated as follows:

E X[ ] 38400 11

0.45 32×----------------------× 0.230259( ) 2.4( )⋅ 0.230259( ) 2.5( )⋅( )2

2---------------------------------------------------+exp×=

E X[ ] 38400 0.069444 0.718307[ ]exp× 0.069444 2.050957 0.142428=×==

E X[ ] Total 0.200805 0.245293 0.142428 0.588526=+ +=

Var X( )9600 60.1 0.713( )+

2

0.45 128( )2×----------------------------------× 2 0.230259( ) 3.6( )⋅ 2 0.230259( ) 2.5( )⋅( )⋅ 2

+[ ]exp×=

Var X( )9600 0.000495 2.320605[ ]exp× 0.000495 10.181831× 0.005041===

Var X( )19200 30.1 1( )+

2

0.45 64( )2×------------------------------× 2 0.230259( ) 3.0( )⋅ 2 0.230259( ) 2.5( )⋅( )⋅ 2

+[ ]exp×=

Var X( )19200 0.001790 2.044294[ ]exp× 0.001790 7.723704× 0.013828===

Var X( )38400 10.1 1( )+

2

0.45 32( )2×------------------------------× 2 0.230259( ) 2.4( )⋅ 2 0.230259( ) 2.5( )⋅( )⋅ 2

+[ ]exp×=

Var X( )38400 0.002387 1.767983[ ]exp× 0.002387 5.859025× 0.013986===


3


Finally, calculate the total variance Var(X)Total for all user types by summing together all of theindividual results.

The final step is to calculate the noise rise, Z, for the total traffic load using a 95% probability factorby using Equation 3-48 (as shown below).

dB

3.4.5 Reverse Link Noise Rise Capacity Estimates for IS-2000 1X

In order to calculate the capacity supported by the air interface in an IS-2000 1X system, it isimportant to determine the values of the various factors that affect the capacity. The IS-2000 1Xreverse link capacity estimates (throughput and Erlangs) provided in this document are based onthe reverse link noise rise capacity estimation equations provided in Section 3.4.2 and utilizing theparameter value assumptions that follow.

The following are the assumptions for the various IS-2000 1X parameter values to be applied tothe reverse link noise rise capacity estimation equations.

3.4.5.1 Noise Rise

For the purpose of determining capacity estimates, a 10 dB maximum noise rise value was selected.Additionally, each rise has a probability factor, Pa, associated with it. The following table providessome of the recommended noise rise values and probability factors used for this exercise.

Since the probability factor is associated with a normal distribution, the 50% probability factorimplies an average noise rise value. Therefore, for the scenarios where the probability factor isgreater than 50%, the average noise rise will be less than the rise value shown. This can beillustrated further through Figure 3-12, where the 50% probability factor is associated with theaverage point in the normal distribution curve. However, a higher probability factor would be

Table 3-4: Interference Rise Scenarios

PercentileProbability (Pa)

AssociatedNoise Rise (Z)

90% 10 dB95% 10 dB98% 10 dB

Var X( )Total 0.005041 0.013828 0.013986 0.032856=+ +=

Z 10– Log10× 1 Pa Var X( )Total E X[ ]–× Total–( )=

Z 10– Log10× 1 1.644848 0.032856 0.588526–×–( )=

Z 10– Log10× 0.113327( ) 9.46==


3


associated with a value that is greater than the average value.

The capacity tables shown in Section 3.4.5.9 provide both the capacity (in Erlangs and throughput)and the average rise values associated with a 10 dB peak noise rise for the 90%, 95%, and 98%probability factors. Typical RF designs should strive to keep the peak percentile probability reversenoise rise value less than 10 dB.

Various probability factors were used in scenarios to estimate the capacity for aggressive (90%),moderate (95%), or conservative (98%) cases. Additionally, a rise value of less than 10 dB can beused to demonstrate the impact on capacity, in order to trade capacity for increased reverse linkcoverage.

In all of the test cases, the cell loading is considered uniform in each sector (homogeneous network)and as such the rise is the same across each cell. In practice, the non-homogeneous nature of cellloading will mean that an individual cell may be able to cope with a peak load higher than thehomogeneous case.

3.4.5.2 F-factor

F-factor is the ratio of own cell interference to own cell plus other cell interference. Simulationshave shown that the F-factor varies with the antenna types and propagation index. For this exercise,the following F-factors have been assumed:

In looking at Equation 3-46 and Equation 3-47, the number of users is proportional to the F-factorin order to maintain the same average and variance load factors. That is, an increase to the F-factor(out of cell interference is reduced compared to own cell interference) will result in an increase inthe number of users. A decrease to the F-factor, implying out of cell interference is more prevalent,will result in a decrease to the number of users.1

Table 3-5: F-factor

Site Type F-factorOmni 0.60

3-Sector 0.456-Sector 0.40

1. Additional information showing the relationship of the F-factor to the antenna type and propagation indexcan be found in the following references.

a. R.H. Owen, Phil Jones, Shirin Dehgan, Dave Lister, "Uplink WCDMA capacity and range as a function ofinter-to-intra cell interference: theory and practice", pp. 298-302, VTC 2000.

b. Szu-Wei Wang and Irving Wang, "Effects of Soft Handoff, Frequency Reuse and Non-Ideal Antenna Sec-torization on CDMA System Capacity", pp. 850-854, IEEE 1993.


3


3.4.5.3 Average Eb/No

Eb/No is defined as energy per bit to the noise spectral density. The appropriate value for therequired Eb/No is such that the desired bit, block, or frame erasure rate of the received signal isachieved. This gives an indication of the lowest signal strength that the receiver can detect abovea certain noise level. Such items as the subscriber speed, the propagation environment, and powercontrol impact the required Eb/No.

The Eb/No numbers used for each data rate in this document are typical numbers that are used fordimensioning purposes. The Eb/No values were obtained from reverse link level simulations. TheEb/No values used for this exercise are shown in Table 3-6.

The link level simulations used to generate the Eb/No values utilized the following assumptions:

• Two receive antennas

• Eb/No values are per antenna

• The power control bit error rate of 4% used

• 1900 MHz

In looking at Equation 3-46 and Equation 3-47 again, the number of users is inversely proportionalto the Eb/No in order to maintain the same average and variance load factor. That is, an increase inthe Eb/No will result in a decrease in the number of users. A decrease to the Eb/No will result in anincrease to the number of users.

3.4.5.4 Eb/No Standard Deviation

A standard deviation of 2.5 dB on the Eb/No is assumed for each rate. This standard deviation forthe Eb/No is used to adjust the average Eb/No to compensate for imperfect power control in the realworld environment.

The number of users is inversely proportional to the Eb/No standard deviation in order to maintainthe same average and variance load factor. That is, an increase in the Eb/No standard deviation willresult in a decrease in the number of users. A decrease to the Eb/No standard deviation will resultin an increase to the number of users.

The Eb/No standard deviation has been assumed to be the same for each data rate. In a real worldsituation this may not be the case, but for an estimate of the capacity (as used for this exercise), onevalue has been assumed for all services.


3


3.4.5.5 Processing Gain

The processing gain is the ratio of the chip rate to the bit rate. For IS-2000 1X, the chip rate is equalto 1.2288 x 106

chips/s. The calculation of the processing gain in linear and in dB units are providedbelow.

Processing Gain linear =

Processing Gain db =

Where:W Bandwidth (1.2288 Mcps for IS-2000 1X)

R Information rate

The following table provides a summary of the Eb/No, Eb/No Standard Deviation, and theprocessing gain values used for the various data rates that were analyzed.

Recall that the Eb/No values shown in the above table were obtained from reverse link levelsimulations and represent typical values that are used for dimensioning purposes. The Eb/No valueswill vary based on the subscriber speed, propagation conditions, percent FER, etc. For detailedcapacity and coverage results, Motorola recommends using the NetPlan simulation tool. Thissimulation tool incorporates a family of Eb/No curves as opposed to only a few Eb/No values.

The bearer rate data in Table 3-6 represents a data link layer rate from the subscriber’s perspective.It does not include any overhead (RLP, framing, etc.). The bearer rates in Table 3-6 are used in thecalculation of the throughput capacity (see Section 3.4.5.8).

3.4.5.6 Activity Factor

The activity factor is defined as the percentage of time that a user transmits on an active trafficchannel. With IS-95, a typical industry accepted voice activity factor was 40%. This roughlyequated to 32% of the time the user was at full rate and 68% of the time the user was at eighth rate.With IS-2000 1X, the voice activity factor needs to be adjusted to account for the reverse pilot

Table 3-6: IS-2000 1X Average Eb/No Values

Bearer Rate(bits/s)

Data Rate(bits/s)

FER Eb/No (dB) Eb/No Std.Dev. (dB)

Proc. Gain(dB)3 kmph 30 kmph

8600 9600 1% 2.56 3.60 2.5 21.114400 19200 5% 0.76 3.00 2.5 18.132000 38400 5% 0.12 2.40 2.5 15.164000 76800 5% -0.36 2.24 2.5 12.0128800 153600 5% -0.65 1.40 2.5 9.0

W R⁄

10 Log10 W R⁄( )×


3


channel and for CRCs being sent at eighth rate. The following calculation provides the adjustmentfor these factors.

For IS-2000 1X, the extra CRC bits being sent produces an effective eighth rate of 1500 bps. The(0.68/6.4) term accounts for the extra CRC bits (where 9600/1500 = 6.4). The (0.68 x 10(-3.75/10))term accounts for the reverse pilot overhead channel.

It should be noted that this adjusted activity factor is utilized in the capacity equation as a meansto derate the capacity due to the reverse pilot overhead channel and CRC bits. In converting thevoice users to an equivalent throughput, the voice activity factor of 40% (0.4) is used.

For the capacity results provided in this section, two different data activity factors (0.9 and 0.2) areassumed to show the impact of a high and low data activity factor user type.

The number of users is inversely proportional to the activity factor in order to maintain the sameaverage and variance load factor. That is, an increase in the activity factor will result in a decreasein the number of users. A decrease to the activity factor will result in an increase to the number ofusers.

3.4.5.7 Traffic Mix

Four different traffic mix scenarios were analyzed as reflected in the following table.

The percentage of users can be interpreted, for example, as follows. In Scenario A, 100% of theusers are voice users at 8.6 kbps. In this scenario, all users in the network are continuouslytransmitting at the relevant voice activity and at the required power to reach their respective Eb/Novalue. For Scenario C, 50% of the users are voice users at 8.6 kbps, 40% of the users are using 64kbps, and the remaining 10% of the users are at 128.8 kbps.

3.4.5.8 Throughput Capacity

With multiple rate high-speed data services being introduced into the call model traffic mix, thecapacity of a cell/sector should now be quantified with a throughput value in addition to the numberof Erlangs. For the capacity analysis results provided below, the estimated throughput capacity is

Table 3-7: Traffic Mix

Scenario Bearer ServiceVoice (8.6 kbps) 64 kbps 128.8 kbps

A 100% - -B 80% 20% -C 50% 40% 10%D 10% 60% 30%

0.32 0.68 6.4⁄ 0.68 103.75 10⁄–( )

0.713=⋅+ +


3


calculated by multiplying the bearer rate, the activity factor, and the number of supported users(continuously transmitting users) together.

For a single data rate user example, consider scenario A with a rise of 10 dB and a probability factorof 95% (see Table 3-8). The voice rate assumed is 8.6 kbps and as such, approximately 27 Erlangsat the pedestrian speed can be supported in a single sector of a 3-sectored cell. This corresponds toa throughput capacity of approximately 93 kbps / sector (8.6 kbps x 0.40 AF x 27 Erlangs). Asstated previously (see Section 3.4.5.6), an adjusted activity factor is utilized in the capacityequation as a means to derate the capacity due to the reverse pilot overhead channel and extra CRCbits. In converting the voice users to an equivalent throughput capacity, the non-adjusted voiceactivity factor of 40% (0.4) is used for the throughput calculation, instead of the adjusted activityfactor of approximately 71.3% (as calculated in Section 3.4.5.6).

For a multiple data rate mixture of users, the throughput capacity is calculated for each individualdata rate user type and then summed together. For example, consider traffic mix scenario C with aprobability of 95% and a data activity factor of 20%. From the results in Table 3-8, an estimated19.3 Erlangs at the pedestrian speed can be supported in a single sector of a 3-sectored cell with atotal throughput of 182 kbps. The traffic distribution for scenario C is 50% for 8.6 kbps voice users,40% for 64.0 kbps data users, and 10% for 128.8 kbps data users. According to the trafficdistribution of scenario C, the throughput capacity is calculated as follows.

8.6 kbps Voice User Thruput = 8.6 kbps x 0.4 AF x (19.3 x 0.5) Erlangs = 33.2 kbps64.0 kbps Data User Thruput = 64.0 kbps x 0.2 AF x (19.3 x 0.4) Erlangs = 98.8 kbps128.8 kbps Data User Thruput = 128.8 kbps x 0.2 AF x (19.3 x 0.1) Erlangs = 49.7 kbps

Total Throughput = 181.7 kbps

3.4.5.9 IS-2000 1X Reverse Noise Rise Capacity Analysis Results

The following two tables provide capacity values (expressed as kbps throughput and Erlangs) persector for the various scenarios assuming an interference rise limit of 10 dB but with varying levelsof probability. For the traffic mix scenarios which include data users (Scenarios B, C, and D),capacity results for two different Data Activity Factors (AF) are provided. A 90% Data AF is usedto estimate the results of high data activity factor users such as a File Transfer Protocol (FTP) user.A 20% Data AF is used to estimate the results of lower data activity factor users such as a LowSpeed Packet Data (LSPD) or a High Speed Packet Data (HSPD) user. All of the traffic mixscenarios in Table 3-8 below assume pedestrian (3 kmph) Eb/No values.


3


Table 3-8: Reverse Capacity per Sector for Various Probabilities of Rise - Pedestrian

Scenario Rise Probability

DataAF

Avg Rise(dB)

Throughput (kbps/Sector) Erlangs/SectorOmni 3-Sector 6-Sector Omni 3-Sector 6-Sector

A 98% N/A 4.7 117 88 78 33.6 25.2 22.4

95% N/A 5.3 124 93 83 35.7 26.8 23.8

90% N/A 5.9 131 98 88 37.7 28.3 25.1

B 98% 90% 3.3 209 156 139 14.6 10.9 9.7

98% 20% 4.2 163 122 109 30.5 22.9 20.3

95% 90% 3.8 232 174 154 16.2 12.1 10.8

95% 20% 4.8 175 132 117 32.8 24.6 21.9

90% 90% 4.5 254 191 170 17.8 13.3 11.9

90% 20% 5.4 187 140 125 35.0 26.3 23.4C 98% 90% 2.6 234 176 156 6.4 4.8 4.3

98% 20% 3.4 220 165 147 23.3 17.5 15.5

95% 90% 3.1 268 201 179 7.4 5.5 4.9

95% 20% 3.9 243 182 162 25.8 19.3 17.2

90% 90% 3.8 303 227 202 8.3 6.2 5.5

90% 20% 4.6 266 200 177 28.2 21.1 18.8

D 98% 90% 2.3 241 181 161 3.5 2.6 2.3

98% 20% 2.8 266 200 177 16.9 12.7 11.3

95% 90% 2.9 279 210 186 4.0 3.0 2.7

95% 20% 3.4 301 226 201 19.1 14.3 12.7

90% 90% 3.5 320 240 213 4.6 3.4 3.1

90% 20% 4.0 336 252 224 21.4 16.0 14.2


3


All of the traffic mix scenarios in Table 3-9 below assume vehicular (30 kmph) Eb/No values.

The results in Table 3-8 and Table 3-9 show the capacity estimates for an IS-2000 1X reverse linkunder the stated configurations, assumptions, and parameter values. As shown above, the capacityestimate can vary greatly depending upon the parameter values that are chosen. Although thestated assumptions and parameter values used for this exercise are deemed to be realistic, theaccuracy of the capacity estimate is highly dependent upon the accuracy of the assumptions andparameter values used for the capacity estimate.

With new higher data rate services being introduced (via IS-95B or IS-2000), it is expected that theforward link will require higher data downloads than the reverse link. As a result, the forward linkis also expected to be the limiting path from a capacity perspective. Even though the forward linkmay be the limiting factor of capacity for some systems, it may still be appropriate to use theprevious reverse link capacity estimates to approximate the CDMA carrier capacity under thegiven assumptions and conditions. In many instances, the capacity analysis results of the reverselink can sometimes provide an adequate budgetary estimate for the CDMA carrier. Ultimately,simulations should be used (i.e. using NetPlan) to obtain more accurate capacity estimations.Simulations can take into account many variable elements for which a general reverse or forward

Table 3-9: Reverse Capacity per Sector for Various Probabilities of Rise - Vehicle

Scenario RiseProbability

DataAF

Avg. Rise(dB)


A 98% N/A 4.4 89 67 59 25.5 19.1 17.0

95% N/A 5.0 95 71 63 27.3 20.4 18.2

90% N/A 5.6 101 76 67 29.0 21.7 19.3

B 98% 90% 2.4 108 81 72 7.5 5.6 5.0

98% 20% 3.5 104 78 69 19.4 14.6 12.9

95% 90% 3.0 124 93 83 8.7 6.5 5.8

95% 20% 4.0 114 86 76 21.4 16.0 14.3

90% 90% 3.6 141 106 94 9.9 7.4 6.6

90% 20% 4.7 125 94 83 23.3 17.5 15.6

C 98% 90% 2.0 113 85 75 3.1 2.3 2.1

98% 20% 2.7 120 90 80 12.8 9.6 8.5

95% 90% 2.5 134 101 89 3.7 2.8 2.5

95% 20% 3.2 137 103 92 14.6 10.9 9.7

90% 90% 3.1 157 118 105 4.3 3.2 2.9

90% 20% 3.8 155 116 103 16.4 12.3 10.9

D 98% 90% 1.8 114 86 76 1.6 1.2 1.1

98% 20% 2.2 132 99 88 8.4 6.3 5.6

95% 90% 2.3 138 103 92 2.0 1.5 1.3

95% 20% 2.7 154 116 103 9.8 7.4 6.5

90% 90% 2.8 163 122 109 2.3 1.8 1.6

90% 20% 3.3 178 133 119 11.3 8.5 7.5


3


link capacity equation cannot adequately model (i.e. non uniform traffic and speed distributions,non uniform cell site layouts, propagation characteristics for a specific area, multiple subscriberclasses with various call models, combined forward and reverse link analysis, etc.).

As a point of reference, the CDMA Development Group (CDG) has published a report2 withsimulation results for voice users showing 29.9 Erlangs for the reverse link and 23.6 Erlangs forthe forward link. These capacity values were based on a generic 37 site system. Furthermore, thesites were three-sector and a vehicular fading model was assumed.

The following figure shows the relationship between the reverse link noise rise and the throughputfor several probability curves. The input parameters used to create the figure are shown below. The50%-ile curve corresponds to the average rise.

Figure 3-14: Reverse Link Rise vs. Throughput


Parameters:• Traffic mix = Scenario B

• Voice activity factor = 57.6%

• Data activity factor = 100%

2. CDG Evolution Study Report, Revision 4.01, January 10,2000

0

2

4

6

8

10

0 50 100 150 200 250

Throughput (Kbps)

No

ise

Ris

e (d

B)

98% 95% 90% 85% 75% 50%


3


• Mean square of activity factor = 0.1 dB

• F-factor = 0.45 (3-sector cell site configuration)

• Vehicular (30 kmph) Eb/No assumptions from Table 3-6 were used

• Eb/No standard deviation = 2.5 dB

The following figure shows the relationship between reverse link noise rise and Erlangs of variousdata rates. The input parameters used to create the figure are shown below.

Figure 3-15: Reverse Link Rise vs. Erlangs for Different Data Rates


Parameters:• Voice and data activity factor = 57.6%



• Probability factor = 95%



The curves in the figure above show the significant impact that data users can have on the capacityof a system. The voice and data activity factors were purposely set to the same value in order toreflect the capacity impact of just varying the data rate.

0

1

2

3

4

5

6

7

8

9

10

0 5 10 15 20 25 30

Erlangs

No

ise

Ris

e (d

B)

Voice @ 9600 Data @ 19200 Data @ 38400 Data @ 76800 Data @ 153600


3


The following figure shows the relationship between the reverse link total throughput and totalErlangs with respect to the data activity factor. The input parameters used to create the figure areshown below.

Figure 3-16: Reverse Link Total Erlangs & Throughput vs. Data Activity Factor



• Peak noise rise = 10 dB







0

20

40

60

80

100

120

90%80%70%60%50%40%30%20%10%

Data Activity Factor

To

tal T

hru

pu

t (K

bp

s)

0.0

5.0

10.0

15.0

20.0

25.0

30.0T

ota

l Erl

ang

s

Total Thruput Total Erlangs


3


3.5 Forward Link Pole Capacity Estimation

Forward link (downlink) capacity calculations are similar to the reverse link calculations in that theratio of energy per bit over the interference density for each subscriber needs to be calculated. Thenature of the interference is slightly different in that the pilot, page and synchronization channelsneed to be considered as interference. Therefore the capacity of the forward link is dependent uponthe strength of these channels. Another factor that may need to be considered in the calculation offorward link capacity is the total amount of base station transmission power required. By using theappropriate input parameters, the following approach can be applied towards both types of systems(IS-95 and IS-2000 1X).

3.5.1 Forward Link Load Factor Estimation

A forward link load factor, , can be defined in a similar approach as the reverse link pole

capacity equations, although some of the parameters are slightly different. The following equationcan be used to represent the forward link load factor.

[EQ 3-49]

Where:Forward link load factor

Number of connections per cell

Activity factor of user j

Signal energy per bit divided by noise spectral density of user j

Bandwidth of the channel

Data rate of user j

Orthogonality of the channel of user j

Ratio of out of cell to in cell base station power received by user j

When compared to the reverse link equations, the primary new parameter is , which represents

the orthogonality factor for the forward link users. Since the forward link employs orthogonalcodes to separate the users, multipath propagation can cause sufficient delay spread in the radiochannel which produces interference. Thus, the orthogonality factor is used to estimate the amountof interference created by the multipath propagation environment, where a value of 1 corresponds

ηFL

ηFL νj

j 1=

N

∑Eb No⁄( )j

W Rj⁄---------------------- 1 α j–( ) ij+[ ]⋅ ⋅=

ηFL

N

νj

Eb No⁄( )j

W

Rj

α j

ij

α j


3


to perfectly orthogonal users and a value of 0 corresponds to no orthogonality. Typically, theorthogonality factor is between 0.4 and 0.9 for multipath channels.

For the forward link, the ratio of out of cell to in cell base station power received, , is dependent

upon the individual user location and is therefore different for each user.

3.5.2 Forward Link Pole Capacity Estimation

When the forward link load factor approaches unity, the system reaches its pole capacity and thenoise rise over thermal goes to infinity. The forward link noise rise pole capacity can be representedby the following equation:

[EQ 3-50]

Where:Noise rise (dB)

Forward link load factor (see Equation 3-49)

The forward link noise rise pole capacity equation can be used to estimate the noise rise overthermal noise due to multiple access interference. This is similar to the reverse link equation (seeEquation 3-44) and has the same characteristics as shown in Figure 3-11.

For forward link dimensioning, it is important to take into account the total amount of base stationtransmission power required. The power estimate should be based on the average transmissionpower for the user and not the maximum transmission power for a user at the cell edge which istypically shown by the link budget. The total base station transmission power for a user at an‘average’ location within the cell can be mathematically expressed by the following equation.

BS_Tx_Power = [EQ 3-51]

Where:Noise spectral density of the subscriber receiver front-end or ,

where k is Boltzmann’s constant J/K, T is temperature in degreesKelvin (290 K), and NF is the subscriber station noise figure

Average attenuation between the base station transmitter and the subscriberstation receiver

Average load factor using Equation 3-49 with average values for and

ij

Z 10Log10 1 ηFL–( )–=

Z

ηFL

Nrf W L νj

j 1=

N

∑Eb No⁄( )j

W Rj⁄----------------------⋅ ⋅ ⋅ ⋅

1 ηFL–-----------------------------------------------------------------------

Nrf Nrf k T⋅ NF+=

1.38 1023–⋅( )

L

ηFL α j ij


3


When using Equation 3-51, the power impacts of the forward link common channels (pilot, page,sync, quick paging channel, etc.) and cable losses should be accounted for in the BS_Tx_Powerallocation.

3.6 Forward Link Fractional Power Capacity Estimation

For the forward link of a CDMA cell site, there is a fixed amount of power that is allocated for aCDMA carrier on a per-cell/per-sector basis. Since this is a fixed resource, an alternate method forestimating forward link capacity is to normalize this fixed power resource and estimate thefractional amount of power required for the average user while taking several factors into account(i.e. distribution of users with 1-way, 2-way, & 3-way links, other cell interference, overheadchannel power, required Eb/Nt, forward power control error, activity factor, etc.).

The following equation represents a first order approximation of the forward link capacity using afractional power approach:

[EQ 3-52]

Where:Traffic load supported (in Erlangs)

Effective Voice or Data Activity

Fraction of total cell power for pilot, page, and sync

Fraction of users in i-way handoff

Fraction of allocated cell power for each i-way link

The next step is to provide a more detailed estimate for the fraction of allocated cell power for eachi-way link.

[EQ 3-53]

Where:Total normalized interference seen by i-way user

Fraction of recovered power by i-way connection

N1 ζpps–( )

Veff 3S3wayζ3way( 2S2wayζ2way S1wayζ1way )+ +--------------------------------------------------------------------------------------------------------------------<

N

Veff

ζpps

Siway

ζ iway

ςi way–

I( on i )( λ i( ) )– 10

Eb

Ntiway

-------------- FPCerror+ 10⁄

⋅

i λ i( )WR-----⋅ ⋅

---------------------------------------------------------------------------------------=

Ion i )(

λ i( )


3


Energy per bit per thermal noise power spectral density per i-way connection

FPCerror Forward power control error in dB

W Bandwidth of channel

R Data rate

The final step is to provide a more detailed estimate for the total normalized interference as seenby each i-way user.

[EQ 3-54]

Where:Adjacent carrier(s) noise factor

Other cell (not including adjacent carrier) normalized interference

For the following examples, the values from Table 3-10 below (0 adjacent carriers is assumed) areentered into Equation 3-52, Equation 3-53, and Equation 3-54 in order to estimate the forward linkcapacity for a Rate Set 1 and Rate Set 2 system.

Table 3-10: Example of Parameter Values

Parameter 1-way 2-way 3-way0.40 0.35 0.25

0.134 0.30 0.30

0.92 0.92 0.80

for 13 kb 15.5 dB 9 dB 7 dB

for 8 kb 13 dB 7 dB 5 dB

1.2 dB (for 13 kb) or 1.5 dB (for 8 kb)

0.37

85.33 (for 13 kb) or 128 (for 8 kb)

0.48 (for 13 kb) or 0.56 (for 8 kb)

(assume 2% per carrier)1.00 (for 0 adjacent carrier),1.02 (for 1 adjacent carrier),1.04 (for 2 adjacent carriers)

Eb

Ntiway---------------

Ion i )( i δ Iocn i )(⋅+=

δ

Iocn i )(

Siway

Iocn i )(

λ i( )

Eb Ntiway⁄

Eb Ntiway⁄

FPCerror

ζpps

W R⁄Veff

δ


3


The following examples assume no adjacent carrier interference ( = 1.00).

Example #1: Rate Set 1

1. Estimate for the total normalized interference as seen by each i-way user.

2. Estimate the fraction of allocated cell power for each i-way link.

3. Estimate the first order approximation of the forward link capacity using a fractional powerapproach.

Erlangs

Example #2: Rate Set 2

1. Estimate for the total normalized interference as seen by each i-way user (same for Rate Set 1).

δ

Ion 1 )( 1 1 0.134 1.134=⋅+=

Ion 2 )( 2 1 0.3 2.3=⋅+=

Ion 3 )( 3 1 0.3 3.3=⋅+=

ς1 way–1.134( 0.92 )– 10

13 1.5+( ) 10⁄⋅1 0.92 128⋅ ⋅

------------------------------------------------------------------------ 0.0512==

ς2 way–2.3( 0.92 )– 10

7 1.5+( ) 10⁄⋅2 0.92 128⋅ ⋅

---------------------------------------------------------------- 0.0415==

ς3 way–3.3( 0.8 )– 10

5 1.5+( ) 10⁄⋅2 0.8 128⋅ ⋅

------------------------------------------------------------- 0.0364==

N1 0.37–( )

0.56 3 0.25 0.0364⋅ ⋅(⋅ 2 0.35 0.0415⋅ ⋅ 0.40 0.0512⋅ )+ +----------------------------------------------------------------------------------------------------------------------------------------------- 14.6=<

Ion 1 )( 1 1 0.134 1.134=⋅+=

Ion 2 )( 2 1 0.3 2.3=⋅+=

Ion 3 )( 3 1 0.3 3.3=⋅+=


3


2. Estimate the fraction of allocated cell power for each i-way link.

3. Estimate the first order approximation of the forward link capacity using a fractional powerapproach.

Erlangs

3.7 Forward Link Noise Rise Capacity Estimation

The amount of noise rise (interference) that can be tolerated by the CDMA subscriber will place alimit upon how many users can be supported by the forward link. As the number of users servedby the forward link is increased, the level of noise rise seen by the subscribers will be increaseddue to the additional energy being transmitted by the site to support all of the subscribers. The cellcapacity is determined by calculating the number of users required to produce a maximum acceptednoise rise. This section is similar to Section 3.4 for the reverse link except it is being applied to theforward link.

This section provides a method of estimating the noise rise for a particular user type. Theestimating approach will also allow the calculation of the total noise rise for multiple user types.As a result, the noise rise estimation approach provided in this section is better suited to estimatethe capacity of a system which utilizes multiple user types (i.e. multiple data rates). Although thiscapacity estimation approach can be applied towards both IS-95 and IS-2000 systems, it may bemore appropriate in estimating the capacity of an IS-2000 system, where it is more common tosupport different user type profiles utilizing different data rates.

For IS-2000 systems, it is important to note that the capacity estimation calculation provided in thissection does not account for the dynamic resource allocation capabilities of an IS-2000 1X packetdata system. Within the IS-2000 1X infrastructure, the subscriber will be assigned supplementalchannel resources based upon several criteria (e.g. the demand requirements for the amount of datato be transmitted, RF capacity availability, Walsh code resource availability, etc.). The allocationof these IS-2000 1X supplemental channel resources are also dynamically adjusted throughout theduration of the packet data call. The capacity estimation calculation provided in this section treatsa packet data user more like a circuit data user. The capacity formulas provided imply a fixedresource allocation where there are X users at 9.6 kbps, Y users at 19.2 kbps, Z users at 38.4 kbps,etc. As a result, the capacity obtained from the capacity estimation approach may differ from that

ς1 way–1.134( 0.92 )– 10

15.5 1.2+( ) 10⁄⋅1 0.92 85.33⋅ ⋅

--------------------------------------------------------------------------- 0.1275==

ς2 way–2.3( 0.92 )– 10

9 1.2+( ) 10⁄⋅2 0.92 85.33⋅ ⋅

---------------------------------------------------------------- 0.0920==

ς3 way–3.3( 0.8 )– 10

7 1.2+( ) 10⁄⋅2 0.8 85.33⋅ ⋅

------------------------------------------------------------- 0.0807==

N1 0.37–( )

0.48 3 0.25 0.0807⋅ ⋅(⋅ 2 0.35 0.0920⋅ ⋅ 0.40 0.1275⋅ )+ +----------------------------------------------------------------------------------------------------------------------------------------------- 7.5=<


3


of an actual IS-2000 1X system. For a more accurate estimation of packet data services, it isrecommended to utilize a simulation tool which simulates the dynamic resource allocationcapabilities of an IS-2000 1X system. The time-sliced simulation function of the NetPlan tool canbe used for this purpose. See Section 3.12 for more information on the simulation capabilities ofthe NetPlan tool.

Another aspect of the forward link capacity is the amount of base station transmission powerrequired. As the subscriber unit experiences more interference, it will request more power from itsserving base station to compensate for increased interference. Therefore, the transmission powerlimitations of the base station may place an upper limit on the forward capacity available.

3.7.1 Forward Link Noise Rise Capacity Limit

The forward link pole capacity is considered to be the point where additional power from the BTSsto support an additional user will cause the noise rise within the subscriber unit to increaseexponentially. This will create an unstable situation where user connections may be lost and thenetwork grade of service will be severely degraded.

The forward link noise rise pole capacity can be represented by the same equation that is providedin Equation 3-50. A graph of the forward noise rise pole capacity equation is the same as the onefor the reverse noise rise pole capacity equation which is shown in Figure 3-11.

In order to estimate the capacity from a number of users perspective, a forward noise rise capacitylimit must be selected. For CDMA RF system designs (for both IS-95A/B and IS-2000), a peaknoise rise of 10 dB is recommended to be the maximum that a system should tolerate (which is thesame limit for the reverse link). In order to account for the noise rise generated by the pilot, page,and sync overhead channels for the forward link, a de-rating of the noise rise limit is recommendedas follows.

Assumptions:Pilot = 20% of total power at maximum capacityPage = 75% of the pilot powerSync = 10% of the pilot powerPPStotal = 20% (for pilot) + 20% x 75% (for paging) + 20% x 10% (for sync) = 37%

Noise Rise De-rating:PPStotal = 37% of total power at maximum capacityTotal User Capacity = 100% - 37% = 63% of total power at maximum capacity10 dB noise rise limit = 10(10/10) = 10 linear unitsDe-rated Noise Rise Limit = 10 x 63% = 6.3 linear = 10log(6.3) = ~8.0 dB

Thus, the recommended de-rated peak noise rise limit is 8 dB. The average noise rise would beseveral dB below this peak value. It is important to note that the 8 dB noise rise limit is a peak valuewhich is associated with a certain probability factor (see Equation 3-48 and Section 3.4.3). Therecommended probability factors associated with the 8 dB peak noise rise recommendation are asfollows.


3


• 8 dB noise rise with a 90% probability factor (for aggressive capacity results)• 8 dB noise rise with a 95% probability factor (for moderate capacity results)• 8 dB noise rise with a 98% probability factor (for conservative capacity results)

Although the above recommendation provides some flexibility in selecting a probability factor, the8 dB noise rise with a 95% probability factor is the typical limit that is normally recommended.

3.7.2 Forward Noise Rise Capacity Estimation

To approximate the number of users that could be supported by a site while staying below a desirednoise rise limit, the following forward link capacity equations can be utilized.

A multi-service traffic loading factor, X, can be expressed as follows:

[EQ 3-55]

The mean value for the multi-service traffic loading factor, X, is expressed as:

[EQ 3-56]

The variance for the multi-service traffic loading factor, X, is expressed as:

[EQ 3-57]

The following equation provides the distribution of the noise rise, Z, for the multi-service traffic loading factor, X (which is the same equation provided for the reverse link, Equation 3-48):

[EQ 3-58]

Where:M Number of different service-types

Traffic load of the mth service-type (in Erlangs)

The energy-per-bit to total-interference-density target of the mth service-type

LN(10)/10

X L m( )

m 1=

M

∑ν m( )

PG m( )--------------×

Eb m( )NT

-------------× 1 α m( )–( ) i m( )+[ ]×=

E X[ ] L m( )

m 1=

M

∑ν m( )

PG m( )--------------× βε m( )

βσ m( )( )2

2---------------------+exp× 1 α m( )–( ) i m( )+[ ]×=

Var X( ) L m( )

m 1=

M

∑ψ m( ) ν m( )( )+

2

PG m( )( )2-----------------------------------× 2βε m( ) 2 βσ m( )( )2

+[ ]exp× 1 α m( )–( ) i m( )+[ ]×=

Z 10– Log10× 1 Pa Var X( ) E X[ ]–×–( )=

L m( )

Eb m( )NT

-------------

β


3


Average Eb/No (dB) of the mth service-type

Eb/No standard deviation, in dB of the mth service-type (to account for

inaccuracies in power control)

Activity Factor of the mth service-type

Mean Square of Activity Factor of the mth service-type (variance = 0.1)

Orthogonality of the channel of the mth service-type

Ratio of out of cell to in cell base station power received by the mth service-type,

where I =

Note: The terms I and i are equivalent to the terms F and f for the reverse link (seeEquation 3-13), but from a forward link perspective. For the forward link, theratio of out of cell to in cell base station power received, , is dependent upon

the individual user location and is therefore different for each user.

Processing gain (Bandwidth/Information rate) of the mth service

Z Interference rise (expressed in dB)

Pa Probability factor (inverse of the standard normal cumulative distribution) with adistribution having a mean of 0 and a standard deviation of 1 (see Section 3.4.3for more details regarding the probability factor)

In a scenario with multiple services, the equations are a bit more complex than for a single service.Basically, an average and variance needs to be determined for each service offered. The net rise,Z, will need to account for all of the users being handled by each service.

3.7.3 Forward Link Noise Rise Capacity Estimation Examples

The following section provides two examples of how to use the forward link noise rise capacityestimation equations provided in Section 3.7.2. The first example estimates the noise rise for asingle service type of traffic load of voice users only. The second example provides the calculationsrequired to estimate the noise rise for a multiple service type of traffic load with a mixture of voiceand data users.

ε m( )

σ m( )

ν m( )

ψ m( )

α m( )

i m( )

InCellInCell OutCell+-------------------------------------------- 1

1OutCellInCell

---------------------+------------------------------ 1

1 i+-----------==

i m( )

PG m( )


3


3.7.3.1 Example #1: Voice Only

The following example calculates the noise rise for, on average, 16.3 IS-2000 1X voice users at9600 bps, in a 3-sectored system with a 95% probability factor. Additional assumptions areprovided below.

Traffic Load:16.3 Voice users (average) at 9600 bps

General Assumptions:• 0.45 = I-factor (3 sector), where

• 1.64 = probability factor for 95% (Pa)• 0.23 = Beta value LN(10)/10 ( )

Traffic Load Assumptions: Voice @ 9600 bps• 16.3 = number of average users at 9600 bps ( )• 21.1 dB = Processing gain ( ) or 1228800/9600 = 128 linear• 6.34 dB = average Eb/No for 1% FER with vehicular fading at 30 kmph ( )• 2.5 dB = Eb/No standard deviation ( )• 0.56 = voice activity factor ( )• 0.1 = mean square of activity factor ( )• 0.6 = Orthogonality factor ( )

The first step is to calculate the mean value of the traffic loading factor, X, for the 16.3 averagevoice users by using Equation 3-56 (repeated below for reference).

Using the input variables from the assumptions above, E[X] is calculated as follows:

The next step is to calculate the variance for the traffic loading factor, X, for the 16.3 average voiceusers by using Equation 3-57 (repeated below for reference).

i m( )1I--- 1

10.45---------- 1–=–=

β

L m( )PG m( )

ε m( )σ m( )

ν m( )ψ m( )

α m( )

E X[ ] L m( )

m 1=

M

∑ν m( )

PG m( )--------------× βε m( )

βσ m( )( )2

2---------------------+exp× 1 α m( )–( ) i m( )+[ ]×=

E X[ ] 16.30.56128----------× 0.23( ) 6.34( )⋅ 0.23( ) 2.5( )⋅( )2

2---------------------------------------+exp× 1 0.6–( ) 1

0.45---------- 1–+×=

E X[ ] 0.115685 1.625527[ ]exp× 0.115685 5.081096 0.587805=×==

Var X( ) L m( )

m 1=

M

∑ψ m( ) ν m( )( )+

2

PG m( )( )2-----------------------------------× 2βε m( ) 2 βσ m( )( )2

+[ ]exp× 1 α m( )–( ) i m( )+[ ]×=


3


The final step is to calculate the noise rise, Z, for the 16.3 average voice users by usingEquation 3-58 (repeated below for reference).

dB

3.7.3.2 Example #2: Voice and Data Users

The following example calculates the noise rise for a multiple service type traffic load environmentconsisting of, on average, 6 IS-2000 1X voice users at 9600 bps, 1 IS-2000 1X data user at 19200bps, and 1 data user at 38400 bps. Additional assumptions are provided below.

Traffic Load:6 Voice users (average) at 9600 bps1 Data user (average) at 19200 bps1 Data user (average) at 38400 bps

General Assumptions:• 0.45 = I-factor (3 sector), where

• 1.64 = probability factor for 95% (Pa)• 0.23 = Beta value LN(10)/10 ( )

Traffic Load Assumptions: Voice @ 9600 bps• 6 = number of average users at 9600 bps ( )• 21.1 dB = Processing gain ( ) or 1228800/9600 = 128 linear• 6.34 dB = average Eb/No for 1% FER with vehicular fading at 30 kmph ( )• 2.5 dB = Eb/No standard deviation ( )• 0.56 = voice activity factor ( )• 0.1 = mean square of activity factor ( )• 0.6 = Orthogonality factor ( )

Var X( ) 16.30.1 0.56( )+

2

128( )2--------------------------------× 2 0.23( ) 6.34( )⋅ 2 0.23( ) 2.5( )⋅( )⋅ 2

+[ ]exp× 1 0.6–( ) 10.45---------- 1–+×=

Var X( ) 0.000668 3.582424[ ]exp× 0.000668 35.960611× 0.024004===

Z 10– Log10× 1 Pa Var X( ) E X[ ]–×–( )=

Z 10– Log10× 1 1.644848 0.024004 0.587805–×–( )=

Z 10– Log10× 0.157354( ) 8.03==

i m( )1I--- 1

10.45---------- 1–=–=

β

L m( )PG m( )

ε m( )σ m( )

ν m( )ψ m( )

α m( )


3


Traffic Load Assumptions: Data @ 19200 bps• 1 = number of average users at 19200 bps ( )• 18.1 dB = Processing gain ( ) or 1228800/19200 = 64 linear• 5.69 dB = average Eb/No for 5% FER with vehicular fading at 30 kmph ( )• 2.5 dB = Eb/No standard deviation ( )• 0.9 = data activity factor ( )• 0.1 = mean square of activity factor ( )• 0.6 = Orthogonality factor ( )

Traffic Load Assumptions: Data @ 38400 bps• 1 = number of average users at 38400 bps ( )• 15.1 dB = Processing gain ( ) or 1228800/38400 = 32 linear• 4.94 dB = average Eb/No for 5% FER with vehicular fading at 30 kmph ( )• 2.5 dB = Eb/No standard deviation ( )• 0.9 = data activity factor ( )• 0.1 = mean square of activity factor ( )• 0.6 = Orthogonality factor ( )

The first step is to calculate the mean value of the traffic loading factor for the 6 average voice usersat 9600 bps by using Equation 3-56. Using the input variables from the assumptions above,E[X]9600 is calculated as follows:

Now, calculate the mean value of the traffic loading factor for the 1 average data user at 19200 bpsby using Equation 3-56. Using the input variables from the assumptions above, E[X]19200 iscalculated as follows:

Now, calculate the mean value of the traffic loading factor for the 1 average data user at 38400 bpsby using Equation 3-56. Using the input variables from the assumptions above, E[X]38400 iscalculated as follows:

L m( )PG m( )

ε m( )σ m( )

ν m( )ψ m( )

α m( )

L m( )PG m( )

ε m( )σ m( )

ν m( )ψ m( )

α m( )

E X[ ] 9600 60.56128----------× 0.23( ) 6.34( )⋅ 0.23( ) 2.5( )⋅( )2

2---------------------------------------+ 1 0.6–( ) 1

0.45---------- 1–+×exp×=

E X[ ] 9600 0.042583 1.625527[ ]exp× 0.042583 5.081096 0.216370=×==

E X[ ] 19200 10.964-------× 0.23( ) 5.69( )⋅ 0.23( ) 2.5( )⋅( )2

2---------------------------------------+exp× 1 0.6–( ) 1

0.45---------- 1–+×=

E X[ ] 19200 0.022813 1.475859[ ]exp× 0.022813 4.374791 0.099800=×==

E X[ ] 38400 10.932-------× 0.23( ) 4.94( )⋅ 0.23( ) 2.5( )⋅( )2

2---------------------------------------+exp× 1 0.6–( ) 1

0.45---------- 1–+×=


3


Finally, calculate the total loading factor E[X]Total for all user types by summing together all of theindividual results.

The next step is to calculate the variance for the traffic loading factor for the 6 average voice usersat 9600 bps by using Equation 3-57. Using the input variables from the assumptions above,Var(X)9600 is calculated as follows:



Finally, calculate the total variance Var(X)Total for all user types by summing together all of theindividual results.

The final step is to calculate the noise rise, Z, for the total traffic load using a 95% probability factorby using Equation 3-58 (as shown below).

E X[ ] 38400 0.045625 1.303164[ ]exp× 0.045625 3.680926 0.167942=×==

E X[ ] Total 0.216370 0.099800 0.167942 0.484112=+ +=

Var X( )9600 60.1 0.56( )+

2

128( )2--------------------------------× 2 0.23( ) 6.34( )⋅ 2 0.23( ) 2.5( )⋅( )⋅ 2

+[ ]exp× 1 0.6–( ) 10.45---------- 1–+×=

Var X( )9600 0.000246 3.582424[ ]exp× 0.000246 35.960611× 0.008836===

Var X( )19200 10.1 0.9( )+

2

64( )2-----------------------------× 2 0.23( ) 5.69( )⋅ 2 0.23( ) 2.5( )⋅( )⋅ 2

+[ ]exp× 1 0.6–( ) 10.45---------- 1–+×=

Var X( )19200 0.000360 3.283088[ ]exp× 0.000360 26.657952× 0.009608===

Var X( )38400 10.1 0.9( )+

2

32( )2-----------------------------× 2 0.23( ) 4.94( )⋅ 2 0.23( ) 2.5( )⋅( )⋅ 2

+[ ] 1 0.6–( ) 10.45---------- 1–+×exp×=

Var X( )38400 0.001442 2.937699[ ]exp× 0.001442 18.872371× 0.027207===

Var X( )Total 0.008836 0.009608 0.027207 0.045650=+ +=


3


dB

3.7.4 Forward Link Noise Rise Capacity Estimates for IS-2000 1X

In order to calculate the capacity supported by the air interface in an IS-2000 1X system, it isimportant to determine the values of the various factors that affect the capacity. The IS-2000 1Xforward link capacity estimates (throughput and Erlangs) provided in this document are based onthe forward link noise rise capacity estimation equations provided in Section 3.7.2 and utilizing theparameter value assumptions that follow.

The following are the assumptions for the various IS-2000 1X parameter values to be applied tothe forward link noise rise capacity estimation equations.

3.7.4.1 Noise Rise

For the purpose of determining capacity estimates, a 10 dB maximum noise rise value was selected.As shown in Section 3.7.1, this 10 dB limit is de-rated to 8 dB in order to account for the overheadchannels. Additionally, each rise has a probability factor, Pa, associated with it. Table 3-11provides some of the recommended noise rise values and probability factors used for this exercise.

Since the probability factor is associated with a normal distribution, the 50% probability factorimplies an average noise rise value. Therefore, for the scenarios where the probability factor isgreater than 50%, the average noise rise will be less than the rise value shown. This can beillustrated further through Figure 3-12, where the 50% probability factor is associated with theaverage point in the normal distribution curve. However, a higher probability factor would beassociated with a value that is greater than the average value.

The capacity tables shown in Section 3.7.4.10 provide both the capacity (in Erlangs andthroughput) and the average rise values associated with a 8 dB peak noise rise for the 90%, 95%,and 98% probability factors. Typical RF designs should strive to keep the peak percentileprobability reverse noise rise value less than 8 dB.

Various probability factors were used in scenarios to estimate the capacity for aggressive (90%),

Table 3-11: Interference Rise Scenarios

PercentileProbability (Pa)

AssociatedNoise Rise (Z)

90% 8 dB95% 8 dB98% 8 dB

Z 10– Log10× 1 Pa Var X( )Total E X[ ]–× Total–( )=

Z 10– Log10× 1 1.644848 0.045650 0.484112–×–( )=

Z 10– Log10× 0.164450( ) 7.84==


3


moderate (95%), or conservative (98%) cases. Additionally, a rise value of less than 8 dB can beused to demonstrate the impact on capacity, in order to trade capacity for increased forward linkcoverage.

In all of the test cases, the cell loading is considered uniform in each sector (homogeneous network)and as such the rise is the same across each cell. In practice, the non-homogeneous nature of cellloading will mean that an individual cell may be able to cope with a peak load higher than thehomogeneous case.

3.7.4.2 I-factor

I-factor is the ratio of own cell interference to own cell plus other cell interference from thesubscriber perspective. The ratio of out of cell to in cell base station power received by thesubscriber is the parameter. The I-factor and parameter have the following relationship.

where I = or

[EQ 3-59]

The terms I and i are equivalent to the terms F and f for the reverse link (see Equation 3-13), butfrom a forward link subscriber perspective. For the forward link, the ratio of out of cell to in cellbase station power received by user m, , is dependent upon the individual user location and is

therefore different for each user.

For this exercise, the following I-factors have been assumed:

3.7.4.3 Average Eb/No

Eb/No is defined as energy per bit to the noise spectral density. The appropriate value for therequired Eb/No is such that the desired bit, block, or frame erasure rate of the received signal isachieved. This gives an indication of the lowest signal strength that the subscriber receiver candetect above a certain noise level. Such items as the subscriber speed, the propagationenvironment, and power control impact the required Eb/No.

Table 3-12: I-factor

Site Type I-factorOmni 0.60

3-Sector 0.456-Sector 0.40

i m( ) i m( )

InCellInCell OutCell+-------------------------------------------- 1

1OutCellInCell

---------------------+------------------------------ 1

1 i+-----------==

i1I--- 1–=

i m( )


3


The Eb/No numbers used for each data rate in this document are typical numbers that are used fordimensioning purposes. The Eb/No values were obtained from forward link level simulations. TheEb/No values used for this exercise are shown in Table 3-13.

In looking at Equation 3-56 and Equation 3-57 again, the number of users is inversely proportionalto the Eb/No in order to maintain the same average and variance load factor. That is, an increase inthe Eb/No will result in a decrease in the number of users. A decrease to the Eb/No will result in anincrease to the number of users.

3.7.4.4 Eb/No Standard Deviation

A standard deviation of 2.5 dB on the Eb/No is assumed for each rate. This standard deviation forthe Eb/No is used to adjust the average Eb/No to compensate for imperfect power control in the realworld environment.

The number of users is inversely proportional to the Eb/No standard deviation in order to maintainthe same average and variance load factor. That is, an increase in the Eb/No standard deviation willresult in a decrease in the number of users. A decrease to the Eb/No standard deviation will resultin an increase to the number of users.

The Eb/No standard deviation has been assumed to be the same for each data rate. In a real worldsituation this may not be the case, but for an estimate of the capacity (as used for this exercise), onevalue has been assumed for all services.

3.7.4.5 Processing Gain

The processing gain is the ratio of the chip rate to the bit rate. For IS-2000 1X, the chip rate is equalto 1.2288 x 106

chips/s. The calculation of the processing gain in linear and in dB units are providedbelow.

Processing Gain linear =

Processing Gain db =

Where:W Bandwidth (1.2288 Mcps for IS-2000 1X)

R Information rate

W R⁄

10 Log10 W R⁄( )×


3


The following table provides a summary of the Eb/No, Eb/No Standard Deviation, and theprocessing gain values for the various data rates that were used in this exercise.

Recall that the Eb/No values shown in the above table were obtained from forward link levelsimulations and represent typical values that are used for dimensioning purposes. The Eb/No valueswill vary based on the subscriber speed, propagation conditions, percent FER, etc. For detailedcapacity and coverage results, Motorola recommends using the NetPlan simulation tool. Thissimulation tool incorporates a family of Eb/No curves as opposed to only a few Eb/No values.

The bearer rate data in Table 3-13 represents a data link layer rate from the subscriber’sperspective. It does not include any overhead (RLP, framing, etc.). The bearer rates in Table 3-13are used in the calculation of the throughput capacity (see Section 3.7.4.9).

3.7.4.6 Activity Factor

The activity factor is defined as the percentage of time that a user transmits on an active trafficchannel. With IS-95, a typical industry accepted voice activity factor was 40%. This roughlyequated to 32% of the time the user was at full rate and 68% of the time the user was at eighth rate.With IS-2000 1X, an adjustment to the voice activity factor of 16% is recommended to account forthe impact of the forward power control bits. Thus a 40% voice activity factor is adjusted up to56%.

It should be noted that this adjusted activity factor (56%) is utilized in the capacity equation as ameans to derate the capacity due to the forward power control bits. In converting the voice usersto an equivalent throughput, the voice activity factor of 40% (0.4) is used.

For the capacity results provided in this section, two different data activity factors (0.9 and 0.2) areassumed to shown the impact of a high and low data activity factor user type.

The number of users is inversely proportional to the activity factor in order to maintain the sameaverage and variance load factor. That is, an increase in the activity factor will result in a decreasein the number of users. A decrease to the activity factor will result in an increase to the number ofusers.

Table 3-13: IS-2000 1X Average Eb/No Values

Bearer Rate(bits/s)

Data Rate(bits/s)

FER Eb/No (dB) Eb/No Std.Dev. (dB)

Proc. Gain(dB)3 kmph 30 kmph

8600 9600 1% 7.56 6.34 2.5 21.114400 19200 5% 6.53 5.69 2.5 18.132000 38400 5% 5.65 4.94 2.5 15.164000 76800 5% 4.90 4.53 2.5 12.0128800 153600 5% 5.10 4.86 2.5 9.0


3


3.7.4.7 Orthogonality Factor

CDMA utilizes orthogonal Walsh codes to separate the multiple users or multiple channels in thedownlink. In the absence of multipath propagation, the orthogonality of the signal received by thesubscriber would be the same as that which is sent by the base station. However, since multipathpropagation can produce sufficient delay spread in the radio channel, the subscriber will see partof the base station signal as multiple access interference.

An orthogonality of 1 corresponds to perfectly orthogonal users. Typically, the orthogonality isbetween 0.4 and 0.9 in multipath channels.

For the capacity analysis provided in this section, an orthogonality factor of 0.6 is used for thevehicular (30 kmph) capacity results and a value of 0.9 is used for the pedestrian (3 kmph) capacityresults. These values correspond to the ITU Vehicular A channel and ITU Pedestrian A channelrespectively.

3.7.4.8 Traffic Mix

Four different traffic mix scenarios were analyzed as reflected in the following table.

The percentage of users can be interpreted, for example, as follows. In Scenario A, 100% of theusers are voice users at 8.6 kbps. In this scenario, all users in the network are continuouslyreceiving the relevant voice activity and at the required signal level to reach their respective Eb/Novalue. For Scenario C, 50% of the users are voice users at 8.6 kbps, 40% of the users are using 64kbps, and the remaining 10% of the users are at 128.8 kbps.

3.7.4.9 Throughput Capacity

With multiple rate high-speed data services being introduced into the call model traffic mix, thecapacity of a cell/sector should now be quantified with a throughput value in addition to the numberof Erlangs. For the capacity analysis results provided below, the estimated throughput capacity iscalculated by multiplying the bearer rate, the activity factor, and the number of supported users(continuously transmitting users) together.

For a single data rate user example, consider scenario A with a rise of 8 dB and a probability factorof 95% (see Table 3-15). The voice rate assumed is 8.6 kbps and as such, approximately 14.3Erlangs at the pedestrian speed can be supported in a single sector of a 3-sectored cell. This

Table 3-14: Traffic Mix

Scenario Bearer ServiceVoice (8.6 kbps) 64 kbps 128.8 kbps

A 100% - -B 80% 20% -C 50% 40% 10%D 10% 60% 30%


3


corresponds to a throughput capacity of approximately 49 kbps / sector (8.6 kbps x 0.40 AF x 14.3Erlangs). As stated previously (see Section 3.7.4.6), an adjusted activity factor is utilized in thecapacity equation as a means to derate the capacity due to the forward power control bits. Inconverting the voice users to an equivalent throughput capacity, the non-adjusted voice activityfactor of 40% (0.4) is used for the throughput calculation, instead of the adjusted activity factor ofapproximately 56% (as calculated in Section 3.7.4.6).

For a multiple data rate mixture of users, the throughput capacity is calculated for each individualdata rate user type and then summed together. For example, consider traffic mix scenario C with aprobability of 95% and a data activity factor of 20%. From the results in Table 3-15, an estimated6.6 Erlangs at the pedestrian speed can be supported in a single sector of a 3-sectored cell with atotal throughput of 62 kbps. The traffic distribution for scenario C is 50% for 8.6 kbps voice users,40% for 64.0 kbps data users, and 10% for 128.8 kbps data users. According to the trafficdistribution of scenario C, the throughput capacity is calculated as follows.

8.6 kbps Voice User Thruput = 8.6 kbps x 0.4 AF x (6.6 x 0.5) Erlangs = 11.4 kbps64.0 kbps Data User Thruput = 64.0 kbps x 0.2 AF x (6.6 x 0.4) Erlangs = 33.8 kbps128.8 kbps Data User Thruput = 128.8 kbps x 0.2 AF x (6.6 x 0.1) Erlangs = 17.0 kbps

Total Throughput = 62.2 kbps

3.7.4.10 IS-2000 1X Forward Noise Rise Capacity Analysis Results

The following two tables provide capacity values (expressed as kbps throughput and Erlangs) persector for the various scenarios assuming an interference rise limit of 8 dB but with varying levelsof probability. For the traffic mix scenarios which include data users (Scenarios B, C, and D),capacity results for two different Data Activity Factors (AF) are provided. A 90% Data AF is usedto estimate the results of high data activity factor users such as a File Transfer Protocol (FTP) user.A 20% Data AF is used to estimate the results of lower data activity factor users such as a LowSpeed Packet Data (LSPD) or a High Speed Packet Data (HSPD) user.


3


All of the traffic mix scenarios in Table 3-15 below assume pedestrian (3 kmph) Eb/No values withan orthogonality factor of 0.9.

Table 3-15: Forward Capacity per Sector for Various Probabilities of Rise - Pedestrian

Scenario Rise Probability

DataAF

Avg Rise(dB)


A 98% N/A 3.0 77 44 37 22.3 12.9 10.7

95% N/A 3.5 85 49 41 24.6 14.3 11.8

90% N/A 4.1 93 54 44 27.0 15.6 12.9

B 98% 90% 1.6 88 51 42 6.2 3.6 3.0

98% 20% 2.4 89 52 43 16.7 9.7 8.0

95% 90% 2.0 106 62 51 7.5 4.3 3.6

95% 20% 2.8 102 59 49 19.1 11.1 9.2

90% 90% 2.5 127 73 61 8.9 5.1 4.3

90% 20% 3.4 115 67 55 21.6 12.5 10.4

C 98% 90% 1.1 76 44 37 2.1 1.2 1.0

98% 20% 1.6 89 52 43 9.5 5.5 4.5

95% 90% 1.5 97 56 46 2.7 1.5 1.3

95% 20% 2.0 108 62 52 11.4 6.6 5.5

90% 90% 1.9 121 70 58 3.3 1.9 1.6

90% 20% 2.5 128 74 61 13.6 7.9 6.5

D 98% 90% 1.0 71 41 34 1.0 0.6 0.5

98% 20% 1.2 87 51 42 5.5 3.2 2.7

95% 90% 1.3 91 53 44 1.3 0.8 0.6

95% 20% 1.6 109 63 52 6.9 4.0 3.3

90% 90% 1.7 116 67 56 1.7 1.0 0.8

90% 20% 2.1 134 78 64 8.5 4.9 4.1


3


All of the traffic mix scenarios in Table 3-16 below assume vehicular (30 kmph) Eb/No values with an orthogonality factor of 0.6.

The results in Table 3-15 and Table 3-16 show the capacity estimates for an IS-2000 1X forwardlink under the stated configurations, assumptions, and parameter values. As shown above, thecapacity estimate can vary greatly depending upon the parameter values that are chosen. Althoughthe stated assumptions and parameter values used for this exercise are deemed to be realistic, theaccuracy of the capacity estimate is highly dependent upon the accuracy of the assumptions andparameter values used for the capacity estimate.

Table 3-16: Forward Capacity per Sector for Various Probabilities of Rise - Vehicle

Scenario RiseProbability

DataAF

Avg. Rise(dB)


A 98% N/A 3.3 78 51 44 22.7 14.9 12.7

95% N/A 3.8 85 56 48 24.8 16.3 13.9

90% N/A 4.4 92 61 52 26.8 17.6 15.0

B 98% 90% 1.6 75 49 42 5.3 3.5 3.0

98% 20% 2.4 82 54 46 15.4 10.1 8.7

95% 90% 2.0 91 60 51 6.4 4.2 3.6

95% 20% 2.9 93 61 52 17.6 11.6 9.9

90% 90% 2.6 108 71 60 7.5 5.0 4.2

90% 20% 3.5 105 69 59 19.8 13.0 11.1

C 98% 90% 1.1 62 41 35 1.7 1.1 1.0

98% 20% 1.6 75 49 42 7.9 5.2 4.5

95% 90% 1.5 78 51 44 2.2 1.4 1.2

95% 20% 2.0 90 59 51 9.6 6.3 5.4

90% 90% 2.0 98 64 55 2.7 1.8 1.5

90% 20% 2.6 107 70 60 11.3 7.5 6.4

D 98% 90% 1.0 57 37 32 0.8 0.5 0.5

98% 20% 1.3 70 46 39 4.4 2.9 2.5

95% 90% 1.3 73 48 41 1.0 0.7 0.6

95% 20% 1.7 87 57 49 5.5 3.6 3.1

90% 90% 1.8 92 61 52 1.3 0.9 0.7

90% 20% 2.2 106 70 60 6.7 4.4 3.8


3


The following figure shows the relationship between the forward link noise rise and the throughputfor several probability curves. The input parameters used to create the figure are shown below. The50%-ile curve corresponds to the average rise.

Figure 3-17: Forward Link Rise vs. Throughput






• I-factor = 0.45 (3-sector cell site configuration)


• Forward link orthogonality factor = 0.6 (30 kmph)


0

2

4

6

8

10

0 50 100 150 200 250

Throughput (Kbps)

No

ise

Ris

e (d

B)

98% 95% 90% 85% 75% 50%


3


The following figure shows the relationship between forward link noise rise and Erlangs of variousdata rates. The input parameters used to create the figure are shown below.

Figure 3-18: Forward Link Rise vs. Erlangs for Different Data Rates


Parameters:• Voice and data activity factor = 57.6%







The curves in the figure above show the significant impact that data users can have on the capacityof a system. The voice and data activity factors were purposely set to the same value in order toreflect the capacity impact of just varying the data rate.

0

1

2

3

4

5

6

7

8

9

10

0 5 10 15 20 25 30

Erlangs

No

ise

Ris

e (d

B)

Voice @ 9600 Data @ 19200 Data @ 38400 Data @ 76800


3


The following figure shows the relationship between the forward link total throughput and totalErlangs with respect to the data activity factor. The input parameters used to create the figure areshown below.

Figure 3-19: Forward Link Total Erlangs & Throughput vs. Data Activity Factor



• Peak noise rise = 8 dB








0

10

20

30

40

50

60

70

80

90%80%70%60%50%40%30%20%10%


To

tal T

hru

pu

t (K

bp

s)

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

To

tal E

rlan

gs

Total Thruput Total Erlangs


3


3.8 Forward vs. Reverse Link Capacity Comparison

The Reverse Link Noise Rise Capacity Estimation approach provided in Section 3.4 is almostidentical to the Forward Link Noise Rise Capacity Estimation approach provided in Section 3.7.The following section will compare the IS-2000 1X capacity results of the forward and reverselinks using the same assumptions and parameter values as stated in the previous sections (refer tothe previous sections for specific details regarding the assumptions and parameter values used).

Figure 3-20 shows a comparison of the IS-2000 1X forward and reverse links for the noise rise vs.throughput capacity results for a 95% probability factor capacity estimation.

Figure 3-20: Forward and Reverse Link Rise vs. Throughput - 95% Probability Factor


Parameters: (unless otherwise noted, the parameters below apply to both forward and reverse links)• Traffic mix = Scenario B




• F-factor or I-factor = 0.45 (3-sector cell site configuration)

• Vehicular (30 kmph) Eb/No assumptions from Table 3-6 and Table 3-13 were used



0

2

4

6

8

10

0.0 20.0 40.0 60.0 80.0 100.0

Throughput (Kbps)

No

ise

RIs

e (d

B)

Fwd 95% Rev 95%


3


Figure 3-21 shows a comparison of the IS-2000 1X forward and reverse links for the noise rise vs.Erlangs, capacity results for the 9600 and 19200 bps data rates.

Figure 3-21: Forward and Reverse Link Rise vs. Erlangs for Different Data Rates


Parameters: (unless otherwise noted, the parameters below apply to both forward and reverse links)• Voice and data activity factor = 57.6%







The voice and data activity factors were purposely set to the same value in order to reflect thecapacity impact of just varying the data rate.

0

1

2

3

4

5

6

7

8

9

10

0 5 10 15 20 25 30

Erlangs

No

ise

Ris

e (d

B)

Fwd Voice @ 9600 Fwd Data @ 19200 Rev Voice @ 9600 Rev Data @ 19200


3


Figure 3-22 shows a comparison of the IS-2000 1X forward and reverse links for Erlangs andthroughput capacity vs. data activity factor.

Figure 3-22: Forward and Reverse Link Erlangs & Thruput vs. Data Activity Factor


Parameters: (unless otherwise noted, the parameters below apply to both forward and reverse links)• Traffic mix = Scenario B

• Forward peak noise rise = 8 dB

• Reverse peak noise rise = 10 dB








The results from all of the figures (Figure 3-20, Figure 3-21, and Figure 3-22) above, show theforward link with less capacity than the reverse link. In a general sense, the forward link may haveless capacity than the reverse link, but the difference between the two may not be as wide asdepicted in the figures above. Keep in mind that utilizing different assumptions and parameters

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

22.0

24.0

90% 80% 70% 60% 50% 40% 30% 20% 10%


To

tal E

rlan

gs

0

20

40

60

80

100

120

Th

rou

gh

pu

t (K

bp

s)

Fwd Erlangs Rev Erlangs Fwd Thruput Rev Thruput


3


may be able to close the gap between the forward and reverse links, or even produce results whichshow the reverse link with less capacity than the forward link.

For example, Figure 3-23 shows a comparison of the IS-2000 1X forward and reverse links forErlangs and throughput capacity vs. data activity factor using the following parameter changesmentioned below the figure.

Figure 3-23: Alternate Forward and Reverse Link Erlangs & Thruput vs. Data Activity Factor


Parameters: (All of the parameters for Figure 3-22 were used, except for the following changes)• Forward Eb/No @ 9600 = 4.4 dB (Figure 3-22 utilized a value of 6.34 dB)

• Forward Eb/No @ 76800 = 3.3 dB (Figure 3-22 utilized a value of 4.53 dB)

• Forward link orthogonality factor = 0.7 (Figure 3-22 utilized a value of 0.6)

The results in Figure 3-23 show that the forward link capacity is now equal to or slightly better thanthat of the reverse link. It is important to note that the parameter changes stated above are realisticparameters to use to model certain propagation environments (i.e. depending upon the multipath,ray imbalance, and geometry environment). Although the forward link may have a higher capacitythan that of the reverse link (similar to the results in Figure 3-23) in some areas of a system, thegeneral expectation is that the forward link will be the limiting factor from a capacity perspective(similar to the results in Figure 3-22, but maybe not as wide of a gap). Which link will be thelimiting factor from a capacity perspective will depend upon the assumptions and parameter valuesused for a particular system analysis. As stated previously, the accuracy of the capacity estimate ishighly dependent upon the accuracy of the assumptions and parameter values used for the capacityestimate.

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

22.0

24.0

90% 80% 70% 60% 50% 40% 30% 20% 10%


To

tal E

rlan

gs

0

20

40

60

80

100

120

Th

rou

gh

pu

t (K

bp

s)

Fwd Erlangs Rev Erlangs Fwd Thruput Rev Thruput


3


It should also be mentioned that these results are what the BTS sector may be able to support. Thedata applications being used by the subscriber unit may be more demanding on one link over theother. For instance, the user may request a file to be downloaded. To request the file will place asmall load on the reverse link, but depending on the size of the file to be downloaded, the load onthe forward link may be quite larger. This is commonly referred to as asymmetrical data transfer.This asymmetrical data transfer will be another reason why one of the links will be the limiting linkwith regards to capacity.

3.9 EIA/TIA Specifications and RF Air Interface Limitations

The CDMA RF Air Interface specifications defines the structure of the Forward and ReverseChannel. These specifications place an upper limitation on the number of channels that can beserved by a CDMA frequency. The following sections provide Forward and Reverse Channelstructure overviews for both IS-95 and IS-2000 Air Interface specifications.

3.9.1 IS-95 Forward Channel Structure

The following figure shows an example of the code channels transmitted by a base station. Out ofthe 64 code channels available for use, the example depicts the Pilot Channel (always required),one Sync Channel, seven Paging Channels (the maximum allowed), and fifty-five TrafficChannels.

Figure 3-24: Example of IS-95 Forward CDMA Channels

Code channels on the forward link are addressed by different Walsh codes. Each of these codechannels is spread by the appropriate Pseudo-Noise Sequence at a fixed Chip Rate of 1.2288 Mega-Chips per second. The uniqueness of the forward channel structure is the use of the Pilot Channel.It is transmitted by each cell site and is used as a coherent carrier reference for demodulation by allsubscriber stations. The pilot signal is unmodulated and uses the zeroth Walsh code which consistsof 64 zeros. Hence, the pilot simply contains the I and Q spreading code. The choice of this codeallows the subscriber to acquire the system faster. The Walsh codes are generated with a 64 x 64Hadamard Matrix. Thus, the maximum number of code channels per carrier is 64 which consistsof a Pilot Channel, a Sync Channel, a maximum of 7 Paging Channels and a minimum of 55 TrafficChannels (TCH). In view of the channel structure, a 1.23 MHz CDMA carrier can support up to 55TCHs if the effect of interference is not considered. Another possible configuration could replace

PILOT CH SYNC CHPAGING

CH 1PAGING

CH 7TCH 1 TCH 55

WALSH 0 WALSH 32 WALSH 1 WALSH 63

CDMA FORWARD CHANNEL1.23 MHz

Traffic Power Control Data Sub-Channel (ADDRESSED BY WALSH CODE)

up to


3


Paging Channels and Sync Channels one for one with TCHs to obtain a maximum of 63 TCHs, 1Pilot Channel, 0 Paging Channel, and 0 Sync Channel. In practice, due to the intense interferencein the spectrum, a satisfactory quality of service in terms of voice quality and FER is difficult tomaintain if all 55 traffic channels are implemented in the system.

The CDMA equipment requires a carrier frequency, a pilot offset, and a Walsh code to encode/decode the channel. The Base Station System (BSS) allocates a Traffic Channel in response to theAssignment Request message from the MSC. The BSS does not allocate traffic channels unless arequest from the MSC is acknowledged. The Traffic Channel will be allocated in the sector withwhich the call is associated.

The BSS maintains a pool of Traffic Channels and Walsh codes in each sector for new call setupsand soft/softer handoffs. Traffic Channel allocation for new originations and soft handoffs requirean assignment of a physical Traffic Channel and a Walsh code. Softer handoff requires just theassignment of a Walsh code, no new Traffic Channel element has to be assigned. The assignmentof Walsh codes and Traffic Channels is separated to allow the allocation process to adjust for thedifferent needs of soft and softer handoff. In order to reduce the risk of soft/softer handoffassignment failure during the conversation, the BSS denies assignment of Traffic Channels andWalsh codes for new call setups if Traffic Channels or Walsh codes are not available or being usedfor soft/softer handoffs.

The number of Traffic Channels is defined by the In-Service Hardware in the BSS. It could be lessthan the number configured if some of the hardware is out of service. The number of Walsh codesassigned to a sector is set to 64 which is the maximum specified by the EIA/TIA standard. Limitingthe number of Walsh codes in a sector is a method of controlling service quality. Since Walsh codesare not associated with any hardware, they cannot go out of service. As a result, 64 is the hard limitof the number of code channels per sector according to the protocol specifications.

3.9.2 IS-95 Reverse Channel Structure

The Reverse CDMA Channel is composed of Access Channels and Reverse Traffic Channels.These channels share the same CDMA frequency assignment. Each Traffic Channel is identifiedby a distinct user long code sequence and each Access Channel is identified by a distinct AccessChannel long code sequence. The following figure shows as example of the signals received by abase station on the Reverse CDMA Channel.


3


Figure 3-25: Example of IS-95 Reverse CDMA Channels

The reverse link employs the same 32768 length binary short PN sequences which are used for theforward link. However, unlike on the forward link, a fixed code phase offset is used. A long PNsequence (242-1) with a user-determined time offset is used to identify the subscriber (analogousto ESN in AMPS). The sequence is then modulo-2 added with a 42 bit wide mask.

The subscriber unit convolutionally encodes the data transmitted on the Reverse Traffic Channeland the Access Channel prior to interleaving. The transmitted digital information is convolutionalencoded using a rate 1/3 code of constraint length 9 for the Access Channel and for Rate Set 1 ofthe Reverse Traffic Channel. For Rate Set 2 of the Reverse Traffic Channel, the convolutional coderate is 1/2. The encoded information is then interleaved over a 20 ms interval. The interleavedinformation is then grouped in code words which consist of 6 symbol groups each. These codewords are used to select one of the 64 orthogonal Walsh codes for transmission. On the reverse link,the Walsh codes are used for information transmission. The reverse CDMA frequency channel cansupport up to 62 TCHs per Paging Channel and 32 Access Channels per Paging Channel.

3.9.3 IS-2000 1X Forward Channel Structure

The following figure shows the Forward Channel Structure for IS-2000.

ACCESS ACCESSCH N

TCH 1 TCH M

CDMA REVERSE CHANNEL

1.23 MHz

CH 0

(ADDRESSED BY LONG PSEUDO-NOISE CODE)

(received at the base station)


3


Figure 3-26: Example of IS-2000 Forward CDMA Channels

3.9.3.1 IS-2000 Forward Channels (Motorola Implementation)

The Common Assignment, Common Power Control, Common Control, and Broadcast Channelsare not implemented in CBSC Release 16. In the Common Pilot Channels, only the Forward PilotChannel is implemented for CBSC Release 16. The following sections provide a brief descriptionof the forward channels that are supported for CBSC Release 16.

Forward Pilot Channel (F-PICH)The IS-2000 Forward Pilot Channel is identical to the Pilot Channel in IS-95A/B, for backwardscompatibility. It is transmitted by each cell site and is used as a coherent carrier reference fordemodulation by all subscriber stations. The pilot signal is un-modulated and uses Walsh code 0,which consists of 64 zeros. A Walsh code can be expressed as a Walsh Function Wn

L, where n =Walsh code number and L = Walsh code length. The Walsh code for a F-PICH can be representedas W0

64. The Pilot Channels do not carry any information and essentially consist of Short PNcodes. A Short PN code pair is generated by a modified linear feedback shift register. The pilotsimply contains the I and Q spreading code.

Forward CDMA Channels

Quick PagingChannels(0-3)

[F-QPCH]

FundamentalChannel (0 or 1)

[F-FCH]

Supplemental CodeChannels (0-7)

[F-SCCH]

PilotChannel

[F-PICH]

Transmit Diversity Pilot Channel[F-TDPICH]

Auxiliary PilotChannel

[F-APICH]

Auxiliary TransmitDiversity Pilot Chan.

[F-ATDPICH]

Common PagingChannels

DedicatedChannels

Dedicated Control Channel (0 or 1)

[F-DCCH]

SupplementalChannels (0-2)

[F-SCH]

PagingChannels (0-7)

[F-PCH]

CommonPilot

Channels

Common PowerControl Channel

[F-CPCCH]

Common ControlChannel

[F-CCCH]

CommonChannels

Common AssignmentChannel

[F-CACH]

SyncChannel

[F-SYNC]

BroadcastChannel[F-BCH]

= Channels NOT implemented in CBSC Release 16


3


Forward Sync Channel (F-SYNC)The Forward Sync Channel is used by the subscriber stations operating within the coverage areaof the base station to acquire CDMA System time and Long PN code synchronization. It alsotransmits the system Protocol Revision (P_REV). There is only one Sync Channel per omni-carrierand there is a Sync Channel for each sector-carrier for sectored cells. The Sync Channel is spreadby Walsh 32 of length 64 (W32

64), just as in IS-95A/B. The bit rate for the Sync Channel is 1200bps and the frame is 26.67ms in duration. For CBSC Release 16, the Sync Channel supports newredirection fields which can redirect subscribers to carriers that support Radio Configurationsgreater than 2 and the Forward Quick Paging Channel (F-QPCH).

Forward Paging Channel (F-PCH)The Forward Paging Channel functionality is basically the same as an IS-95A/B Paging Channelexcept that there exists new messages specified for IS-2000. The base station uses the PagingChannel to transmit overhead/SMS messages, pages, acknowledgements, channel assignments,and authentications to idle subscribers. IS-2000 supports up to 7 Paging Channels per sector-carrier, but as in earlier releases, CBSC Release 16 only supports 1 Paging Channel per sector-carrier. The primary Paging Channel number is Paging Channel number 1. This is the mode wherethe IS-2000 handset emulates an IS-95A/B handset. It is spread by a Walsh i of length 64 (Wi

64),where ‘i’ is the Paging Channel number. The bit rate that a Paging Channel uses is 9600 bps or4800 bps.

Forward Quick Paging Channel (F-QPCH)The Forward Quick Paging Channel is introduced in IS-2000 to enhance the subscriber’s idle timebattery life. It is used by the base station to inform subscriber stations, operating in the slotted mode(where the subscriber only “listens” during an assigned slot), that a page will be transmitted on thenext designated slot on the Paging Channel. It is covered by Walsh code 80, 48, or 112 of length128 (W80

128,W48128,W112

128). The bit rate for a Quick Paging Channel is 4800 or 2400 bps and itis divided into 2048 slots of 80ms duration (the same number of slots as a Paging Channel asdetermined by the slot cycle index). A subscriber will hash (based upon the IMSI) to 1 of 376 bits(for 4800 bps) or 1 of 188 bits (for 2400 bps) to determine whether it needs to monitor the PagingChannel slot for an impending page message. The slots are sub-divided into Paging Indicators andConfiguration Change or Broadcast Indicators. Two Paging Indicators are transmitted in eachQPCH slot for each subscriber station that will be paged in the associated Paging Channel slot.

Prior to the occurrence of the Quick Paging/Paging slot, the Access/Paging MCC determines thePaging Indicator bits based on the page messages found which support Quick Paging. It buffers thebits and transmits them when the Quick Paging Channel slot begins. As shown in Figure 3-27,approximately 20ms after the QPCH slot, the associated paging messages are transmitted on thePaging Channel. The Access/Paging MCC schedules only those page messages which have beenquick paged on the QPCH slot which occurred 100ms prior to this PCH slot as shown in the figure.Each paging indication is a single bit at a data rate of 4800 bps or 2400 bps. The effective rate is9600 bps or 4800 bps, respectively as each bit is sent twice (time diversity).

The base station enables the Configuration Change Indicators in each QPCH slot for a period oftime following a change in configuration parameters. Configuration Change Indicators are onlyused on QPCH number 1 and either 4 or 8 of the Paging Indicators are reserved for Configuration


3


Change Indicators depending upon the data rate. Quick Paging capability allows a subscriber toconserve power and hence support extended battery life, by monitoring certain Paging Indicatorbits within a Quick Paging slot on a Quick Paging Channel. The structure of the QPCH allows theuse of a less complex demodulator which can enhance the battery life even further.

Figure 3-27: QPCH to PCH Timing

Forward Fundamental Channel (F-FCH)The Forward Fundamental Channel, as in IS-95A/B, is used for transmission of user and signalinginformation to a specific subscriber station for voice or low bit rate data applications during a call.RC 1 and RC 2 channels are backwards compatible to the TCH in IS-95A/B supporting data ratesof 9600 or 14400 bps and 20 ms frames. As in IS-95A/B, this channel may be transmitted at avariable rate (on a frame-by-frame basis). New to IS-2000 is that each channel is transmitted on adifferent variable length Walsh code channel (expressed as Wn

L, where n = Walsh code numberand L = Walsh code length). For RC 1 or RC 2 and RC 3 or RC 5, each channel is assigned to codechannel Wn

64, where 1 < n < 63. For RC 4, each channel is assigned a code channel Wn128, where

1 < n < 127.

Forward Dedicated Control Channel (F-DCCH)The Forward Dedicated Control Channel introduced in IS-2000 is used to carry user data as wellas signaling and control data while the call is in progress. It does not support voice traffic. The

0 1 2 3

Paging Channel

Paging Channel Slot (80 ms)

1 2 3 4 11 2 3 4

Quick Paging Channel Slot (80 ms)

20ms 20ms

1

Quick Paging

Channel

Paging Indicators Paging Indicators

Configuration Change Indicators


3


Forward TCH channel may contain one Dedicated Control Channel. For RC 3 or RC 5, eachchannel is assigned to code channel Wn

64, where 1 < n < 63 and for RC 4, each channel is assigned

a code channel Wn128, where 1 < n < 127. This channel uses a data rate of 9600 bps (for RC 3 and

RC 4) or 14400 bps (for RC 5).

Forward Supplemental Channel (F-SCH)The Forward Supplemental Channel (packet based) introduced in IS-2000 is used for thetransmission of user data to a specific subscriber station during a call. It is always accompanied bya dedicated FCH or DCCH. In IS-2000, the Forward Supplemental Channel is designed to reachdata rates as high as 1,036,800 bps on a single RF carrier using a Spreading Rate (SR) of 3x. Alsowith IS-2000, each Forward TCH can have up to 2 Forward Supplemental Channels. ForMotorola’s CBSC Release 16 implementation, only 1 F-SCH per user with a maximum data rateof 153,600 bps will be supported using a Spreading Factor of 1x. These channels are sharedresources which are allocated dynamically in order to meet the required data rate. The resourcesare scheduled into time slices which leads to a more efficient use of the channel elements. Itsupports variable data rates with the use of a variable length Walsh code. For RC 3 or RC 4, eachchannel is assigned a code channel Wn

L, where 1 < n < L-1 [L=4, 8, 16, 32, 64, 128 (where 128 isfor RC 4 only)].

Forward Supplemental Code Channel (F-SCCH)The Forward Supplemental Code Channels are used to transmit user’s data from the base stationto the subscriber station during a call and are primarily defined for backward compatibility withIS-95B for RC 1 and RC 2 only. The F-SCCH in IS-2000 can simultaneously use up to 7Supplemental Code Channels in order to enable higher data speeds (for 3G-Type Services) oncarriers under RC 1 and RC 2 and each channel is assigned a code channel Wn

64, where 1 < n <63. Motorola’s implementation of the F-SCCH only supports 5 channels for RS1 and 4 channelsfor RS2 (similar to Motorola’s implementation of IS-95B).These channels are dedicated resourceswhich are assigned to a specific user to achieve data rates up to 64 kbps.

3.9.3.2 IS-2000 Forward Link Radio Configurations

The following table briefly explains the Radio Configurations (RC) supported by the forward linkin IS-2000 for Spreading Rates (SR) 1 and 3.

Table 3-17: IS-2000 Forward Link Radio Configurations

RC SRData Rates

(kbps)Coding

RateModulation

RC 1 1 1.2, 2.4, 4.8, 9.6 1/2 BPSK

RC 2 1 1.8, 3.6. 7.2, 14.4 1/2 BPSK

RC 3 1 1.5, 2.7, 4.8, 9.6, 19.2, 38.4, 76.8, 153.6 1/4 QPSK

RC 4 1 1.5, 2.7, 4.8, 9.6, 19.2, 38.4, 76.8, 153.6, 307.2 1/2 QPSK


3


Motorola IS-2000 BSS Implementation for CBSC Release 16

The following table provides the forward link Radio Configuration and data rates that aresupported with CBSC Release 16.

RC 5 1 1.8, 3.6. 7.2, 14.4, 28.8, 57.6, 115.2, 230.4 1/4 QPSK

RC 6 3 1.5, 2.7, 4.8, 9.6, 19.2, 38.4, 76.8, 153.6, 307.2 1/6 QPSK

RC 7 31.5, 2.7, 4.8, 9.6, 19.2, 38.4,

76.8, 153.6, 307.2, 614.41/3 QPSK

RC 8 31.8, 3.6. 7.2, 14.4, 28.8,57.6, 115.2, 230.4, 460.8

1/4 or1/3

QPSK

RC 9 31.8, 3.6. 7.2, 14.4, 28.8, 57.6,

115.2, 230.4, 460.8, 518.4, 1036.81/2 or

1/3QPSK

Table 3-18: Forward Link Radio Configuration Support for CBSC Release 16

RC SRData Rates

(kbps)Coding

RateModulation CBSC Release 16 Notes

RC 1 1 1.2, 2.4, 4.8, 9.6 1/2 BPSKRate Set 1

Backward Compatible

RC 2 1 1.8, 3.6. 7.2, 14.4 1/2 BPSKRate Set 2

Backward Compatible

RC 3 11.5, 2.7, 4.8, 9.6,

19.2, 38.4, 76.8, 153.61/4 QPSK

Supported in 1X Mode only

RC 4 11.5, 2.7, 4.8, 9.6,

19.2, 38.4, 76.8, 153.61/2 QPSK Supported up to 153.6

RC 5 1 1.8, 3.6. 7.2, 14.4 1/4 QPSK Supported up to 14.4

Table 3-17: IS-2000 Forward Link Radio Configurations

RC SRData Rates

(kbps)Coding

RateModulation


3


The following table shows the number of channel element (CE) resources that are required for thevarious data rates for RC 3 and RC 4.

The maximum data rate (153.6 kbps) supported on the forward link is obtained by utilizing RC 3or RC 4. As shown above, RC 4 requires half as many CE resources compared to RC 3 to supportthe maximum data rate.

3.9.3.3 IS-2000 Walsh Code Allocation

Unlike IS-95A/B, the number of Walsh codes is not hard limited to 64 in IS-2000. To increase thenumber of usable Walsh codes, Complex or QPSK modulation is employed where 2 informationbits are mapped into a QPSK symbol. Using the same coding rate, this method allows for anincrease in the number of Walsh codes by a factor of 2 relative to BPSK, thereby allowing longerWalsh codes (i.e. 128 for RC 4, instead of 64). Implementing QPSK modulation, also allowsdoubling the original data rate on the same available bandwidth.

A Supplemental Channel in IS-2000 is designed to reach data rates up to 1,036,800 bps on a singleRF carrier (refer to Section 3.9.3.2 above for the data rates supported by Motorola). With the codechip rate fixed at 1228800 chips/sec, the length of the Walsh code spreading must be substantiallyreduced to achieve the high data rates.

The variable length Walsh code implementation can be visualized as shown in Figure 3-28. Asseen in Figure 3-28, codes on different levels of the tree have different Walsh code lengths. Thenew levels in the tree are constructed by concatenating a root code word with a replica or an inverseof itself generating a long code word. During spreading, each bit is multiplied by an entire codeword and longer codes are associated with lower bit rates. The root code word (which is shorter inlength) is not guaranteed to be orthogonal to the derived long code words. The short code word ismodulated exactly as the long code word is built and hence there is no way to differentiate thesignals. Thus, if a root code is assigned to a certain user, then the derivative code words (thebranches of the tree structure) should not be used because they are not orthogonal to the root code.Thus assigning a Walsh code at a particular rate will make some higher rate codes and some of thelower rate codes unavailable for assignment.

In this scenario if Walsh code C2,1 is assigned at a particular rate, Walsh codes C4,1 and C4,2 arenot orthogonal to C2,1and hence they should not be assigned. At each level, all the code words arethe rows of a Hadamard matrix.

Table 3-19: Forward Link Channel Element Resource Requirement

Data Rate(kbps)

Radio Configuration 3CE Resources


9.6 1 119.2 2 138.4 4 276.8 8 4153.6 16 8


3


Figure 3-28: IS-2000 Walsh Code Tree

Motorola IS-2000 BSS Implementation for Release 16

For the multiple data rates achieved with the CBSC Release 16 implementation, a maximum datarate of 153,600 bps is achieved with one F-SCH. A Walsh code allocation tree with a 153,600 bpsmaximum data rate is shown in Figure 3-29.

As seen in the figure, assigning a Walsh code at a particular rate would make some higher ratecodes as well as lower rate codes unorthogonal and unavailable for assignment. WC0, WC1, andWC32 are reserved for Pilot, Page, and Sync channels respectively. The figure shows the numberof Walsh codes available for each of the multiple data rates that CBSC Release 16 supports. The"X" on some of the higher and lower data rate Walsh codes indicates that they are unavailable orreserved due to the Pilot, Page, and Sync Walsh code allocations.

C1,1=(1,1)

C2,1=(1,1)

C2,2=(1,-1)

C4,2=(1,1,-1,-1)

C4,1=(1,1,1,1)

C4,3=(1,-1,1,-1)

C4,4=(1,-1,-1,1)

1

C8,2=(1,1,1,1,-1,-1,-1,-1)

C8,3=(1,1,-1,-1,1,1,-1,-1)

C8,4=(1,1,-1,-1,-1,-1,1,1)

C8,5=(1,-1,1,-1,1,-1,1,-1)

C8,6=(1,-1,1,-1,-1,1,-1,1)

C8,7=(1,-1,-1,1,1,-1,-1,1)

C8,8=(1,-1,-1,1,-1,1,1,-1)

C8,1=(1,1,1,1,1,1,1,1)


3


Figure 3-29: Walsh Code Allocation Tree

Shorter length Walsh codes limit the number of simultaneous users in the forward link, because ofthe smaller Walsh code set. If the remaining two high rate (153,600 bps) Walsh codes are alsoassigned to data users as shown in Figure 3-30, all of the lower rate Walsh codes below those codesbecome unavailable (shaded Walsh codes). In this scenario, only 29 Walsh codes are available forvoice call assignments (9600 bps) as seen in Figure 3-30 below.

Figure 3-30: Walsh Code Allocation Tree

X X

XX

X

9.6 kbps

19.2 kbps

38.4 kbps

153.6 kbps

76.8 kbps

XX

X

WC32 WC0WC1

X X

XX

X

9.6 kbps

19.2 kbps

38.4 kbps

153.6 kbps

76.8 kbps

XX

X

WC32 WC0WC1

X X

X

X

X

9.6 kbps

19.2 kbps

38.4 kbps

153.6 kbps

76.8 kbps

XX

X

WC32 WC0WC1

X X

X

X

X

9.6 kbps

19.2 kbps

38.4 kbps

153.6 kbps

76.8 kbps

XX

X

WC32 WC0WC1


3


3.9.4 IS-2000 Reverse Channel Structure

The following figure shows the Reverse Channel Structure for IS-2000.

Figure 3-31: Example of IS-2000 Reverse CDMA Channels

3.9.4.1 IS-2000 Reverse Channels (Motorola Implementation)

The Reverse link in IS-2000 essentially consists of three new channels. They are Pilot,Supplemental, and Dedicated Control Channels, in addition to the IS-95A/B Access andFundamental Channels. The following sections provide a brief description of the reverse channelsthat are supported for CBSC Release 16.

Reverse Pilot Channel (R-PICH)The Reverse Pilot Channel introduced in IS-2000 is used to assist the base station in detectingsubscriber station transmissions. There exists a Pilot Channel for each subscriber on a TCH in theuplink and it is used for the timing and phase reference to the BTS for coherent demodulation. Asin the forward link, the pilot signal is un-modulated and it uses zeroth Walsh code 0 but of length32 (W0

32). The Pilot Channels do not carry any information and essentially consist of Short PNcodes. It allows the use of Walsh code and simultaneous channel transmission on the reverse link.It is only supported on Reverse RCs greater than 2, because RC 1 and RC 2 have to be compatiblewith IS-95A/B which does not support a Reverse Pilot Channel. The R-PICH also includes a

Reverse CDMA Channels

FundamentalChannel[R-FCH]

SupplementalCode Channels (0-7)

[R-SCCH]

Traffic Channels(RC 1, RC 2)

Enhanced AccessChannel

[R-EACH]+

PilotChannel

[R-PICH]

CommonControl

Channels

PilotChannel

[R-PICH]

Dedicated ControlChannel (0 or 1)

[R-DCCH]

FundamentalChannel (0 or 1)

[R-FCH]

SupplementalChannels (0-2)

[R-SCH]

AccessChannel[R-ACH]

AccessChannels

CommonControl Channel

[R-CCCH]+

PilotChannel

[R-PICH]

Traffic Channels(RC 3-6)

= Channels NOT implemented in CBSC Release 16


3


Reverse Power Control Sub-Channel when operating on a TCH with RC 3 and RC 4. It is used bythe subscriber station to transmit Forward Power Control commands to the base station.

Reverse Access Channel (R-ACH)The Reverse Access Channel functionality is the same as an IS-95A/B Access Channel, supportingRC 1 and RC 2, in order to allow for the backwards compatibility. It is identified by a Long PNCode offset. There are 32 Access Channels associated to one Paging Channel and the informationon the Access Channel is transmitted at data rate of 4800 bps. Motorola’s implementation supportsonly 1 Access Channel per Paging Channel.

Reverse Fundamental Channel (R-FCH)For RC 1 and RC 2, the Reverse Fundamental Channel functionality is the same as in IS-95A/B.Only one Reverse Fundamental Channel can be used by the subscriber station during a call. As inIS-95A/B, it supports the basic rates of 9600 bps and 14400 bps. The R-FCH uses Walsh code 4 oflength 16 (W4

16) for spreading. It supports orthogonal modulation with RC 1 and RC 2 andorthogonal spreading with RC 3 and RC 4. It performs discontinuous transmission using repetitioncoding, where a subscriber station operating with RCs 3 through 6 may discontinue transmissionof the R-FCH for up to three 5 ms frames in a 20 ms frame.

Reverse Supplemental Channel (R-SCH)The Reverse Supplemental Channel introduced in IS-2000 is used for the transmission of user datato the base station during a call. An R-SCH is always accompanied by a dedicated R-FCH or R-DCCH. They operate with RCs 3 through 6 only (for CBSC Release 16, Motorola only supportsRC 3 and RC 4 for the reverse link). There are up to 2 Supplemental Channels. The data rate isselected on a time slice basis and it supports data rates up to 307,200 bps. For spreading, R-SCHuses Walsh code W1

2 or W24. Although IS-2000 supports up to 2 reverse Supplemental Channels,

CBSC Release 16 supports only 1 R-SCH with a maximum data rate of 153,600 bps. If the secondR-SCH were supported, it would use W2

4 or W68 for spreading.

Reverse Dedicated Control Channel (R-DCCH)The Reverse Dedicated Control Channel introduced in IS-2000 is used to carry user data as well assignalling and control information during a call. One Dedicated Control Channel may accompanyan R-SCH, but the R-DCCH does not support voice traffic. The subscriber transmits at a fixed datarate of 9600 bps or 14400 bps and it uses Walsh code 8 of length 16 (W8

16) for spreading. Itsupports orthogonal spreading with RC 3 and RC 4

3.9.4.2 IS-2000 Reverse Link Radio Configurations

The following table briefly explains the Radio Configurations (RC) supported by the reverse linkin IS-2000 for Spreading Rates (SR) 1 and 3.


3


Motorola IS-2000 BSS Implementation for CBSC Release 16

The following table provides the reverse link Radio Configuration and data rates that are supportedwith CBSC Release 16.

Table 3-20: IS-2000 Reverse Link Radio Configurations

RC SRData Rates

(kbps)Coding

RateModulation

RC 1 1 1.2, 2.4, 4.8, 9.6 1/3 64-aryOrthogonal

RC 2 1 1.8, 3.6. 7.2, 14.4 1/2 64-aryOrthogonal

RC 3 1

1.2, 1.35, 1.5, 2.4, 2.7, 4.8,9.6, 19.2, 38.4, 76.8, 153.6

1/4 BPSKw/Pilot

307.2 1/2

RC 4 1 1.8, 3.6. 7.2, 14.4, 28.8, 57.6, 115.2, 230.4 1/4BPSKw/Pilot

RC 5 3

1.2, 1.35, 1.5, 2.4, 2.7, 4.8,9.6, 19.2, 38.4, 76.8, 153.6

1/4 BPSKw/Pilot

307.2, 614.4 1/3

RC 6 3

1.8, 3.6. 7.2, 14.4, 28.8,57.6, 115.2, 230.4, 460.8

1/4 BPSKw/Pilot

1036.8 1/2

Table 3-21: Reverse Link Radio Configuration Support for CBSC Release 16

RC SRData Rates

(kbps)Coding

RateModulation CBSC Release 16 Notes

RC 1 1 1.2, 2.4, 4.8, 9.6 1/3 64-aryOrthogonal

Rate Set 1Backward Compatible

RC 2 1 1.8, 3.6. 7.2, 14.4 1/2 64-aryOrthogonal

Rate Set 2Backward Compatible

RC 3 11.5, 2.7, 4.8, 9.6,

19.2, 38.4, 76.8, 153.61/4

BPSKw/Pilot

Supported up to 153.6

RC 4 1 1.8, 3.6, 7.2, 14.4 1/4BPSKw/Pilot

Supported up to 14.4


3


The following table shows the number of channel element resources that are required for thevarious data rates for RC 3.

The maximum data rate (153.6 kbps) supported on the reverse link is with RC 3.

3.10 Handoffs

The new IS-2000 air interface provides the ability to handoff voice and data calls, as well as otherservices from an IS-95 system to an IS-2000 system and from an IS-2000 system to an IS-95system. The following handoff methods are supported in both IS-95 and IS-2000 systems:

• Soft (or Softer) handoff

• Inter-CBSC Soft Handoff

• Hard handoff

3.10.1 Soft Handoff

A soft handoff is a handoff in which a new base transceiver station (BTS) commencescommunications with the subscriber station without interrupting the communications from the oldBTS. The BTS can direct the subscriber station to perform a soft handoff only when all ForwardTraffic Channels assigned to the subscriber station have identical frequency assignments. Whenperforming a soft handoff, the subscriber collects the signal-to-noise ratio (pilot Ec/Io) receivedfrom each active sector on the downlink along with all candidate sectors. Each active BTS thatreceives the uplink transmission from the subscriber will relay it to the transcoder (XC). The XCwill make the final decision on the eligibility of candidates and the handoff will proceed. While ina soft handoff state, more than 1 TCH is assigned to the subscriber.

The soft handoff factor (SHOF) is used to determine the overhead Erlangs to support differentkinds of soft handoffs. The factor is likely to vary from 1.3 to 2.0. It should be noted that the softhandoff factor defined here is a linear scaling factor of the actual usable Erlangs but not the numberof traffic channels.

Soft Handoff Factor = 1*(1-a-b) + 2*a + 3*b [EQ 3-60]

Table 3-22: Reverse Link Channel Element Resource Requirement

Data Rate(kbps)


9.6 119.2 138.4 276.8 4153.6 8


3


where:• 2-way soft handoff fraction, a = Average 2-way soft handoff duration per hold time

• 3-way soft handoff fraction, b = Average 3-way soft handoff duration per hold time

3.10.2 Inter-CBSC Soft Handoff

Inter-CBSC Soft Handoff (ICBSC-SHO) happens when the subscriber communicates with sectorsof different BTSs and the BTSs are controlled by different CBSCs. In a Motorola system, when thesubscriber reports a handoff pilot that refers to an external sector database that has inter-CBSC softhandoffs enabled, the call goes into inter-CBSC soft handoff. In this case, the external sector canreside in the source CBSC or can be backhauled from the target CBSC. The source CBSC remainsin control of the call until no source handoff legs remain, then control is transferred to the targetCBSC by a Anchor Handoff (which is a form of a hard handoff).

3.10.3 Hard Handoffs

Hard Handoffs take place during all "break before make" handoff situations. In an IS-95 and/or IS-2000 system, hard handoffs can be represented by a change from one radio configuration toanother, or when a multi-mode subscriber station transitions from CDMA operation to operationon an analog system. In a Motorola system, hard handoffs which result in the subscriber beingsupported by a new PDSN will cause the connection to the old PDSN to be dropped. The subscribermust then initiate a new PPP session as well as an IP registration following a hard handoff.

3.10.3.1 Anchor Handoff

Anchor Handoffs are handoffs triggered when a subscriber is in Inter-CBSC soft handoff, and a setof criteria have been met within the database. When the criteria are met (typically no source CBSChandoff legs are active), the target CBSC determines the current strongest Inter-CBSC soft handoffsector and initiates a hard handoff to that sector. The source CBSC maintains control of the calluntil the criteria is met, then control is transferred to the target CBSC resulting in a change in Walshcodes.

3.10.3.2 IS-95 to IS-2000 Hand-up

Hand-up from IS-95 to IS-2000 happens when an IS-2000 capable subscriber station is directedfrom an IS-95 channel to an IS-2000 channel. In a Motorola system, before allocating a channelelement for a handoff request, the MM checks the Radio Configuration Class capability of thecurrent sector against the candidate sector. If the candidate sector supports a higher RadioConfiguration Class, the MM can pick a channel element with a higher Radio Configuration Classthat is supported by the subscriber. For example, if a IS-2000 capable subscriber is on a call usingIS-95 with RC 2 radio resources and wishes to add a leg from a BTS that has IS-2000 with RC 3radio resources available, the MM could decide to perform a hard handoff and hand the subscriberup to the IS-2000 channel with RC 3 radio resources. Increasing the call to a higher RadioConfiguration Class is referred to as a hand-up.


3


3.10.3.3 IS-2000 to IS-95 Hand-down

An IS-2000 to IS-95 hand-down happens when an IS-2000 capable subscriber station is assignedto an IS-2000 channel in the source BTS, and the target BTS has assigned an IS-95 channel. In aMotorola system, the MM checks the Radio Configuration Class capability of the current sectoragainst the candidate sector. If the candidate sector supports a lower Radio Configuration Class,the MM can pick a channel element with a lower Radio Configuration that is supported by thesubscriber. The subscriber would then hand down to the IS-95 channel. An example of this is whenthe call starts out on an IS-2000 channel with RC 3 radio resources and the subscriber wishes tohandoff to a BTS that does not have IS-2000 resources available. The MM could decide to performa hard handoff and hand the subscriber down from IS-2000 to IS-95. As part of this handoffprocess, the source radio channel is also handed down to IS-95. Decreasing the call to a lowerRadio Configuration Class is referred to as a hand-down.

3.10.3.4 Packet Data Handoffs

In a Motorola system, when the base station determines that a Hard Handoff is required for a packetdata call, the base station will transition a packet data call into dormant mode by initiating a callrelease. During the release procedure the base station sends the subscriber a Service Option Controlmessage indicating the minimum amount of time the subscriber must wait before trying to transferthe packet data. The subscriber will attempt to access the system again using the best serving cell.Once access has been granted, the subscriber will resume the transfer of the packet data.

3.10.3.5 Inter-Carrier Hand-across

An IS-2000 to IS-2000 inter-carrier hand-across happens when an IS-2000 capable subscriber isassigned to an IS-2000 channel in the source sector, and the target sector can assign an IS-2000channel. The subscriber would then handoff to the IS-2000 channel. In the case of the hand-across,the source and target sectors are located under two different frequencies, and a hard handoff to theIS-2000 target cell is required. This inter-carrier hand across case can also occur among IS-95channels.

3.11 Budgetary Estimate of Sites for Capacity (Voice Only)

The following section provides a budgetary estimate of sites from a capacity perspective for aChicago Metropolitan Area example. This example provides a simplified traffic engineeringapproach to estimating the number of sites required from a capacity perspective for an IS-95 voiceonly system. If some simplifying assumptions were made towards the voice and data call models,a similar approach could also be performed to estimate the number of sites required from a capacityperspective for a voice and data system as well (IS-95B and/or IS-2000 1X).

It is important to note that the site estimates provided in this section are for budgetary purposesonly. Many other issues such as cell coverage, cell location, antenna configurations, unique trafficcall models (voice and data), etc. have to be taken into consideration for an actual system design.It is recommended that simulations be performed using a tool like Motorola’s NetPlan tool (seeSection 3.12) before finalizing a system design.


3


This example illustrates the case that the cellular operator decides to deploy a single carrier CDMAsystem and allocate 1.8 MHz (including the guard band) out of the 12.5 MHz cellular band forCDMA deployment. The system shall be designed to provide service to 40,000 new CDMAsubscribers. Prior to the design of the system, information concerning the propagation environmentand subscriber distribution has to be gathered for each particular service area.

3.11.1 Required Parameters for Initial System Design

Prior to the design of an IS-95 voice only system, the propagation parameters and the subscriberprofile must be available. This section is intended to give an overview of some importantparameters and the correct way to apply them to system design. A completed example follows.

3.11.1.1 Busy Hour Call Attempts and Completions

Busy hour is defined as the continuous one hour period in the day during which the highest averagetraffic density is experienced by the system. Busy Hour Call Attempts (BHCA) is the number ofcall setup requests during the busy hour. Busy Hour Call Completion (BHCC) is the portion of therequests which succeed in making it to the conversation state.

3.11.1.2 Average Holding Time

Holding time is defined as the average length of time an active user occupies a traffic channel.

3.11.1.3 Erlangs per Subscriber

An Erlang is the traffic intensity of a traffic channel which is continuously occupied. Erlang persubscriber is the product of BHCA per subscriber and the average holding time per access.


3


Figure 3-32: Subscriber Distribution of Chicago Metropolitan Area

CHICAGODOWNTOWN

NORTHWESTSUBURBS

UPTOWNAREA

WESTSUBURBS

SOUTHWESTSUBURBS

SOUTHSUBURBS


3


Table 3-23: Subscriber Distribution of Chicago Metropolitan Area

System Parameters:

• Spread Bandwidth = 1.23 MHz• Data Rate = 9600 bps (Rate Set 1)• Median (Eb/Io) = 7 dB• Power Control standard deviation = 2.5 dB• Voice or Data Activity Factor = 0.4• Noise Rise Threshold (Io/No) = 10

Assumptions:

1. Each subscriber’s required energy per bit-to-interference density ratio (Eb/Io) is variedaccording to propagation conditions to achieve the specified FER of 0.01

2. All the sectors support the same number of subscribers.

3. The subscribers are uniformly distributed over each sector.

4. There is no overflow from the CDMA network to the AMPS network

5. There are 40,000 subscribers distributed across the system as shown in Table 3-23.

6. The Average Hold time per Access is 65 seconds.

7. The path loss slope for a dense urban environment of 32.8 dB/decade is assumed with ashadowing standard deviation of 7.7 dB.

8. The path loss slope for an urban environment of 38.4 dB/decade is assumed with ashadowing standard deviation of 8 dB.

9. 40% of the subscribers will be in soft handoff between two or more sites.

10. The sectorization improvement going from a single sector to three sectors is 2.4 times.

AreaSubscriber

Distribution Environment

Classifications

BHCA per subscriber

1 City core area 50% dense urban 1.40

2 Northwest Suburb 25% suburban 1.40

3 Uptown area 10% dense urban 1.38

4 West Suburb 8% suburban 1.30

5 Southwest Suburb 5% suburban 1.30

6 South Suburb 2% suburban 1.20


3


From the Figure 3-7: Probability of Blocking vs. Erlangs per CDMA Sector with Various PathLoss Slope Values with Rate Set 1 Vocoder, Page 28, with fully loaded neighbor cells (worst case),the maximum capacity for 2% probability of blocking is approximately 15 Erlangs per CDMAsector for dense urban areas, and 17.8 Erlangs per CDMA sector for suburban areas.

These results in addition to following are approximations based on the curves and the assumptionswhich went into generating the curves. Actual system designs will vary from system to system.

For Area 1,

Number of subscribers in the city core = 40,000*50% = 20,000

Required traffic capacity for this area

= BHCA/sub * # of Sub * Average Hold Time per Access(sec) / 3600= 1.4 * 20,000 * 65 / 3600= 505.56 Erlangs (0.0253 Erlang per sub)

Required traffic capacity including soft handoff

= Required traffic capacity * soft handoff factor= 505.56 * 1.4= 707.78 Erlangs

Required number of CDMA sectors

= 707.78 / 15 Erlangs per CDMA sector= 48 CDMA sectors

Required number of CDMA sector cells

= 48 / 2.4 (2.4 is the sectorization gain)= 20 cells

For Area 2,

Number of subscribers in the city core = 40,000*25% = 10,000

Required traffic capacity for this area

= BHCA/sub * # of Sub * Average Hold Time per Access(sec) / 3600= 1.4 * 10,000 * 65 / 3600= 252.78 Erlangs

Required traffic capacity including soft handoff

= Required traffic capacity * soft handoff factor= 252.78 * 1.4= 353.89 Erlangs


3


Required number of CDMA sectors

= 353.89 / 17.8 Erlangs per CDMA sector= 20 CDMA sectors

Required Number of CDMA sector cells

= 20 / 2.4= 9 cells

Using a sectorization gain of 2.45 for a three sector CDMA site, a total of 20 sector cells arerequired for area 1. Propagation studies have to be performed to determine if the system is coveragelimited as opposed to capacity limited. If the number of sector cell sites required in this case forcoverage is larger than 20 (the system is coverage limited), the system should be designed basedon the number of cell sites required for coverage. Propagation studies could be a detailed systemwide simulation or a simple link budget analysis based on certain well-known propagation modelsuch as the Okumura Model or the Hata Model (depending on the degree of accuracy required).

By the same method, the calculation of the other areas is summarized in following table:

Table 3-24: Chicago Metropolitan Area Summary

Area BHCA

perSub

Subs.%

Subs. in

Region(k)

Required Traffic

(Erlangs)

SHO Factor

(Erlangs)

Required Traffic w/

SHO (Erlangs)

Max.Traffic

per Sector

RequiredSectorCells

1 1.40 50 20 505.56 1.4 707.78 15.0 20

2 1.40 25 10 252.78 1.4 353.89 17.8 9

3 1.38 10 4 99.67 1.4 139.53 15.0 4

4 1.30 8 3.2 75.11 1.4 105.16 17.8 3

5 1.30 5 2 46.94 1.4 65.72 17.8 2

6 1.20 2 0.8 17.33 1.4 24.27 17.8 1

Total 100 40 997.39 1396.35 39


3


3.12 IS-95 and IS-2000 Simulations

Planning a wireless system revolves around three main characteristics: Coverage, Capacity, andQuality. In a CDMA system, these three characteristics must be carefully balanced against oneanother in order to arrive at the desired level of system performance. If high capacity is desired,there will be some degree of degradation in coverage and/or quality. Likewise, if a better systemquality is desired, there will be some degree of degradation in capacity and/or coverage. Theimportant point to realize is that these parameters are intertwined.

It is up to the system designer to determine how to balance these parameters to best serve aparticular area. The best balance point will change from cell site to cell site depending on wherethat cell site is located in the system or the design objectives. Sites in dense downtown areas willtrade off coverage for capacity. Conversely, cell sites at the edges of a system could sacrificecapacity for additional coverage.

The capacity of a CDMA site and system is dependent upon many factors which can be uniquefrom one system to the next. Some of these factors that have an impact to both IS-95 and IS-20001X systems are:

• Propagation loss (path loss slope, log normal fading, antenna types)• Amount of delay spread in the environment• Terrain and clutter environment• Traffic distribution of the subscribers• Speed distribution of the subscribers• Voice/data call models and activity factors • Soft and softer handoff factors• Channel power settings (Pilot, Page, Sync, FCH, SCH, etc.)• Environmental characteristics (noise, interference from other services, etc.)• Level of reliability• Quantity and placement of sites, in addition to the amount of cell overlap

For IS-2000 1X, the dimensioning of a complex traffic model with variable data rates, whichsupports both circuit voice call models and packet data call models, creates a new challenge incapacity design. In IS-95 and IS-2000 1X, voice calls are handled by allocating dedicated channels.For IS-95B, data calls use dedicated supplemental code channels, but for IS-2000 1X, data callsemploy shared supplemental channels. Therefore, the IS-2000 1X channel structure assuresefficient use of the supplemental channels.

Various formulas can be used, dependent upon the level of complexity and accuracy desired, toestimate the capacity of a site. The more accurate calculations will require more time to performor many simulations executed to obtain results which are statistically and reasonably valid. Due tothe variability of the many different factors mentioned above, there is no single capacity number,but a range of values over an environment. The forward and reverse link capacity estimationequations provided in this chapter can only be used as an approximation of capacity of the systemand should be used for budgetary purposes only. They do not take into account the size of the cellor the spacing between the sites. These equations do not totally account for the benefits of soft


3


handoff, since they assume that all sites serving a given subscriber will experience peak rises at thesame time, which in reality is a very small probability. In addition, these budgetary equationsassume that the subscriber distribution is uniform, which is not likely. One sector may need tosupport many users, whereas the nearby sectors may be lightly loaded and therefore result in alower f-factor which allows for greater capacity. A more accurate estimation can be performed witha more sophisticated CDMA simulation program, such as Motorola’s NetPlan tool. NetPlan can beused to model the forward and reverse links for thousands of subscribers in a realistic systemenvironment with different voice and data traffic mixes.

The NetPlan CDMA Simulator incorporates both IS-95 and IS-2000 1X parameters and can be runin one of two simulation modes: non time-sliced and time-sliced. Non time-sliced simulationsutilize a simulation technique where all of the dropped subscribers are actively bursting (althoughthe power is adjusted according to an activity factor) at simulation time, and data rates assignedaccording to available capacity. For time-sliced simulations, data subscribers are modeledaccording to a dynamic source model, which employs a State machine consisting of the ReverseRequest State, Server Delay State, Forward Reference or Download State, Think State, andDormant State. Each subscriber cycles through these states during the time-sliced simulation.These states represent different bursting and non-bursting stages of the data call. For moreinformation on the dynamic source model, please refer to the CDMA RF System Design Procedure(Chapter 6 and Appendix A4). Both of the simulation modes incorporate T-ADD, T-DROP, SoftSlope, Add Intercept, Drop Intercept, overhead channel power requirements, as well as genericantenna parameters such as horizontal and vertical antenna patterns, bearing, downtilt, and gain.

Various path loss models (statistical and deterministic) may be used by the simulator to aid indefining the CDMA coverage area. Each path loss model has its benefits and disadvantages. Whilemost statistical models, such as Hata, do not consider terrain variation, they do allow for quickbudgetary simulations. The Xlos propagation model incorporates terrain variation, antenna pattern,overlay (clutter) data, etc., in an attempt to model actual installations. The location of the CDMAsubscriber units within a system will greatly affect total system capacity, coverage and quality, aswell as the achieved data rate and distribution of resources. Subscriber positioning may be uniformor may be more accurately modeled with a subscriber traffic map.

In essence, the NetPlan CDMA Simulator is a tool to layout a DS-CDMA system resulting ininformation on predicted capacity, required system parameter values, system quality, predictedcoverage and hardware loading information. It permits investigations into real cellular systemconcerns such as edge effects, propagation anomalies, antenna types, subscriber distribution, callquality, receiver sensitivity impact on capacity, interference mitigation, power control andhandoffs. It provides statistical information for the cell, and end-user. Cell statistics include thenumber of blocked subscribers due to unavailable Walsh codes, good subscriber percentage, totalTCH power per data rate, forward and reverse SCH data rate, sector throughput and end userthroughput, just to name a few. Because of CDMA system complexity and the inter-dependencebetween coverage, capacity and quality, it is only when these properties are considered togetherthat a system representation with a higher degree of accuracy can be developed.


3


3.13 References

1. R.H. Owen, Phil Jones, Shirin Dehgan, Dave Lister, "Uplink WCDMA capacity andrange as a function of inter-to-intra cell interference: theory and practice", pp. 298-302,VTC 2000.

2. Szu-Wei Wang and Irving Wang, "Effects of Soft Handoff, Frequency Reuse and Non-Ideal Antenna Sectorization on CDMA System Capacity", pp. 850-854, IEEE 1993.

3. William C. Y. Lee, "Mobile Cellular Telecommunications Systems", McGraw-HillBook Company, Second Edition 1995, figure 4.3, p. 110.

4. A. Viterbi & Viterbi, "Erlang Capacity of a Power_Controlled CDMA System", IEEESelected Areas in Communications, August 1993, pp. 892-900.

5. A. Viterbi, "CDMA Principles of Spread Spectrum Communication", Addison-WesleyPublishing Company, Copyright 1995.

6. R. Padovani, "Reverse Link Performance of IS-95 Based Cellular Systems", IEEEPersonal Communications Third Quarter 1994, page 28-34.

7. Charles Noblet, Ray Owen, Simon Burley, Allan Bartlett, “UMTS NetworkDimensioning From Theory to Simulations”, version 1.00

8. CDG Evolution Study Report, Revision 4.01, January 10,2000

9. H. Holma & A. Toskala, "WCDMA for UMTS", John Wiley & Sons, Ltd, Copyright2000, pp. 163-167.



Table of Contents

4.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 3

4.2 Radio Frequency Link Budget. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 44.2.1 Propagation Related Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 6

4.2.1.1 Building Loss. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 64.2.1.2 Vehicle Loss. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 94.2.1.3 Body Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 94.2.1.4 Ambient Noise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 94.2.1.5 RF Feeder Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 94.2.1.6 Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 12

4.2.2 CDMA Specific Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 144.2.2.1 Interference Noise Rise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 144.2.2.2 Soft Handoff Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 184.2.2.3 Eb/No . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 19

4.2.3 Product Specific Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 204.2.3.1 Product Transmit Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 204.2.3.2 Product Receiver Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 24

4.2.4 Reliability (Shadow Fade Margin) . . . . . . . . . . . . . . . . . . . . . . . . 4 - 294.2.5 Example Reverse (Uplink - Subscriber to Base) Link Budget. . . 4 - 364.2.6 RF Link Budget Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 40

4.3 Propagation Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 414.3.1 Free Space Propagation Model. . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 414.3.2 Hata Propagation Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 434.3.3 COST-231-Hata Propagation Model . . . . . . . . . . . . . . . . . . . . . . 4 - 444.3.4 Additional Propagation Models . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 45

4.4 Forward Link Coverage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 464.4.1 BTS Equipment Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 474.4.2 CDMA Signal Power Distribution Characteristics and PA Sizing 4 - 514.4.3 General Power Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 514.4.4 Design Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 53

4.4.4.1 Comparison to Average Rated Power . . . . . . . . . . . . . . . . . . . . . . . 4 - 534.4.4.2 Comparison to High Power Alarm Rating . . . . . . . . . . . . . . . . . . . 4 - 544.4.4.3 Comparison to Walsh Code Limit . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 54

Chapter

4 Link Budgets andCoverage


4

CDMA/CDMA2000 1X RF Planning GuideChapter 4: Link Budgets and Coverage

4.4.5 General Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 544.4.5.1 Minimum ARP Based on LT-AVG Estimate . . . . . . . . . . . . . . . . . 4 - 554.4.5.2 Minimum HPA Based on VST-AVG Estimate . . . . . . . . . . . . . . . 4 - 564.4.5.3 Exceeding the High Power Alarm Rating . . . . . . . . . . . . . . . . . . . 4 - 564.4.5.4 Carrier Load Management Overview . . . . . . . . . . . . . . . . . . . . . . 4 - 57

4.4.6 Power Allocation in Mixed Mode Systems . . . . . . . . . . . . . . . . . 4 - 584.4.7 Government Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 65

4.5 CDMA Repeaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 654.5.1 CDMA Repeater Design Considerations . . . . . . . . . . . . . . . . . . . 4 - 66

4.5.1.1 Coverage Impact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 664.5.1.2 Cascaded Noise Figure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 694.5.1.3 Interference and Capacity Issues . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 734.5.1.4 Filtering Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 73

4.5.2 CDMA Repeater Installation Considerations . . . . . . . . . . . . . . . . 4 - 744.5.2.1 Antenna Isolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 744.5.2.2 Repeater Antenna Considerations . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 774.5.2.3 Repeater Gain Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 78

4.5.3 CDMA Repeater Optimization Considerations . . . . . . . . . . . . . . 4 - 794.5.3.1 Timing Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 794.5.3.2 Optimization Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 81

4.5.4 CDMA Repeater Maintenance Considerations . . . . . . . . . . . . . . 4 - 814.5.4.1 Future Expansion Considerations . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 824.5.4.2 Environmental Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 834.5.4.3 Operations and Maintenance Considerations. . . . . . . . . . . . . . . . . 4 - 83

4.6 Theoretical vs. Simulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 83

4.7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 85


4


4.1 Introduction

The RF design of a wireless system revolves around three main principles. Those principles arecoverage, capacity and quality. The coverage of a system relates to the area within the system thathas sufficient RF signal strength to provide for a quality call. The capacity of a system relates tothe ability of the system to support a given number of users. Finally, the quality of the systemrelates to the ability of being able to adequately reproduce analog voice with a digital system. WithCDMA, all three of these quantities are interrelated. To improve quality, some coverage andcapacity has to be sacrificed. To improve coverage, capacity and quality would be sacrificed.Finally, to improve capacity, coverage and quality would be sacrificed.

The CDMA system design process consists primarily of three levels or phases. These levels rangefrom an initial budgetary design to a final design used to implement the system. The amount oftime and effort required to complete a design increases as the design process moves from abudgetary design to a final design. However, this additional time and effort results in a moreaccurate system design.

The first level of the design process is a budgetary level. It uses the RF link budget along with astatistical propagation model (such as Hata or COST-231 Hata) to estimate the coverage of the sitesand ultimately determine how many sites are required for the particular system. This type ofpropagation model has a slope and intercept value for each type of environment (Urban, Suburban,Open, etc.) and does not include terrain effects. This relatively simplistic approach allows for aquick analysis of the number of sites that may be required to cover a given area.

The next level of a system design requires a more detailed propagation model. This propagationmodel takes into account the characteristics of the selected antenna, the terrain, and the land useand land clutter surrounding the site. Since these factors are accounted for, this propagation modelwill determine a better estimate of the coverage of the sites than the previous statistical propagationmodel. Thus, its use, in conjunction with the RF link budget, produces a more accuratedetermination of the number of cells required. This second level of the design process uses thereverse RF link budget to assist in determining the required propagation path loss. Motorola usesthe NetPlan tool for this portion of the design process.

However to complete a system design, the forward link must also be analyzed to determine powersettings and pilot coverage. The forward RF link budget consists of many variables includingsubscriber speed, location, soft handoff, noise figure, voice activity, and pilot range. It isrecommended that a simulation be used to analyze the forward link by accounting for the statisticalvariation in these parameters. Such simulator studies are part of the final design phase.

The final level or phase of the design process incorporates further detail into the design by the useof simulation studies. Motorola uses the NetPlan CDMA Simulator for this analysis. Thesimulation studies account for subscriber distributions within a coverage area and also for CDMAsystem and site level parameters. The simulator analyzes both the forward and the reverse links.This final design process is required in the deployment of a system or in determining warrantycoverage.

The one element common to all three levels of a system design is the RF link budget. The followingsection discusses this element in greater detail.


4


4.2 Radio Frequency Link Budget

There are two main purposes for establishing the RF link budget for CDMA designs. The firstpurpose is to establish system design assumptions for all of the gains and losses in the RF path(such as vehicle loss, building loss, ambient noise margin, maximum subscriber transmit power,etc.). The second purpose of a link budget is to establish an estimate for maximum allowable pathloss. This maximum allowable path loss number is used in conjunction with the propagation modelto estimate cell site coverage, which ultimately determines the number of cells required foradequate system RF signal coverage and hence the system cost. Figure 4-1 shows the impact to thequantity of sites required due to changes in the RF link budget. For example, if the RF link budget(maximum allowable path loss) was improved by 5 dB, approximately half the number of siteswould be required.

Figure 4-1: Percentage of Cells Based on dB Changes to the Link Budget

The above figure is derived using the COST 231 Hata Suburban propagation model. Other modelsmay differ slightly from this. This figure can be utilized as a quick aid to help quantify the numberof sites required based upon a change made to the RF link budget. It should be pointed out thatother environmental factors may contribute to the above not holding true. For instance, in a veryhilly terrain location, dB improvements may not provide for extra range if the terrain is blockingthe propagation.

The system designer will need to determine the specific RF link budget parameters to be used whendesigning the system. The parameters within the RF link budget can be divided into four majorcategories. The following lists some of these parameters:


4


1. Propagation related• Building Loss• Vehicle Loss• Body Loss• Ambient Noise• RF Feeder Losses• Antenna Gain

2. CDMA specific• Interference Noise Rise (other users)• Eb/No• Processing Gain (ratio of bandwidth to data rate)

3. Product specific• Product Transmit Power• Product Receiver Sensitivity

4. Reliability• Shadow Fade Margin

The following figure shows the typical gains and losses that are encountered in the RF link.

Figure 4-2: RF Link Budget Gains & Losses

A RF link budget must be determined for each sector of each site. The RF link budget for eachsector must incorporate any specific parameters that have been supplied (such as buildingpenetrations, antenna heights, antenna gains, cable losses, coverage criteria, coverage reliability,etc.). It is common that all sectors of a given site may have the same link budget or even that several

BTS

Sub.Subscriber Line LossSubscriber Antenna Gain

Body LossVehicle LossBuilding LossMan-made Noise

RF Path Loss

Shadow Fade Margin (Reliability)

BTS Antenna GainTransmission Line LossJumpers & Connector Loss

RFGains

&Losses

Subscriber Tx PowerSubscriber Rx Sensitivity

BTS Tx PowerBTS Rx Sensitivity


4


sites may have the same link budget due to common installation practices being followed. If this isthe case, then the same link budget can be used for all of the similarly configured sectors. However,if the parameters change from sector to sector and site to site, then separate link budgets will needto be calculated for each unique sector.

CDMA RF link budgets may make simplifying assumptions regarding noise rise and Eb/Norequirements. For instance, in the RF link budget, the Eb/No value is considered a constant. Inactuality, Eb/No is not a constant value but varies with respect to speed, delay spread and otherfactors. Some of the simplifying assumptions are addressed in the detailed design phase.

4.2.1 Propagation Related Parameters

Propagation related parameters are those gains or losses of a link budget that are constant,independent of the multiple access technology chosen or vendor. The values of these parameters,though, are frequency dependent (i.e. differences would exist between an 800 MHz design and a1900 MHz design or between a mobile and a fixed environment). These parameters include suchfactors as: building loss, vehicle loss, body loss, man-made noise margin, RF feeder losses, andantennas. If comparing link budget information between vendors, these propagation relatedparameters should be set the same so as to obtain a realistic comparison.

4.2.1.1 Building Loss

Building loss is associated with the degradation of the RF signal strength caused by a buildingstructure, when a subscriber handset operating within a building is communicating with a basestation. An adequate RF signal strength within a building can be accomplished in one of two ways.One method involves the propagation scenario, where a base station located outdoorscommunicates with a subscriber unit that is inside a building (see Figure 4-3). The second methodinvolves the propagation scenario, where both the base station and the subscriber unit are withinthe same building.

Figure 4-3: In-Building Propagation Scenarios

For this chapter on link budgets, only building losses associated with the building penetration of

INTOPropagation Scenario where a basestation communicates with a radio

transceiver that is inside a building.

WITHINPropagation Scenario where boththe transmitter and receiver are

within the same building.


4


the RF signal from an outdoor source are considered (refer to Figure 4-3, the diagram labeledINTO). Refer to Section 7.2 of Chapter 7 for further information on in-building designs.

One approach for modeling the “into” building penetration is as an extension of an outdoorpropagation model. This method uses a distance-dependent path loss for a subscriber unit that isoutside a building, and adds a building loss factor.

This typical approach adds building loss factor to the macro cell link budget. This building loss ishighly variable and is a function of such items as: construction material, building layout, userlocation inside the building, proximity to the base station, and direction from the base station.

Building losses can range anywhere from 5 to 40 dB or more. If actual field data is not availablefor a given area, a value of building penetration may be assumed. The following table of values canbe used for a mobile design as a possible guideline in the absence of field data for the particularenvironment:

This table of building losses represents the average difference in RF signal strength between theoutside environment and numerous points throughout the inside of the building.

Another approach is that radio transmission into buildings should be undertaken separately and notas an extension of the outdoor propagation models plus the building loss factor. Besides theantenna heights and path length, the floor area, number of rooms on the floor, angle of illuminationof the building to the base station and the construction of the walls should be considered whentrying to determine a new propagation model. This approached is not addressed in this planningguide.

For a fixed system, the subscriber unit is not moving around inside the building but is instead fixedto a position. Since the Fixed Wireless Terminal (FWT) unit is stationary, the installation shouldbe in a position that allows for the best signal to be received from the base station. The preferredinstallation is to have the FWT with its whip antenna located near a window, preferably on the sideof the building closest to the base station. This would minimize the loss required for the signal topenetrate into the building. In addition, the preferred FWT location would have it being mountedabove desk height. If this optimum location is achieved, the building loss will be minimized.Careful placement of the fixed wireless terminal’s antenna near a window could reduce thebuilding loss value down to a 3 to 6 dB value. The following figure shows the preferred locationof the FWT with whip antennas. Refer to the FWT vendor to determine the recommendations ofthe FWT placement.

Table 4-1: Example Building Penetration Losses (800 & 1900 MHz)

Environment Penetration LossDense Urban 20 dBUrban 15 dBSuburban 10 dBRural 8 dB


4


Figure 4-4: Preferred FWT Locations Without External Antennas

There are numerous papers that exist which describe building penetration losses. The papers covermany different factors that affect building loss such as: height of base station antennas, angle ofillumination to the building, differing heights of buildings, various building constructions, and theimpact of frequency on building loss. Some of these papers are contradictory. For example, a paperby Turkmani1 2 concluded that building penetration losses decrease with an increase in frequency.On the other hand, Aguirre3 reached the conclusion that higher penetration losses wereexperienced at higher frequencies. It should be pointed out that Turkmani’s study had antennasabove the rooftop, whereas Aguirre’s study had antennas below the rooftop.

Due to the differences in the papers, an assumption for building penetration loss can be made byutilizing the results that are from a test case more in line with how the operator plans to provide forthe building penetration.

As the floors of a building are ascended, the relative signal strength increases. This effect is usuallyattributed to the increased probability of line of site propagation between the higher floors of thebuilding and the base site. This is commonly referred to as a height gain per floor. This height gaincan effectively reduce the building loss by approximately 1.3 to 2 dB per floor. Since the normaldesign is for a worst case scenario, the height gain would not be considered unless the particulardesign is to provide coverage only to a given floor(s).

1. Turkmani, Parsons and Lewis, "Measurement of building penetration loss on radio signals at 441, 900 and1400 MHz", Journal of the Institution of Electronic and Radio Engineers, Vol. 58, No. 6 (Supplement), pp.S169-S174, September-December 1988

2. Turkmani and Toledo, "Modelling of radio transmissions into and within multistory buildings at 900, 1800and 2300 MHz", IEEE Proceedings-I, Vol. 140, No. 6, December 1993

3. Aguirre, "Radio Propagation Into Buildings at 912, 1920, and 5990 MHz Using Microcells", 0-7803-1823-4/94 IEEE, session 1.6 & 1.7, pp. 129-134

GoodReception

BetterReception

Install FWT near windowthat faces the generaldirection of the cell site.


4


4.2.1.2 Vehicle Loss

Vehicle loss is the degradation of the RF signal strength caused by a vehicular enclosure. Asubscriber handset communicating to a cell site from within a vehicle will have a lower signalstrength than if that same subscriber unit was operating outside of the vehicle. Vehicle loss hasbeen seen to range from 5 to 12 dB. If the design for a system is to include a vehicle penetrationloss, an average range is approximately 5 to 8 dB.

Due to the nature of a fixed system, vehicle loss should not be accounted for.

4.2.1.3 Body Loss

Body loss, also referred to as head loss, is the degradation of the RF signal strength due to the closeproximity of the subscriber handset antenna to the person’s body. A 2 dB loss is associated withthe antenna in a vertical position; 6 dB is associated with the antenna in a horizontal position. It isassumed that the typical user will rotate the phone or move slightly to help improve the quality ofthe call. Therefore, a lower body loss of 2 to 3 dB is often used in system designs.

For a fixed system, there will be no body loss since the FWT antenna is either connected directlyto the FWT or is installed outdoors.

4.2.1.4 Ambient Noise

The ambient noise defines the environmental noise that is in excess of kTB for the sector. Thisnoise could be generated from automobiles, factories, machinery, and other man-made noise. Theambient noise margin parameter can be added to the link budget to allow for an adjustment to thethermal noise value. Since each environment is unique, a noise floor study should be performed todetermine if an adjustment is required to the theoretical thermal noise floor value.

Man-made noise is less significant at 1900 MHz than at 800 MHz. Also, galactic or sky noise is ata minimum.4

4.2.1.5 RF Feeder Losses

RF feeder losses include all of the losses that are encountered between the base station cabinet andthe base antenna, or with respect to a subscriber unit, all of the losses between the PA and theantenna. Since a majority of subscriber units for a mobility system being sold to customers areportable, there is minimal feeder loss; therefore, RF feeder loss at the subscriber unit is notconsidered in the link budget. However, the feeder loss at the base site can account for several dBof loss. The example RF link budgets provided in Table 4-6 on page 4-37 and Table 4-7 on page 4-39 only reflect the line loss at the base site.

For a fixed system, the Fixed Wireless Terminal (FWT) may have an antenna connected directlyto the unit or the antenna may be installed on the outside of the building, thus requiring a

4. Lee, William C.Y. "Mobile Communications Engineering", Copyright 1982, McGraw-Hill Inc. pg. 33-40.


4


transmission run from the FWT to the antenna. For the scenario of an external antenna connectedto an FWT, subscriber unit feeder loss needs to be accounted for in the RF link budget. This feederloss would be the loss encountered from the FWT to the external antenna, which is a function ofthe size of transmission line and the length of the run. Since this transmission line may need to windits way from the FWT to the external antenna, the size of the line may be small to allow for betterbending radii. A lightning arrestor will also need to be accounted for in this subscriber unit feederloss.

The base station RF feeder line loss calculations include such losses as: top jumper, maintransmission line, bottom jumper, lightning arrestors (surge protector), connectors, duplexers,splitters, combiners, and couplers (see Figure 4-5). The loss associated with the RF feeder systemcan be minimized by reducing the transmission line run between the base station and its antennas,and/or utilizing lower loss transmission lines. Transmission lines can range from 1/2” to 1-5/8”, orgreater, diameter cables. The larger the diameter of the cable, the less lossy the medium, but thesacrifice is more rigid lines, larger bending radius, greater weight, more wind loading and largerarea required. Transmission lines are also available with either air or foam dielectrics. The airdielectric cables are more expensive to install and maintain, but are less lossy than the foam lines.Figure 4-5 reflects most of the different components that are encountered between the base siteantenna and the base station equipment.

When estimating the amount of transmission line loss, keep in mind that the line loss is frequencydependent. Transmission cables are more lossy at higher frequencies. At 800 MHz, a 7/8” line maysuffice, but a 1-5/8” line for 1900 MHz may be required to maintain a similar loss. The followingtable shows an example of the difference that can exist in transmission line loss as a function of theoperating frequency.

Consult the transmission line vendor for the specifications of the installed transmission line or thesystem operator, if actual field measurements have been made.

Table 4-2: Example of Main Transmission Line Losses

850 MHz 1900 MHz

7/8” Foam Dielectric Coaxial Cable 1.24 dB/100ft.4.07 dB/100meters

1.97 dB/100ft.6.46 dB/100meters

1-5/8” Foam Dielectric Coaxial Cable 0.77 dB/100ft.2.54 dB/100meters

1.25 dB/100ft.4.1 dB/100meters


4


Figure 4-5: Typical Components in the RF Feeder Run

Additionally, the reference point used in the base station specifications should be known. Forinstance, the duplexer loss and its jumpers/connectors to the base station may already be includedin the specifications for the base station’s noise figure and PA output. Typically, the specificationsfor the base station are at the top of the frame. Therefore, if the duplexer or other components arelocated within the base station frame, additional loss would not need to be factored in. If, on theother hand, the device is located external to the base station frame, this loss would need to beaccounted for.

For sites with multiple CDMA carriers, the Rx signal distribution and the Tx combining schemesare typically addressed within the equipment specifications of the base station frame. If combiningor splitting of the RF signal is being performed external to the base station frame, the lossassociated with the combining or splitting would need to be added to the link budget.

From a budgetary or approximation viewpoint, one RF feeder loss value could be assumed as thetypical value for all of the sites. In real world situations, however, it is rare that one loss value will

Antenna

(A) Top Jumper

(B) Main Transmission Line

(C) Antenna Surge Protector

(D) Jumper to Directional Coupler

(E) Directional Coupler

(F) Jumper to Duplexer

(H) Jumper to Tx and Rx Antenna Port

BTS

Waveguide Entry Port

Note: Each Jumper consists of:Two connectors andOne line

(G) Duplexer


4


be common for all of the sites. Some sites (and sectors) may have longer or shorter lengths oftransmission line due to being installed with a taller antenna supporting structure or due to the basestation equipment being located on the top of a building.

In performing propagation predictions, it is important that each site (sector) is represented asaccurately as possible. Therefore, an analysis should be done for each particular sector to determinethe RF feeder line loss. This calculation should include all losses between the antenna and the basestation such as those components depicted in Figure 4-5. The value of the line loss listed inTable 4-6 on page 4-37 is an example which assumes that the base station will be operating at 1900MHz and the main transmission antenna run is 30 meters (approximately 100 feet). A 1-5/8” heliaxcable at 1900 MHz has approximately 4.1 dB loss per 100 meters (1.25 dB loss per 100 feet).Another 0.75 dB was assumed for jumpers and connectors.

Refer to Chapter 6, Section 6.7.3 for additional information on transmission lines.

4.2.1.6 Antennas

Antennas can be either omni or directional. Omni antennas provide approximately the sameamount of gain throughout the entire 360° horizontal pattern. Directional antennas, sometimesreferred to as sector antennas, have a maximum gain in one direction with the backside being 15to 25 dB below the maximum gain.

The gain of the antenna is a function of the horizontal pattern, vertical pattern, and number ofelements that make up the antenna array. The number of elements will dictate the size of theantenna. The horizontal and vertical beamwidths are referenced as the amount of degrees betweenthe points on the pattern where the gain is down 3 dB from the maximum gain.

The following points should be considered when selecting an antenna:

• The size and weight of the antenna will impact tower loading or the ability to place theantenna in the optimum position.

• Typically, antenna patterns with narrower horizontal and/or vertical beamwidths willresult in a higher antenna gain, assuming similar lengths.

• The horizontal and vertical beamwidths will have an impact upon the performance of thesite at the locations midway between the sectors. The larger horizontal beamwidths willresult in more overlap of signal between sectors and thus increase the amount of softerhandoff between sectors and soft handoff with other sites. This impacts the amount ofinterference seen (thus impacting capacity) and the ability to contain pilot pollution.

• The front to back ratio of the antenna also impacts the amount of interference seen atother sites and the ability to minimize pilot pollution.

The horizontal and vertical patterns provided by the selected antenna should be verified to ensurethat there will be coverage in the desired area. For instance, as a means to improve forward gain ofthe antenna, the vertical beamwidth may be reduced. In some situations, this reduction in thevertical beamwidth may produce unsatisfactory signal strengths near the cell site tower due to theantenna overshooting the area to be covered.


4


Another item to keep in mind is whether the antenna gain is in reference to a dipole or an isotropicantenna. The difference is usually signified by dBd or dBi. A zero dBd gain antenna wouldcorrespond to a 2.14 dBi gain antenna. Cellular often referenced antennas in dBd, but PCS RF linkbudgets normally refer to dBi gain antennas. The important point to be made is that a propagationmodel may be referenced to an isotropic or dipole antenna. Thus, care should be taken to ensurethe correct antenna gain is used with the propagation model, and thereby avoiding a potential errorof 4.3 dB.

Refer to Chapter 6 for additional information on antennas.

4.2.1.6.1 Base Station Antenna

The antennas located at the base site can be either omni or directional. In early cellular designs,most sites started out as omni. Fewer antennas were required and the system was lightly loaded.As the traffic requirements grew, sites were required to be sectorized to provide for this additionaltraffic and to restrict the amount of co-channel and adjacent channel interference.

PCS systems at 1900 MHz initially did not require an abundance of capacity, but utilizeddirectional antennas because of the extra gain associated with a directional antenna as compared toan omni antenna. A 4 dB improvement could easily be achieved by using directional antennasinstead of omni antennas. This 4 dB improvement could potentially reduce the quantity of sitesrequired at 1900 MHz by approximately 40%.

It is not mandatory that all sites use the same antenna. The system planner may deploy either omnior directional antennas at a cell site to meet the coverage goals desired.

As mentioned above, the antennas need to be selected to ensure coverage will be provided over thedesired area. In addition, antennas need to be selected to minimize the level of interference.Decreasing the level of interference will allow for greater site capacity and improved systemperformance. Antenna patterns that provide a faster rolloff past the half power points (i.e. 3 dBdown from main lobe) will provide for better interference protection. In frequency reuse systems(AMPS, GSM, USDC), improved interference control, such as through the use of sectorized sites,allows for a set of frequencies to be used at closer distances (i.e. tighter reuse pattern), thusproviding increased capacity. For CDMA, as mentioned in the chapter on capacity (Chapter 3),interference from other cells and other sectors has an impact on the capacity that can be supported.

4.2.1.6.2 Subscriber Unit Antenna

Our assumptions here are that the portable subscriber unit antenna has a gain of 0 dBi (-2.14 dBd)without factoring in body loss and is an omni antenna. It is possible that differences may exist. Thesystem could be designed for mobile coverage, in which case, the antenna mounted on the externalof the vehicle may have higher gain.

Another scenario is a fixed application. An option for the FWT is to have a whip antenna connecteddirectly to the FWT unit. This whip antenna gain may differ based upon product or vendor. Anotheroption is that the FWT installation may utilize yagi or patch antennas with much greater gain anddirectivity.


4


In some circumstances for a fixed application, particularly for users in fringe coverage areas,external antennas are appropriate alternatives to the simple whip antenna. The vendor of the FWTsshould be contacted to determine what antenna options may be available.

4.2.2 CDMA Specific Parameters

CDMA specific parameters are those items in the RF link budget which will have different valuesbased on the technology chosen. CDMA parameters include such factors as: interference margin,soft handoff gain and Eb/No.

4.2.2.1 Interference Noise Rise

In determining RF coverage in CDMA systems, the effect of interference generated from otherusers on the serving cell as well as the neighboring cells must be considered. As discussed inChapter 3, this is in contrast to the RF coverage analysis for AMPS cells where interference mainlyaffects the frequency assignment, but not the coverage.

The interference noise rise margin is dependent upon the amount of loading assumed in the system.Different cell deployment strategies can be modeled by varying the interference margin. CDMAcell deployments could be based on loading individual frequencies one by one, until they achievethe target load (for instance, a 6 dB noise rise). An alternative deployment could utilize moreCDMA radio carriers, initially operating at a reduced load, to further extend the range of the cells(for instance, 3 dB noise rise) while trading off capacity (exploiting any immediate spectrumavailable). This 3 dB system rise improvement would result in approximately 30% fewer CDMAcell sites at system turn-on.

The following equation can be used as a first pass approximation for the amount of interferencemargin to be added to the reverse RF link budget to account for loading the CDMA system withusers.

[EQ 4-1]

Where X is the system load, specified as a fraction of pole capacity. For example, a cell siteoperating near full capacity has X equal to seventy-five percent (75%). Noise rise varies as afunction of propagation, environment, load, user distribution, etc.

The derivation for Equation 4-1 can be shown as follows.

Assuming a CDMA system with subscribers in the cell of interest and perfect reverse link powercontrol such that the power received at the base site due to each subscriber unit is the same,

, the signal to noise plus total (in-cell and out of cell) inbound

interference ratio on the traffic channel can be defined as:

NoiseRise 101

1 X–------------

log=

N

Pr1Pr2

.... PrNPr= = =


4


[EQ 4-2]

[EQ 4-3]

[EQ 4-4]

Where: is the signal to noise plus total interference ratio

is the power (in Watts) received at the base site from each individual in-cell

subscriber unit. Note that, although the power received at the base site from aparticular subscriber unit is a function of several factors (i.e. subscriber unit’stransmit power, subscriber unit antenna gain, base site antenna gain, individualpath loss and fading), the reverse link power control ensures that the receivedpower from any subscriber unit in the cell is approximately at the same level .

is the spread bandwidth (in Hz) of the CDMA system

is the thermal noise power spectral density (in Watts/Hz) at the input to the

receiver Low Noise Amplifier (LNA)

, is the interference power spectral density (in Watts/Hz) from all

of the subscriber units within the cell at the input to the receiver LNA. Note that,in the cell of interest, out of a total of subscriber units, only one subscriber unitis the one of interest, hence there are interfering subscriber units.

is the voice activity factor or the fraction of time voice is transmitted during a call

is the interference power spectral density (in Watts/Hz) from all of the subscriber

units in other cells at the input to the receiver LNA and is the function of theirrespective path loss characteristics, load, size and power control

is the figure of merit for digital systems and is defined as energy per bit to noise

plus total interference power spectral density ratio

, is the Processing Gain of the CDMA system. MHz for

an IS-95 and IS-2000 1X CDMA system and is the bit rate of the traffic

channel (e.g. 9.6 kbps traffic channel or 14.4 kbps traffic channel).

SNRPr

NoW IoW IocW+ +( )---------------------------------------------------=

Eb

Nt------ SNR PG⋅ SNR

WRb------⋅= =

SNREb Nt⁄W Rb⁄---------------=

SNR

Pr

Pr

W

No

Io

N 1–( )αPr

W----------------------------=

NN 1–

α

Ioc

Eb Nt⁄

PG W Rb⁄= W 1.2288=

Rb


4


Furthermore, the frequency reuse factor or the F-factor of a cell is defined as the ratio of inboundinterference from subscriber units within the cell (intra-cell) to the total inbound interference fromsubscriber units in all the cells (including the cell of interest). Since each subscriber unit is apotential interferer, F-factor is given by

[EQ 4-5]

Some references to the frequency reuse factor may be in terms of out of cell interference to in cellinterference (f = OutCell/InCell). The frequency reuse factors F and f can be equated with thefollowing equation:

[EQ 4-6]

Substituting the value of into Equation 4-5 results in:

[EQ 4-7]

Substituting the value of into Equation 4-2 and dividing both numerator and denominator by

, can be rewritten as

[EQ 4-8]

[EQ 4-9]

Substituting the value of F-factor from Equation 4-7 into Equation 4-9 results in,

[EQ 4-10]

[EQ 4-11]

FInCell

InCell OutCell+--------------------------------------------

Io

Io Ioc+-----------------= =

F1

1 f+-----------=

Io

FN 1–( )αPr

N 1–( )αPr IocW+----------------------------------------------=

Io

NoW SNR

SNRPr

NoW N 1–( )αPr IocW+ +----------------------------------------------------------------

Pr N( oW )⁄

1N 1–( )αPr

NoW----------------------------

IocW

NoW------------+ +

--------------------------------------------------------= =

SNRPr N( oW )⁄

1NαPr IocW+( )

NoW-------------------------------------

αPr

NoW-----------–+

-----------------------------------------------------------------Pr N( oW )⁄

1N 1–( )αPr IocW+

NoW----------------------------------------------+

--------------------------------------------------------= =

SNRPr N( oW )⁄

11

NoW-----------

N 1–( )αPr

F----------------------------⋅+

------------------------------------------------------Pr N( oW )⁄

1α N 1–( )

F----------------------

Pr

NoW-----------

+

-------------------------------------------------= =

SNRs

1αF--- N 1–( )s+

----------------------------------=


4


where, .

Solving Equation 4-11 for s,

[EQ 4-12]

where is defined as the loading factor of the system and is given by

[EQ 4-13]

The upper bound on the number of users or the pole capacity of the cell of interest can be obtainedby substituting into Equation 4-13 and replacing SNR with Equation 4-4 to yield:

[EQ 4-14]

The system rise is defined as the ratio of thermal noise plus total inbound interference to thermalnoise and is given by

[EQ 4-15]

From Equation 4-2 and Equation 4-15 yields the following:

[EQ 4-16]

Substituting the value of from Equation 4-12 in Equation 4-16 results in:

or [EQ 4-17]

R (dB) is the median rise. In other words, noise rise is above (or below) this level 50% of the time.This is due to the voice activity ( ) term used in the SNR calculation.

Figure 4-6 is a graphical representation of Equation 4-17 and plots rise versus the loading factor X.From the plot, 50% loading corresponds to a rise of 3 dB and 75% loading corresponds to a 6 dBrise.

s Pr N( oW )⁄=

sSNR

1αF--- N 1–( ) SNR⋅–

----------------------------------------------- SNR1 X–------------= =

X

XαF--- N 1–( ) SNR⋅=

X 1=

Npole 1F

α SNR⋅-------------------+ 1

Fα---

W Rb⁄Eb Nt⁄---------------⋅+= =

RNoW I+ oW IocW+

NoW----------------------------------------------=

RPr N( oW )⁄

SNR--------------------------- s

SNR-----------= =

s

R1

1 X–------------= R (dB) 10 1 X–( )log–=

α


4


Figure 4-6: Rise (dB) at the cell of interest versus X (% load) at the cell of interest

4.2.2.2 Soft Handoff Gain

Soft handoff is the term that is normally associated with the fact that a CDMA system makes aconnection to a target cell prior to releasing (breaking) from the source site, commonly referred toas “make-before-break”. A hard handoff, associated with AMPS, GSM, or USDC, requires that thesignal strength from the target cell be greater than the signal strength from the source cell by ahysteresis value in order to reduce the number of handoffs per call and the “ping-pong” effect. Thishysteresis requires an overlap between the cell coverage areas. The soft handoff gain correspondsto a decreased shadow fade margin required by the CDMA soft handoff over that of a hard handoffsystem.

Some proponents of CDMA may have a separate entry in the RF link budget for soft handoff gain.The purpose of this is to provide information as to the benefits of CDMA over other technologies.Some system designers believe that the soft handoff gain should be accounted for in the reliabilityvalue (shadow fade margin). The example RF link budget provided in a later section incorporatesthe soft handoff gain in with the shadow fade margin. Refer to the section on Reliability for furtherdiscussion on the shadow fade margin.

For a fixed system, the gain offered by soft handoff may or may not be present depending upon thesystem design. For instance, a single isolated site supporting a fixed system would have noneighboring sites to even allow soft handoff to occur. In this situation, the soft handoff gain wouldbe zero. Another situation is for a fixed system utilizing external FWT antennas. These directionalantennas tend to be sited to the best signal source and therefore minimal advantage from soft


4


handoff would be recognized. Even for the situation of a fixed system using the FWT whipantennas, soft handoff gain may be lower than seen in a mobile environment. The FWT installationcauses a form of building directionality which may decrease the soft handoff advantage.

4.2.2.3 Eb/No

Eb/No corresponds to energy per bit over interference plus noise density for a given target FrameErasure Rate (FER, typical voice FER target is 1%). In digital communications, it is customary todesignate one-sided noise density with No. In CDMA, interference is dominated by the noisegenerated due to other users in the system. The notation, No, in this section refers to the total powerdensity due to interference and noise.

Included in the CDMA Eb/No value is diversity improvement arising from performance inRayleigh fading. This is distinct from the entry “Soft Handoff Gain” which represents an estimateof the performance improvement of soft handoff, relative to hard handoff, when experiencing lognormal shadowing.

In general, the required downlink Eb/No, to provide an acceptable audio quality, improves at higherspeeds and in soft handoff. In the uplink path, the required Eb/No improves at lower speeds (whichis the opposite of the downlink). The worst case Eb/No value for voice communication on theuplink is at about 30 kmph.

The uplink Eb/No value accounts for rake (non-coherent combining) receiver, dual antenna, andinterleaving/coding. The downlink Eb/No value accounts for rake (coherent, maximal ratiocombining) receiver, and interleaving/coding.

For mobile systems, the Eb/No target varies dynamically as the subscriber moves around. However,FWTs are fixed and the only movement is that of people around the FWT in a building and largevehicles or pedestrians close to an outdoor FWT antenna. Optimized FWT deployment maysignificantly reduce the Eb/No target by avoiding the fading caused by the surroundingenvironment.

In a mobile environment, the fading characteristic is Rayleigh. For a fixed system, the fadingenvironment may be more Rician. The Eb/No value assumes a certain type of fading environment.The Eb/No requirement for a fixed system will therefore be different than for a mobile environment.The Eb/No target value may range from 4 dB to 8 dB for CDMA fixed systems. The Eb/No targetvalue should be set to 8 dB for isolated cells using indoor omni FWT antennas or for cells withlittle SHO benefits in the fringe areas. However, if external directional FWT antennas are used anda Line Of Site (LOS) path exists between the cell site and the FWT antenna, an Eb/No target valueof 4 dB may be used.

As improvements are made to the hardware (chip sets) and to the software (how the energy ismanaged), the Eb/No requirement level may be lessened. Typical Eb/No values used for fixedsystems are stated above. The early requirements for a mobile system are approximately 7 to 7.5


4


dB for the 8 kbps and 13 kbps vocoder respectively. With the latest chip sets (e.g. QualcommCSM5000, Motorola EMAXX), the Eb/No values are approximately 1.5 to 2 dB less for voicecommunications.

IS-95A and IS-95B assume the same Eb/No values. For the IS-2000 RF reverse link, there areseparate Eb/No values provided for the fundamental channel rate and each supplemental channelrate. The Eb/No values for the supplemental channel rates (19.2 kbps and greater) are less than thefundamental Eb/No. Two main factors are contributing to this. A higher FER for the higher datarates may be targeted as compared to lower FER for lower data rates for speech (9600 bps e.g.).This will reduce the required Eb/No. The RF link budget shown in Table 4-7 on page 4-39 assumesan FER of 5% for the supplemental channel rates and an FER of 1% for the fundamental channel.It is viewed that the radio link protocols (RLP) will allow for relaxed FER requirements for thesupplemental channel. The control channel information carried on the fundamental channelrequires the better FER. Turbo coding is the other factor contributing to the lower Eb/No value forthe supplemental channels. Turbo coding improves upon the error correction at the higher datarates. The higher the data rate, the larger the benefit from Turbo coding (Turbo coding gain growsas the number of bits sent increases for a given frame size) which results in a lower Eb/No for agiven FER target.

From a link budget analysis, only one Eb/No value can be assumed for a given scenario. Theappropriate Eb/No value to be used in the RF link budget is based upon the system designassumptions (base station equipment and vocoder rate).

The Motorola NetPlan CDMA Simulator incorporates a family of curves to more accuratelyaccount for the Eb/No requirements needed to meet a desired FER for each link that is beinganalyzed between the user and the site. Refer to Section 4.6 for additional discussion on thesimulator.

4.2.3 Product Specific Parameters

Product specific parameters are those items in the RF link budget which can vary based on theproduct (base station and subscriber) chosen. There may be differences between products withinMotorola’s base station product line, such as differences in PA power. Differences will also existbetween different equipment vendors. Each equipment vendor will have their own vision of thetype of market their equipment is to satisfy.

4.2.3.1 Product Transmit Power

The transmit power is typically referenced by the power output of the piece of equipment prior tothe RF transmission lines and antennas. The point at which the transmit power is being measuredneeds to be determined to ensure that there are no gains or losses left out of the link budget.


4


4.2.3.1.1 Subscriber Unit

The IS-95A standard provides the maximum effective radiated power (ERP) for any class ofpersonal station transmitter in Table 6.1.2.1-1. The Class II personal station is not to exceed 2.5Watts (34 dBm). For the Class III personal station, the minimum ERP is 0.2 Watts (23 dBm) andthe maximum ERP is 1 Watt (30 dBm).

The CDMA standard for 1.8 to 2.0 GHz (ANSI J-STD-008) provides the maximum effectiveisotropic radiated power (EIRP) for any class of personal station transmitter in Section 2.1.2.1. TheClass I personal station is not to exceed 2 Watts (33 dBm). For the Class II personal station, theminimum EIRP is 0.2 Watts (23 dBm) and the maximum EIRP is 1 Watt (30 dBm).

There is a slight difference between the PCS and Cellular specifications. Cellular references theoutput power with respect to a dipole (ERP), whereas PCS makes reference to an isotropic radiator(EIRP). Therefore, there is approximately a 2 dB difference between the specifications given in thestandards documents.

The latest version of 3GPP2 C.S0011, Recommended Minimum Performance Standards forcdma2000 Spread Spectrum Mobile Stations, also provides a table of radiated powers for thevarious band classes that exist.

The typical subscriber value to be used in the reverse link (uplink - subscriber transmit to basereceive) is 23 dBm.

With respect to the reverse RF link budget, one parameter could be used for the transmit power ofthe subscriber unit (the EIRP or ERP value) or it may be desirable to break up this value into threeparts. The three parts are: subscriber PA output, transmission line and connector losses, and theantenna gain.

Since the subscriber unit, portable or FWT, can be purchased from different vendors, thespecifications for each subscriber unit should be obtained.

With IS-95B, high speed packet data is supported by concatenating multiple RF channels on theforward link (Walsh codes). To enable the concatenation of multiple channels, IS-95B compatiblesubscriber units are required. Motorola’s IS-95B HSPD was not implemented on the reverse link,thus only one RF channel is supported on the reverse link. It is assumed that the IS-95B subscriberunit’s physical characteristics will be the same as those that were used for IS-95A voice. If adifferent device is used for data than for voice, the subscriber PA output, transmission line andconnector losses, and the antenna gain parameters would need to be determined.

With IS-2000, high speed packet data is supported with the use of supplemental channels. IS-2000compatible subscriber units are required to support this air interface specification. With IS-2000,the reverse link can support multiple channels (e.g. reverse pilot channel, fundamental channel,supplemental channel). The example IS-2000 reverse RF link budget in Table 4-7 on page 4-39 hastwo additional rows to show the amount of power that would be dedicated to the fundamental ordedicated control channel and to the supplemental channel (for reverse data rates greater than 9.6kbps). The following definitions were obtained from the IS-2000 specifications.


4


• The Reverse Fundamental Channel (R-FCH) corresponds to a portion of the ReverseTraffic Channel, which carries higher-level data and control information from asubscriber station to a base station.

• The Reverse Supplemental Channel (R-SCH) corresponds to a portion of RadioConfiguration 3 through 6 Reverse Traffic Channel, which operates in conjunction withthe Reverse Fundamental Channel or the Reverse Dedicated Control Channel. TheReverse Supplemental Channel will provide higher data rate services, and is the channelon which higher-level data is transmitted.

• The Reverse Dedicated Control Channel (R-DCCH) corresponds to the portion of aRadio Configuration 3 through 6 Reverse Traffic Channel used for the transmission ofhigher-level data and control information from a subscriber station to a base station.

• The Reverse Traffic Channel corresponds to a traffic channel on which data andsignaling are transmitted from a subscriber station to a base station. The Reverse TrafficChannel is composed of up to one Reverse Dedicated Control Channel (IS-2000), up toone Reverse Fundamental Channel (IS-95A/B or IS-2000), zero to two ReverseSupplemental Channels (IS-2000), and zero to seven Reverse Supplemental CodeChannels (IS-95B).

The subscriber unit transmit power associated with the R-FCH or R-DCCH is dependent upon theprocessing gain and Eb/No requirements associated with the fundamental channel. The subscriberunit transmit power associated with the R-SCH is dependent upon the processing gain and Eb/Norequirements associated with the data rate of the R-SCH (19.2, 38.4, 76.8 or 153.6 kbps). When asupplemental channel is required, some of the subscriber unit’s transmit power needs to beallocated for the R-FCH or R-DCCH. The remaining transmit power can be utilized for the R-SCH.The difference in the transmit power between the R-SCH and the R-FCH or R-DCCH is based onthe difference of the processing gain and Eb/No requirements of the different channels. Thefollowing set of equations provide a method to determine the transmit powers for the variousreverse traffic channels.

PT = PFCH + PSCH

PSCH = 10^[(Processing_Gain_DeltadB + Eb/No_DeltadB)/10] * PFCH

PT = PFCH + 10^[(Processing_Gain_DeltadB + Eb/No_DeltadB)/10] * PFCH

PFCH = PT / 1 + 10^[(Processing_Gain_DeltadB + Eb/No_DeltadB)/10]

Where:PT is the total subscriber unit transmit power available (mW)

PFCH is the portion of the total subscriber unit transmit power available for the reversefundamental channel or reverse dedicated control channel (mW)

PSCH is the portion of the total subscriber unit transmit power available for the reversesupplemental channel (mW)


4


The following set of calculations provide an example of how the subscriber unit transmit powersassociated with the R-FCH and R-SCH for the 19.2 kbps data rate, represented in Table 4-7 onpage 4-39, were obtained. A similar approach would be followed for each of the othersupplemental channel rates.

PT = 200 mW

PFCH = 200 /1+10^[(10*Log(19200/9600)+(3.5-5.6))/10]

= 89.7 mW

PSCH = 200 - 89.7 = 110.3 mW

= 10 * Log(PSCH) = 20.4 dBm

4.2.3.1.2 Base Station

The CDMA standard for 1.8 to 2.0 GHz (ANSI J-STD-008) in Section 3.1.2 states that the basestation shall not transmit more than 1,640 Watts of effective isotropic radiated power (62.1 dBmEIRP) in any direction in a 1.25 MHz band for antenna heights above average terrain less than 300meters. The base transceiver station power is used in the forward link (downlink - base transmit tosubscriber receive).

With respect to the forward RF link budget, one value could be used for the transmit power of thebase station (the EIRP value) but typically this value is separated into three parts. The three partsare: base station PA output, transmission line and connector losses, and the antenna gain. Thesubscriber units are typically more uniform, having similar line losses and antenna gains. The basestation, on the other hand, can vary quite a bit from one base station to the next. Based on theconfiguration of the site, location of antennas with respect to the base station infrastructure, andpower out required, it is not as simple to have one EIRP value that is common across the majorityof the sites. Since each base station site can be unique, the uniqueness of the site needs to beaccounted for to ensure the appropriate EIRP is being designed for. For instance, one site mayrequire a 100 ft. run of main transmission line, whereas another site may only require a 50 ft. run.The additional loss for the longer run would alter the EIRP from the site. Another difference wouldexist based on differences of antennas and their associated gains.

The power output of the base station is normally assumed to be the power out at the top of thecabinet. It is possible that each vendor will have different transmit powers for their equipment. Inaddition, one vendor may have different transmit powers for each product in their portfolio of basestation products. Obtain the specifications for the particular base station(s) that will be used in thesystem design. In looking at the specifications, the power amplifiers may be for multiple carriersor for a single tone (carrier). Refer to Section 4.4 for additional information on the Motorola BTSPAs.


4


4.2.3.2 Product Receiver Sensitivity

The sensitivity of a radio receiver is a measure of its ability to receive weak signals. The followingequation can be utilized in calculating the sensitivity of a radio receiver.

[EQ 4-18]

Where:k Boltzmann’s constant = 1.38x10-23 W/(Hz K)

T Room temperature in degrees Kelvin = 290 K

W Bandwidth of the carrier = 1228800 Hz

NF Noise figure of the equipment

Eb/No Energy bit density over noise

R Information bit rate

[EQ 4-19]

The processing gain, PG, is the result of the bandwidth (W) divided by the data rate (R). For IS-95Rate Set 1 (8 kbps vocoder), the data rate is 9600 bps. The resulting processing gain for this caseis obtained as follows:

PG = W/R = 1228800 / 9600 = 128

PGdB = 10 * Log (128) = 21.1 dB

The following table provides the data rate (R) and the resulting processing gain for various RateSets and radio configurations. The data rates provided in the table are those that are supported inCBSC Release 16.0. Refer to the latest IS-95A/B and IS-2000 standards for all of the data rates thatexist in the air interface standards.

Table 4-3: Processing Gain

Air Interface Reverse Link Radio Configurations Data Rate (bps) Processing Gain (dB)

IS-95A/B Rate Set 1 - Standard 8 kbps Vocoder orEVRC (Enhanced Variable Rate Coder)

9600 21.07

IS-95A/B Rate Set 2 - 13 kbps Vocoder 14400 19.31

IS-2000 1X Reverse Link Radio Configuration 1 9600 21.07


RxSensitivity kT( )dBm Hz⁄ WdB Hz⋅ NF( )dB Eb No⁄( )dB W R⁄( )dB–+ + +=

RxSensitivity 113– dBm NF( )dB Eb No⁄( )dB PGdB–+ +=


4


IS-95B supports high speed packet data, but because of the data applications that were beingdeployed, only the fundamental rate was provided on the reverse link. Therefore, the above tableonly provides the processing gain for the two different fundamental rates.

Differences in the receive sensitivity will exist between the subscriber unit and base station due tothe differences in Eb/No values, as discussed in Section 4.2.2.3, and the noise figure of theequipment. The other parameters in the receive sensitivity calculation will be the same for bothends of the link.

4.2.3.2.1 Base Station

The noise figure, or NF, of a network is a value used to compare the noise in a network with thenoise in an ideal or noiseless network. It is a measure of the degradation in signal-to-noise ratio(SNR) between the input and output ports of the network. Noise factor (F) is the numerical ratio ofNF, where NF is expressed in dB. The equation for converting noise factor to noise figure is:

[EQ 4-20]

Typically the noise figure value to be used in determining the receiver sensitivity value can beobtained from the specification sheet for the particular product. The noise figure for the base stationis approximately 6 to 7 dB maximum with a typical value of approximately 4.5 dB. Consult thebase station equipment vendor for the specifics.

In some instances, a tower top amplifier (TTA) may be installed at a site to improve the level ofthe received signal at the base station. The TTA includes an amplifier and therefore a new noisefigure needs to be determined since the configuration now has cascaded amplifiers. A TTA willonly benefit the reverse path (subscriber to base station). Since the TTA is only improving thereverse link, the forward link may become more of the limiting path. It may be that a larger poweramplifier is needed in the forward link in order to balance both paths.






IS-2000 1X Reverse Link Radio Configuration 4(Only the fundamental is initiallysupported by Motorola.)

14400 19.3

Table 4-3: Processing Gain

Air Interface Reverse Link Radio Configurations Data Rate (bps) Processing Gain (dB)

NF dB( ) 10 F( )log=


4


For a TTA scenario as mentioned above, it will be necessary to calculate the noise figure of a groupof amplifiers that are connected in series. This can be accomplished if the noise figure of eachindividual amplifier is known. The equation for determining the cascaded noise factor is:

[EQ 4-21]

Where:Fn is the noise factor of each stage

Gn is the numerical gain of each stage (not in dB)

The equation for converting Gain dB to linear Gain is:

[EQ 4-22]

One important point to be made with respect to Equation 4-21 is that if the gain of the first stageG1 is sufficiently high, the denominators of the subsequent terms will force those terms to be small,

leaving only F1. Therefore, the NF of the first stage will typically determine the NF of the cascaded

configuration.

The NF of two or more cascaded lossy networks can be found by simply adding the losses (in dB)of each network element. Examples of a lossy network element are: transmission lines, jumpers,duplexers, filters and mixers. If a duplexer with an insertion loss of 0.5 dB is followed by a maintransmission line loss of 3 dB, the combined noise figure of this cascaded network is 3.5 dB.

The following figure shows two different sites. One site has an amplifier located on the top of thetower. The other site is the more conventional site, that has no additional amplification beyond thebase station. This diagram will be used to run through an example showing the noise figureimprovement with the TTA. In this diagram, stage 2 in the tower top amplifier example and stage1 of the without tower top amplifier example represent cascaded lossy network elements which areable to be summed together.

FTotal F1

F2 1–

G1---------------

F3 1–

G1G2---------------

F4 1–

G1G2G3---------------------…+ + +=

G dB( ) 10 GLinear( )log=


4


Figure 4-7: Example of Two Different Receive Path Configurations

The following table lists the noise figures, noise factors, and gains for each stage shown above.

Table 4-4: Receive Path Noise Figures and Gains

With Tower Top Amplifier Without Tower Top AmplifierNF1 2.5 dB F1 1.78 NF1 3.0 dB F1 2.0

NF2 3.5 dB F2 2.24 NF2 6.0 dB F2 3.98

NF3 9.5 dB F3 8.91

G1 12.0 dB G1 15.85 G1 -3.0 dB G1 0.5

G2 -3.5 dB G2 0.45

Antenna

Jumper to Antenna

Main Transmission Line

Antenna Surge Protector

Jumper to Directional Coupler

Directional Coupler

Jumper to Duplexer

Jumper to Tx and Rx Antenna Port

BTS

Waveguide Entry Port

Duplexer

Tower Top Amplifier

BTS

Jumper

12 dBd

0.5 dB

3 dB

NF = 2.5 dB, Gain 12 dB

0.5 dB

12 dBd

0.5 dB

3 dB

A

B

C

D

With Tower TopAmplifier

Without TowerTop Amplifier

NF = 9.5 dB NF = 6 dB

Stage1

Stage2

Stage1

Stage2

Stage3


4


Based upon the information in Table 4-4 and Equation 4-20, Equation 4-21, and Equation 4-22, thenoise factor at reference point B in Figure 4-7 for the receive path with the TTA can be calculatedas follows:

[EQ 4-23]

FB = 2.97

Using Equation 4-20, the cascaded noise figure would be:

NFB = 4.73 dB

The design without the tower top amplifier would result in the following noise factor at referencepoint D shown in Figure 4-7:

[EQ 4-24]

FD = 7.96

NFD = 9.0 dB

The noise figure at point D could have also been determined by just adding the noise figure of stage1 to the noise figure of stage 2 because the elements which made up stage 1 were all lossy.

From the above calculations, the low noise figure and the gain of the TTA produces a cascadednoise figure of 4.73 dB at reference point B. This is a 4.77 dB improvement in the noise figure ascompared to the noise figure at point A. Point D, in the non-TTA case, can be compared to point Bto show the improvement in the noise figure and thus the reverse link improvement that can beachieved with the TTA. The reverse link has improved 4.27 dB (9 - 4.73) with the TTA.

If the impact of the TTA is to be applied to a link budget, the following values would be used:

Please note that for the example in Figure 4-7, the base station product which includes a TTA wasmodified to have a higher noise figure than the typical base station. The higher noise figure for thebase station/TTA configuration was implemented so that the gain of the TTA does not overdrivethe front-end of the base station.

Table 4-5: Link Budget Inputs

Parameter With TTA Without TTABase Rx Feeder Loss 0.5 dB 3.5 dBBase Noise Figure 4.73 dB 6 dBYields Rx Sensitivity @ point B C

FB 1.782.24 1–15.85

------------------- 8.91 1–15.85 0.45×------------------------------+ +=

FD 23.98 1–

0.5-------------------+=


4


Though the above scenario shows a reverse link budget advantage when a TTA is installed, not allaspects of a TTA may be as advantageous. The following lists some of the drawbacks of TTAs:

• Increased susceptibility to reverse interference noise • Since the TTA only improves the reverse link, an increase to the forward power may be

required to maintain a balanced link• Timing concerns (How large can a site be without causing timing issues?)• Active electronics at the top of the antenna structure (more susceptible to lightning,

more difficult for maintenance, etc.)

Due to the increased susceptibility to noise, Motorola does not typically recommend TTAs.Though in some scenarios (for example in rural applications), TTAs may be beneficial.

4.2.3.2.2 Subscriber Unit

The noise figure for the subscriber unit is approximately 10 dB. The required Eb/No value toprovide acceptable audio quality for the subscriber unit is highly dependent on several parameters.These parameters include: the speed, the environmental parameters, multipath and soft handoff ofthe subscriber unit. This is one of the reasons why it is difficult to determine a forward link budget.It is best left to a CDMA simulator that takes these situations into account.

4.2.4 Reliability (Shadow Fade Margin)

The shadow fade margin (also known as slow or log-normal fading margin) corresponds to thevariation in mean signal level caused by the subscriber passing through the shadows of hills orbuildings. The log-normal distribution has been found to be a good estimate of the statistical natureof shadowing and is used to calculate the probability of RF coverage at each point in the cell. Atpoints near the base station, the average received signal level and the probability of coverage willbe high. At points near the edge of the cell, the average received signal level and probability ofcoverage will be lower. The total probability of coverage for the entire cell is determined byintegrating the point probabilities over the cell area. The desired area coverage (e.g. 90%) isachieved by adjusting the fade margin to the necessary level. A normal distribution of signals canbe used in calculating the reliability. The following figure shows that adding a margin to the linkbudget will increase the reliability (confidence) of achieving the desired signal level.


4


Figure 4-8: Impact of Fade Margin on Reliability

The desired level of reliability is used to determine the amount of shadow fade margin that isrequired, where a 97% design requires several dB more margin than a 95% design. To improve theRF reliability, going further out on the tail of the distribution, additional margin is added to allusers. For a fixed system this may not be efficient nor cost effective since subscriber unit placementhas a big effect in determining the worst 5% of the users. The cost of increasing the reliability(increasing dB margin that will impact all users) should be replaced with fixing the worst 5% ofthe users, and thus saving the dB margin for the average users. For a fixed system, the fade margin,building penetration margin, and soft handoff gain should to be considered together to provide forthe best achievable link budget.

The fade margin is the amount of margin necessary to achieve the required area reliability (as perJakes’ equations5) for a given standard deviation. The standard deviation is a measured value thatis obtained from various clutter types. It basically represents the variance (log-normally distributedaround the mean value) of the measured RF signal strengths at a certain distance from the site.

5. Jakes, W.C., “Microwave Mobile Communications”, IEEE Press Reissue 1993 (Wiley, New York, 1974),pp. 125-127

No Fade Margin

Margin

Edge Reliability at 50%

Edge Reliability at greater than 50%


4


Therefore, the standard deviation would vary by clutter type. Depending on the propagationenvironment, the log-normal standard deviation can easily vary between 5 and 9 dB or evengreater. Assuming flat terrain, rural or open clutter types would typically have lower standarddeviation levels than the suburban or urban clutter types. This is due to the highly obstructiveproperties encountered in an urban environment, that in turn will produce higher standard deviationto mean signal strengths than that experienced in a rural area.

Jakes’ single cell reliability equations (refer to the following equations) that determine the edge andarea reliability of a single cell model are commonly used to approximate the reliability of a site.

[EQ 4-25]

Where:Edge reliability

xo Signal threshold level

x Signal mean at edge of the cell

Log normal standard deviation

[EQ 4-26]

[EQ 4-27]

[EQ 4-28]

Where:Fu is the fraction of the total cell area where the signal exceeds a threshold

determined by

Signal mean at edge of the cell

n propagation exponent value

A composite standard deviation can be obtained by the following:

[EQ 4-29]

PxoR( ) 1

2--- 1

2---erf

xo x–

σ 2-------------

–=

PxoR( )

σ

Fu12--- 1 erf a( )–

1 2ab–

b2

------------------ 1 erf

ab 1–b

--------------- +exp+

=

axo α–

σ 2--------------=

b10nLog10 e( )

σ 2--------------------------------=

Pxo

α

σc σ1( )2 σ2( )2… σn( )2+=


4


Where: Log normal standard deviation for environment, n

This composite standard deviation may sometimes be used if there are two or more environments(for instance, outdoors and in-building) which have their own standard deviation. For example ifthe standard deviation is 6 dB for outdoors and 8 dB for in-building, the composite standarddeviation to use in Jake’s equation would be 10 dB.

The following two figures (Figure 4-9 and Figure 4-10) are results from Jake’s single cell model.The edge reliability, Figure 4-9, has been shown for three different standard deviations (6.5, 8, and10 dB) to demonstrate the impact of the standard deviation.

Figure 4-9: Edge Reliability vs. Fade Margin

Figure 4-9 shows that edge reliability is dependent on the standard deviation and fade marginassumed. The following observations can be seen.

• As the standard deviation increases, the edge reliability is reduced for the same fademargin.

• As the standard deviation increases, a larger fade margin is required to maintain thesame edge reliability.

σn

Uplink Shadow Fade Margin (dB)

Edg

e R

elia

bili

ty

40%

50%

60%

70%

80%

90%

100%

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

6.5

8.0

10.0


4


The area reliability, Figure 4-10, assumes a standard deviation of 8 dB for the three curves. Thedifference in the curves is due to three different path loss slopes (32, 35, and 40 dB/decade).

Figure 4-10: Area Reliability vs. Fade Margin

Note: Within the legend of Figure 4-10, the first value corresponds to the propagation lossslope in dB per decade. The second value corresponds to the standard deviation in dB.

Figure 4-10 shows that the area reliability is dependent on the standard deviation, fade margin, andpropagation loss slope (the slope is dependent on the height of the antennas). The followingobservations can be seen.

• As the standard deviation increases, a larger fade margin is required to maintain thesame area reliability, assuming the same propagation slope.

• As the level of area reliability increases, a larger fade margin is required, assuming thesame standard deviation and propagation slope.

• As the propagation slope (path loss exponent) increases, a smaller fade margin isrequired to maintain the same area reliability, assuming the same standard deviation.

The preceding information is for a single cell. When multiple cells and soft handoff are accountedfor, the probability of meeting a given signal strength is increased. Soft handoff is not an absolute


Are

a R

elia

bili

ty

70%

75%

80%

85%

90%

95%

100%

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

40, 6.5

35, 6.5

32, 6.5

40, 8

35, 8

32, 8

40, 10

35, 10

32, 10


4


gain but can be viewed as a reduction in the fade margin requirement needed to meet a desired edgeor area reliability goal. For isolated sites, there would be no improvement since there would be nosites to enter into soft handoff with.

Since most systems are comprised of more than a single cell, the benefit of multiple cell effectscould be used. Simulations can be performed, given various assumptions (path loss slope, standarddeviation, correlation), to determine the appropriate shadow fade margin to be added to the linkbudget to provide for the reliability desired. This multiple cell effect accounts for the overlap ofadjacent cells and the fast handoff capability of the CDMA soft handoff method. As mentioned inthe previous soft handoff section, the gain associated with soft handoff can be rolled into oneshadow fade margin.

Motorola has performed various simulations for a multiple cell system and generated somereliability curves. The curves in Figure 4-11 show that 4.7 to 5.6 dB fade margin is required toreach 95% area reliability for a sector site. The curves show that the area reliability is a function ofthe configuration of the site, as well as the standard deviation and site-to-site correlation assumed.Motorola typically recommends the 5.6 dB shadow fade margin to design systems with an areareliability of 95% or slightly better.

The following two figures illustrate examples of the required fade margin based on simulations.These simulations account for the soft handoff advantage in a multi-cell system. The two figuresillustrate the cell area and edge reliability as a function of shadow fade margin. Note that therequired margin varies as a function of the propagation model and sectorization. The notation (x1,x2, x3), in the figures refer to the propagation model, where x1 is the path loss slope, x2 is thelognormal shadow fading standard deviation, and x3 is the site-to-site correlation (Note: path lossslope x1 converts to path loss dB/decade by multiplying x1 by a factor of 10).


4


Figure 4-11: Area Reliability as a Function of Shadow Fade Margin

For the above analysis, the sector sites assumed an antenna with 90° horizontal beamwidth. For agiven area reliability, the sector sites required a larger fade margin to account for the reduction ofgain experienced between the sectors.

Sector (3.5, 6.5, 0.5)

Sector (4, 8, 0.5)

Omni (3.5, 6.5, 0.5)

Omni (4, 8, 0.5)


Are

a R

elia

bilit

y


4


Figure 4-12: Edge Reliability as a Function of Shadow Fade Margin

As mentioned in the section on soft handoff gain, some RF link budgets may have separate entriesfor soft handoff gain and shadow fade margin. Typically when this is done, Jakes’ single cell modelfade margin is used to obtain the reliability level desired. The CDMA RF link budget, though, stillneeds to account for the benefit of soft handoff. Therefore, an approximation for the benefit of softhandoff gain is required in the link budget. In the RF link budget spreadsheet analysis, Motorolatypically assumes the benefit for soft handoff in a mobile environment to be approximately 3.5 dBfor a cluster of sties. If there is only a single entry in the RF link budget for the fade margin, thenthe composite fade margin would be the single cell shadow fade margin minus the benefitassociated with soft handoff and multiple cells. For example, assuming a 9.1 dB shadow fademargin and 3.5 dB benefit from soft handoff and multiple cells, the composite fade margin wouldbe 5.6 dB (9.1 minus 3.5).This is an approximation based on a single cell model plus an assumedsoft handoff benefit.

4.2.5 Example Reverse (Uplink - Subscriber to Base) Link Budget

The following table provides an example of a reverse path RF link budget for both a mobile/portable system and a fixed IS-95 system. This basic RF link budget example could be appliedtowards an IS-95A or IS-95B system. Antenna gains, feeder losses, noise rise, building losses,vehicle losses, shadow fade margins, etc. will differ from system to system and from site to site

Sector (3.5, 6.5, 0.5)

Sector (4, 8, 0.5)

Omni (3.5, 6.5, 0.5)

Omni (4, 8, 0.5)


Edg

e R

elia

bili

ty


4


(possibly even from sector to sector) based on the design objectives of the system planner.

Table 4-6: Example of an IS-95 CDMA Reverse RF Link Budget

Note: 1. It is assumed that the latest version of chip sets are being utilized.2. Path Loss values shown assume a medium traffic load on the reverse link for the

CDMA system.3. The shadow fade margin assumes the effects of soft handoff and multiple cells.

Where:Sensitivity and path loss are calculated as follows:

S = kTB + Nfb + E - PG

Lp = Pp - Lfp + Gp + Gb - Lfb - S - Im - Tm - Hm - Vm - Bm - Fm

Li = Lp + (2 * 2.14)

Parameter Unit Reference Mobile13 kbps

Mobile8 kbps

Fixed8 kbps

Subscriber Unit Tx Power dBm Pp Section 4.2.3.1.1 23 23 23

Subscriber Unit Tx FeederLoss

dB Lfp Section 4.2.1.5 0 0 0

Subscriber Unit AntennaGain

dBd Gp Section 4.2.1.6 -2.1 -2.1 -1.0

Body Loss dB Hm Section 4.2.1.3 2 2 0

Vehicle Loss dB Vm Section 4.2.1.2 7 7 0

Building Loss dB Bm Section 4.2.1.1 0 0 6

Base Antenna Gain dBd Gb Section 4.2.1.6 14.5 14.5 14.5

Line Loss dB Lfb Section 4.2.1.5 3 3 3

kTB dBm kTB Section 4.2.3.2 -113.1 -113.1 -113.1

Noise Figure dB Nfb Section 4.2.3.2.1 6 6 6

Eb/No (Note: 1) dB E Section 4.2.2.3 6.0 5.6 5.6

Processing Gain dB PG Section 4.2.3.2 19.3 21.1 21.1

Base Rx Sensitivity dBm S Section 4.2.3.2 -120.4 -122.6 -122.6

Interference Margin(Note: 2)

dB Im Section 4.2.2.1 3 3 3

Ambient Noise Rise dB Tm Section 4.2.1.4 0 0 0

Shadow Fade Margin(Note: 3)

dB Fm Section 4.2.2.2 &Section 4.2.4

5.6 5.6 5.6

Max. Allowable Path Loss dB Lp 135.2 137.4 141.5

Isotropic Path Loss dB Li 139.5 141.7 145.8


4


In comparing the link budget between mobile (portable) and fixed, there are three main differences.The first being that the fixed link budget has a subscriber antenna gain of 1.1 dB better than themobile case (assumes FWT has the whip antenna installed, but could be higher with externalantennas). It is also assumed that the FWT whip antenna is connected directly to the FWT base unitand therefore there is no line loss between the FWT base and antenna. Other scenarios may requirethat a line loss be added for antennas not connected directly to the base unit. A second differenceis that there is no body loss assumed for the fixed case. The antenna gain and body loss differencesgive a 3.1 dB link budget advantage of fixed over mobile.

The third difference is with respect to the building/vehicle penetration loss. For the fixed case, abuilding loss value of 6 dB is shown based upon the assumption that the FWT with whip antennawill be placed close to a window and in a location that will minimize the impact of the buildingloss. The amount of building penetration will need to be adjusted (could be greater or less than the6 dB value assumed here) based on the installation location of the FWT antenna and the buildingcharacteristics (some buildings may allow RF to pass better than others).

For the mobile case, 7 dB is assumed for a vehicle penetration value. If in-building is desired, thenthis value would need to be modified accordingly. If it is desired to provide in-building coverage,additional margin would be required.

The fade margin is set the same for fixed and mobile for these link budget examples. One view isthat the fade margin should be increased to provide for better reliability for a fixed system. Thisincreased fade margin, though, would apply to all subscribers. Another way to improve thereliability for a fixed system is not by adding margin in the link budget, which effects all users, butto take the worst performing FWT and replace the whip antenna with an external antenna. This willimprove its performance, which ultimately improves the overall reliability. Another view is thatthe reliability for fixed should be higher since fixed is competing with the wireline service. Theamount of fade margin is related to the reliability. If the reliability criteria is increased, the fademargin will also need to be increased.

Another value which differs between the fixed and mobile is the subscriber antenna height. This isnot part of the link budget above, but would be required in the propagation models. The typicalsubscriber antenna height assumed for the mobile (portable) case is 1.5 meters. The FWT antennahas the ability of being positioned at various heights (on a desk, on a wall, externally on the roof),therefore the height of the FWT could range from 1 to 3 or more meters.

The following table provides an example of an IS-2000 1X reverse path RF link budget for amobile/portable system. It represents the reverse Radio Configuration 3. A similar approach canbe done for reverse Radio Configuration 4 by replacing the subscriber transmit power, processinggain and Eb/Nos with the appropriate values. Antenna gains, feeder losses, noise rise, buildinglosses, vehicle losses, shadow fade margins, etc. will differ from system to system and from site tosite (possibly even from sector to sector) based on the design objectives of the system planner.


4


Table 4-7: Example of an IS-2000 1X CDMA RF Link Budget

Note: 1. Path Loss values shown assume a medium traffic load on the reverse link for theCDMA system.

2. The shadow fade margin assumes the effects of soft handoff and multiple cells.

An observation of the above table shows that the allowable path loss decreases as the data rateincreases. This means that a smaller cell radius would be required to support higher data rates. Forexample, more sites would be required if a system was to be designed based on a reverse link

Parameter Unit Reference 9.6 kbps

9.6 kbps

19.2 kbps

38.4 kbps

76.8 kbps

153.6 kbps

Reverse Traffic Channel FCH SCH SCH SCH SCH SCH

Total Subscriber Unit TxPower

mW PT Section 4.2.3.1.1 200 200 200 200 200 200

Subscriber Unit R-FCH orR-DCCH Tx Power

mW PFCH Section 4.2.3.1.1 200 111 90 63 41 25

Subscriber Unit R-SCHTx Power

mW PSCH Section 4.2.3.1.1 - 89 110 137 159 175

Subscriber Unit Tx Power(for the specified reversetraffic channel)

dBm Pp Section 4.2.3.1.1 23 19.5 20.4 21.4 22.0 22.4

Subscriber Unit Tx FeederLoss

dB Lfp Section 4.2.1.5 0 0 0 0 0 0

Subscriber Unit AntennaGain

dBd Gp Section 4.2.1.6 -2.1 -2.1 -2.1 -2.1 -2.1 -2.1

Body Loss dB Hm Section 4.2.1.3 2 2 2 2 2 2

Vehicle Loss dB Vm Section 4.2.1.2 6 6 6 6 6 6

Building Loss dB Bm Section 4.2.1.1 0 0 0 0 0 0

Base Antenna Gain dBd Gb Section 4.2.1.6 14.5 14.5 14.5 14.5 14.5 14.5

Line Loss dB Lfb Section 4.2.1.5 3 3 3 3 3 3

kTB dBm kTB Section 4.2.3.2.1 -113.1 -113.1 -113.1 -113.1 -113.1 -113.1

Noise Figure dB Nfb Section 4.2.3.2.1 6 6 6 6 6 6

Eb/No dB E Section 4.2.2.3 5.6 4.6 3.5 3.0 2.5 2.1

Processing Gain dB PG Section 4.2.3.2 21.1 21.1 18.1 15.1 12.0 9.0

Base Rx Sensitivity dBm S Section 4.2.3.2 -122.6 -123.6 -121.6 -119.1 -116.6 -114.0

Interference Margin(Note: 1)

dB Im Section 4.2.2.1 3 3 3 3 3 3

Ambient Noise Rise dB Tm Section 4.2.1.4 0 0 0 0 0 0

Shadow Fade Margin(Note: 2)

dB Fm Section 4.2.2.2 &Section 4.2.4

5.6 5.6 5.6 5.6 5.6 5.6

Max. Allowable Path Loss dB Lp 138.4 135.9 134.8 133.3 131.4 129.2

Isotropic Path Loss dB Li 142.7 140.2 139.1 137.6 135.7 133.5


4


assuming 76.8 kbps than if the system requirement was for 9.6 kbps. Assuming a propagationexponent of 3.5, the 7 dB path loss difference between these two data rates would correspond tothe 76.8 kbps scenario requiring approximately 2.5 times the number of sites as the 9.6 kbpsscenario.

IS-2000 provides the ability to have asymmetrical data transmission. That is, the data rate on theforward link can be different than the data rate employed on the reverse link. Initial dataapplications for IS-2000 are assumed to demand more data to be transferred on the forward linkthan on the reverse link (i.e. the forward link data rate will need to be faster than the reverse linkdata rate). Additionally, it is viewed that the reverse link will be the limiting link with regards tocoverage, whereas the forward link will be the limiting link with regards to capacity. It is possiblethat an RF reverse link based on a fundamental rate of 9.6 kbps would allow for sufficient path lossso that a forward link of 76.8 kbps could be achieved. This means that the reverse link coverage tosupport 9.6 kbps may provide for sufficient coverage on the forward link to support a user needing76.8 kbps. This is not saying that a user rate of 153.6 kbps is not supported. A user, in closeproximity to the site, could have a forward and/or reverse supplemental channel at 153.6 kbps, butnot at the fringe of the site. Given these views, a system design based on the RF reverse link forreverse data rates above 19.2 kbps may not be necessary. If data applications require a high volumeof reverse data, then higher data rates need to be considered.

These link budgets are examples and may need to be modified to accommodate specific designgoals for a system. Refer to the previous discussion on each of the parameters to determine ifalterations are required for a specific design.

4.2.6 RF Link Budget Summary

The RF link budget propagation related parameters have the most variability. These propagationrelated parameters are typically vendor and technology independent. The link budget parameters,but not the values, listed above can apply to all technologies and frequencies. For instance, the lossassociated with the transmission line is dependent upon the frequency of operation, but not that itwill be used for CDMA instead of GSM.

The following figure demonstrates the impact to the quantity of sites required if one assumption ismade over another. The figure only shows 5 examples. There are many other combinations that arepossible.


4


Figure 4-13: Impact of dB Trade-off to Number of Sites

4.3 Propagation Models

The propagation model is used in conjunction with the RF link budget to obtain an estimate of thecell radius based on the allowable path loss from the link budget. Statistical propagation modelsare used in budgetary designs to give quick estimates of cell radii within various environments andultimately to estimate the number of cells required for a system.

There are many RF propagation factors which could extend or restrict the coverage of a site (e.g.proximity to buildings, actual terrain, antenna heights, topology, morphology, etc.). More detailedpropagation models, which include some or all of these factors, will produce more accuratepredictions of cell radii. The following sections give additional detail concerning statisticalpropagation models.

4.3.1 Free Space Propagation Model

The free space power received by a receiver antenna, which is at a distance of d from the transmitterantenna, is given by the Friis free space equation.

[EQ 4-30]PR PT G⋅ T GRλ

4πd----------

2

⋅ ⋅=


4


Where:PT is the transmitted power

GT is the transmitting antenna gain

GR is the receiving antenna gain

d is the separation distance between antennas

The path loss, which represents the signal attenuation as a positive quantity, is defined as thedifference between the effective transmitted power and the received power. It may or may notinclude the effects of the antenna gains. The path loss for the free space model, when the antennasare assumed to have unity gain, is provided by the following equation.

[EQ 4-31]

Expressed in dB as:

[EQ 4-32]

Where:d is in meters

f is in Hertz

c is equal to the speed of light (3 x 108 meters per second)

[EQ 4-33]

[EQ 4-34]

[EQ 4-35]

[EQ 4-36]

[EQ 4-37]

The above free space equations show that 6 dB of loss is associated with a doubling of thefrequency. This same relationship also holds for the distance, if the distance is doubled, 6 dB ofadditional loss will be encountered.

PT

PR------ 4πd

λ----------

2 4πdfc

------------

2

==

LFS dB( ) 10PT

PR------

204πc

------ 20 f( ) 20 d( )log+log+log=log=

LFS dB( ) 147.56 20 fHz( ) 20 dmeters( )log+log+–=

LFS dB( ) 32.44 20 f( MHz ) 20 d( km )log+log+=

LFS dB( ) 27.55– 20 f( MHz ) 20 d( meters )log+log+=

LFS dB( ) 36.58 20 f( MHz ) 20 d( miles )log+log+=

LFS dB( ) 37.87– 20 f( MHz ) 20 d( feet )log+log+=


4


4.3.2 Hata Propagation Model

Among the many technical reports that are concerned with propagation prediction methods formobile radio, Okumura’s6 report is believed to be the most comprehensive one. In his report, manyuseful curves to predict a median value of the received signal strength are presented based on thedata collected in the Tokyo area. The Tokyo urban area was then used as a basic predictor for urbanareas. The correction factors for suburban and open areas are determined based on the transmitfrequency. Based on Okumura’s prediction curves, empirical formulas for the median path loss,Lp, between two isotropic antennas were obtained by Hata and are known as the Hata empirical

formulas for path loss7. The Hata propagation formulas are used with the link budget calculationto translate a path loss value to a cell radius.

For Urban Area:

[EQ 4-38]

For Suburban Area:

[EQ 4-39]

For Quasi Open Area:

[EQ 4-40]

For Open Rural Area:

[EQ 4-41]

Where:AHm Correction Factor For Vehicular Station Antenna Height

For a medium-small city:[EQ 4-42]

For a large city:

[EQ 4-43]

6. Okumura, Y., Ohmori, E., Kawano, T., Fukada, K.: "Field strength and ITs Variability in VHF and UHFLand-Mobile Radio Service", Rev. Elec. Commun. Lab., 16 (1968), pp. 825-873

7. Hata, M.: "Empirical formula for propagation loss in land mobile radio services", IEEE Trans. on Vehicu-lar and Technology, VT-29 (1980), pp. 317-325

LU 69.55 26.16 fc( )log× 13.82 Hb( )log×– AHm– 44.9 6.55 Hb( )log× ] r( )log×–[+ +=

LS LU 2fc

28------

log2

×– 5.4–=

Lq LU 4.78 fc( )log[ ]× 2– 18.33 fc( )log× 35.94–+=

Lq LU 4.78 fc( )log[ ]× 2– 18.33 fc( )log× 40.94–+=

AHm 1.1 fc( ) 0.7–log×[ ] Hm× 1.56 fc( ) 0.8–log×[ ]–=

AHm 3.2 11.75 Hm×( ) ]log[× 24.97–=


4


Lu, Ls, Lq Isotropic path loss values

fc Carrier frequency in MHz (valid 150 to 1000 MHz)

Hb Base antenna height in meters (valid 30 to 200 meters)

Hm Subscriber antenna height in meters (valid 1 to 10 meters)

r Radius of site in kilometers (valid 1 to 20 km)

This model is valid for large and small cells (i.e. base station antenna heights above roof-top levelsof buildings adjacent to the base station).

4.3.3 COST-231-Hata Propagation Model

The COST 231 Subgroup on Propagation Models proposed an improved propagation model forurban areas to be applied above 1500 MHz8. Like Hata’s model, the COST-231-Hata model isbased on the measurements of Okumura. The COST-231-Hata propagation model has been derivedby analyzing Okumura’s propagation curves in the upper frequency band. Hata’s analysis wasrestricted to frequencies below 1000 MHz. The COST-231-Hata propagation model extended therange of parameters to include 1500 to 2000 MHz. Their modified model was based on Hata’sformula for the basic transmission loss in urban areas (see above).

For Urban Area:

[EQ 4-44]

For Suburban Area:

[EQ 4-45]

For Quasi Open Area:

[EQ 4-46]

For Open Rural Area:

[EQ 4-47]

8. COST 231 - UHF Propagation, "Urban transmission loss models for mobile radio in the 900- and 1,800-MHz bands", COST 231 TD (91) 73 The Hagne, September, 1991

LU 46.3 33.9 fc( )log× 13.82 Hb( )log×– AHm– 44.9 6.55 Hb( )log× ] r( )log×–[+ +=

LS LU 2fc

28------

log2

×– 5.4–=

Lq LU 4.78 fc( )log[ ]× 2– 18.33 fc( )log× 35.94–+=

Lq LU 4.78 fc( )log[ ]× 2– 18.33 fc( )log× 40.94–+=


4


Where:AHm Correction Factor For Vehicular Station Antenna Height

For a medium-small city:[EQ 4-48]

For a metropolitan center:[EQ 4-49]

Lu, Ls, Lq Isotropic path loss values

fc Carrier frequency in MHz (valid 1500 to 2000 MHz)

Hb Base antenna height in meters (valid 30 to 200 meters)

Hm Subscriber antenna height in meters (valid 1 to 10 meters)

r Radius of site in kilometers (valid 1 to 20 km)

This model is valid for large and small cells (i.e. base station antenna heights above roof-top levelsof buildings adjacent to the base station).

A comparison between the Hata and COST-231-Hata equations show that they are similar exceptfor the following terms:

Hata yields

COST-231-Hata yields

Measurements which have been taken at 1900 MHz have shown the path loss difference between800 MHz and 1900 MHz closer to 11 dB. The COST-231-Hata model was developed to accountfor this difference.

4.3.4 Additional Propagation Models

The above propagation models are widely known and are usually referenced when conversing inmore general terms. Numerous books can be referenced for further discussion on these models,such as those listed in references9,10.

9. Parsons, David, "The Mobile Radio Propagation Channel", Copyright 1992, Reprinted 1996 by John Wiley& Sons Ltd.

10. Rappaport, Theodore S., "Wireless Communications Principles & Practices", Copyright 1996 by PrenticeHall PTR

AHm 1.1 fc( ) 0.7–log×[ ] Hm× 1.56 fc( ) 0.8–log×[ ]–=

AHm 1.1 fc( ) 0.7–log×[ ] Hm× 1.56 fc( ) 0.8–log×[ ]– 3–=

69.55 26.16 fc( ) AHm–log+

46.3 33.9 fc( ) AHm–log+


4


These propagation models can be used to obtain an estimate of the expected radius of a site.However, they do not include the effects of the antenna patterns, ground clutter and terrainexperienced between the transmitter and receiver. In addition, the Hata and COST-231-Hata modelare dependent upon the environment classification. Defining the area types are fairly subjective andthe entire cell site is considered to be the defined area type. For instance, if an area is assumed tobe urban but is more realistically suburban, a 12 dB impact results (many more sites would bespecified than what would really be needed). In addition, these propagation models do not portrayground clutter such as a forested area, though modifications can be made to the propagation modelor the link budget to account for loss due to foliage or forest.

One model that does include these effects is the Xlos propagation model in Motorola’s NetPlanpropagation analysis tool. This propagation model is based on work from Longley & Rice,Okumura, Bullington and Motorola’s extensive field measurement data. It takes into account theeffects of ground reflections, diffractions and line of sight propagation. It defines the path loss withrespect to dipole antennas. Hata or COST-231-Hata propagation models assume path loss isdefined with respect to isotropic antennas.

As was mentioned in the introduction, this sophistication in a propagation tool is required toprovide a more realistic portrayal of the coverage for a system.

4.4 Forward Link Coverage

In Section 4.2, the CDMA subscriber-to-base link (reverse or uplink) was discussed. This is amany-to-one link, where many subscribers communicate with a single base station (or a fixednumber of base stations). Hence, the link can be simply characterized using a link budget withadditional margin included for interference. This margin is typically measured in terms of noiserise at the cell, which is specified in terms of the operating point relative to a fixed asymptoticcapacity (pole) (e.g. operating at 75% of the pole results in a 6 dB noise rise).

The CDMA base-to-subscriber (forward or downlink) is a one-to-many link, where a single basestation (or a fixed number of base stations) communicates with many subscribers. This link issomewhat more complicated to analyze, and it does not lend itself easily to a simple RF link budgetmethod. The reason for the difficulty is:

• In the absence of multipath, the use of orthogonal Walsh codes on the downlink removesthe intra-cell interference. With multipath, intra-cell interference causes a reduction insignal-to-noise ratio. However, this is mitigated (in most cases) by the fact thatmultipath improves the subscriber receiver sensitivity.

• Subscriber receiver sensitivity is characterized in terms of Eb/(Ioc+No), energy-per-bitover other-cell interference (plus noise) power density. It is assumed that there issufficient power allocated on the downlink such that thermal noise does not significantlyeffect the performance. It has been determined, using simulations, that 13 Watts issufficient to balance the uplink and downlink of the IS-95A/B CDMA system (assumingthat the Base Station receiver uses the CSM (MCC8) demodulator.) Otherwise, in newerBase Stations (the SC4812T series, the JCDMA SC9640, SC4840, and SC2440, theSC300 and SC340), that have receivers with the EMAXX (MCC24) chip set which


4


offers improved receiver sensitivity, 27.5 Watts is needed to balance the uplink anddownlink of the IS-95A/B CDMA system. These simulations assumed a subscribernoise figure = 10 dB, base noise figure = 6 dB, and subscriber PA power of 200 mW. Ithas also been determined by simulations that 25 Watts is sufficient to balance the uplinkand downlink of an IS-2000 1X system. These simulations assumed EMAXX equivalentBase Station receiver performance, forward Radio Configuration 4 (RC 4), subscribernoise figure = 10 dB, base noise figure = 5 dB, and subscriber PA power of 200 mW.

• The downlink Eb/Ioc varies substantially with multipath (or soft handoff) and subscriberspeed. For example, Eb/Ioc in 1-path (i.e. no multipath) Rayleigh fading at slowsubscriber speed can be as high as 20-25 dB, whereas with 3-path, Eb/Ioc can be lessthan 8 dB.

• Soft handoff also complicates the downlink, because typically subscribers in softhandoff require less power (from each cell site). On the other hand, the subscribers at theedge of the soft handoff region experience high interference, and the Eb/Ioc performance(without multipath) is the worst. Thus, for downlink, it is not sufficient to balance thelink to the edge of the cell, but it has to be balanced to the edge of the soft handoffregion. Note that the soft handoff regions vary dynamically as a function of load in thedesired and the surrounding cells, as well as the propagation environment.

Though a forward link budget is not addressed, it is important to account for the powerrequirements when designing (simulation studies) and optimizing a CDMA system. Forward linkpower at the base station may limit coverage and capacity. The following sections provide someguidelines to assist the system engineer.

4.4.1 BTS Equipment Capabilities

In these guidelines, two PA parameters are frequently referred to: the Average Rated Power (ARPor Steady State Rating) and the High Power Alarm Rating (HPA). The table below is neithercomprehensive nor, necessarily, current; refer to equipment specifications for details on the BaseTransmission Station (BTS) product of interest.

Table 4-8: PA Ratings for Some BTS Productsef

BTS Product Frequency(MHz)

Number of PA

ModulesSector

Average Rated Power

(W)Sector/Carrier

High Power Alarm Rating

(W)Sector/Carrier


(dB)a

Sector/Carrier

SC300 1X Microcell

800/1900 1 10 31.6 5

SC340 1X Picocell

Japan 800 1 0.2 N/A N/A

SC340 1X Microcell

Japan 800 1 5 20 6


4


a. The High Power Alarm Rating (dB) is represented here in terms of dB above the Average Rated Power. It is also a worst case specification; typical ratings are 0.5 to 1.0 dB better.

b. This is a TrunkedPower™ BTS. It has four LPA modules serving one three-sector carrier. Its Carrier ARP is shared across all three sectors. The High Power Alarm functions on a total carrier power basis, as opposed to an individual sector basis as for non-trunked BTSs. A sector-equivalent HPA rating is shown here only for comparative purposes, and is based on a conservative trunking benefit of 1.1 dB.

c. This product, having no fans, has its Average Rated Power thermally limited.

d. This is a TrunkedPowerTM BTS. It has four Trunked LPA modules serving one three-sector carrier. Its Carrier ARP is shared across all three sectors. (A six-sector carrier is served by two sets of Trunked LPA modules.) The High Power Alarm functions on a total carrier power basis, as opposed to an individual sector basis as for non-trunked BTSs. A sector-equivalent HPA rating is shown here only for comparative purposes, and is based on B1 specifications.

e. At the time of this revision, it is believed that the power ratings listed above will be the same for the IS-2000 1X modes.

f. The models compatible at this time with IS-2000 1X are those in the SC4812T family, the SC300 1X, the JCDMA models, SC9640, SC4840, and SC2440, and the JCDMA microcellular SC340 1X.

The following table illustrates the pilot RF power adjustment range capability for several differentCDMA BTS products. The upper specification is determined by the BTS RF gain when the BTSis operating with a pilot digital gain of 127. The lower specification, corresponding to the sum ofthe pilot, page, and sync signals, depends on a specific BTS transmit dynamic range. For a BTS

SC611 1900 1 7c 28 6

SC614T 1900 (4b) 16/48 32b/76 3b/2

SC4812T/ET/ET Lite

1900 (4d) 22.5/67.5 70.8d/107.2 5d/2

SC4852E 1900 2 20 32 2

SC4852R 1900 4 45 71 2

SC604 1900 2 10c 24 3.8

SC611 800 1 7c 32 6.6

SC614 800 2 20 32 2

SC2450 800 2 20 40 2

SC4812 800 2 22.5 36 2

SC4812T/ET/ET Lite

800 (4d) 22.5/67.5 70.8d/107.2 5d/2

Table 4-8: PA Ratings for Some BTS Productsef

BTS Product Frequency(MHz)

Number of PA

ModulesSector

Average Rated Power

(W)Sector/Carrier


(W)Sector/Carrier


(dB)a

Sector/Carrier


4


equipped with a Single Tone LPA, an external attenuator is required when operating at lower thanthe minimum specification. For a BTS equipped with a multitone LPA, the minimum total power(shown in note b. of the table) must be maintained for proper operation. This can be achieved byimplementing one of the following: 1) multi-carrier operation, 2) raising the minimum operatinglevel, or 3) adding an external attenuator. The table below is neither comprehensive nor,necessarily, current; refer to equipment specifications for details on the BTS product of interest.

a. Maximum pilot RF power as determined by the BTS RF gain with pilot digital gain of 127. The minimum limit is with overhead channels (pilot+page+sync) except SC300 and SC340, see note d.

b. LPA power must be converged first before operating at the minimum level, which is assumed for the pilot beacon application. The minimum level for the LPA to converge depends on the LPA types: 36 dBm for 125W ELPA; 40 dBm for 70W NAMPS/SC9600 LPA; and 42 dBm for 125W NAMPS/SC9600 LPA.

c. Maximum pilot power limits to 36 dBm with SGLF4009KE BBX.d. Pilot only.e. The models compatible at this time with IS-2000 1X are those in the SC4812T family, the SC300 1X, and

the JCDMA models, SC9640, SC4840, SC2440 and SC340 1X.

Table 4-9: BTS Pilot Power Adjustment Rangeae

Pilot Power Adjustment RangeBTS Product Frequency

(MHz)

Minimum PPSa

(dBm)

Maximum Pilot

(dBm)

SC300 1X Microcell 800/1900 +14.0d +33.0

SC340 1X Picocell Japan 800 -2.0d +16.0

SC340 1X Microcell Japan 800 +14.0d +32.0

SC604 1900 +24.0 +33.0SC604 800 +27.0 +36.0SC614T 1900 +27.0 +36.0SC6x1 800/1700/1900 +23.0 +33.0SC2400 ELPA 800 +23.0b +40.0

SC2450 800 +30.0 +33.0c

SC4820 1700 +27.0 +36.0SC485x/SC485xE 1900 +27.0 +36.0SC4812 800 +23.0 +36.0SC4812T/ET/ET Lite 800 +28.0 +36.0SC4812T/ET/ET Lite 1900 +28.0 +36.0SC9600/SC9620 800 +23.0b +40.0

SC9640/SC4840/SC2440 800 (JCDMA) +23.0b +40.0


4


Additional factors that will have an impact on the power amplifier are:

• The use of external duplexers should be accounted for by including an additional 0.5 dBof loss, nominally. For Motorola’s SC4800-series “E” options (i.e. outdoor products)and the SC600-series, duplexers are included and the specifications will already reflectthe duplexer loss.

• For multiple carriers, the use of external combining should be accounted for. Nominalfigures include ~3.5 dB of loss; although low-loss combiners (~1.8 dB) are available.For example, if the insertion loss of cavity combiners and associated cabling was on theorder of 1.8 dB, then the 20 Watts associated with the SC2450 would drop to 13.2 Watts.For Motorola products with internal combiners (e.g. SC4812T), the specifications willalready reflect the combiner loss.

• Products exploiting PA trunking across sectors (e.g. SC4812T) have both sector-carrierand site-carrier limits of which to be aware. For example, a three-sector SC4812T ateither 800 MHz or 1900 MHz can deliver 67.5 Watts total for the site-carrier, but is ratedfor 22.5 Watts for an individual sector-carrier (not including duplexer loss).

• Verify that the Pilot, Page, Sync, and Traffic Channel power relationships can beestablished. Although the PA may be rated to deliver the desired total power output,other devices may limit the input signals into the LPA or the ratios among them. Forexample, there are gain limits on the Paging, Sync, and Traffic channels of 127 (7FHEX),but the Pilot has an upper limit of 1023 (3FFHEX). Adjusting the Pilot power to achieve~4 Watts or more may require the Pilot gain setting to exceed 127, and thereby impactthe ratio of maximum traffic channel gain to Pilot gain, which may impact performance.

• Account for any thermal limitations. Typically for indoor products, the operatingtemperature range is 0°C to 50°C. The ARP is expressed in dBm or Watts at 25°C, themidpoint in the temperature range. An allowance for variation due to temperature isprovided. For example, the 800 MHz SC4812T specification is as follows.

Transmitter Sector Output Power with equal power sharing per sector (non-duplexed):43.5 dBm (22.5 W) @25°C ±2 dB over temperature.

When the base station is to be operating inside an air conditioned environment, then the43.5 dBm would be used for planning purposes. But, if the base station is to be subjectedto warm extremes (i.e. close to 50°C), then greater consideration should be given to theanticipated power requirements.

Some self-contained products have their ARP “thermally limited” due to lack of fans.Additionally, to protect against overheating, the SC601 and SC604 products have athermal “foldback” feature that dynamically and proportionately reduces the outputpower beginning at 35°C (for operation at the specified ARP) up to a maximum of 3 dBat 50°C. (Note that IS-97 tolerates a power out variation of +2 dB to -4dB over thetemperature range.) Conversely, the SC611, SC614, and SC614T products onlyfoldback output power above the ARP or maximum operating temperaturespecifications.


4


The SC4852E is rated for 180 Watts or 18 PA modules. This permits 3 sectors of 2carriers with each sector-carrier at 30 Watts or, alternatively, 2 sectors of 2 carriers witheach sector-carrier at 40 Watts. The SC4852 is rated for 40 Watts ARP for all 6 sector-carriers.

4.4.2 CDMA Signal Power Distribution Characteristics and PA Sizing

There are three characteristics of the CDMA signal power distribution that are useful in discussionson PA requirements, which can be compared to PA equipment capabilities. These include:

1. The Long Term Average (LT-AVG): represents an average over 30 minutes or more.For the PA to be sized correctly, the LT-AVG must be less than or equal to the AverageRated Power (ARP).

2. The Short Term Average (ST-AVG): represents an average over 5 minutes.For products that are not thermally limited, it may prove useful, as a rule of thumb, tocompare the ST-AVG to the ARP. Greater detail on this can be found in the next section.

3. The Very Short Term Average (VST-AVG): represents an average over less than 2seconds.For the PA to be sized correctly, the VST-AVG must be less than or equal to the HighPower Alarm Rating.

Note that any peak excursions significantly higher than the VST-AVG are of very shortduration and are managed by PA overload protection mechanisms.

4.4.3 General Power Relationships

As a result of various simulation studies, the following characteristics of a system that isinterference limited (i.e. fully loaded) have been derived and may be considered rules of thumb:

1. The LT-AVG is approximately 5 times the Pilot power.2. The ST-AVG is approximately 10 times the Pilot power. This is 3 dB over the LT-AVG.3. The VST-AVG is approximately 15 times the Pilot power. This is ~4.8 dB over the LT-

AVG and ~1.8 dB over the ST-AVG.

Given the deviation of the power distribution, the system designer will generally find the indoorproducts (i.e. SC4852, SC2450, and SC4812) and the outdoor products with fans (i.e. SC614,SC614T, SC4852E) to be High Power Alarm (HPA) limited. Since the ST-AVG is ~1.8 dB belowthe VST-AVG and the Average Rated Power (ARP) is 2 dB below the HPA (worst case), using aST-AVG comparison to the ARP can provide a convenient rule of thumb for estimating the PArequirements for these products. Specifically, the ST-AVG should be no greater than the ARP.

Those products that have no fans (i.e. are thermally limited) include the SC601, SC604, and theSC611. Both the SC601 and the SC604, with their HPA rating 3.8 and 4.8 dB over the ARP (worstcase), respectively, are close to being balanced in terms of HPA and ARP limits relative to theCDMA signal power distribution. Conversely, the SC611, at 1900 MHz and 800 MHz, is anexception; with its HPA of 6 dB or more over the ARP, it is definitely ARP limited.


4


Based on simulations of CDMA carriers at capacity, the average forward link power per trafficchannel relative to the Pilot power can be estimated. For Rate Set 1 (RS1), ~13.5% of the Pilotpower would be consumed on average. For Rate Set 2 (RS2), ~27.8%. For a 2 Watt Pilot, theaverage traffic channel power is ~270mW and 556mW for RS1 and RS2, respectively. Thesefigures take into account the Voice Activity Factor. IS-2000 forward link RC 3, RC 4, and RC 5may have up to twice the Forward Link capacity of IS-95A/B; therefore, the average TCH powersin these modes may be approximately 1/2 that indicated above. [Greater detail on these estimatescan be found in Section 4.4.5.] The number of forward links associated with this estimate is the98th percentile of forward links and would include soft/softer links (i.e. 2% Erlang B on Walshcode usage). This would also correspond to the ST-AVG.

Since RS2 consumes approximately double the power of RS1, a RS2 system can only supportapproximately half the subscribers. Consequently, an LPA sized correctly for a RS2 carrier atcapacity would be sized correctly for RS1 as well. The transition, therefore, between RS2 and RS1(i.e. EVRC) would not require any additional PA power.

The RS1 and RS2 traffic channels correspond to the fundamental rates of 9600 bps and 14400 bpsmodes of RC 1 and RC 2 of IS-2000. The IS-2000 1X BTS will also support RC 3, RC 4, and RC5. These Radio Configurations employ different error correcting schemes, and offer higher datarates than RC 1 and RC 2 (up to 153,600 bps will be supported in RC 3 and RC 4). In general, datarates higher than 14400 bps will require proportionately higher traffic channel powers (and lowertraffic channel capacities) than discussed above.

There is a level of Pilot power which will balance the reverse link. To increase the Pilot powerbeyond this level will not significantly improve the composite area reliability, since the reverse linkbecomes limiting. For this reason, it is recommended that the Pilot powers be designed to levelssufficient to balance the reverse link, but not excessively so as to conserve the PA resource.

The introduction of the EMAXX chip set (supported in CBSC Release 8.0 and only with certainBTS products) improves the reverse link budget by an approximate 3 dB for systems that are fullyloaded (average rise levels > 2 dB). This improvement would, for initial system designs,necessitate a compensatory increase in forward power by 3 dB to balance the links.

Note: In IS-2000 1X upgraded models, the Qualcomm CSM5000 chip set is used in place of theEMAXX chip set. Thus, in these upgraded models, the full reverse link improvement is notavailable in RC 1 and RC 2.

The introduction of a tower-top amplifier will improve the reverse link by effectively negating thelosses between the antenna and the top of the rack (approximately 3 to 4 dB, refer back toSection 4.2.3.2.1). This improvement (as with the introduction of the EMAXX chip set) wouldnecessitate a compensatory increase in forward power to balance the links. When a TTA isintroduced under the assumption of light loading (e.g. “highway site”), it is more likely that thelinks can be balanced. It is not recommended to use TTAs elsewhere.

A 2:1 deployment in overlaying analog will require an approximate 3 dB increase in forward powerto overcome the Inter-System Interference (ISI). For a 1:1 overlay of analog, the PA requirementsare no different than normal.


4


4.4.4 Design Guidelines

When initially designing a CDMA system, the following two points should be kept in mind in orderto minimize the chance of sectors not having sufficient power out capabilities.

• Design the system with low pilot powers in mind. It may be advisable to consider usinga 1 Watt pilot as the default.

• Inter-system Interference (ISI) will require higher pilot powers.

Motorola’s NetPlan CDMA Simulator (or comparable design tool) can be utilized to generatestatistics for a CDMA design. These statistics can be analyzed to determine if any sectors will havea potential PA issue.

• Evaluate the coverage/capacity/quality impacts of reduced pilot powers.• The confidence level is impacted by the number of Monte Carlo runs performed in

generating the data.• Evaluate the power requirements of each sector-carrier. Outputs from the CDMA

Simulator include statistics on traffic channel (TCH) power and forward links (i.e.Walsh codes). Details on this evaluation should be found in the RF Design Procedure.

For conventionally powered BTS products (i.e. no sharing of PA resources acrossmultiple sectors and/or carriers), it is only necessary to determine the LT-AVG andVST-AVG requirements for the sector-carrier and then compare them with the ARP andHPA ratings, respectively. The ratings must exceed the requirements.

For TrunkedPower™ BTS products, there are two steps:1. Determine the LT-AVG and VST-AVG requirements over the appropriate set ofsector-carriers over which the PA resource is shared and then compare them with theARP and HPA ratings, respectively. The ratings must exceed the requirements.2. Determine the LT-AVG requirement for each individual sector-carrier and thencompare this with the ARP rating for a sector-carrier. The rating must exceed therequirement.

As has been stated earlier, the SC4812T is rated for 22.5 Watts ARP in any individualsector-carrier and 67.5 Watts total for 3 sectors of 1 carrier (not including duplexer loss).

4.4.4.1 Comparison to Average Rated Power

The following steps can be performed to obtain the LT-AVG for the sector-carrier(s) which can becompared with the product ARP specification (for many products, these values are provided inTable 4-8).


4


1. Take the average of the TCH power distribution.For trunked PAs, generate the average for the individual sector-carrier for comparisonagainst sector-carrier ARP limits and then again for all the sector-carriers over which theresource is to be shared for comparison against total ARP limits. For the total ARPcomparison, the power statistics must first be summed across the appropriate set ofsector-carriers within each Monte Carlo run. Although this will not impact the average,it will impact the deviation.

2. Add in the constant power components associated with the Pilot, Page, and Syncchannels.

3. Compare this with the ARP of the PA. It must be lower.

Note: to compare the ST-AVG to the ARP, use the 98th percentile of the TCH power distribution.

4.4.4.2 Comparison to High Power Alarm Rating

The following steps can be performed to obtain the VST-AVG for the sector-carrier(s) which canbe compared with the product HPA specification (for some products, these values are provided inTable 4-8).

1. Determine the 98th percentile of the TCH power distribution.For trunked PAs, generate the average for all the sector-carriers over which the resourceis to be shared for comparison against total HPA limits. The power statistics must firstbe summed across the appropriate set of sector-carriers within each Monte Carlo run.The 98th percentile is then taken across the summed set of statistics.

2. Scale it up by a factor of 1.5. This compensates for variations in the voice activity factor(up to a level that corresponds to the 98th percentile of the binomial distribution).

3. Add in the constant power components associated with the Pilot, Page, and Syncchannels.

4. Compare this with the High Power Alarm Rating. It should be lower.

4.4.4.3 Comparison to Walsh Code Limit1. Take the average number of forward links. This may be interpreted as Walsh code

Erlangs.2. Calculate a maximum number of forward links based on 2% GOS Erlang B for the

number of Walsh code Erlangs derived in step 1.3. Compare step 2 results to the Walsh code limit. It should be lower.

4.4.5 General Power Requirements

In the absence of more precise simulations, here are some definitions and equations that can beused to provide power requirements as a function of Rate Set, pilot power, and number of forwardlinks.


4


Definitions:• Ppilot is the Pilot power.• Ppage is the Page power (commonly 75% of P_pilot).• Psync is the Sync power (commonly 10% of P_pilot).• FwdLinks50th-ile is equivalent to Walsh code Erlangs. It can be derived from the

Effective Traffic Load using the Soft/Softer Handoff Factor.• FwdLinks98th-ile is equivalent to the number of Walsh codes that result from taking

Walsh code Erlangs at 2% Erlang B.• Veff (Effective Voice Activity Factor) is scaled up from the normal VAF (Voice

Activity Factor) to compensate for Power Control Bit puncturing on the forward link.The PCB bits are transmitted at a constant high power to maintain the integrity of theclosed loop power control mechanism. Scaling the VAF is one method of compensatingfor the effect on forward power output. V_eff is 0.55 and 0.47 for Rate Sets 1 and 2 ofIS-95 systems, and Radio Configurations 1 and 2 of IS-2000 1X systems, respectively.

• Vwc represents, for the VAF binomial distribution, a ratio of the 98th percentile to themean. A value of 1.5 is used.

• Ptch_avg is the Average Traffic Channel Power. As a fraction of Ppilot, these powers aretypically 24.6% and 59.1% for Rate Sets 1 and 2, respectively.

Assume:[EQ 4-50]

4.4.5.1 Minimum ARP Based on LT-AVG Estimate

The following equations can be used to determine the minimum ARP specification based on thePilot power and the average number of links.

[EQ 4-51]

Rate Set 1:

[EQ 4-52]

Rate Set 2:

[EQ 4-53]

Notes:1. To compare the ST-AVG to the ARP, use FwdLinks98th-ile in place of FwdLinks50th-ile2. Formulas for Rate Set 1 and 2 also apply to RC 1 and RC 2 respectively.3. IS-2000 1X RC 3, RC 4, and RC 5 are expected to have twice the Forward Link capacity

of IS-95A/B for the same ARP; therefore, the average TCH powers in these modes maybe approximately 1/2 those indicated above.

PPilot PPage PSync+ + 1.85 PPilot×=

AverageRatedPower PPilot PPage PSync FwdLink50th ile– Ptch_avg× Veff×+ + +=

AverageRatedPower PPilot 1.85[× F( wdLink50th ile– 0.1353 ) ]×+=

AverageRatedPower PPilot 1.85[× F( wdLink50th ile– 0.2778 ) ]×+=


4


4.4.5.2 Minimum HPA Based on VST-AVG Estimate

The following equations can be used to determine the minimum HPA specification based on Ppilotand FwdLinks98th-ile.

[EQ 4-54]

Rate Set 1:

[EQ 4-55]

Rate Set 2:

[EQ 4-56]

Alternatively, an upper estimate on FwdLinks98th-ile can be determined based on the HPA ratingand Ppilot. This may serve as a Walsh code limit that will block traffic at levels that near the HPArating.

Rate Set 1:

[EQ 4-57]

Rate Set 2:

[EQ 4-58]

4.4.5.3 Exceeding the High Power Alarm Rating

On systems lacking carrier load management features, an LPA module which exceeds its HighPower Alarm Rating will enter an OOS_RAM maintenance state. The consequences and possibleoperational response to this event were outlined in FYI No. SCCDM-1997.84 March 20, 1997.LPA modules in systems having these features installed will not enter OOS_RAM.

If OOS_RAM events are occurring, the following design and optimization options could be taken:

• Add more PA power. Depending upon the BTS product and the installed configuration,there may be an ability to add an additional PA module.

• Reoptimize the pilot power to a lower level. Be careful to review the potentialconsequences on coverage. If the sites involved have the potential for significantoverlap, then lowering pilot powers may be the appropriate response.

• Reoptimize the forward power control parameters. For example, reducing the NominalTraffic Channel Gain can reduce the overall output power and PA requirements.

HighPowerAlarmRating PPilot PPage PSync FwdLink98 th ile– Ptch_avg× Veff Vwc××+ + +=

HighPowerAlarmRating PPilot 1.85[× F( wdLink98th ile– 0.2030 ) ]×+=

HighPowerAlarmRating PPilot 1.85[× F( wdLink98th ile– 0.4167 ) ]×+=

FwdLink98th ile– HighPowerAlarmRating PPilot )⁄ 1.85 ] 0.2030⁄–([=

FwdLink98th ile– HighPowerAlarmRating PPilot )⁄ 1.85 ] 0.4167⁄–([=


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• A Walsh code limit can be implemented which will maintain traffic on a sector-carrierbasis to levels which should not exceed the High Power Alarm Rating of the PA.Determining this threshold can be based on the information provided here. Once Walshcode limits are in place, Walsh code usage and blocking statistics may be monitored andprojected against the limit per standard traffic engineering guidelines.

4.4.5.4 Carrier Load Management Overview

With feature 1225B, a Fixed Power Threshold (dBm) sets the maximum output allowed per sector/carrier and will limit the LPAs providing power to that sector/carrier. This parameter is used onlywhen the system has the Activate Fixed Overload Protection parameter enabled. This attributeestablishes a high water mark at which the CDMA transceivers will actively reduce gain if thispower threshold is exceeded for the given sector/carrier.

With feature 415B, the decision by the mobility manager (MM) to allocate a Walsh code or channelelement for subscriber originations and terminations is conditional upon the RF load in the forwardand reverse directions on the carrier selected for an allocation attempt.

The Group Line Interface (GLI) or Motorola Advanced Wideband Interface (MAWI) card at eachBTS is responsible for gathering real time forward and reverse link quality data from the trafficchannel elements and CDMA transceivers within each sector-carrier under its control. Forward andreverse channel RF quality information is sent to the MM via SCAP (Application Protocol)messaging and used by the MM to make decisions about whether or not to allow new call channelallocation within a sector-carrier and to load balance channel allocation among carriers within aparticular sector. Forward and reverse FER statistics for each sector-carrier are reported to the MM,where they are used to automatically adjust per sector-carrier thresholds and to allow/disallowchannel allocation within each sector-carrier.

The GLI or MAWI will also set a flag in the SCAP measurement report when the sector-carrier'sCDMA transceiver exceeds a user defined power output. The MM will deny origination/terminations in the sector-carrier until the flag is cleared in a subsequent SCAP message.

The GLI or MAWI will also calculate the actual power being used by each sector-carrier's CDMAtransceiver, as well as the total power output of the LPA associated with the sector-carrier, andforward the information to the MM via the periodic SCAP RF metrics reporting messages. Thisdata is for statistics collection and not used by the MM to make channel allocation decisions.

With feature 4472C (available starting with CBSC Release 16.0), in addition to gathering real-timeforward and reverse link quality data from the traffic channel elements and CDMA transceiverswithin each sector-carrier under its control, the RF Load Manager at each BTS is responsible forusing the received forward and reverse FER statistics for each sector-carrier to automatically adjustper sector-carrier thresholds and to provide near real-time updates of forward and reverse loadconditions to the Time Slice Manager. The Time Slice Manager is a BTS based mechanism toschedule data activity in a series of small periods of time to maximize use of the forward andreverse power capacity.

The RF Load Manager will also inhibit supplemental allocation in the sector-carrier when the


4


sector-carrier’s CDMA transceiver exceeds a user-defined fixed limit power output or if the sector-carrier’s LPA is in gain limiting mode due to an LPA overload condition. It accomplishes this bymanipulating the various thresholds.

4.4.6 Power Allocation in Mixed Mode Systems

Note: IS-2000 CDMA is not used in mixed mode with analog cellular.

The subject of base station transmitter power considerations in mixed-mode (IS-95 CDMA plusanalog) systems is generally not well understood by those responsible for setting the levels. Thefollowing sections provide an explanation on estimating the CDMA forward channel carrier powerrequirements and a calculation of the derated LPA power specification. The formulas for deratingthe rated power output of AMPS Band ELPA, the Combined-Shelf AMPS Band ELPA, and theAMPS Band LPAs for any combination of analog and CDMA carriers are presented. Other linearpower amplifier models will have different derating recommendations. Also provided is anexample on how to allocate available transmitter power between IS-95 CDMA carriers and theanalog carriers on a sector of a mixed-mode base station, which is intended to illustrate theconcepts and considerations involved in determining these requirements. It should be noted thateach mixed-mode site will be unique, and that in general, the results will differ from the example.System Engineering must design the site for the desired coverage, performance, and traffic channelcapacity, without exceeding the PA power limitations of the base station, preferably by using thebest sophisticated simulation tools available, such as the CDMA Simulator option of the NetPlansystem design tool package. In the absence of a sophisticated simulation tool, the followingcalculations can be used to estimate the mixed mode power allocation of available transmitterpower of a linear power amplifier.

CDMA Forward Channel Carrier Power

CDMA forward channel carrier power varies greatly depending on how many traffic channels arein use, the characteristics of the users voices, the Forward Power Control settings as requested byeach subscriber unit in use, and the power allocated for overhead functions (Pilot, Page and Sync).An approximation of the CDMA forward channel carrier power can be defined as the power underthe following conditions:

Number of Forward Links (or total Traffic Channels): The number of traffic channelsrequired at the 2% Blocked-Calls-Cleared (Erlang B) Grade of Service level plus thenumber of traffic channels that are in Soft Handoff with another cell, and/or in SofterHandoff with another sector of the same cell, i.e., Nfwd_links = N2%_GOS x SSHOF,where SSHOF is the Soft plus Softer Handoff Factor

Traffic Channel power: The power of the average traffic channel due to averagemodulation plus full rate Power Control Bits, i.e., approximately 0.15 x Ppilot for RateSet 1, and approximately 0.27 x Ppilot for Rate Set 2


4


Forward Power Control: The average Forward Power Control setting, at this setting theaverage traffic channel power is still approximately 0.15 x Ppilot for Rate Set 1, andapproximately 0.27 x Ppilot for Rate Set 2

Overhead power: Pilot plus Page plus Sync power is equal to Ppilot plus 0.75 x Ppilot plus0.1 x Ppilot = 1.85x Ppilot

Since the component parts of the CDMA carrier power are all expressed in terms of Pilot power,and since Pilot power is generally determined by the site coverage requirements, the power may besummed up as follows:

Pcdma = Overhead power + Traffic Channel power

Pcdma = 1.85 x Ppilot + Nfwd_links x 0.15 x Ppilot (for Rate Set 1) or,

Pcdma = 1.85 x Ppilot + Nfwd_links x 0.27 x Ppilot (for Rate Set 2)

It must be realized that these formulas are approximations, since the power level of the overheadcomponents and the number and power level of the traffic channels continuously vary in the realworld.

Linear Power Amplifier Derating

A. AMPS Band ELPA

The present AMPS band version of ELPA may contain two, three, or four ELPA modules,depending on the site or sector power requirement.

The four-module AMPS band ELPA can provide up to 120 Watts of output power at the output ofthe ELPA frame for either 1 CDMA carrier or up to 20 analog carriers. When more than 20 analogcarriers or more than 1 CDMA carrier are being amplified, the output power specification followsa derating curve from 120 Watts to about 109 Watts for a very large number of analog and CDMAcarriers. This is due to the increasing peak to average power ratio of the composite signal. Thereare similar derating curves when three or two modules are installed.

For purposes of determining the derated power specification of the ELPA amplifier in systemplanning scenarios, each CDMA carrier is counted as 20 equivalent analog carriers (EAC). Forexample, if the ELPA is going to be used to amplify 36 analog carriers and 3 CDMA carriers, itwill be expected to handle 96 equivalent analog carriers.

The derating equations for all of the possible four-module ELPA configurations follow:

The derating equation for two ELPA modules installed is:

EAC = equivalent analog carriersEAC = (# of analog carriers) + 20 * (# of CDMA carriers)


4


Pout = ELPA maximum output power rating

if EAC = 20:Pout = 60 Watts

if EAC > 20

Pout = 54.55 + (72 / EAC) + (720 / (EAC)2) Watts

The derating equation for three ELPA modules installed is:




if EAC > 20


The derating equation for four ELPA modules installed is:




if EAC > 20


Four installed modules in an ELPA with 96 EAC has a Pout rating of 110.8 Watts. Four installedmodules with 40 EAC (1 CDMA & 20 Analog Carriers) has a Pout rating of 113.6 Watts. Fourinstalled modules with 35 EAC (1 CDMA & 15 Analog Carriers) has a Pout rating of 114.4 Watts.

This power is available to be divided between the analog and CDMA carriers with any ratio. Validexamples follow for 96 EAC:

Three 25 Watt CDMA carriers and Thirty-six 0.99 Watt analog carriers = 110.6 Watts.Three 10 Watt CDMA carriers and Thirty-six 2.24 Watt analog carriers = 110.6 Watts.Three 1.6 Watt CDMA carriers and Thirty-six 2.94 Watt analog carriers = 110.6 Watts.


4


B. Combined-Shelf AMPS Band ELPA

Higher power output is available from the combined-shelf ELPA models. Within these ELPAframes, two four-module ELPA shelves are combined. The number of ELPA modules in each four-module ELPA shelf must be the same, i.e., two, three, or four. The resulting combinations thereforeconsist of four, six, or eight ELPA modules.

An eight-module AMPS band ELPA can provide up to 200 Watts of output power at the output ofthe ELPA frame for either 1 CDMA carrier or up to 20 analog carriers. When more than 20 analogcarriers or more than 1 CDMA carrier are being amplified, the output power specification followsa derating curve from 200 Watts to about 182 Watts for a very large number of analog and CDMAcarriers. This is due to the increasing peak to average power ratio of the composite signal. Thereare similar derating curves for the cases when six or four modules are installed.

For the purposes of determining the derated power specification of the ELPA amplifier in systemplanning scenarios, each CDMA carrier is counted as 20 equivalent analog carriers (EAC). Forexample, if the ELPA is going to be used to amplify 36 analog carriers and 3 CDMA carriers, itwill be expected to handle 96 equivalent analog carriers.

The derating equations for all of the possible combined ELPA configurations follow:





if EAC > 20


The derating equation for six ELPA modules installed is:




if EAC > 20

Pout = 136.4+ (180 / EAC) + (1800 / (EAC)2) Watts


4


The derating equation for eight ELPA modules installed is:

EAC = equivalent analog carriersEAC = (# of analog carriers) + 20 * (# of CDMA carriers)Pout = ELPA maximum output power rating


if EAC > 20


Eight installed modules in a combined ELPA with 96 EAC has a Pout rating of 184.6 Watts. Eightinstalled modules with 40 EAC (1 CDMA & 20 Analog Carriers) has a Pout rating of 189.3 Watts.Eight installed modules with 35 EAC (1 CDMA & 15 Analog Carriers) has a Pout rating of 190.6Watts.

This power is available to be divided between the analog and CDMA carriers with any ratio. Validexamples follow for 156 EAC (6 CDMA carriers and 36 analog carriers) which has a Pout rating of183.4 Watts:

Six 25 Watt CDMA carriers and Thirty-six 0.92 Watt analog carriers = 183.1 Watts.Six 10 Watt CDMA carriers and Thirty-six 3.42 Watt analog carriers = 183.1 Watts.Six 0.9 Watt CDMA carriers and Thirty-six 4.94 Watt analog carriers = 183.2 Watts.

C. AMPS Band LPA

The derating equation for the standard power (70 Watt) LPA is:

For 5 or less EAC: Pout = 110 Watts

For more than 5 EAC: Pout = 64 + 80/EAC + 800/(EAC)2 Watts

The derating equation for the high power (125 Watt) LPA is:

For 12 or less EAC: Pout = 140 Watts

For more than 12 EAC: Pout = 114.2 + 144/EAC + 1440/(EAC)2 Watts

D. Other Linear Power Amplifiers

Other LPA and ELPA models may have different power derating equations, or may require noderating at all. This information should be available from the literature for the product of interest.


4


Example of a Mixed-Mode Site with Rate Set 1:

In this example of a mixed-mode SC9600 type of site, a sector is being planned to have one CDMAcarrier and 20 AMPS/NAMPS carriers; the equivalent number of analog carriers is therefore 40.Under these conditions, the power output rating of a four-module AMPS band ELPA at the top ofthe ELPA frame is determined as follows:


EAC = 40

Pout = 109.1 + (144 / 40) + (1440 / (40)2) Watts

Pout = 113.6 Watts

Note that the power rating given above is at the output of the AMPS Band ELPA frame. At theoutput of the Site Interface Frame (SIF), this power level will be reduced by the insertion loss ofthe cables and hardware in the transmit path. The maximum value for this loss is about 1.5 dB(about 71% remaining power). Using this value, the resulting maximum available power level atthe output of the SIF would be:

Pout_sif = 80.4 Watts (worst loss)

Alternatively, the actual measured loss from the ELPA frame output to the SIF frame output maybe used to determine the maximum available power level at the output of the SIF. Doing so willresult in a slightly higher output power.

In this example, the CDMA carrier will have Rate Set 1 voice traffic channels (for Rate Set 1, themaximum bit rate of each voice traffic channel is 9.6 kbps). Also assume that for sector coveragereasons, the required Pilot Power of the CDMA carrier has been determined to be 2 Watts. Theapproximation of the CDMA carrier power is as follows:

Pcdma = 1.85 x Ppilot + Nfwd_links x 0.15 x Ppilot

Ppilot = 2 Watts

Pcdma = 1.85 x 2 Watts + Nfwd_links x 0.15 x 2 Watts

Pcdma = 3.7 Watts + Nfwd_links x 0.3 Watts

An estimate of the maximum number of Forward Links (traffic channels) expected on the CDMAcarrier is required to complete this calculation.

Nfwd_links = N2%_GOS x (SSHOF)


4


For a multi-Sector site, a conservative value for the Soft Plus Softer Handoff Factor is:

SSHOF = 2

Therefore,

Nfwd_links = N2%_GOS x 2

The maximum value for the number of Erlangs on a heavily loaded sector during Busy Hour is:

NErlangs = 14

The number of Traffic Channels required to handle this traffic load with 2% Blocked Call Gradeof Service (Erlang B) is:

N2%_GOS = 21

Including the Traffic Channels that are in Soft or Softer Handoff, the maximum number of ForwardLinks required on this CDMA carrier (with 14 Erlangs, 2% GOS, & SSHOF=2) is expected to be:

Nfwd_links = 42

Note that under no circumstances can this number exceed the number of available Walsh codes (i.e.42 Walsh codes for IS-95A/B).

The power required by the CDMA carrier is therefore:

Pcdma = 3.7 Watts + 42 x 0.3 Watts

Pcdma = 3.7 Watts + 12.6 Watts

Pcdma = 16.3 Watts

In a conservative mixed-mode site design, the total power available for the analog carriers is:

Panalog = Pout_sif - Pcdma

Panalog = 80.4 Watts - 16.3 Watts

Panalog = 64.1 Watts

If there are 20 analog carriers, the power available for each one is:

Ptch_analog = 64.1 Watts / 20 = 3.21 Watts


4


If the power needed for each analog channel is higher than 3.21 Watts, the maximum number ofanalog channels will need to be reduced to something less than 20. For example, if each analogcarrier is required to be 6.41 Watts, the analog carrier capacity would be reduced to a maximum of10.

Of equal importance, if the CDMA Busy Hour traffic load was higher than 14 Erlangs (if it waspossible), this would cause the CDMA carrier to consume more than its allocated share of thepower available from the ELPA.

In the presence of all 20 analog carriers, excessively high CDMA power can result in activation ofthe ELPA RF Overdrive Protection (approximately 20 dB ELPA gain reduction). The combinationcan also cause distortion of the CDMA signal (poor voice quality and dropped calls), generation ofhigher than normal CDMA sidebands, interference to the adjacent analog cellular channels, andexcessive thermal stress on the ELPA.

If an increased traffic load on the CDMA carrier is expected to be possible, then either the powerallocated to each analog carrier or the maximum number of analog carriers must be reduced.

4.4.7 Government Regulations

Certain government rules and regulations may exist which prohibit an operator from transmittingan excess of power. For instance, the FCC regulations limit the Base Station output power to 1640Watts EIRP per carrier for PCS systems.11 Knowing the maximum power for a sector at the top ofthe rack, this FCC limit will translate into a limit on antenna gain offset by cable losses. Forexample, the three-sector SC4812T is rated for 45 Watts maximum for a sector-carrier.Consequently, the maximum gain permitted between the top of the rack and the effective radiatedpower would be Gmax:

[EQ 4-59]

The RF system designer is advised to determine if any regulations exist in the area of their system.

4.5 CDMA Repeaters

Repeaters have been successfully deployed in CDMA markets. By carefully following theguidelines provided by the repeater vendor, it should be possible to deploy a repeater to enhancesystem coverage for most repeater applications. The following sections provide considerationsregarding the design, installation, optimization, and maintenance of a repeater system. All of therepeater information provided should be evaluated prior to deciding upon a specific repeaterapplication.

11. Title 47, Part 24, Sub-Part E, Section 24.232.

Gmax 10 Pout Pin⁄( )log× 10 1640 45⁄( )log× 15.62 dB= = =


4


4.5.1 CDMA Repeater Design Considerations

The following sections provide useful information that should be considered during the designphase of a repeater deployment.

4.5.1.1 Coverage Impact

CDMA system coverage can be traded off for more capacity. This is reflected in the link budget ofthe reverse link by determining the acceptable interference margin allowed, which will determinethe reverse link coverage. By designing the system with a relatively small interference margin, lessusers can be supported, but a larger coverage area is supported. For a relatively larger interferencemargin, more users can be supported, but for a smaller coverage area. Similarly on the forward link,it is the required PA power that is used to determine the desired mixture of coverage and capacity.For a given load, a smaller coverage area produces a smaller PA power requirement, while a largercoverage area produces a larger PA power requirement. For a given coverage area, the required PApower is directly proportional to the load. This relationship is maintained up to the point where thesystem becomes forward link interference limited, such that increasing PA power does notmaintain or improve SNR.

4.5.1.1.1 Typical CDMA Repeater Applications

In some cases, it is desirable to use transceivers called repeaters (see Figure 4-14) to boost CDMAsignals, which in effect spreads the capacity of the BTS to a larger coverage area. This is especiallyuseful in areas where the signal from the BTS is blocked by some kind of RF obstruction. In thiscase, a repeater can be used between the donor BTS and the served subscriber to boost the signals.The repeater helps to get both the BTS and subscriber signals around or through such RFobstructions.

Figure 4-14: Typical Repeater Application

Repeaters can typically be used to provide improved coverage for the following applications:terrain limited coverage, in-building coverage, and tunnel/subway/parking garage/undergroundcoverage. Using repeaters in this way maintains the coverage of the donor BTS while eliminating

BaseStation Repeater

RepeaterCoverage

BTS CellCoverage

DonorAntenna

SubscriberAntenna


4


the need for another BTS (assuming the donor BTS has enough capacity availability to accept theadditional load from the repeater). This is economical as long as the repeater is significantlycheaper than the type of BTS to be added (in comparison to a macro-cell, micro-cell, or pico-cell)and/or the site costs are less expensive. In the overlap areas of coverage between the donor BTSand the repeater, there is enough delay in the repeater signal path such that the subscriber canresolve the signals between the two sources. The same will be true for the reverse link.

4.5.1.1.2 CDMA Repeaters Used for Range Extension

Another application for repeaters are to use them to extend the range of a CDMA cell site or sectorfor the case where there is no RF obstruction, such as down a highway. For this type of application,the range extension obtained is largely limited by the following:

• How much the repeater desensitizes the base station (for maximizing range of therepeater, typically a 3 dB desense of the donor BTS allows optimum range of the BTS &repeater combination). Note: maximizing overall coverage of the BTS and repeater willcause a 3 dB desense reduction in the donor BTS’s range.

• The cascaded noise figure at the repeater (determined by the noise figures of the repeaterand base station including the transmission gain between them).

• Repeater receiver sensitivity on the reverse link and ability to maintain diversityreception back at the donor base station (repeater with transmit diversity is used for linkback to donor base station to compensate for repeater not having diversity reception andrake receiver for subscriber to repeater link).

• The effect of the loss of soft handoff of the donor site at the repeater location.• The size of the repeater PA used on its forward link (typically 6 Watts).

Given these assumptions, it has been determined that approximately 24-26% increase in rangeextension may be achieved by using existing commercial repeaters (see Figure 4-15).

Figure 4-15: Repeater Range Analysis Results

R ange Impr ov ement U s ing R epeater

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

S ys tem Con f igu r at ion

Perc

ent I

ncre

ase

in R

ang

e

R ev L ink Increas e

F w d L ink Increas e

R ev L ink Incr eas e 26% 26% 26% 26% 24% 24%

F w d L ink Increas e 58% 59% 35% 38% 10% 13%

CS M 17dB i CS M 23dB i EMAX X 17dB i EMAX X 23dB iCS M

T T A .17dB iCS M

T T A .23dB i

B T S NF =4.5 dBR ptr NF =7.0dB

NIM=0dB or 3dB des ens e


4


Figure 4-15 shows the percent improvement in range due to adding a repeater (normalized to theBTS range without the repeater) for different BTS donor configurations. This analysis used atypical noise figure value of 4.5 dB. For a guaranteed coverage calculation or prediction, it may benecessary to use the six sigma value for the noise figure specification which is usually 1.5 to 2.5dB higher than the typical value. A 20Watt LPA was assumed for all cases above. The dBi numbersrepresent antenna gain and TTA indicates a tower top LNA was used at the BTS to reduce the BTSeffective noise figure. The range is largely limited by the reverse link allowing about a 25%increase in range. While the forward link range extension can be large (above 50%) for a donor siteusing a CSM chip set, it quickly drops as the receiver sensitivity is improved by using an EMAXXchip set and then again if tower top low noise amplifiers (LNAs) are used to reduce antenna cableloss. Going from left to right, the CSM to the EMAXX, and then to the CSM w/TTA, eachconfiguration improves the receiver sensitivity of the BTS, which in effect increases thenormalized range of the BTS. This also increases the power requirements of the BTS LPAs, whichis why the forward link improvement decreases quickly due to the fixed 20Watt LPA assumption.By observing the increase in normalized range with each configuration change, the overall reverselink improvement in range is increasing, but the percentage improvement due to the repeater is stillaround the 24% range. Figure 4-16 represents an alternate repeater analysis with the followingassumptions.

• The total loss/gain is the same between the forward and reverse links• The forward link loss/gain is measured from the Forward Tx output of the base station to

the Forward Tx output of the repeater• The reverse link loss/gain is measured from the Reverse Rx input of the repeater to the

Reverse Rx input of the base station• The base and repeater antennas have the same cable losses and antenna gains serving the

subscribersFigure 4-16: Alternate Repeater Analysis

The Y axis in Figure 4-16 represents the difference in repeater forward Tx power relative to theBTS power plus the difference in the repeater forward Tx gain relative to the repeater reverse Rx

B T S an d R epeater R X R ange3.26 R F pr op los s

-20.0

-15.0

-10.0

- 5 .0

0.0

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 1.30 1.40 1.50 1.60 1.70 1.80 1.90 2.00

N ormaliz ed R X Cell cover age r efer enced to B T S nois e f igure

Rep

ea

ter F

orw

ard

TX

po

we

r re

lativ

e to

BTS

dis tance B T S dis tance R epeater

B T S los es -4 dB s oft han doff gain R epeater los es -1 dB fadin g to B T S - 0 .5 dB E c/Io F inger s

P ath L os sMobile to R epeater

P ath L os sMobile to B T S

L in k L os s = P ath L os s + Cable L os s es + An ten na Gains + R epeater GainAs s umption

R ever s e L ink R epeater to B T S = F or war d L in k B T S to R epeater


4


gain. This is identical to that of Figure 4-25 (see page 78 for further details). In a maximum rangeextension application, the repeater Tx and Rx gains are typically equal and thus cancel themselvesout. As a result, the title in the above figure only mentions the difference in repeater to BTS Txpowers. This alternate analysis also shows a ~26% increase in range. An interesting point to noteis that in this type of repeater configuration (maximum range), the donor BTS range is reduced byover 40%, primarily due to the lack of soft handoff gain and the repeater desense of the BTSreceiver. It also shows the expected reductions in overall range as the relative power levels arechanged.

4.5.1.2 Cascaded Noise Figure

The calculation of the cascaded noise figure for multiple amplifiers in a cabled system is differentthan that for a non-cabled repeater system. The following sections provide an explanation of howto calculate the cascaded noise figures for both cabled and repeater (non-cabled) systems.

4.5.1.2.1 Cascaded Noise Figure for Cabled Systems

In a multiple amplifier cabled system (i.e. only one antenna input), Equation 4-20 and Equation 4-21 can be used to calculate the cascaded noise figure, if the noise figure (or noise factor) for eachof the individual amplifiers which are connected in series is known.

Figure 4-17: Cabled Cascaded Noise Figure

For the example in Figure 4-17 Cabled Cascaded Noise Figure where the noise figures areillustrated by setting the thermal noise, kTB = 1 (-113 dBm for CDMA), the cascaded noisereferenced to the first amplifier input is as follows (note that all values are linear, not dB).

Cascaded Noise @ Input =

To simplify the calculation, let’s assume that the noise figures for F1, F2, and F3 are 3 dB (2.0linear) and the gain for G1, G2, and G3 are 10 dB (10 linear). For the example in Figure 4-17Cabled Cascaded Noise Figure, the cascaded noise at the input is as follows (assuming no cableloss between the amplifiers):

Cascaded Noise @ Input = = 2.101 = 3.2 dB

G1 G2 G3

F1 - 1 F2 - 1 F3 - 11

Input

kTB=1Output

F1F2 1–

G1---------------- F3 1–

G1 G2•---------------------+ +

22 1–10

------------ 2 1–10 10•-----------------+ +


4


4.5.1.2.2 Cascaded Noise Figure for Single Repeater System

The reverse link cascaded noise figure for a BTS repeater system can be easier to comprehend if afew simplifying assumptions are made. First, the total loss/gain is assumed to be the same betweenthe forward and reverse links. Second, the BTS and repeater antennas have the same cable lossesand antenna gains serving the subscribers. Using the above assumptions, the forward loss/gain ismeasured as the difference between the Forward Tx output of the BTS and the Forward Tx outputof the repeater. Also, the reverse loss/gain is measured as the difference between the Reverse Rxinput of the repeater and the Reverse Rx input of the BTS. Using the simplifying assumptions, thecascaded noise figure looking into the repeater Rx will be higher than the cascaded noise figurelooking into the BTS Rx by the reverse loss/gain (in dB).

Figure 4-18: Base Station & Repeater Diagram

For the simple example in Figure 4-18 Base Station & Repeater Diagram, the repeater Tx pilot is10 dB lower than the BTS Tx pilot. Knowledge of the individual components of the forward lossis not required (i.e. the cable losses, antenna gains, and repeater gain are all hidden to our analysis).Using symmetry between the forward and reverse links, the reverse loss is also 10 dB. A CDMAsubscriber received at the repeater at a level of -110 dBm will be presented to the BTS receiver at-120 dBm. Using the simplifying assumptions, the cascaded noise figure looking into the repeaterRx is 10 dB higher than the cascaded noise figure looking into the BTS Rx.

An important point to note is that a cascaded noise figure calculation for a repeater system (non-cabled) is not the same as the cascaded cabled amplifier equation. In a repeater system (non-cabled), Equation 4-21 cannot be used to calculate the cascaded noise figure. Cascaded amplifiersonly have one antenna input. Therefore, thermal noise (kTB) is only injected at the 1st amplifierinput. Also, subscribers are only received at the 1st amplifier. A repeater and BTS system has twoinput antennas. Thermal noise (kTB) and the subscriber signal are injected at both receiver inputs.Figure 4-19 Repeater Cascaded Noise Figure provides an example of a reverse link cascaded noisefigure for a simple repeater system.

RepeaterBTS

Tx_BTS

Rx_BTS

Tx_R

Rx_R

Forward Loss = 10 dB

Pilot = 2 watts Pilot = 0.2 watts

Reverse Loss = 10 dB


4


Figure 4-19: Repeater Cascaded Noise Figure

As an alternate approach, the calculation of a cascaded noise figure for a repeater system reverselink can be analyzed as follows (see Figure 4-19 Repeater Cascaded Noise Figure). Thermal noise(kTB) is introduced at the repeater Rx by the source impedance of the antenna. The 3 dB noisefigure of the repeater doubles the noise by adding another kTB. A reverse loss of 10 dB will lowerthe repeater noise at the BTS antenna to 0.2(kTB). The BTS receiver antenna and noise figure addanother 2(kTB). As a result, the total noise at the BTS receiver is 2.2(kTB). Thus, the cascadednoise figure is 3.4 dB (10log(2.2)) looking into the BTS Rx. A simple equation for the cascadednoise figure at the BTS receiver can be written as follows. All of the variables are in linear units(i.e. 2.2 = 2 + (2 * 0.1)).

Cascaded NF @ BTS = BTS NF + (Repeater NF * reverse loss) [EQ 4-60]

Now, a subscriber looking into the repeater receiver will see a different cascaded noise figure thana subscriber looking into the BTS receiver. Referenced to the repeater receiver input, the 2.2(kTB)noise at the BTS receiver is ten times (10dB) higher at 22(kTB). As a result, the repeater cascadednoise figure is 10 dB higher at 13.4 dB (10log(22)). Notice that the 10 dB difference is exactly thesame as the reverse loss. A simple equation for the cascaded noise figure at the repeater receivercan be written as follows. Again, all variables are linear (i.e. 22 = 2.2 / 0.1).

Cascaded NF @ Repeater = Cascaded NF @ BTS / reverse loss [EQ 4-61]

In this example, the repeater is 10 dB less sensitive than the BTS. For a subscriber signal to bereceived at the BTS at -120 dBm, it must received at the repeater at -110 dBm. A subscriber signalgoing straight to the BTS would be received at the BTS at -120 dBm.

As a result, the cascaded noise figures for a repeater and base station system are easy to calculate.They are determined by the repeater and BTS noise figures and the ratio of repeater pilot power toBTS pilot power. The simplifying assumptions are that the forward and reverse links are balanced.For unbalanced forward and reverse links or to include the effects of CDMA load, first calculatethe simple cascaded noise figure and then add in the other effects.

4.5.1.2.3 Cascaded Noise Figure for Cascaded Repeater Systems

For some highway applications where linear range needs to be maximized, a cascaded repeater

1.0

F1 - 1

0.1

F2 - 1

F2 = 3dBF1 = 3dB

kTBSubscriberkTBkTB

RepeaterBase Station (BTS)

0.2(kTB)2.2(kTB)

kTBSubscriber



4


system may be a viable choice. Similar to the approach used in Section 4.5.1.1.2, a cascadedrepeater system will impact the capacity and range of the donor BTS in order to maximize the rangeof the entire BTS/repeater system. Utilizing the same simplifying assumptions, the same approachto calculating the cascaded noise figure for the single repeater system can be applied to thecascaded repeater system. Figure 4-20 Multiple Repeater Cascaded Noise Figure provides anexample of a reverse link cascaded noise figure calculation for a cascaded repeater system. (Note:The values used in the following example are not indicative of a cascaded repeater systemoptimized for maximum range extension. The values are chosen to simplify the calculations.)

Figure 4-20: Multiple Repeater Cascaded Noise Figure

The following calculations are similar to the single repeater example. Thermal noise (kTB) isintroduced at Repeater #2 Rx by the source impedance of the antenna. The 3 dB noise figure of therepeater doubles the noise by adding another kTB. A reverse loss of 10 dB will lower the repeaternoise at the Repeater #1 antenna to 0.2(kTB). The Repeater #1 receiver antenna and noise figureadd another 2(kTB). Another reverse loss of 10 dB will lower the combined repeater noise at theBTS antenna to 0.22(kTB). Finally, the BTS receiver antenna and noise figure add another 2(kTB).As a result, the total noise at the BTS receiver is 2.22(kTB), which produces a cascaded noisefigure of 3.46 dB looking into the BTS Rx. A simple equation for the cascaded noise figure at theBTS receiver is as follows. All variables are linear (i.e. 2.22 = 2 + (2 * 0.1) + (2 * 0.01)).

Cascaded NF @ BTS = BTS NF + (Repeater #1 NF * reverse loss to BTS) + (Repeater #2 NF * total reverse loss to BTS) [EQ 4-62]

Similar to the single repeater example, the cascaded noise figure looking into Repeater #1 andRepeater #2 are as follows. Referenced to Repeater #1 receiver input, the 2.22(kTB) noise at theBTS receiver is ten times (10 dB) higher at 22.2(kTB). As a result, the Repeater #1 cascaded noisefigure is 10 dB higher at 13.46 dB. Referenced to Repeater #2 receiver input, the 22.2(kTB) noiseat the Repeater #1 receiver is ten times (10 dB) higher at 222(kTB). As a result, the Repeater #2cascaded noise figure is 10 dB higher at 23.46 dB. A simple equation for the cascaded noise figureat the Repeater #1 and #2 receiver is as follows.

Cascaded NF @ Repeater #1 = Cascaded NF @ BTS / Repeater #1 reverse loss [EQ 4-63]

1.0

F1 - 1

0.1

F2 - 1

F2 = 3dBF1 = 3dB

kTBSubscriberkTBkTB

Repeater #1Base Station (BTS)

2.22(kTB)

kTBSubscriber


0.1

F3 - 1

F3 = 3dB

kTBSubscriber

kTB

Repeater #2



0.22(kTB) 0.2(kTB)


4


Example. Cascaded NF @ Repeater #1 = 2.22 / 0.1 = 22.2 = 13.46 dB

Cascaded NF @ Repeater #2 = Cascaded NF @ BTS / Repeater #2 reverse loss [EQ 4-64]

Example. Cascaded NF @ Repeater #2 = 2.22 / 0.01 = 222 = 23.46 dB

It is important to note that the reverse loss for Repeater #2 is the total reverse loss from Repeater#2 to the BTS (which includes the loss from Repeater #1 to the BTS). For the example given inFigure 4-20 Multiple Repeater Cascaded Noise Figure, the total reverse loss from Repeater #2 tothe BTS is 20 dB.

4.5.1.3 Interference and Capacity Issues

The interference and capacity impact of a repeater will most likely depend upon its specificapplication and installation/optimization. The interference and capacity impact should be minimalfor a repeater, that is used for a typical application (i.e. to overcome RF obstructions) and that hasbeen properly installed and optimized. A repeater that has not been properly installed or optimizedcan have an impact on the interference and capacity of the donor BTS.

A CDMA repeater application that is set up for maximum range extension can have a significantcapacity impact upon the donor BTS. Since this repeater application is designed to trade-offcapacity for coverage, the donor BTS capacity impact depends upon the amount of interferencemargin that is traded-off for coverage. Again, a repeater that has not been properly installed oroptimized for the range extension desired can have a greater capacity impact on the donor BTS thanwhat it was originally designed for.

In order to reduce the number of BTSs for a new system deployment, a system operator mayconsider implementing a wide scale repeater deployment. A system with a wide scale deploymentof repeaters can create multiple paths of interference (direct path from the subscriber, indirect paththrough the repeater, and indirect paths through multiple other repeaters). Depending upon thesystem design, a system of this type may increase the reverse link noise rise which may decreasethe system capacity. Reverse link simulations of a couple of wide scale repeater design scenarioshave shown a decrease in RF carrier capacity of approximately 9-16%. In order to estimate thecapacity impact, simulations are highly recommended for any specific wide scale repeaterdeployment design.

The probability of interference from IM and spectral regrowth are increased with the use of arepeater. The situation may be worse for repeaters because the repeater receiver will add someadditional amount of IM and regrowth to the signal that is transmitted. The receiver absorbing thisundesired energy at the end of the chain will need to cope with these increased levels of IM andregrowth.

4.5.1.4 Filtering Issues

Depending upon the specific system design (i.e. repeater application, spectrum planning, adjacentband technology, etc.), additional filtering may be required to minimize the interference betweenthe repeater and the adjacent band technologies that are being used. The Sideband Noise (SBN)


4


performance of the repeater may require additional filters to be installed at the repeater site. Adetailed guard band interference analysis should be performed to determine the appropriate guardband and filter requirements to allow the repeater and the adjacent band technologies to co-existwith an acceptable interference impact. An analysis of both repeater links (Rx and Tx) is necessaryto determine if filtering is required for either link. Separate filters may be required for each of therepeater links.

If additional filtering is required, the additional space requirements must be taken into accountwhen designing the repeater site. If two separate filters are required, then the amount of spacerequired to house and mount the filter hardware needs to be considered. With the potential use offilters at the CDMA donor BTS, at the receiver input of the repeater, and at the output of therepeater, the total group delay of the filters can become a concern. Too much group delay willdistort the CDMA waveform, which may cause unacceptable "rho" performance (a measure ofwaveform quality). The total maximum group delay must be split between the three filters. Sincethe group delay for the built-in filters of the donor BTS and of the repeater are already established,a lower group delay specification for the additional repeater filter may be required. It may bedifficult to find an economical and compact filter to satisfy the group delay requirements inaddition to the other filter requirements determined from the detailed analysis.

If it has been determined that additional filtering is required, then the cost impact of the additionalfiltering should be taken into consideration when designing a repeater site. Since a repeater doesnot add any capacity to the system, the additional cost of the filtering should be added to the totalcost analysis to determine if a regular BTS (macro-cell, micro-cell, or pico-cell) may be moreappropriate for the application.

4.5.2 CDMA Repeater Installation Considerations

When using repeaters for a typical application to overcome an RF obstruction within a BTS’scoverage area or for a highway application to maximize linear range extension, it is important tofollow the repeater vendor’s installation engineering guidelines.

4.5.2.1 Antenna Isolation

Antenna isolation is a critical parameter for an over-the-air repeater system. If the repeater’santennas do not have adequate isolation from each other, the repeater’s amplifiers may startoscillating. Proper donor to subscriber antenna isolation at the repeater may be difficult to achievefor some applications. The amount of antenna isolation that is normally required is equal to 15 dBplus the gain of the repeater (refer to the repeater vendor’s recommendation for the actual value touse). Antenna isolation values of 80 dB (repeater gain = 65 + 15 = 80 dB) or greater are notuncommon. Since the environmental surroundings and the physical construction of the site canhave an impact, it is highly recommended to actually measure the antenna isolation for each andevery repeater site. The ability to measure the antenna isolation properly and accurately is animportant step in the repeater installation. Do not rely on estimated antenna isolation calculationsto validate the isolation requirements.

The repeater diagram in Figure 4-14 shows the donor antenna at a higher elevation than the


4


subscriber antenna. This represents a repeater application which takes advantage of verticalseparation between the donor and subscriber antenna in order to achieve the isolation requirements.Placing the donor antenna at a higher elevation may also provide a direct line-of-sight path to thedonor base station, which is highly recommended for all repeater implementations. In someapplications, the subscriber antenna may be mounted at a higher elevation than the donor antenna(see Figure 4-21).

Figure 4-21: Alternate Repeater Antenna Configuration

A viable configuration which utilizes horizontal separation along with a barrier is shown inFigure 4-22. For this application, the building is acting as a physical barrier in order to increase theattenuation between the antennas, which will increase the antenna isolation.

Figure 4-22: Horizontal Separation Using a Barrier

Just as long as the measured isolation and the direct line-of-sight requirements are satisfied, theoptimal antenna locations may depend upon the particular application.

In some cases where vertical and/or horizontal separation does not provide enough antennaisolation, it may be possible to install custom RF shielding between the donor and subscriberantennas in order to achieve the desired antenna isolation requirements. RF shields can be


RepeaterCoverage

BTS CellCoverage

DonorAntenna

SubscriberAntenna

BaseStation

Repeater

RepeaterCoverage

BTS CellCoverage

DonorAntenna

SubscriberAntenna

Building


4


constructed with various materials (hardware cloth, cyclone chain-link fence, metal screen, solidmetal, etc.) and various types of configurations (flat shield, flat shield with corners, curved shield,etc.). The actual attenuation will depend upon the specific application, but nominal values in therange of 10-30 dB of attenuation may be achievable.

As an alternate solution, a micro-wave or fiber linked repeater may be used instead of an over-the-air type repeater. A linked repeater does not have the same antenna isolation requirements as anover-the-air repeater. An example of a micro-wave linked repeater is shown in Figure 4-23.

Figure 4-23: Micro-wave Linked Repeater

Since the micro-wave link is operating at a different frequency and transmitted in a differentformat, the isolation between the subscriber antenna and the micro-wave antenna is not as criticalas the over-the-air repeater. An example of a fiber linked repeater is shown in Figure 4-24.

Figure 4-24: Fiber Linked Repeater

Since the fiber link is not transmitting over the air, antenna isolation is not even a factor for thisrepeater application.


RepeaterCoverage

BTS CellCoverage

SubscriberAntenna

Micro-wave Link


RepeaterCoverage

BTS CellCoverage

SubscriberAntenna

Fiber Link


4


4.5.2.2 Repeater Antenna Considerations

The following sections provide information regarding the repeater donor and subscriber antennas.

4.5.2.2.1 Repeater Donor Antenna

The repeater donor antenna should have a very narrow beamwidth in order to isolate a single donorBTS. In an area with a dense population of BTSs, isolating a single donor BTS may be difficult. Ifmore than one BTS is seen by the repeater, the performance in the repeater’s coverage area may bedegraded. As a result, it is typically recommended to use a highly directional, high gain, high front-to-back ratio (for horizontal separation), and/or high side lobe attenuation (for vertical separation)donor antenna with 15° of horizontal beamwidth or less. Parabolic antennas (solid or grid) aresuited very well for this application, which also have an added advantage of high side lobeattenuation, which can help achieve the vertical antenna isolation requirements for the site.

Pilot pollution can be made worse if the repeater donor antenna is not narrow enough and localizedto the desired donor base station sector. Since the repeater repeats the entire CDMA carrier (signalplus noise), it is important that the repeater location be line-of-sight to the donor BTS with adominant PN. It is highly recommended to choose a repeater application that will allow a line-of-sight (LOS) path with a clear Fresnel zone (ideally with 60% of the first Fresnel clearance) betweenthe repeater and the donor BTS. A LOS path will ensure a highly reliable repeater link, which canutilize a smaller fade margin. If a LOS path is not possible, then a path loss measurement isrequired to estimate the mean path loss of the donor link.

Since a LOS path which isolates a single donor BTS is important, donor antenna alignment is alsovery critical to the installation of a repeater site. A mis-aligned highly directional donor antennacan also create significant performance issues with the operation of a repeater site.

4.5.2.2.2 Repeater Subscriber Antenna

The subscriber antenna should be chosen (i.e. gain, H/V beamwidth, etc.) to cover the desired area.For over-the-air repeater applications, it is typically recommended to use an antenna with 105° ofhorizontal beamwidth or less, due to isolation/interference concerns and the unreliability of thebeam patterns. It would be very difficult to achieve the antenna isolation requirements using anomni subscriber antenna with an over-the-air repeater application and as such, they are notrecommended. On the other hand, micro-wave and fiber linked repeaters do not have the sameisolation requirements as the over-the-air repeaters. Thus, the horizontal beamwidth restrictions donot apply towards the micro-wave/fiber linked repeater applications.

For those repeaters which have a diversity receive path capability, two subscriber antennas will berequired. The same subscriber antenna restrictions mentioned above would apply for over-the-airdiversity receive repeaters. As an alternative, a dual polarized slant 45° antenna may be a logicalchoice for diversity receive repeaters. Dual pole antennas (see Chapter 7) with the desiredhorizontal and vertical beamwidths have an advantage of providing two separate antennas in asingle housing.


4


4.5.2.3 Repeater Gain Settings

The repeater gain settings are a critical component to the successful installation and performanceof the repeater. Setting the gain too high for the repeater’s Tx path to the subscriber could causethe repeater Tx PA to be over driven under a loaded condition. Although this may not be a majorconcern if the repeater PA is designed with gain compression, a significant amount ofintermodulation (IM) distortion and spectral regrowth may be generated, which can impact thespectral purity (rho) of the CDMA signal beyond acceptable levels.

Setting the repeater’s Rx path back to the donor BTS too high could cause the BTS receiver todesense. To ensure that the repeater does not desense the donor BTS in a normal application (i.e.the repeater is NOT being used for maximum range extension), the repeater vendors typicallyrecommend that the repeater Rx gain back to the BTS should be set lower (up to 10 dB) than therepeater Tx gain to the subscriber.

It is important to set the repeater gain levels for the Rx & Tx paths properly. Figure 4-25 belowshows the potential effects of reducing the range of a donor BTS if the gain settings are not setproperly.

Figure 4-25: Potential Range Reduction Due to Repeaters

With the assumption stated in the chart, the Y axis in the figure above represents the difference inrepeater forward Tx power relative to the BTS power plus the difference in the repeater forwardTx gain relative to the repeater reverse Rx gain. Table 4-10 provides an example of how tocalculate the relative Tx & Rx link difference.

B T S R X R ange1, 2, or 4 R epeater s

3.26 R F prop los s

-20.0

-15.0

-10.0

- 5.0

0.0

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00

Normalized R X Cell coverage referenced to B T S nois e f igure

Rela

tive

Tx

& R

x Li

nk D

iffe

renc

es

1 R epeater

2 R epeaters

4 R epeaters

dis tance B T S with 1 R epeater

B T S

P ath L os sMobile to B T S

L ink L os s = P ath L os s + Cable L os s + Antenna Gain+ R epeater GainAs s umption

R evers e L ink R epeater to B T S = F orward L ink B T S to R epeater


4


Table 4-10: Relative Tx & Rx Link Difference Example

With this example, the donor BTS’s normalized Rx cell coverage at a -10dB relative Tx & Rx linkdifference is ~96% of the BTS’s coverage area without the repeater (i.e. the repeater reduced thecoverage area by ~4%). Typical settings of the relative Tx & Rx link differences are -15 dB orbetter which will cause little to no effect on the normal coverage area of the donor BTS.

4.5.3 CDMA Repeater Optimization Considerations

This section discusses some of the optimization considerations around repeater applications.

4.5.3.1 Timing Impacts

The following sections provide some optimization considerations regarding the timing impacts ofadding a repeater to a system.

4.5.3.1.1 Search Windows and Parameters

One of the main optimization considerations for the deployment of a repeater is the adjustment ofthe network parameters associated with search windows and timing. Since the repeater unit itselfwill add approximately 5-8 micro-seconds (µs) of delay (typically around 6 µs) in both the forwardand reverse links, certain timing related parameters need to be expanded in order to handle thisextra timing delay. There are four basic timing related considerations for repeaters.

• Access Channel Search Window (Cell Radius - PamSz & AchPamWinSz)• Traffic Channel Search Window (TchAqcWinSz)• Subscriber Search Windows (SrchWinA, SrchWinN, SrchWinR)• PN Offset Interference Protection (Pilot_Inc)

Access Channel Search Window. The access channel search window establishes the maximumround trip propagation delay that the BTS will search for subscriber origination attempts. In effect,it establishes the maximum radius that the BTS will be able to receive an origination attempt. Sincea repeater not only increases the radius (distance) of the donor BTS, it also adds delay to the signalwhich is similar to adding propagation delay. The added delay can be translated back to distance.Thus, the access channel search window of the donor BTS needs to be expanded to compensate forthe added distance (repeater coverage plus repeater delay) that the repeater provides. For the

BTS Tx Pilot Power 30 dBm a

Repeater Tx Pilot Power 25 dBm b

Repeater Tx Path Gain 70 dB c

Repeater Rx Path Gain 65 dB d

Relative Tx & Rx Link Differences -10 dB (b-a) + (d-c)


4


Motorola infrastructure, the access channel search window is set by adjusting the Cell Radiusparameter (which automatically adjusts the PamSz & AchPamWinSz parameters). Adjustments tothe Cell Radius parameter can be calculated as follows:

Cell Radius = Donor BTS Range (km) + Repeater Delay (µs) * 0.299 (km/µs) + Repeater Range (km) [EQ 4-65]

Traffic Channel Search Window. For the Motorola infrastructure, the traffic channel searchwindow is set by the TchAqcWinSz parameter. This parameter defines the traffic channelacquisition in PN chips, which is used during the handover acquisition of a call. For normalapplications (including repeater applications), it should be set at least as large as theAchPamWinSz parameter (which is established by the Cell Radius parameter).

Subscriber Search Windows. The subscriber search window parameters are SrchWinA,SrchWinN, and SrchWinR. SrchWinA is the active/candidate pilot set search window size whichshould be made large enough to incorporate ~95% of the expected delay spread energy. Since arepeater has an internal delay of 5-8 µs and a subscriber will find itself in places where the BTSand repeater signals are both strong enough to demodulate, a repeater will normally increase theeffective delay spread of the donor BTS. The default setting for SrchWinA is 5 which correspondsto 20 PN chips (16 µs or +8 µs from the earliest arriving “usable” delay spread component). Thedefault setting may be adequate for some repeater applications. An evaluation of the specificrepeater application is necessary to determine if the SrchWinA parameter for the donor BTS needsto be increased.

The SrchWinN and SrchWinR parameters represent the search window sizes associated with theNeighbor Set and Remaining Set pilots. The size should be made large enough to account fordifferential time delay between the subscriber and a potential handoff BTS given in thesubscriber’s neighbor list. The worst case differential delay would be a scenario where thesubscriber is next to a serving site and the subscriber attempts to handoff to a distant site. Since arepeater can increase the differential delay, increasing the SrchWinN and SrchWinR parametersmay be necessary for some repeater applications. It is important to note that handoff relationshipsare symmetrical and reciprocal for the neighboring cells which are candidates for the donor sector.Thus, the SrchWinN and SrchWinR parameters will need to be adjusted for both the donor BTSand the neighbor cells to the donor BTS.

PN Offset Interference Protection. Some level of PN Offset interference protection is providedwith the Pilot_Inc parameter. An increase in the Pilot_Inc increases the separation betweenadjacent PN offset pilots which provides improved adjacent offset interference protection. Theincreased separation between adjacent PN offsets also reduces the total number of valid PN offsets.A Pilot_Inc of 2 will decrease the total number of valid PN offsets from 512 to 256. Since the cellradius (or propagation delay) is a factor to consider when selecting the appropriate Pilot_Incsetting, adding repeaters to a system may require a re-evaluation of the Pilot_Inc setting. In mostcases, adjustments to the Pilot_Inc parameter due to repeater applications will not be necessary, ifproper PN offset planning is performed. In some cases, a re-evaluation of the Pilot_Inc setting maybe necessary and an adjustment to the setting may be required.

For more detailed information on PN offset planning and search window parameters please referto Chapter 5.


4


4.5.3.1.2 Location Based Services

Another timing related issue to consider is that some implementations of location based servicesmay be affected by the use of repeaters. For a fixed network equipment based solution, TimeDifference of Arrival (TDA) measurements are made which will now include both repeater andpropagation delays. The repeater delay will add variance to the TDA measurements and may makeit difficult to achieve accurate location calculations. There is also a handset based GPS solutionwhich still requires some coordination with the fixed network equipment. Both of these locationbased service implementations may require some sort of custom solution in order to make thelocation based feature accurate for repeater applications.

4.5.3.2 Optimization Considerations

Once the repeater site has been fully designed, installed, and verified (i.e. repeater gain settingsverification, donor BTS-to-repeater link verification, antenna isolation verification, etc.), the nextstep is to conduct drive test optimization. After the timing related parameters have been evaluatedand adjusted appropriately, there are six drive test areas that need to be analyzed.

• Donor BTS coverage area• Repeater coverage area• Donor BTS to repeater transition zone coverage area• Donor BTS to adjacent cell handoff zones• Repeater to adjacent cell handoff zones• Donor BTS to repeater transition zone to adjacent cell handoff zones

Most of the same basic drive test data collection and optimization techniques used for a normalBTS can also be applied towards a repeater site. Although, the added complexity and functionalityof a repeater should be taken in account during the troubleshooting of any performance issues thatare identified through the drive test optimization process. Since one PN offset will be transmittedfrom two separate antennas at two different locations, the optimization engineer needs to befamiliar with the donor BTS and repeater antenna configurations, in order to optimize the coverageof the one PN offset.

Since the repeater repeats the entire CDMA carrier (signal plus noise), it is important that therepeater location be line-of-sight to the donor BTS with a dominant PN. Pilot pollution can bemade worse if the repeater donor antenna is not narrow enough and localized to the desired donorBTS sector. A repeater deployment should create a dominant pilot area and improve the pilot signalstrength coverage.

4.5.4 CDMA Repeater Maintenance Considerations

This section discusses some of the maintenance considerations around repeater applications.


4


4.5.4.1 Future Expansion Considerations

As the capacity of a system grows over time, a natural progression is to deploy an additionalCDMA carrier to the system. Prior to deploying a repeater for a specific repeater application, thelong term expansion planning of the repeater site should be considered. The following sectionsprovide information about two future expansion considerations.

• Multiple Repeater Expansion• Repeater to BTS Conversion

4.5.4.1.1 Multiple Repeater Expansion

The expansion design of a multiple carrier repeater system becomes more complex. Duplication ofrepeater hardware & installation is required with each additional carrier added to the donor BTS.If a new carrier is added to an area where repeaters are deployed, re-engineering of the repeater siteis required to accommodate a multiple repeater configuration. Below are a few design issues toconsider when looking at multiple carrier repeater sites.

• Antenna sharing configuration (splitters, combiners, duplexers, etc.)• Separate antennas

If the additional repeater is required to share the antennas of the existing repeater, the antennasharing combining/splitting/filtering losses for the new antenna configuration will need to beevaluated. Adjustments to the repeater design may be required to overcome the additionalcombining/splitting/filtering losses of the new antenna sharing configuration. If the additionalrepeater requires separate antennas, an evaluation of the interference and antenna isolation is stillrequired. For either antenna configuration (antenna sharing or separate antennas), a re-evaluationof the following is required.

• Re-evaluation of interference for additional filtering• Re-evaluation of repeater gain settings• Re-evaluation of repeater antenna isolation requirements• Re-evaluation of donor BTS-to-repeater link engineering

Once the new antenna configuration has been designed and implemented, the new repeaterconfiguration should be reverified (i.e. repeater gain settings verification, donor BTS-to-repeaterlink verification, antenna isolation verification, etc.). The long term planning and design of arepeater application (i.e. multiple repeaters for multiple carrier support) should be consideredduring the initial design and deployment of a specific repeater site.

4.5.4.1.2 Repeater to BTS Conversion

Typically, a new carrier is added to expand the capacity of the system. A repeater does not provideany capacity benefit to the system (it only provides expanded coverage). If a new carrier is addedto an area where repeaters are deployed, it may make sense to convert the repeater to a regularcapacity bearing cell site.


4


A significant amount of cell site design, installation, and optimization work at the repeater site isnecessary to convert the repeater site to a capacity bearing cell site. All of the initial work in therepeater design, installation, and optimization including RF propagation modeling, antennaisolation measurements, custom shielding, linked network equipment installation, donor antennaalignment, subscriber antenna adjustments, repeater gain settings and verifications, parametersettings, and drive test optimization, will not apply to the capacity bearing cell site. Most of the cellsite design, installation, and optimization work required to deploy a new cell site into a system isalso required to convert a repeater site to a regular cell site. The long term planning and design ofa repeater application (i.e. repeater to BTS conversion) should include a cost analysis of therepeater site which incorporates the cost of all of the rework to convert the repeater to a capacitybearing site.

4.5.4.2 Environmental Changes

Future changes in the environmental conditions surrounding an over-the-air repeater site can havean impact on the performance of the repeater. Changes in the surrounding environment (i.e.changes in the ground clutter such as new buildings, changes to landscaping, seasonal changes tothe surrounding foliage, etc.) can have a negative impact on the donor BTS-to-repeater linkperformance. It may also have a negative impact on the donor-to-subscriber antenna isolation. Bothof these conditions can affect the performance of an over-the-air repeater.

4.5.4.3 Operations and Maintenance Considerations

The Operations and Maintenance (O&M) of a repeater network will be different than that of a BTSnetwork. The hardware, software, monitoring access (POTS line w/modem, wireless modem, etc.),configuration management, and alarm monitoring O&M practices and procedures for a repeaternetwork will be different and will require specialized knowledge and skill sets. Different resourcesor additional training will be required to properly plan, design, install, operate, and maintain arepeater system.

System Capacity planning becomes more complicated with repeaters. Since repeaters connected toone sector will cover more area than sectors without repeaters, the site’s capacity limit will bereached more quickly due to the additional area the sector with the repeater is covering. This maycause a highly imbalanced system where one sector is lightly loaded while another sector is heavilyloaded. To overcome capacity loaded donor sectors, a new carrier can be added, the repeater canbe replaced with a new cell site, or the repeater can be moved to a lightly loaded donor sector.

4.6 Theoretical vs. Simulator

It should be emphasized that a RF link budget and associated statistical propagation model (i.e.Hata), although useful as an analysis technique to evaluate relative differences between radiosystems or to obtain a qualitative description of a CDMA system, cannot be used to guaranteecapacity or coverage reliability. A detailed system design needs to be completed which takes intoaccount the specific characteristics of the given area. Some of the specific characteristics to beaccounted for are: site locations, subscriber distribution, terrain, and ground clutter. The genericassumptions of flat terrain, uniform subscriber distribution, and ideal site locations implied within


4


the propagation and traffic distribution models do not adequately account for specificcharacteristics of actual systems.

The actual terrain of the area to be covered can greatly influence the range to which a site willpropagate. Instead of an ideal line of sight propagation, reflections, diffractions and shadowing ofthe RF signal are taken into account to adjust the distance that the signal will propagate. In additionto the terrain, what is on the terrain, ground clutter, is quite important. A given RF signal willpropagate further in an area that is desolate (little to no buildings or foliage), than in an area whichis comprised of many buildings. Also, the placement of the site within this terrain is very important.Simply stated, if the site is surrounded by obstructions, the coverage of the site will be less than ifthere are no obstructions.

The actual traffic characteristics of systems are non-uniform with large variations possible fromsector to sector. The more spectrally efficient a given radio technology is, the more economical itis to maintain the grade of service in these sectors by simply adding additional traffic channels. Inless efficient radio systems, cell splitting is the only option available to maintain the grade ofservice. This often requires the addition of several cells to resolve the blocking problem in a singlesector. This characteristic is not accounted for in the RF link budgets.

Many different criteria exist for determining the CDMA coverage area of a system. Among thesecriteria, differentiation should be made between the forward and reverse links, as well as, betweenthe criteria that can be simulated as opposed to being field test measured. Differentiation of thesubscriber unit needs to be considered. Fixed systems need to have different assumptions orconsiderations applied to the design that will be different from a system being designed to supportmobility. Finally, a distinction must be made between coverage area as defined in the loadedsystem as opposed to the unloaded system. Coverage will change with loading. Any coverage testneeds to keep loading in perspective.

Because of the interrelated nature of CDMA coverage, quality and capacity, and all of the issueshighlighted above, Motorola utilizes the NetPlan CDMA Simulator to estimate the performance ofindividual system installations.

The Motorola NetPlan CDMA Simulator may be used for analyzing DS-CDMA performance inproposed and existing systems resulting in predicted capacity, required system parameters andhardware loading information. It provides for a method of understanding the inter-relationshipbetween coverage, capacity, and quality. It permits investigations into real Cellular/PCS systemconcerns such as edge effects, excess background noise, propagation anomalies, antennabeamwidth, subscriber distribution, receiver sensitivity impact, interference mitigation, powercontrol and handoff. It also provides performance levels and determines required power allocationfor page, sync, pilot, forward and reverse traffic channels (TCH) for different channel models, cellloading, and receiver characteristics. Both the reverse and forward link are simulated.

It should be noted that the accuracy of the simulator is dependent on the accuracy of the input itrequires (such as path loss, traffic distribution, vehicle speed, etc.).


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4.7 References

1. Turkmani, Parsons and Lewis, "Measurement of building penetration loss on radiosignals at 441, 900 and 1400 MHz", Journal of the Institution of Electronic and RadioEngineers, Vol. 58, No. 6 (Supplement), pp. S169-S174, September-December 1988

2. Turkmani and Toledo, "Modelling of radio transmissions into and within multistorybuildings at 900, 1800 and 2300 MHz", IEEE Proceedings-I, Vol. 140, No. 6, December1993

3. Aguirre, "Radio Propagation Into Buildings at 912, 1920, and 5990 MHz UsingMicrocells", 0-7803-1823-4/94 IEEE, session 1.6 & 1.7, pp. 129-134

4. Lee, William C.Y. "Mobile Communications Engineering", Copyright 1982, McGraw-Hill Inc. pg. 33-40.

5. Jakes, W.C., "Microwave Mobile Communications", IEEE Press Reissue 1993, (Wiley,New York, 1974), pp. 125-127

6. Okumura, Y., Ohmori, E., Kawano, T., Fukada, K.: "Field strength and ITs Variabilityin VHF and UHF Land-Mobile Radio Service", Rev. Elec. Commun. Lab., 16 (1968),pp. 825-873

7. Hata, M.: "Empirical formula for propagation loss in land mobile radio services", IEEETrans. on Vehicular and Technology, VT-29 (1980), pp. 317-325

8. COST 231 - UHF Propagation, "Urban transmission loss models for mobile radio in the900- and 1,800- MHz bands", COST 231 TD (91) 73 The Hagne, September, 1991

9. Parsons, David, "The Mobile Radio Propagation Channel", Copyright 1992, Reprinted1996 by John Wiley & Sons Ltd.

10. Rappaport, Theodore S., "Wireless Communications Principles & Practices", Copyright1996 by Prentice Hall PTR

11. Title 47, Part 24, Sub-Part E, Section 24.232.


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Table of Contents

5.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 3

5.2 Number of Pilot Offsets per CDMA Frequency. . . . . . . . . . . . . . . . . . . 5 - 3

5.3 PN Offset Planning - General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 35.3.1 Consequences and Sources of Offset Interference . . . . . . . . . . . . 5 - 35.3.2 PN Offset Planning - Parameters and Terms . . . . . . . . . . . . . . . . 5 - 55.3.3 Converting Between Chips and Time or Distance . . . . . . . . . . . . 5 - 85.3.4 Search Windows and Geography . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 95.3.5 Search Windows and Scan Intervals . . . . . . . . . . . . . . . . . . . . . . 5 - 11

5.4 PN Offset Planning - Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 125.4.1 Mitigating Adjacent Offset Interference - General . . . . . . . . . . . 5 - 12

5.4.1.1 Adjacent Offset Interference Protection Based on Timing . . . . . . . 5 - 125.4.1.2 Adjacent Offset Interference Protection Based on Signal Strength 5 - 14

5.4.2 Protection Against Co-Offset Interference . . . . . . . . . . . . . . . . . . 5 - 155.4.3 Incorrect Identification of an Offset by the Base Station . . . . . . . 5 - 185.4.4 PILOT_INC and the Scan Rate of Remaining Set Pilots . . . . . . . 5 - 195.4.5 Summary of Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 205.4.6 Guidelines for Assigning Offsets . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 225.4.7 Guidelines for Changing PILOT_INC

at Inter-CBSC Boundaries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 25

5.5 Reuse Patterns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 26

5.6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 27

Chapter

5 PN Offset Planning andSearch Windows


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CDMA/CDMA2000 1X RF Planning GuideChapter 5: PN Offset Planning and Search Windows

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5


5.1 Introduction

This chapter will discuss the PN Offset Planning. Section 5.3 provides insight into the sources andconsequences of offset interference. The definition of important terms and parameters are given.Also, since a knowledge of search windows is considered fundamental, a detailed explanation ofthis topic is included. Section 5.4 provides the theory that justifies placing certain boundaries onthe value of PILOT_INC, which is central to PN Offset Planning. Section 5.4.5 and Section 5.4.6will prove very useful to the offset planner by providing a summary of the factors pertinent toPILOT_INC selection along with a concise listing of all the planning guidelines. Section 5.4.7provides guidelines for offset planning at an Inter-CBSC boundary when different PILOT_INCvalues are involved. Some information has been provided that will benefit system optimizers. Thisincludes information on scanning rates (Section 5.3.5 and Section 5.4.4). Finally, references areprovided for further study of this important topic.

Please note that all of the information provided on this topic applies equally to IS-95A, IS-95B,and IS-2000 specifications.

5.2 Number of Pilot Offsets per CDMA Frequency

The Pilot Channel is a spread spectrum signal carrying no data and is always transmitted on adownlink CDMA channel. The subscriber stations use the pilot to acquire the system, and to assistin several signal processing functions such as synchronization, demodulation (phase reference),soft handoff and channel estimation. The uniqueness of the pilot is achieved through time shifts ofa basic sequence known as zero shift pilot or short PN sequence. Since sectors are distinguished bytime shifts of a given pseudo-noise sequence, enough separation between time offsets must beprovided to avoid “mutual pilot interference”. Per TIA/EIA IS-95 Interim Standard, the chosenlength for the pilot PN sequences is 32,768 chips (Section 7.1.3.1.9) with a minimum separation of64 chips (Section 7.1.3.2.1) between adjacent offsets. This leaves a maximum of 512 (32768/64)distinct pilot offsets available for a CDMA frequency.

5.3 PN Offset Planning - General

Before actually doing a PN offset plan, it will be beneficial to have a general understanding ofscenarios to avoid when designing the PN offset plan, to learn the general terms and definitions thatare associated with PN offset planning, and to gain an understanding to the various searchwindows.

5.3.1 Consequences and Sources of Offset Interference

The design of a PN offset plan for CDMA is comparable to that of a signalling channel frequencyplan in analog. The consequences of poor offset planning include the following:

• Active Set Pilot Interference - This phenomenon would occur in the active area andinvolve the active search window (SRCH_WIN_A). The interfering signal would need


5


to be strong enough to be processed as an active finger (except in the less likely casewhere the timing was perfectly coincident with a true active finger).

• Neighbor Set Pilot Falsing - A neighbor set pilot may falsely appear strong enough forthe subscriber to promote the pilot to the candidate set and recommend to the basestation (BS) to perform a soft handoff ‘add’ via the Pilot Strength MeasurementMessage (PSMM). This falsing would occur in the neighbor area and involve theneighbor search window (SRCH_WIN_N). The falsing signal strength would need tomeet the T-ADD threshold criteria.

The probability for interference or falsing is dependent upon two factors: timing andstrength. Time differentials can be translated into geographic regions and have as theirthreshold the search window size. A detailed discussion of this topic will be found laterwithin this chapter. If a signal falls outside of a search window, its energy becomesnothing more than uncorrelated interference. Note that the term active area is meant torefer to the area in which a signal may be (or is intended to be) actively demodulated. Theterm neighbor area refers to the area in which a signal will be sought as a candidate. Ingeographic terms, the neighbor area greatly expands the region where problems mayoccur since the search for a neighbor signal lies in many areas outside of the active area.The use of large or generous neighbor lists along with the technique of merging neighborlists when in soft/softer handoff creates further expansion. Mitigating this expansion ofthe geographic space in which falsing may occur is the heightened signal strengththreshold at which interference may occur (a T-ADD of -14dB versus a finger-lockingthreshold of approximately -24dB).

• Incorrect BS Identification - A signal may travel far enough to be incorrectlyidentified by the BS when it translates the subscriber reported phase into a PILOT_PNoffset index.

In this document, the phrases interference and falsing may be used interchangeably.

In analog systems, ‘co’ and adjacent channel interference are major factors in the system design.The co-channel interference was managed via the antenna configuration and the reuse pattern/distance. The adjacent channel interference was managed through the application of a simplefrequency planning rule.

With the CDMA channel, all sites reuse the same frequency. Interference isolation on the forwardCDMA channel is obtained via short PN code offsets (inter-sector) and Walsh codes (intra-sector).The possible sources of interference/falsing include ‘co’ and adjacent offsets.

Since CDMA pilots are distinguished through offsets of the same short PN code, adjacent channelinterference has its counterpart in CDMA when phase shifts occur caused by propagation delays.Using phase for cell identification may therefore cause falsing problems as depicted in Figure 5-1.


5


Figure 5-1: PN Offset Planning

The phase delay used in the figure above need not be so exact to create problems. The falsing ofone signal need only fall within the search window of the subscriber.1

The valid set of offsets is limited to multiples of PILOT_INC. In Figure 5-2 below, a PILOT_INCof 2 was chosen. Offset 4 is adjacent to and can interfere with 6 if it arrives ~2 offsets late whichimplies that 4, the interfering signal, is traversing a significant distance. Conversely, offset 6 mayinterfere with 4, but 6 would need to arrive ~2 offsets early which implies that the subscriber isacting at a significant distance from the site using offset 4. If the PILOT_INC is chosen carefully,there should be little concern with 2 interfering with 6 or 6 with 2.

Figure 5-2: Short PN Sequence w/PILOT_INC = 2

As with analog, a reuse distance must be maintained between sectors implementing the same PNoffset to avoid interference. Since the pilot signal is integral to the operation of a CDMA system,careful PN offset planning should be performed to mitigate interference between sites using thesame offset and falsing between adjacent PN codes which result from phase delay.

5.3.2 PN Offset Planning - Parameters and Terms

There are various parameters and terms which come into play when discussing PN offsets and theirfunction in CDMA.

1. Note also how time, distance, and chips are all related. Refer to Section 5.3.3.

PN 0

PN 1

t0 = 102 µsec

t1 = 50 µsec

Avoid ambiguity which could result from phase delay.

∆t = t0 - t1 = 102 µsec - 50 µsec = 52 µsecPN 1 - PN 0 = 64 chips = 52 µsec = 9.6 milesTraversing the additional distance of 9.6 miles, the PN 0 signal has phaseshifted sufficiently so as to be received by the subscriber with essentially thesame phase as PN 1.

2 4 6 8 10


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System Time

All base station digital transmissions are referenced to a common CDMA system-wide time scalethat uses the Global Positioning System (GPS) time scale, which is traceable to and synchronouswith Universal Coordinated Time (UTC).2

Time Reference

The subscriber establishes a time reference which is used to derive system time. This timereference will be the earliest arriving multipath component being used for demodulation.3 Thisreflects the assumption that the subscriber’s fix on system time is always skewed by delayassociated with the shortest active link.

PILOT_PN

The Pilot PN sequence offset (index), in units of 64 PN chips. It ranges from 0 to 511. Everytransmit sector will have an offset assigned to it.

Active Set

The pilots associated with the Forward Traffic Channels assigned to the subscriber.4 It is the basestation that assigns all active set pilots to subscribers.

Candidate Set

The pilots that are not currently in the Active Set but have been received by the subscriber withsufficient strength to indicate that the associated Forward Traffic Channels could be successfullydemodulated. As a property of the Mobile Assisted HandOff (MAHO), the subscriber promotes aNeighbor Set or Remaining Set pilot to the Candidate Set when certain pilot strength criteria aremet and then recommends the pilot to the base station for inclusion in the Active Set.

Neighbor Set

The pilots that are not currently in the Active Set or the Candidate Set and are likely candidates forhandoff. Neighbor Set pilots are identified by the base station via Neighbor List and Neighbor ListUpdate messages.

Remaining Set

The set of all possible pilots in the current system on the current CDMA frequency assignment,excluding pilots in the other sets. These pilots must be integer multiples of PILOT_INC (definedbelow).

2. EIA/TIA/IS-95A, Mobile Station - Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System,§1.2.3. Ibid., §6.1.5.1.4. Ibid., §6.6.6.1.2.


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SRCH_WIN_N, SRCH_WIN_R

These parameters represent the search window sizes associated with Neighbor Set and RemainingSet pilots.5 The subscriber centers the search window for each pilot around the pilot’s PN sequenceoffset using timing defined by the subscriber’s time reference.

In general, a neighbor search window, SRCH_WIN_N, will be sized so as to encompass thegeographic area in which the neighbor may be added (a soft handoff “add” zone or “initialdetection area”). The largest a neighbor search window need be is such that it is sufficient to coverthe distance between the neighbors, , plus an accommodation of the time-of-flight delay(approx. 3 chips).

SRCH_WIN_A

This parameter represents the search window size associated with the Active Set and Candidate Setpilots.6 The subscriber centers the search window for each pilot around the earliest arriving usablemultipath component of the pilot. Note that in contrast to the neighbor or remaining set searchwindows, the active/candidate search windows "float" with the desired signals. That is to say thatthe center position of the search window is updated every scan to track the new location of theearliest arriving multipath component.

To better illustrate the relationships between search windows, consider the following scenario:

A subscriber monitors a neighbor pilot. The neighbor search window is centered on the neighborpilot offset. This centering is relative based on timing derived from the time reference. When thepilot strength of a neighbor pilot recommends promotion to the candidate set, then the searchwindow will be tightened to the active search window size. The active search window is sized tocompensate for delay spread only and is, therefore, smaller than the neighbor search window. Inaddition, the active search window locks onto and tracks the candidate pilot.

PILOT_ARRIVAL

The pilot arrival time is the time of occurrence of the earliest arriving usable multipath componentof a pilot relative to the subscriber’s time reference.7

PILOT_PN_PHASE

The subscriber reports pilot strength and phase measurements for each active and candidate pilotin the Pilot Strength Measurement Message when recommending a change in the handoff status(i.e. mobile assisted handoff). The subscriber computes the reported PILOT_PN_PHASE as afunction of the PILOT_ARRIVAL and the PILOT_PN.8 The pilot arrival component representsthe time delay of the pilot relative to the time reference or, in other words, how skewed the pilot is

5. Ibid., §6.6.6.2.1.6. Ibid.7. Ibid., §6.6.6.2.4.8. Ibid.

3R


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from the subscriber’s concept of system time. Both the PILOT_ARRIVAL andPILOT_PN_PHASE measurements are in chips (15 bits, 0 to 32,767 or 215-1) while thePILOT_PN is in offsets (9 bits, 0 to 511). The difference (6 bits) corresponds to the 64 chip intervalbetween successive PN offsets.

Note also that the subscriber does not identify pilots by their offset index directly, but by theirphase measurement. If the pilot arrival was larger than 32 chips (1/2 of a pilot offset or 4.8 miles),then this could undermine the ability of the base station to properly translate pilot phase into pilotoffset index (given a PILOT_INC of 1).

PILOT_INC

The pilot PN sequence offset index increment is the interval between pilots, in increments of 64chips. Its valid range is from 1 to 15. The subscriber uses this parameter in only one manner, todetermine which pilots to scan from among the Remaining set. Only valid pilots (i.e. those pilotsthat are multiples of PILOT_INC) will be scanned. For the subscriber, PILOT_INC impacts onlythe scanning rate applied to Remaining pilots. It accomplishes this by reducing the number ofRemaining pilots that need to be scanned.

For the base station, the effect of the PILOT_INC is different. In the base station, it is used inproperly translating pilot phase back into pilot offset index. The consequence is that the operatormay artificially increase the separation between valid time offsets. By selecting a PILOT_INC of2, for instance, an operator chooses to limit the number of valid offsets to 256 (i.e. 0, 2, 4,..., 508,510) instead of 512. The increased separation means that the pilot arrival must be larger beforeadjacent offset ambiguity is possible and consequently the likelihood of a strong adjacent interfereris reduced.

5.3.3 Converting Between Chips and Time or Distance

Chips are related to time by the following relationship:

[EQ 5-1]

Chips are related to distance by the following relationship:

[EQ 5-2]

Or, in kilometers:

[EQ 5-3]

Note that the chip rate (1.2288 Mcps) and the speed of light (186,000 miles/sec) are fundamentalto these conversions.

Time (us)Chips

1.2288 Mcps------------------------------- Chips 0.8138 us/chip×= =

Distance (miles) Chips 0.8138 us/chip 186,000 miles/1,000,000 us×× Chips 0.1514 miles/chip×= =

Distance (km) Chips 0.8138 us/chip 299,311 km 1,000,000 us⁄×× Chips 0.244 km/chip×= =


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5.3.4 Search Windows and Geography

Before discussing offset planning in any detail, a brief discussion of search windows and theirspatial relationships to cell sites and subscribers is needed. Base Stations, by virtue of their GPStracking, have an exact concept of system time. This, in turn, means that signals leaving these siteshave precise offsets and identities. On the other hand, subscribers derive their timing from a timereference. Their concept of system time is skewed late by the time-of-flight delay associated withthis time reference signal. The greater the distance between the subscriber and the time referencesite, the greater the skewing.

Consider the diagram below:

Figure 5-3: Subscriber Location Relative to Search Window

Let subscriber A, Site 1 and Site 2 be co-linear with subscriber A positioned exactly between Sites1 and 2 and with Site 1 active. The subscriber’s concept of system time is skewed from real systemtime by X, the distance between the subscriber’s concept of time and its time reference. When thesubscriber searches for a neighbor, it will center the search window on the offset associated withthe neighbor, but based on its own system time (which, of course, is a little late compared with realsystem time). Assuming Site 2 to be a neighbor of interest, its signal traverses a distance tosubscriber A that is exactly as late as the subscriber’s time reference. Under these circumstances,the time differential between the two signals is zero (i.e. X-X = 0) and the signal from Site 2 willfall directly in the center of the neighbor search window in which the subscriber is searching forSite 2.

Now, consider subscribers B and B’. Subscriber B is located 1 chip closer to Site 1 with Site 1active; therefore, subscriber B’s system time is skewed by only X-1. The signal from Site 2traverses X+1 and the time differential between the two signals is (X-1) - (X+1) = -2; consequently,the signal from Site 2 is arriving 2 chips late and will appear 2 chips off center in the neighborsearch window. Please note that a 1 chip shift in spatial location has had a 2 chip impact onthe location within the search window. Conversely, subscriber B’ has timing skewed by X+1while Site 2’s signal traverses only X-1 chips, leading to a time differential of (X+1) - (X-1) or 2chips. Site 2’s signal is arriving early by 2 chips. To design a search window large enough toencompass locations B and B’, a search window of at least 4 chips or + 2 chips wide would berequired.

The worst case time differential is when the subscriber is located directly adjacent to one site whiletrying to detect or demodulate the signal from the other site. For example, subscriber C effectivelyhas timing that is coincident with system time (i.e. its skewing is 0). Site 2’s signal is arriving D

A

B’C

2 1

B

D = distance between Site 1 and Site 2X = D/2

1 chip


5


chips late. For this signal to fall into the search window, it must be sized + D chips or 2D chipswide. Since this is the worst case scenario, the following should be understood: if a search windowis sized large enough to compensate for the distance between the two sites (i.e. 2D), then there isno location where a subscriber would have one site as its time reference and not see the other sitein its search window.

Here is a more generalized depiction of search windows in space:

Figure 5-4: Search Windows in Space

The two sites are located at (0,0) and (10,0) and are 10 units apart. The curves represent constanttime differentials between the two sites and will correspond to the edges of certain search windowsizes. Search windows will be centered on the perpendicular line half-way between the sites. Thewidth of the search window in space will correspond to half of the search window size in chips.For example, the two lines corresponding to time differentials of -4 and +4 demarcate an area thatcorresponds to a search window that is + 4 units or 8 units in width. In geographic space, the widthof the area on the line between the two sites will only be 4 units wide or 1/2 of the search windowsize. Between the curves, a subscriber tied to one site will see the other site fall within its searchwindow. Conversely, no matter how strong a neighbor signal may be, if the subscriber is locatedoutside of the search window area, it will not detect the signal.

Note how the curves bend as the search window is enlarged. When the search window is madelarge enough to compensate for the distance between the two sites, the curves collapse uponthemselves indicating that there is no longer any region in space where the signal will not fallwithin the search window. In general, a generous attitude toward search window sizing shouldexist. The ability to demodulate a signal depends on being able to see it. The table below correlatesdistance between neighbors to search window sizes.

Diff = -8

Diff = -6Diff = -4

Diff = -2 Diff = 2 Diff = 6Diff = 4

Diff = 8

Diff = -10 Diff = 10


5


The SrchWin sizes come from their definition in IS-95A/J-STD-8. The equation correlatingWindow Size (in chips) to distance between neighbors (in miles) is:

[EQ 5-4]

The two chips removed from the Window Size compensate for time-of-flight (i.e. real world)delays. If starting with a distance between sites to calculate a window size, two chips would needto be added.

This discussion on search windows was designed to help the system engineer visualize the spatialrelationship of search windows to cell sites. An individual out in the field can estimate how largea search window would need to be for a particular location by estimating the time differentialbetween the two sites of interest (use the absolute value only), adding 1 chip (to compensate fortime-of-flight delays), and multiplying by 2.

5.3.5 Search Windows and Scan Intervals

The following information is provided to give insight to system optimizers and is based onMotorola’s general understanding of subscriber vendor pilot scan algorithms. It is important to notethat such algorithms are not specified through IS-95A/J-STD-008 and are, therefore, manufacturerspecific. Also, pilot scanning rates/intervals are a function of many variables.

In general, active and candidate pilots are scanned at a rate of 50 times/second or better. This wouldbe valid for up to a total of 6 pilots and is not impacted by the number of neighbors or remainingset pilots.

Neighbor set pilots are scanned anywhere between 2 to 40 times/second with a common rangebeing 4 to 15 times/second. The rate is dependent on the number of actives/candidates andneighbors.

Remaining set pilots are scanned on the order of seconds. The remaining set pilots will be scannedNR times slower than the neighbors (where NR represents the number of remaining set pilots, afunction of PILOT_INC).

Table 5-1: Search Window Size vs. Neighbor Separation

SrchWin 0 1 2 3 4 5 6 7Window Size (chips) 4 6 8 10 14 20 28 40Delay (µs) 1.6 3.3 4.9 6.5 9.8 14.6 21.2 30.9Neighbor Separation (mi) 0.2 0.3 0.5 0.6 0.9 1.4 2.0 2.9SrchWin 8 9 10 11 12 13 14 15Window Size (chips) 60 80 100 130 160 226 320 452Delay (µs) 47.2 63.5 79.8 104.2 128.6 182.3 258.8 366.2Neighbor Separation (mi) 4.4 5.9 7.5 9.7 12.0 17.0 24.2 34.2

distance miles( )Window Size 2–( )

2---------------------------------------------- 0.1516×=


5


5.4 PN Offset Planning - Solutions

Current concepts for PN offset planning generally center on finding an appropriate value forPILOT_INC. A large value would provide good protection against adjacent offset interferencesince the pilot needs to travel a greater distance before potentially falsing (since signal attenuationis highly correlated with propagation distance). However, too large a value implies too few validPN offsets and too small a reuse distance, thereby increasing the likelihood of co-offsetinterference. Conversely, a small value of PILOT_INC delivers a large set of valid PN offsets, alarge reuse pattern and reuse distance, thereby reducing the likelihood of any co-offsetinterference. However, too small a value will not provide good isolation against adjacent offsetinterference or ambiguity.

Prior to discussing in detail the planning limits for PILOT_INC, it is important to note thefollowing concerning R, the radius of the cell site. CDMA’s use of soft handoff makes the radiusof the active area significantly larger than that which is accustomed with analog and which isassociated with a hexagonal grid. Speaking of the radius of a site conveys significant informationsince both reuse distance, D, and cluster size, N, are related as follows:

[EQ 5-5]

However, with CDMA and soft handoff there is significantly greater overlap between sites. If thehexagon/analog oriented radius is labeled as Rhex and the CDMA active area radius is labeled asRcdma, then it needs to be understood that Rcdma can easily be twice as large as Rhex, perhapsslightly larger. Many discussions of offset planning have failed to characterize this difference andconsequently lead to faulty conclusions. Specifically, consider a recommendation that suggeststhat 5R is sufficient separation for reusing sites. If the R is taken to be Rhex, then D/R would be 5and the cluster size would be 9. However, if it is understood that R is Rcdma, then D/R would bemore on the order of 10 and the cluster size would be 36, which is a significant difference.

5.4.1 Mitigating Adjacent Offset Interference - General

The following explanations, which define the limits of adjacent offset interference based on timingand signal strength considerations, are not impacted by antenna configuration (whether the sitesare omni, 3-sector, or 6-sector). This attribute simplifies the discussion.

5.4.1.1 Adjacent Offset Interference Protection Based on Timing

For an adjacent offset to have the potential of falsing, it must meet a timing criteria. That is to saythat it must fall into the search window. This is depicted below:

DR---- 3 N×=


5


Figure 5-5: Minimum Distance for Adjacent Offset Interference

A signal from a potential adjacent interferer must traverse a minimum distance to be able to fallinto the search window of the adjacent offset.

[EQ 5-6]

In this equation, S is 1/2 of the search window size. For example, with a PILOT_INC = 3 andSRCH_WIN_N = + 30 chips, this minimum distance corresponds to 3 x 64 - 30 = 162 chips = 39.5km = 24.6 miles. A larger PILOT_INC provides greater isolation; conversely, largerSRCH_WIN_N values mitigate the isolation.

Of course, the value of 60 chips for SRCH_WIN_N is a recommended starting value and will takeon larger or smaller values. Since SRCH_WIN_A is always smaller than SRCH_WIN_N, anadjacent offset interferer must always travel a greater distance to potentially interfere in the activesearch window.

Table 5-2: Distance/Timing Restriction on Adjacent Interference(assuming SRCH_WIN_N = + 30 chips)a

a. For ease of performing mental math, note that each offset of 64 chips contributes a little lessthan ~10 miles (9.7) or a little more than ~15 km (15.6). The 30 chip search window accountsfor a 7.3 km or 4.5 mile reduction.

PILOT_INC (offsets)

PILOT_INC (chips)

Minimum Distance (chips)

Minimum Distance

(km)

Minimum Distance (miles)

1 64 34 8.3 5.2

2 128 98 23.9 14.9

3 192 162 39.5 24.6

4 256 226 55.1 34.3

5 320 290 70.8 44.0

6 384 354 86.4 53.7

3 6

PILOT_INC

SRCH_WIN_X = + S

Minimum Distance PILOT_INC S–=


5


Due to this timing requirement, a general rule can be established concerning placement of anadjacent offset and its neighbors. They should be located under the PILOT_INC - S umbrella(Equation 5-6) within the cluster. To the degree that this criteria is met, it eliminates the potentialfor adjacent interference within the cluster. The limit of this example is to place adjacents withsectors that are co-located. Under these conditions, there is no time differential between signalsleaving the site and only distant reflections can possibly achieve the time constraints ofinterference, which is highly unlikely.

5.4.1.2 Adjacent Offset Interference Protection Based on Signal Strength

The timing discussion can be expanded by taking into account signal strength considerations. Thelower bound on PILOT_INC is identified and will correlate to an acceptable C/I threshold.Consider this equation which seeks to guarantee a bounded interference between correlated pilots,effectively yielding the PILOT_INC.9

[EQ 5-7]

In this equation, R is the radius of the cell in chips, S is 1/2 of the search window size, a is thedesired C/I in dB, and law represents the propagation exponent. The result, m, represents therequired offset, in chips, between any two pilots so that the desired C/I can be achieved. Therelationship can be interpreted as recommending that for each chip of R, there should be k chips ofseparation for an adjacent offset so that a minimum C/I threshold is achieved. In this equation, thepresence of S reflects the fact that the correlation need not be perfect for interference to exist. Theadjacent signal need only fall into the search window (a less stringent timing criteria).10 Note alsothat Equation 5-6 and Equation 5-7 are identical in form. Equation 5-7 is stating that at a distanceof PILOT_INC - S (or m - S), the C/I threshold will be achieved. The following table shows a fewdifferent examples of the calculation:

9. Qualcomm, “The CDMA Network Engineering Handbook”, March 1, 1993, §9.4.2.

10. An earlier, more conservative version of this relationship had S also scaled by k.

Table 5-3: Pilot Sequence Offset Index Assignment(assuming a = 18.0 dB, law = 3.0, k = 2.98)

R (km)

R(miles)

R(chips)

S(chips)

m(chips)

PILOT_INC (offsets)

Number of Valid Offsets

Cluster Size

(3-sector)

24.9 15.5 102 80 384 6 85 28

20.9 13.0 85.5 65 320 5 102 34

16.9 10.5 69.1 50 256 4 128 42

12.4 7.7 51.0 40 192 3 170 57

8.0 5.0 32.9 30 128 2 256 85

4.1 2.5 16.8 14 64 1 512 170

m 10a law 10×( )⁄

1–( ) R× S+≥ k R× S+=


5


A conservative propagation exponent was chosen to compensate for the simplicity of the approach(for example, the assumption of uniform power at both sites). The C/I threshold was set at 18.0 dBto correspond to a 12 dB C/I threshold (6 dB fade margin, 90% area reliability w/8dB deviation)for a 2 cell system. This 12 dB imbalance seems sufficient to predict that the searcher will not selectthe interfering energy within the active window. Under unloaded conditions (worst case), thisthreshold corresponds to an interferer Ec/Io of -14.9 dB which is below the normal range for theT-ADD setting; therefore, neighbor window falsing is unlikely. Additionally, to generate the tablevalues, neighbor search window sizes, which vary with cell radius, were used.

Although these table values seem fairly generous, there is one element mitigating the results. Anappropriate value for R must take into account two factors. First, the R is Rcdma. Additionally, sincepath loss is not isotropic and systems are not ideally laid out on grids (i.e. are non-uniform) theselection of R should reflect a limiting case. Since a system-wide value of PILOT_INC is beingdetermined, the value of R should more closely represent the 90th percentile rather than the mean.The radius of highway sites and other larger radius sites that are not clustered need not dominatethe analysis since spatial separation may be used to mitigate interference in those cases.

5.4.2 Protection Against Co-Offset Interference

The following explanations, which define the limits of co-offset interference based on timing andsignal strength considerations are impacted by both the antenna configuration (i.e. omni or sector)and whether the subscriber is in the active area or in the larger neighbor area. As such, they willneed to be more extensive.

The study of co-offset interference is started by looking at the timing considerations involved ininterfering within the active search window. Consider the following diagrams:

Figure 5-6: Active Window Interference Timing Criteria

It has been stated elsewhere11 that if two users of the same offset where positioned 2R + S awayfrom each other (where S is 1/2 of the search window size), then the potential for co-offsetinterference is avoided due to the timing criteria not being met. From the discussion on searchwindows in Section 5.3.4, it can be seen that if two sites met this criteria for separation, then the

11. Qualcomm, “The CDMA Network Engineering Handbook”, March 1, 1993, §9.4.2.

A

B

SActive

R

R

OMNI SECTOR

A

B

SActive

R


5


search window would spatially fall completely outside of R. For the sectorized case, therequirement was modified to R+S.

While meeting this criteria is sufficient to protect against interference within the active searchwindow, it does not protect against falsing within the neighbor search window. From a timingperspective, neighbor falsing will be limiting. Consider the following diagrams:

Figure 5-7: Neighbor Window Interference Timing Criteria

Here are some guidelines used in generating these approximations:

• There can be no common neighbors among users with the same offset, no sector mayshare an offset assignment with one of its neighbors nor may any of its neighbors sharethe same offset assignment.

• The distance 2R + SActive is sufficient to define non-neighbors.

• A’s Neighbor Area is limited to 3R + SActive for omni and 2R + SActive for sector.

• For omni systems, B must be separated by SNeighbor from A’s Neighbor Area to avoidneighbor falsing.

• For sector systems, B possesses back-side neighbors (i.e. the co-located sectors) whichmust be separated by SActive from A’s Neighbor Area to avoid sharing commonneighbors.

The conclusions from this exercise are summarized in the following table:

Table 5-4: Estimates of Reuse Distance and Cluster Size Based on Timing(assuming Rcdma = 2Rhex, SNeighbor ≅ 2Rhex and SActive ≅ 1Rhex)

Antenna Configuration Reuse Distance Equation Reuse Distance Cluster SizeOmni 4Rcdma + SActive + SNeighbor 11Rhex 43

Sector 3Rcdma + 2 x SActive 8Rhex ~21

A

B

C

SActive

R

R

R

R

SNeighbor

OMNI

Neighbor Area Radius A

B

SActive

R

R

SActive

SECTOR

Neighbor Area

Radius

R


5


The previous analysis, though simple, can help establish a safe margin easily. A somewhat moredetailed analysis below may help determine an absolute minimum reuse distance based on timing.

Figure 5-8: Active and Neighbor Areas

To help visualize the true requirements of the situation, consider Figure 5-8. The sector labelledwith 0 represents the sector of interest. The active area for this sector is depicted in yellow.Depicted in blue is all of the active area pertaining to the top 10 neighbors. (As with search windowsizing, it is also recommended to be generous with neighbor lists.) Keep in mind that the blue arearepresents the neighbor area to which is being referenced. That is to say, areas where a subscribermight be looking for the offset of sector 0 even though it is well outside of the area where sector 0is actively demodulated. By this means alone, the neighbor area represents an expansion of greaterthan 300% over the active area. If the next six most significant neighbors (sectors labelled 2) wereincluded as neighbors, the neighbor area expands even further (area depicted in cyan). Note howboth the front and back of sector 0 have neighbor search areas. The front is more pronounced whilethe back is affected mostly by the co-located sectors. (These neighbor relationships and subscriberlocations are based on soft handoff relationships identified through CDMA static simulations foran ideal grid and uniform distribution.)

Estimates based on this perspective will prove more optimistic than those derived earlier since theyaccount for the overlapping of cells and they better estimate the true neighbor area size.

01

1

1

1

1

1

1

11

12

2

2 22

2

Sector 0Top 10 Neighbors11 - 16 Neighbors


5


Note: To take advantage of sectorization, the planner must reuse offsets with the same orientation.

5.4.3 Incorrect Identification of an Offset by the Base Station

The CBSC (i.e. the XC subsystem) translates phase measurements to offsets by pooling them tothe nearest valid offset based on its knowledge of PILOT_INC. For correct identification, thisprocess assumes that the PILOT_ARRIVAL component of the phase measurement never exceeds1/2 of PILOT_INC. As a check on the selection of PILOT_INC, planners should ask whether ornot locations exist within the system where subscribers may be active with a site at a distancegreater than 1/2 of PILOT_INC. [Note: the process by which phase measurements are translated tooffset indices is not specified by IS-95A/J-STD-008.

Figure 5-9: Phase Measurement Translations

Now, compare the relationship between SRCH_WIN_N and PILOT_INC. It is a rule thatSRCH_WIN_N (and SRCH_WIN_R) never exceed PILOT_INC. The consequences of doing soare that the two adjacent windows would overlap. The BS may incorrectly identify the offset andthe subscriber may report multiple signals where only one is present. This guideline, easy toexpress and understand, is frequently the truly limiting factor on the lower bound for PILOT_INC

Table 5-5: Calculation of Reuse Distance(Assuming SNeighbor ≅ 2R, SActive ≅ 1R and Active Area Radius (A) ≅ 2.2R)

Front(F)

Back(B)

ReuseEquationa

a. The reuse equation is based on spatial relationships depicted in Figure 5-7. The Front range correspondsto the Neighbor Area Radius.

Reuse Distance

ClusterSize

Top 10 Neighbors - Sector 3.1 R 2.2 R F + SActive + Bb

b. Under these conditions, the back-side requirement for 2A + SNeighbor ≅ 6.4R would become limiting.

6.3 R 13

Expanded Neighbor List - Sector 4.3 R 2.2 R F + SActive + B 7.5 R 19

1 Tier - Omni 2.7 R - F + SNeighbor + A 6.9 R 16

2 Tier - Omni 4.4 R - F + SNeighbor + A 8.6 R 25

0 3 6 9 12

PILOT_INC = 3 = spacing between ‘valid’ offsets

0 3 6 9 12

pilot phase reported by subscriber in PSMM

SRCH_WIN_N


5


(and conversely, the upper bound on cluster size). When situations arise where an area of thesystem requires very large search windows, so as to permit soft handoff between distant neighbors(across water or mountains with large time differentials), the PILOT_INC (a global parameter)must be resized large enough to accommodate the search window.

5.4.4 PILOT_INC and the Scan Rate of Remaining Set Pilots

The following information is provided to give insight to system optimizers and is based onMotorola’s general understanding of subscriber vendor pilot scan algorithms. It is important to notethat such algorithms are not specified through IS-95A/J-STD-008 and are, therefore, manufacturerspecific.

As was noted in the definition of PILOT_INC, according to IS-95A/J-STD-008, the only impactof PILOT_INC on the subscriber is to influence the scanning rate of remaining set pilots. Pleasenote that for optimum system performance, the scanning rate of remaining set pilots is notconsidered a dominant factor in determining the size of PILOT_INC. Remaining set pilots are at adistinct disadvantage over neighbor set pilots due to the scanning prioritization of pilot sets. Forexample, all active and candidate set pilots are scanned between scans of individual neighbor orremaining set pilots. All neighbor set pilots are scanned between scans of individual remaining setpilots. The scanning order is represented as follows for 3 active set pilots and 1 candidate set pilot[please remember that the actual scanning order is subscriber manufacturer specific]:

A1A2A3C1N1A1A2A3C1N2A1A2A3C1N3...A1A2A3C1NNA1A2A3C1R1A1A2A3C1N1...A1A2A3C1NNA1A2A3C1RNBegin again from the top.

A remaining set pilot is scanned N times slower than a neighbor set pilot where N is the number ofremaining set pilots. In addition to their low scanning priority, IS-98 specifies no performancecriteria for remaining set pilots.

Any remaining set pilot that appears strong enough (and long enough) to recommend promotion tothe active set needs to be analyzed as part of the optimization process. Perhaps, it should be addedto the neighbor list (or have its coverage adjusted). Feedback on these events can be derived fromcallproc logs in the pre-commercial phase and Call Detail Logs (CDLs) in the commercial phase.

Note: Since remaining set pilots are prioritized low and, currently, Motorola does not honorrequests to enter into soft handoff with a remaining set pilot, some operators have consideredreducing SRCH_WIN_R to a minimum (i.e. 4 chips) and trading off the remaining set scan timefor improved scan time on actives, candidates and neighbors. This is not recommended. The mostsignificant reason is that the remaining set search window provides a means by which “truncated”neighbors can be recognized by the system. When in soft/softer handoff, a merging of neighborlists take place. If the merge yields more than 20 neighbors, the subscriber limit of 20 neighborsrequires that the list be truncated to only higher prioritized neighbors. Although these neighborsmay not be identified to the subscriber as neighbors, they nevertheless may be detected through aremaining set scan. The system will recognize and honor these remaining set pilot requests. Asecondary motivation for permitting the windows to stay “open” is that they provide a means for


5


optimizing neighbors lists by recognizing those sites which should be neighbors, but are not on theneighbor list. On the other hand, the improvement in the scan interval will only be modest onaverage (~6%).

5.4.5 Summary of Guidelines

The table below and the following text provide a summary of the PN offset planning guidelines.

To summarize the key guidelines for sectorized systems on sizing PILOT_INC are:

1. Minimum cluster size is 19 for 3-sector or 6-sector systems. Refer to Section 5.4.2 fordetails.

Table 5-6: Summary of PN Offset Planning Guidelines

PILOT_INCComments

8 6 4 3 2 1

Cluster Size (3-sector) 19 25 37 52 76 148 co-offset

D/R (3-sector) 7.5 8.7 10.5 12.5 15.1 21.1 co-offset

Extra Sites (3-sector) 2 3 5 4 8 20 insurance

Cluster Size (6-sector) 9 13 19 25 37 76 co-offset

D/R (6-sector) 5.2 6.2 7.5 8.7 10.5 15.1 co-offset

Extra Sites (6-sector) 1 1 2 3 5 8 insurance

C/I (5km/10km)a

a. Refer to Section 5.4.1.2.

40.3/31.9

36.6/28.3

31.3/23.4

27.8/20.2

20.4/15.9

16.1/10.4

adjacent offset - PCS

C/I (8km/16km) 34.5/26.4

30.9/23.0

25.9/18.5

22.5/15.6

18.0/11.9

12.1/7.4

adjacent offset - 800

S (chips) 80 65 50 40 30 14 varies w/cell radius

PILOT_INC - S (chips)

432 319 206 152 98 50 adjacent offset

PILOT_INC - S (km) 105.4 77.8 50.2 37.1 23.9 12.2 adjacent offset

PILOT_INC (chips) 512 384 256 192 128 64 compare w/SRCH_WIN_N

PILOT_INC/2 (chips) 256 192 128 96 64 32 Neighbor Proximity Check?

PILOT_INC/2 (km) 62.5 46.8 31.2 23.4 15.6 7.8 Neighbor Proximity Check?

C/I 30 m S–( ) R⁄ 1+( )log=


5


2. Maximum PILOT_INC is 8 for 3-sector and 4 for 6-sector. This correlates to theminimum cluster size.

3. For Suburban environments at 1900 MHz, minimum PILOT_INC is 3 (based on aminimum C/I threshold of 18.5 dB and unloaded carriers). This will serve the Urban/Dense Urban areas as well.

Note: Due to the approximate 9 dB difference between path loss at 1900 MHz and 800MHz, PCS systems have smaller sites and consequently lower minimum PILOT_INCvalues.

4. For Suburban environments at 800 MHz, minimum PILOT_INC is 4 (based on aminimum C/I threshold of 18.5 dB and unloaded carriers). This will serve the Urban/Dense Urban areas as well.

5. PILOT_INC must be larger than the Neighbor and Remaining Set search windows,SRCH_WIN_N and SRCH_WIN_R. All timing differentials must be less thanPILOT_INC/2. Carefully review the system design for any neighbors that are separatedby more than PILOT_INC/2 since potentially these neighbors can generate sufficientlylarge timing differentials to cause translation errors (i.e. Neighbor Proximity Check).Refer to Section 5.4.3 for details.

6. To eliminate the potential for adjacent interference within a cluster, an adjacent offsetand its neighbors should be separated from the potential interferer by a distance nogreater than PILOT_INC - S. The distance PILOT_INC/2 is a safer limit (since S is avariable with an upper limit of PILOT_INC/2). This criteria can best be met by eitherco-locating the adjacent offsets within the same site or by assigning them to 1st tierneighbors. Refer to Section 5.4.1.1 for details.

7. If the system is truly characterized by Urban/Dense Urban environments, then smallerPILOT_INC values may be justified. If an entire CBSC is characterized by smaller radii,then that CBSC may have its PILOT_INC set lower.

8. Small sized trials are very easy to plan for. The largest PILOT_INC which will notrequire the trial system to have any reuse at all is suggested. Under these conditions, co-offset interference is non-existent and adjacent interference protection is maximized. Ifthe PILOT_INC is selected to be a multiple of that which will ultimately bemigrated to, then implementing changes in PILOT_INC later will not force achange to the sector level PN offset assignments.

9. Multiple carriers in a sector are all assigned the same PN offset.10. The implementation of CDMA at 1900 MHz is, generally, not tied to an already existing

analog base with its locations and antennas where significant cell splitting has takenplace. The site grid should be more uniform than the mature analog counterpart. Thisshould lend itself to a simpler repeat pattern implementation.

11. From a practical perspective, it should be understood that the majority of Motorolasystems that are commercial use a PILOT_INC in the range of 2 to 4. The systems usinga PILOT_INC of 2 can be characterized as possessing small radius sites. The systemsemploying a PILOT_INC of 4 can be characterized as possessing some areas ofextensive propagation (water, mountains) that have required resizing SRCH_WIN_N,and consequently PILOT_INC, larger.


5


5.4.6 Guidelines for Assigning Offsets

It has already been explained that there should be a goal for locating adjacent offsets close to eachother. In the figure below, the Adjacent Sectors configuration shows co-located sectors containingadjacent offsets. This represents the absolute limit on how close adjacent offsets can be located.Under these conditions, two-thirds of all adjacent assignments (for 3 sector sites) will have reducedthe time differential to zero. For the remaining third, the adjacent offset is located in an adjacentsite. This approach also has the benefit of easy recognition of co-located sectors during systemoptimization.

Figure 5-10: Adjacent Sector and Adjacent Site Offset Assignment Approaches

Previously, this has been the only recommendation. There is now an alternative recommendation,Adjacent Sites, which locates all adjacent offset assignments within adjacent sites (and not withinadjacent sectors of the same site). The Adjacent Sites approach has Offset Groupings associatedwith it that are found in Table 5-7 and Table 5-8. Although this represents a slight compromise withrespect to the timing margin of the Adjacent Sectors configuration, there are several characteristicswith this approach that make it worth recommending:

• Virtually all adjacent offsets possess the same antenna orientation (as co-offsetsnormally do). This provides an additional measure of interference protection andsimplifies system optimization.

• A uniform increment of 168 exists between co-located sectors regardless of thePILOT_INC in use. This will help optimization through easier recognition of co-siteoffsets. (The Adjacent Sectors approach also benefits from easy recognition of co-siteoffsets.)

• A 3-sector site uses one group while a 6-sector site uses 2 groups. (The Adjacent Sectorsapproach possesses this benefit as well.)

• Table 5-7 contains 84 groupings for a PILOT_INC of 2. Subsets of this table apply toPILOT_INC values of 4 (42 sets), 6 (28 sets), 8 (21 sets), and 12 (14 sets). Thesegroupings will prove useful in any transition or migration between differentPILOT_INCs.

ADJACENT SECTORS ADJACENT SITES

63

9

1215

18

6174

342

9177

345


5


• Table 5-8 contains 56 groupings for a PILOT_INC of 3. Subsets of this table apply toPILOT_INC values of 6 (28 sets) and 12 (14 sets). These groupings will prove useful inany transition or migration between different PILOT_INCs.

For example, to transition between PILOT_INCs 2 and 3, the design would need atransition zone of 6. All of the appropriate groupings for a PILOT_INC of 6 already existwithin the separate 2 and 3 sets.

Generic information on reuse patterns can be found in Section 5.5. Here are some possible clusterconfigurations:

Table 5-7: Offset Groupings for PILOT_INC = 2 (also 4, 6, 8, and 12)

Alpha 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42

Beta 170 172 174 176 178 180 182 184 186 188 190 192 194 196 198 200 202 204 206 208 210

Gamma 338 340 342 344 346 348 350 352 354 356 358 360 362 364 366 368 370 372 374 376 378

Alpha 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84

Beta 212 214 216 218 220 222 224 226 228 230 232 234 236 238 240 242 244 246 248 250 252

Gamma 380 382 384 386 388 390 392 394 396 398 400 402 404 406 408 410 412 414 416 418 420

Alpha 86 88 90 92 94 96 98 100 102 104 106 108 110 112 114 116 118 120 122 124 126

Beta 254 256 258 260 262 264 266 268 270 272 274 276 278 280 282 284 286 288 290 292 294

Gamma 422 424 426 428 430 432 434 436 438 440 442 444 446 448 450 452 454 456 458 460 462

Alpha 128 130 132 134 136 138 140 142 144 146 148 150 152 154 156 158 160 162 164 166 168

Beta 296 298 300 302 304 306 308 310 312 314 316 318 320 322 324 326 328 330 332 334 336

Gamma 464 466 468 470 472 474 476 478 480 482 484 486 488 490 492 494 496 498 500 502 504

Table 5-8: Offset Groupings for PILOT_INC = 3 (also 6 and 12)

Alpha 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60 63

Beta 171 174 177 180 183 186 189 192 195 198 201 204 207 210 213 216 219 222 225 228 231

Gamma 339 342 345 348 351 354 357 360 363 366 369 372 375 378 381 384 387 390 393 396 399

Alpha 66 69 72 75 78 81 84 87 90 93 96 99 102 105 108 111 114 117 120 123 126

Beta 234 237 240 243 246 249 252 255 258 261 264 267 270 273 276 279 282 285 288 291 294

Gamma 402 405 408 411 414 417 420 423 426 429 432 435 438 441 444 447 450 453 456 459 462

Alpha 129 132 135 138 141 144 147 150 153 156 159 162 165 168

Beta 297 300 303 306 309 312 315 318 321 324 327 330 333 336

Gamma 465 468 471 474 477 480 483 486 489 492 495 498 501 504


5


The 19-cell repeat pattern is easy to use. A site number, N,within the pattern can easily be translated into a PN offsetassignment for a particular sector.

For Adjacent Sectors, 6-sector, and PILOT_INC of 4:SECTOR x OFFSET= ((N-1) * 6 + x) * 4

For Adjacent Sites, 6-sector, and PILOT_INC of 4:SECTOR x OFFSET= N*4 + (x-1)*168; (x = 1,2,3)SECTOR x OFFSET= (N+21)*4 + (x-4)*168; (x = 4,5,6)

The 25-cell repeat pattern is easy to use. A sitenumber, N, within the pattern can easily be translatedinto a PN offset assignment for a particular sector.


For Adjacent Sites, 6-sector, and PILOT_INC of 3:SECTOR x OFFSET= N*3 + (x-1)*168; (x = 1,2,3)SECTOR x OFFSET= (N+28)*3 + (x-4)*168;(x = 4,5,6)

The 37-cell repeat pattern is easy to use. A sitenumber, N, within the pattern can easily be translatedinto a PN offset assignment for a particular sector.


For Adjacent Sites, 3-sector, and PILOT_INC of 4:SECTOR x OFFSET= N*4 + (x-1)*168; (x = 1,2,3)

17 9 1 12 4

10 2 13 5

16 8 19 11

3 14 6

15 7 18

3

10

17614

4 8 13 19 22

7 14 18 23

3 9 12 20

15 17 24

2 10 11

1 6 15

11 16 25

24

25 16

21 21

22

5

6

4

5

1

2

23 12 1 27 16

13 2 28 17

22 11 37 26

3 29 18

21 10 36

20 9 35

4 30 19

31

32 25

33 15

34

24

14

5

6

7

8


5


The 52-cell repeat pattern is easy to use. A site number,N, within the pattern can easily be translated into a PNoffset assignment for a particular sector.


For Adjacent Sites, 3-sector, and PILOT_INC of 3:SECTOR x OFFSET= N*3 + (x-1)*168; (x = 1,2,3)

5.4.7 Guidelines for Changing PILOT_INC at Inter-CBSC Boundaries.

PILOT_INC is a CBSC global parameter. As such, PILOT_INC can only be changed at CBSCboundaries. When such a change is required, the preferred methodology includes the followingguidelines:

Figure 5-11: Inter-CBSC PILOT_INC Boundary

• One side shall have a PILOT_INC which is a multiple of the other side. For example,transitioning between 2 and 4 or 3 and 6.

• The challenge in transitioning is characterized by subscribers on one side seeing a sitefrom the other side, but the home CBSC does not interpret the phase correctly because adifferent PILOT_INC is in use. For the example in Figure 5-11, CBSC A is using 2 andCBSC B is using 4. A subscriber tied to B sees an A site using offset 6 and reports it in aPSMM. CBSC B will interpret the offset as either 4 or 8, because it does not recognize6. This problem does not manifest itself in the other direction since all multiples of 4 arealready multiples of 2.

21 47 1 27 7

48 2 28 8

20 46 26 52

3 29 9

19 45 25

18 44 24

4 30 10

38

39 51

40 6

41

22

49

33

34

35

36

37 17 4311

12

23

42

16

15

14

13

32

315

50

5

10

12

16

23

31

36

50

42

CBSC A

PILOT_INC = 2

CBSC B

PILOT_INC = 4

TRANSITION ZONE

6

8

4

16

multiple of 2, but not of 4

multiple of 4


5


• A transition zone should be planned on the A side (using PILOT_INC = 2) of the bordersuch that for a few layers of cells, all sites are using multiples of 4. In other words thetransition is planned as an extension of the B side.

• If the PILOT_INC on one CBSC is not the multiple of the PILOT_INC in use on theother CBSC, then a transition zone consisting of offsets based on a common multipleshould be used. For example, to transition between 2 and 3, the common multiple of 6 isused.

• A pseudo-requirement of Inter-CBSC Soft Handoff is that PILOT_INCs should be thesame across all CBSCs that are connected. Since target CBSC BTSs are being controlledby a source/anchor CBSC, they are subject to using the anchor PILOT_INC during anInter-CBSC soft handoff. If No Legs-Wait or No Legs is used as the anchor handofftrigger, then this technique may still work and may require a larger transition area.

5.5 Reuse Patterns

This table can help in defining reuse patterns through use of i & j coordinates. For example, tocreate a normal analog 7 cell reuse pattern, follow along the i axis for 2 cells and then follow the jaxis (either clockwise or counter-clockwise, but be consistent) for 1 cell. The grayed out tableelements pertain to cluster sizes not likely to be used in CDMA.

Table 5-9: Reuse Pattern Coordinates, i & j,and Cluster Size, N, and D/R

i j N D/R i j N D/R1 0 1 1.73 7 1 57 13.08

1 1 3 3.00 5 4 61(4 ring)

13.53

2 0 4 3.46 6 3 63 13.75

2 1 7(1 ring)

4.58 8 0 64 13.86

3 0 9 5.20 7 2 67 14.18

2 2 12 6.00 8 1 73 14.803 1 13 6.24 5 5 75 15.00

4 0 16 6.93 6 4 76 15.10

3 2 19(2 ring)

7.55 7 3 79 15.39

4 1 21 7.94 8 2 84 15.87

5 0 25 8.66 6 5 91(5 ring)

16.52

3 3 27 9.00 7 4 93 16.704 2 28 9.17 8 3 97 17.06

5 1 31 9.64 6 6 108 18.00

6 0 36 10.39 7 5 109 18.08

4 3 37(3 ring)

10.54 8 4 112 18.33


5


5.6 References

Prior discussions of topics significant to PN Offset Planning which are useful references includethe following:

1. TIA/EIA/IS-95A, Mobile Station-Base Station Compatibility Standard for Dual-ModeWideband Spread Spectrum Cellular System, version 0.07, §6.1.5.1, §6.6.6.1.2,§6.6.6.2.1, §6.6.6.2.4.

2. Qualcomm, “The CDMA Network Engineering Handbook”, March 1, 1993, §9.1.1,§9.2.3, §9.4.

3. Scott M. Hall (Motorola), “Simple CDMA PN Search Windows”, January 5, 1995.

IEEE Conference Papers on this topic include:

4. Chu Rui Chang, Jane Zhen Wan and Meng F. Lee (NORTEL Wireless EngineeringServices), “PN offset planning strategies for non-uniform CDMA networks”, 1997 IEEE47th Vehicular Technology Conference, May 4-7, 1997.

5. Jin Yang, Derek Bao and Mo Ali (Airtouch Cellular), “PN offset planning in IS-95based CDMA systems”, 1997 IEEE 47th Vehicular Technology Conference, May 4-7,1997.

5 2 39 10.82 7 6 127(6 ring)

19.52

6 1 43 11.36 8 5 129 19.674 4 48 12.00 7 7 147 21.00

5 3 49 12.12 8 6 148 21.07

7 0 49 12.12 8 7 169(7 ring)

22.52

6 2 52 12.49 8 8 192 24.00

Table 5-9: Reuse Pattern Coordinates, i & j,and Cluster Size, N, and D/R

i j N D/R i j N D/R


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NOTES

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Table of Contents

6.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 3

6.2 CDMA Cell Site Antenna Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 36.2.1 Antenna Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 36.2.2 Antenna Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 46.2.3 Antenna Beamwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 66.2.4 Voltage Standing Wave Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 66.2.5 Return Loss. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 66.2.6 Power Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 76.2.7 Front to Back Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 76.2.8 Side Lobes & Back Lobes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 76.2.9 Antenna Downtilting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 86.2.10 Antenna Height. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 8

6.3 CDMA Antenna Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 96.3.1 Antenna Isolation Considerations. . . . . . . . . . . . . . . . . . . . . . . . . 6 - 9

6.3.1.1 CDMA/AMPS Transmit/Receive Antenna Isolation Requirements 6 - 106.3.1.2 Measuring Port-to-Port Antenna Isolation . . . . . . . . . . . . . . . . . . . 6 - 136.3.1.3 Reducing the Required Antenna Isolation. . . . . . . . . . . . . . . . . . . . 6 - 136.3.1.4 Typical Antenna Isolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 146.3.1.5 CDMA Antenna Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 14

6.3.2 Antenna Diversity (Spacial) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 156.3.2.1 Horizontal Antenna Diversity and Recommended Separation . . . . 6 - 166.3.2.2 Vertical Antenna Diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 16

6.4 CDMA Antenna Sharing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 176.4.1 Multiple Frame Antenna Sharing with 800 MHz BTS Products . 6 - 176.4.2 Multiple Carrier Cavity Combining

With 1900 MHz BTS Products. . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 206.4.2.1 Output Power Without Combining . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 206.4.2.2 Type of Combining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 206.4.2.3 Multiple Carrier Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 21

6.4.3 Duplexing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 226.4.3.1 Pre-Engineered Kits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 236.4.3.2 Duplexers and Intermodulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 236.4.3.3 Proper Installation and Maintenance of Duplexed Antennas . . . . . 6 - 24

RF Antenna SystemsChapter

6


6

CDMA/CDMA2000 1X RF Planning GuideChapter 6: RF Antenna Systems

6.5 CDMA Antenna Sharing With Other Technologies . . . . . . . . . . . . . . . 6 - 286.5.1 SC9600 BTS/HDII Shared Facilities . . . . . . . . . . . . . . . . . . . . . . 6 - 28

6.5.1.1 Common Transmit Antenna. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 296.5.1.2 Common Receive Antenna(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 32

6.5.2 Duplexed AMPS/CDMA Antennas . . . . . . . . . . . . . . . . . . . . . . . 6 - 39

6.6 GPS Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 41

6.7 Ancillary Antenna System Components . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 416.7.1 Directional Couplers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 416.7.2 Surge (Lightning) Protectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 416.7.3 Transmission Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 42

6.7.3.1 RF Performance of Transmission Lines. . . . . . . . . . . . . . . . . . . . . 6 - 426.7.3.2 Physical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 426.7.3.3 Choice of Transmission Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 43

6.7.4 Transition Feeder Cables (Jumper Cables). . . . . . . . . . . . . . . . . . 6 - 43

6.8 RF Diagnostic System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 - 44


6


6.1 Introduction

This chapter will outline RF engineering considerations that should be incorporated into the designof CDMA "antenna systems". The antenna system is defined as those elements between the BTSequipment cabinet (top of rack) and the Tx or Rx antenna. A detailed discussion of the variousavailable equipment and antenna sharing configurations and requirements are discussed, includingthose involving co-location with other technologies, duplexing, and multiple carrier combining.

The guidelines below are intended to assure the most efficient implementation of Motorola’sCDMA system while minimizing the risk to other fixed and mobile radio operators.

6.2 CDMA Cell Site Antenna Parameters

This section of the document will outline the main antenna parameters that the system engineershould consider when choosing the optimum antenna to be used in a CDMA system. Guidelinesare provided where possible, although it is recognized that a number of issues are beyond the scopeof this document and may require site specific engineering.

6.2.1 Antenna Type

If separate omni-directional type transmit antennas are to be used for the CDMA system (e.g. noantenna sharing), a type similar to those used for other cellular technologies, such as AMPS orGSM, can be used, obviously dependent on the required antenna operating frequencyspecifications.

The same convention is basically held for sector type directional CDMA antennas, with theexception of the consideration of desired beamwidths. Typically, antennas with narrowerhorizontal beamwidths than their AMPS or GSM supporting counterparts are used for CDMA tohelp limit noise contribution to adjacent sectors. As a result, suitable antenna types should bechosen if the CDMA system being installed is not to share antennas currently existing at the site.

Sufficient isolation between CDMA antennas and other existing antennas at the site should bereadily obtained. Considering that physical separation between co-located antennas may berequired to assist in achieving this isolation, physically smaller antenna types may be required toallow for proper installation on the tower.

In general, the log-periodic reflector type directional antennas have smaller height and widthdimensions for the same forward gain than dipole panel antennas or collinear dipole reflector typeantennas. They, of course, have a larger dimension in the direction of maximum gain due to thelength of the log-periodic array(s) which form the overall antenna system. Because of the smallerarea occupied on the face of the tower or its platform, it should be possible to fit at least seven ofthese antennas in the same space originally allocated for the AMPS sector antennas.

Log-periodic reflector type antennas also appear to have excellent front-to-back and front-to-sideratios. It appears that the isolation between adjacent antennas is significantly higher than for dipoletype directional antennas. This is based on measured data taken by Allgon System AB on their line


6


of log-periodic reflector antennas. This provides the same isolation with closer spacing than forcomparable gain panel antennas or greater isolation for the same spacing.

Special consideration should be given to the antenna bandwidth. If the use of duplexers is requiredthen a wideband antenna capable of supporting the primary and the secondary CDMA carriersshould be selected (see tables below)

Refer to Chapter 2 concerning other frequency bands that might be utilized.

6.2.2 Antenna Gain

This is often referred to as "power gain" and is the ratio of the maximum radiation in a givendirection to that of a reference antenna in the same direction for equal power input. Usually thisgain is referenced to either an isotropic antenna or a half wave dipole in free space at 0° elevation.

Table 6-1: CDMA Carrier Frequency Range

Frequency Band

Primary CDMA Carrier - Center Channel

(& Broadband Channel Range)

Frequency Range in MHz (Base Rx/Tx)

A 283 (263-303) 832.89-834.09 / 877.89-879.09

B 384 (364-404) 835.92-837.12 / 880.92-882.12

Frequency Band

Secondary CDMA Carrier - Center Channel

(& Broadband Channel Range)

Frequency Range in MHz (Base Rx/Tx)

A 691 (671-711) 845.13-846.33 / 890.13-891.33

B 777 (757-797) 847.71-848.91 / 892.71-893.91

Table 6-2: PCS Carrier Frequency Range

Frequency BandFrequency Range in MHz

(Base Rx/Tx)

A 1850-1865/1930-1945

D 1865-1870/1945-1950

B 1870-1885/1950-1965

E 1885-1890/1965-1970

F 1890-1895/1970-1975

C 1895-1910/1975-1990


6


An isotropic reference (dBi) generally pertains to a theoretical antenna having a spherical radiationpattern with equal gain in all directions. When used as a gain reference, the isotropic antenna hasa power of 0 dBi. The halfwave dipole (dBd) is an antenna which is center fed as to have equalcurrent distribution in both halves. When used as a theoretical reference antenna it has a power gainof 0 dBd, which equates to a 2.14 dB difference compared to an Isotropic antenna. For a graphicalrepresentation of the different antenna patterns, please refer to the following figure.

dBi = dBd + 2.14 dBd = dBi - 2.14

Figure 6-1: dBd vs. dBi

The gain of the antenna will impact other antenna characteristics such as: size, weight, horizontalbeamwidth, vertical beamwidth, cost. The RF Engineer will need to select the appropriate antennafor the particular situation. A trade-off will need to be made by the RF Engineer as to whether ahigher gain or lower gain antenna should be chosen. The higher gain antenna typically is physicallylarger, more expensive and has a narrower vertical beamwidth than would a lower gain antenna.

The gain of an antenna has a direct interaction with other antenna parameters, (the technical depthof which is beyond the scope of this document). The following paragraphs will provide the systemengineer with general guidelines:

Vertical Beamwidth - Generally, the greater the gain of the antenna, the narrower the verticalbeamwidth. The vertical beam can be used to focus coverage in some circumstances, but theengineer should ensure that the optimum vertical beamwidth is used to prevent the creation of"nulls" or coverage holes near to the site.

Physical Size - The size of an antenna will generally be greater as an antenna gain increases. Thisis due to the greater number of dipole array and electrical elements required to reach the desiredgain. The system engineer should remember that PCS frequencies are approximately half thewavelength of 800 MHz and therefore the antennas will typically be smaller for a common gain.


6


6.2.3 Antenna Beamwidth

Antenna beamwidth is measured in degrees between the half power points (3 dB) of the major lobeof the antenna. Beamwidth can be expressed in terms of azimuth (horizontal or H-plane) andelevation (vertical or E-plane).

The predominant type of antenna configuration within urban areas will be three sectored. Thisimplies that each sector should utilize an antenna with 120° horizontal beamwidth; however, it hasbeen found through simulation that the use of 120° antennas provide too much overlap. As thecoverage of any sector within a CDMA system is directly affected by the noise generated by itsneighboring sectors and traffic within those sectors, the use of 120° can lead to reduced coveragearea through the rise in system noise. The excessive overlap of sectors can also lead to increasedsofter handoff and therefore the reduction of call processing capability.

If narrow horizontal beamwidth antennas are used, for example 60°, simulation has shown thatinsufficient coverage (i.e. coverage holes) can exist between adjacent sectors. The use of 60° highgain antennas can also restrict the vertical beamwidth and can lead to coverage nulls close to thecell site.

From current simulation, the optimum horizontal antenna beamwidth for PCS systems has beenfound to be between 90° and 100°. This beamwidth has been proven to minimize softer handoffwhile providing adequate coverage. However, before choosing an antenna of this beamwidth, thesystem engineer should ensure that all factors outlined within this "Antenna Parameters" sectionhave been identified.

6.2.4 Voltage Standing Wave Ratio

Voltage Standing Wave Ratio (VSWR) is another parameter used to describe an antennaperformance. It deals with the impedance match of the antenna feed point to the feed ortransmission line. The antenna input impedance establishes a load on the transmission line as wellas on the radio link transmitter and receiver. To have RF energy produced by the transmitterradiated with minimum loss or the energy picked up by the antenna passed to the receiver withminimum loss, the input or base impedance of the antenna must be matched to the characteristicsof the transmission line. The VSWR of a CDMA antenna should be less than 1.5:1.

6.2.5 Return Loss

Return Loss (RL) is the decibel difference between the power incident upon a mismatchedcontinuity and the power reflected from that discontinuity. Return loss is related to the reflectioncoefficient (p) and VSWR as follows;

RLdB = 20 log (1/p)Where p = (VSWR-1)/(VSWR+1)VSWR = Vmax/Vmin


6


In other words, the return loss of an antenna can be considered as the difference in power in theforward and reverse directions due to impedance mismatches in the antenna design.

All other things being equal, the higher the antenna return loss, the better the antenna. The systemengineer should choose an antenna with a return loss of 14 dB or better. Note that 14 dBcorresponds to a VSWR of 1.5:1 as per the following example;

VSWR = 1.5/1 = 1.5p = (1.5-1)/(1.5+1) = 0.5/2.5 = 0.2RLdB = 20log (1/0.2)RLdB = 13.979 dB

6.2.6 Power Rating

The Power Rating of an antenna is the maximum power, normally expressed in Watts that theantenna will pass without degraded performance. Typical values for the power rating of an antennaare between 300 and 500 Watts. As CDMA will employ a smaller number of carriers and due tothe losses associated with combining, the power rating of an antenna is not expected to be a limitingfactor for antenna choice. Even so, when choosing an antenna, the system engineer should considersystem expansion and the theoretical maximum configuration of carriers that could be placed ontoa single antenna (please refer to Section 6.4.2).

6.2.7 Front to Back Ratio

The front to back ratio of an antenna is an important measure of performance. It is the ratio of thepower radiated from the main ray beam forward to that radiated from the back lobe behind theantenna. Front to back ratio is normally expressed in terms of dB. This means that a signal at theback of the antenna should be X dB down on a signal at a mirror angle in front of the antenna. Thefront to back ratio for a typical CDMA antenna should be in the region of 25 dB.

6.2.8 Side Lobes & Back Lobes

Side and Back lobes are those undesirable directions where the chosen "directional" antenna maypresent gain. The system engineer should pay particular attention to these characteristics whendowntilting an antenna, the mechanical downtilting of an antenna will directly affect the radiationof both side and back lobes. The mounting of panel antennas on buildings or the use of antennawith electronic down/up tilt are two possible ways to limit back lobe interference.

The system engineer should choose the optimum directivity and gain of an antenna while limitingthe number of side lobes and the strength of the back lobe (refer to previous paragraph - front toback ratio).


6


6.2.9 Antenna Downtilting

Downtilting is the method of effectively adjusting the vertical radiation pattern of the antenna todirect the main energy more downwards and reduce the energy directed towards the horizon.Downtilting can be used to increase the amount of coverage close to the site where "nulls" (holes)may exist due to the effective height of the antenna. Downtilting can also be used to reduce "pilotpollution" caused by reflections or undesired RF propagation beyond a predetermined footprint.There are principally two types of antenna downtilting possible, mechanical and electronic.

Mechanical downtilting can be achieved through the mechanical adjustment of an antenna’sphysical position. The main advantage of the mechanical type of downtilting is the ease (dependentupon location) of mechanically adjusting the antenna’s direction following system optimization.Note that any CDMA network will require some degree of system optimization based upon sitespecific variables. The adjustment of antenna downtilt has historically been one of the principlemethods of tuning system performance, therefore the system engineer should consider if the chosenantenna can be downtilted and if so, by how much?

The second method of downtilting that can be used is electronic downtilt. This is the only way toimplement downtilt for an omni directional antenna. The level of electronic downtilt for an antennacan be preset and ordered directly from the antenna manufacturer. The system engineer should beaware that electronic antenna downtilt is preset. Thus, the field adjustment of downtilt andtherefore vertical radiation can not normally be reduced. There are antenna suppliers that providethe capability of being able to alter the downtilt characteristics of the antenna from the base of thecell site. This may take the form of motors to perform the physical downtilt or electronics used toalter the electrical characteristics of the antenna. Refer to the numerous antenna vendors for thevarious antennas that they supply.

The system engineer should also remember that the amount of gain in the antenna will also have adirect affect both on the physical size of the antenna and the vertical beamwidth. If a low gainantenna is utilized, the vertical beamwidth will be relatively broad and therefore the benefits ofdowntilting will be minimal.

6.2.10 Antenna Height

In general the 6 dB per octave rule will apply to the cell site antenna height in a flat terrain, that isdoubling the antenna height causes a gain increase of 6 dB. The system engineer should comparethis possible gain height increase with the effects of doubling the transmission line loss and thepossible appearance of nulls close to the site.

Figure 6-2 shows the comparative number of cell sites required for a given area based upondiffering base station antenna heights and the Cost-231 Hata propagation model (i.e. flat terrainonly). If 100 ft. (30 m) is considered as the reference point, the system engineer should note thatby doubling the antenna height to 200 ft., there is a reduction of 50% in cell sites required.


6


Figure 6-2: The Relationship of Antenna Height to Number of Cell Sites.

6.3 CDMA Antenna Placement

The placement of required CDMA antennas will typically depend on two main factors:

• the isolation required between the CDMA antennas to be installed and other antennasexisting at the site

• the amount of spatial diversity provided between CDMA Rx antennas.

It is important that enough physical separation be used between affected antennas to ensure the bestpossible performance of the CDMA BTS while minimizing the threat of interference to/from otherco-located technologies. The following sections discuss the above considerations in more detail.

6.3.1 Antenna Isolation Considerations

The following recommendations are general guidelines on the base station antenna isolationrequired between two or more of the following radio systems:

• 800 MHz AMPS• 800 MHz CDMA• 1900 MHz CDMA PCS


6


Typical examples of site sharing are an 800 MHz CDMA system overlayed on an existing 800MHz AMPS system, or a 1900 MHz CDMA PCS system sharing the same tower/rooftop with anexisting 800 MHz AMPS/CDMA system. This section describes the RF isolation requirementsbetween the various transmit and receive antennas of two or more of the above radio systems whichshare a common tower/platform/rooftop location. The following antenna isolation scenarios needto be considered.

Tx to Tx Antenna Isolation: There must be sufficient isolation between any two transmit antennasto attenuate the signals from one antenna sufficiently before they enter another transmit antennaand create transmitter IM products in the associated transmitters that are strong enough to cause aproblem for the system.

Rx to Rx Antenna Isolation: For adequate receive diversity performance there must be sufficientspacing between the two antennas to achieve the desired degree of de-correlation of the tworeceiver feeds for the signals being received.

Tx to Rx Antenna Isolation: The isolation between the transmit and receive antennas at a cell sitemust be high enough to provide sufficient attenuation to eliminate the following three potentialproblems:

1. Receiver overload caused by the high level transmit carriers being picked up by thereceive antennas and causing receiver desensitization and/or generating IM productswithin the receiver which interfere with the reception of the desired signals.

2. Interference with the reception of the desired signals caused by transmitter sidebandnoise and/or spurious signals generated in the transmitter which fall in the receive bandand whose energy is radiated from the transmit antennas and picked up by the receiveantennas.

3. Interference with the reception of the desired signals caused by transmit IM productsfalling in the receive band that are generated in the transmit antenna systems consistingof feed line and jumper connectors and/or the transmit antennas themselves. These IMproducts are produced after the transmitter output filtering and therefore cannot beeliminated by any transmitter filtering. These IM products will be radiated by thetransmit antennas and picked up by the receive antennas.

Also included in this section are several antenna placement examples as well as a discussion ofsome typical isolations that can be expected between various combinations of 800 MHz and 1900MHz antennas.

Additional base station antenna isolation requirements, involving scenarios such as the co-locationof 800 MHz CDMA and TACS antennas, the co-location of DCS 1800 and PCS 1900 CDMAantenna and the co-location of PCS 1900 CDMA and microwave antennas, are considered inChapter 9.

6.3.1.1 CDMA/AMPS Transmit/Receive Antenna Isolation Requirements

The following sections provide the calculations for antenna isolation requirements.


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800/1900 MHz Tx-Tx ANTENNA ISOLATION

CDMA Tx - CDMA TxThe maximum Tx reverse signal that can be applied to a BTS Tx port is +30 dBm (1 Watt). Atypical high power LPA can deliver +50 dBm (100 Watts) to the antenna system. Taking intoconsideration the coupling from the adjacent sectors, the minimum antenna-to-antenna isolationshould be:

50 dBm + 3 dB - 30 dBm = 23 dB

Since the minimum AMPS transmit antenna-to-antenna isolation is typically 20 dB, the worst caseantenna isolation required between any AMPS and CDMA transmit antenna combination will bechosen to be 23 dB. (This applies to both 800 and 1900 MHz transmit antennas.)

800/1900 MHz Rx-Rx ANTENNA ISOLATION

A minimum isolation of 20 dB is desired between any two antennas. This would apply to separateAMPS and CDMA receive antennas mounted in close proximity to each other. When evaluatingtwo receive antennas connected to the same BTS for diversity reception, a more important factoris the spatial separation of the two antennas. If their responses are uncorrelated to fading, gooddiversity reception is assured. (According to Lee, William C.Y. in “Mobile CellularTelecommunications Systems”, uncorrelated antennas require from 8 to 14 wavelengths ofhorizontal separation. This equates to about 3 to 5 meters at 800 MHz or about half that much at1900 MHz.) The internal requirement of the BTS is 20 dB isolation, so the antenna system needonly be 20 dB also. The physical spacing required for spatial separation greatly exceeds 20 dB ofisolation between the two receive antennas.

800/1900 MHz Tx-Rx ANTENNA ISOLATION

In Cases 1 through 3 below, Transmit to Receive Antenna Isolation requirements are estimatedbased on reducing transmitter noise and spurs in the receive band to the point where only 0.5 dBof receiver noise floor rise or receiver threshold sensitivity is produced. If either more or lessdegradation is tolerable, the information given in Table 6-3 can be used to modify them as desired.Similarly, if specific information as to the transmitter noise and spurious signal levels for aparticular Base Station model of interest is known, Cases 1 through 3 can be used as a guide.

a: The added noise at this level is equal to kTBF

Table 6-3: Degradation to Sensitivity Based on Noise Level Below kTBF

Noise level below kTBF Degradation to sensitivity16 dB 0.1 dB13 dB 0.2 dB9 dB 0.5 dB6 dB 1.0 dB3 dB 1.8 dB

0 dB a 3.0 dB


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Case 1: CDMA Tx - CDMA Rx

From Table 6-3, a 0.5 dB sensitivity degradation occurs when the transmitter noise is ata level of 9 dB below kTBF. For a CDMA receiver with a Noise Figure of 4 dB, kTBF is-109 dBm. This results in a maximum acceptable interference power of -118 dBm.

Typical CDMA Tx noise level due to CDMA spurs (CDMA Tx IM) in the receive bandis less than -85 dBm in a 1 MHz bandwidth. In the CDMA receiver bandwidth of 1.2288MHz this is -84 dBm. The resulting antenna-to-antenna isolation requirement for 0.5 dBsensitivity degradation is:

-84 dBm - (-118 dBm) = 34 dB

Case 2: AMPS Tx - CDMA Rx

The AMPS Tx specification requires the AMPS Rx band spurs to be at a maximum levelof -90 dBm/30 kHz. The total Tx SBN and spurs in the CDMA Rx band is maintained at-85 dBm/1 MHz with proper frequency planning (no 3rd order IM inside CDMA Rx).The resulting antenna-to-antenna isolation requirement for a 0.5 dB degradation is:

-84 dBm - (-118 dBm) = 34 dB

For a multitone LPA application, the worst case Tx SBN measured in the Rx band shouldbe less than -85 dBm/1 MHz.

Case 3: CDMA Tx - AMPS Rx

Typical CDMA Tx noise level due to CDMA spurs (CDMA Tx IM) in the receive bandis less than -85 dBm in a bandwidth of 1 MHz. This is -100 dBm in the AMPS receiverbandwidth of 30 kHz. The kTBF for a typical AMPS receiver is -123 dBm. UsingTable 6-3, 0.5 dB sensitivity degradation occurs when the Transmitter noise is 9 dB belowkTBF, which is -132 dBm in this case. The resulting antenna-to-antenna isolationrequirement for 0.5 dB sensitivity degradation is:

-100 dBm - (-132 dBm) = 32 dB

The worst case AMPS or CDMA transmit antenna to AMPS or CDMA receiveantenna isolation will be chosen to be 34 dB. (This also holds for any combination of800 and 1900 MHz antennas.)

Since the required isolation between the Tx-Tx, Rx-Rx, and Tx-Rx pairs of antennas is for the mostpart identical for all of the combinations of both 800 MHz AMPS/CDMA and 1900 MHz CDMAPCS systems, it is appropriate that a single set of isolation requirements should be adopted. Table6-4 summarizes the isolation requirements between two transmit antennas, two receive antennas,or a transmit and receive antenna pair which share a common location and are operating in the 800MHz Cellular and/or 1900 MHz PCS bands and utilizing analog or CDMA technology.


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Table 6-4: Antenna Isolation Requirements

The antenna isolation requirements in Table 6-4 represent the port-to-port isolation between theequipment end of the bottom jumper of one antenna system to the equipment end of the bottomjumper of the other antenna system. Therefore, if the combined jumper and main transmission linelosses of the transmit and receive antenna systems are say 5 dB then the required isolation betweenthe two antennas themselves would only have to be 29 dB to achieve the required 34 dB port-to-port isolation listed in Table 6-4.

6.3.1.2 Measuring Port-to-Port Antenna Isolation

The Tx-Rx isolation can be measured by feeding a test signal into the transmit antenna bottomjumper input (normally connected to the transmitter output port) and measuring the level of thesignal at the output end of the receive antenna bottom jumper (normally connected to the receiverinput port).

A typical measurement setup for port-to-port isolation between two antennas is a signal generatorfeeding the desired transmit frequency (at a level of about -20 dBm) into the transmit antennabottom jumper and a spectrum analyzer or calibrated test receiver (adjusted to measure the level ofthe transmit test signal) connected to the receive antenna bottom jumper. The difference betweenthe received level and signal generator test level is the port-to-port isolation. For example, if thelevel of the received signal is -60 dBm for a signal generator output level of -20 dBm, the port-to-port isolation would be 40 dB.

6.3.1.3 Reducing the Required Antenna Isolation

Except for overload of the victim receiver front ends by interfering transmit carriers, which requirea minimum isolation between the transmit and receive antennas of 20 dB, all of the isolationrequirements above 20 dB outlined above are due to the effects of either the noise energy or IMproducts that are produced in the interfering base station PAs/LPAs and which fall in the receiverband.

If the receive band attenuation of the bandpass filter in the output of an interfering LPA is increased(or additional external receiver band filtering is added), the required antenna isolation may bereduced. However, transmitter IM products generated by hardware in the RF path following thebandpass or an added external filter may limit the amount of improvement that can be achieved.

Cellular Band (824-894 MHz) PCS Band (1.7-2.0 GHz)

Tx-Tx Rx-Rx Tx-Rx Tx-Tx Rx-Rx Tx-Rx

Cellular 23 dB 20 dB 34 dB 23 dB 20 dB 34 dB

PCS 23 dB 20 dB 34 dB 23 dB 20 dB 34 dB


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6.3.1.4 Typical Antenna Isolation

For 800 MHz directional panel antennas it should be possible to achieve 25-30 dB of isolation with0.45-0.6 meters of spacing and 35 dB or so at 1 meter of horizontal spacing. However, reflectionsfrom the tower structure and coupling effects from other antennas may reduce the isolationobtainable. This is especially true for the advertised front-to-back ratios for many directionalantennas which do not have metal reflector panels on the back sides of the panel structures.

1900 MHz PCS directional panel antennas should be able to achieve isolation levels comparableto similar 800 MHz types at spacings approaching half of the 800 MHz spacings. Because of thisthe tower platform sizes at 1900 MHz can be significantly smaller than those at 800 MHz.

On the basis of limited testing by several of the antenna vendors it would appear that the cross bandisolation between 800 MHz and 1900 MHz antennas in close proximity can run 10-15 dB betterthan the same band isolation would be for similar physical spacings. Because of differencesbetween various antenna types, the actual antenna isolation of a proposed site sharing configurationshould be measured using the techniques in Section 6.3.1.2.

6.3.1.5 CDMA Antenna Placement

In consideration of the above isolation requirements, Motorola recommends that any requiredCDMA antennas be mounted on the tower above or below any existing antennas being used byother wireless technologies such that superior isolation provided by vertical spacing is obtainedwhile at the same time providing the required CDMA coverage to the surrounding area.

The goal of this approach is to leave any existing antennas untouched. If, however, CDMAantennas are to be installed on a tower platform that is already supporting antennas from othertechnologies (provided that enough isolation is provided), it may be necessary to replace theexisting antennas with smaller antennas to physically accommodate the newly-added CDMAantennas. Figure 6-3 provides an antenna placement example using a “shared” platform approach.

Figure 6-3: Antenna Placement - Shared Platform

AMPSRx

(Main)

CDMARx

(Main)

CDMARx

(Diversity)

AMPSRx

(Diversity)

CDMATx

20 dB of isolationdesirable



34 dB of isolationrequired


AMPSTx

Notes: 1. Only 1 face of a 120° S/S implementation is shown here.


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Figure 6-4 provides an antenna placement example using a “separate” platform approach.

Figure 6-4: Antenna Placement - Separate Platforms

With reference to Figure 6-3, the shared platform approach can be readily utilized for an 800 MHzAMPS/CDMA configuration with shared receive antennas and one or two sets of separate transmitantennas. An eight antenna configuration involving two receive and two transmit antennas for eachof the AMPS and CDMA systems, can get rather unwieldy, and the separate platform approach inFigure 6-4 might be more appropriate.

For 800 MHz and 1900 MHz shared sites, the separate platform approach would appear to be thebetter choice, not that sufficient isolation could not be obtained with the single platform butbecause of the potential for conflicts should either of the systems want to change existing antennasor add additional antennas. Any physical changes in the antennas for one system could impact theother system because of a reduction in antenna isolations on the same platform. Separate platformswill normally provide a higher degree of isolation between the two systems which reduces thepossibility of "political problems" between the two systems when either system desires changes intheir antennas.

6.3.2 Antenna Diversity (Spacial)

The CDMA system employs time, space and frequency diversity. Spatial diversity is implementedthrough the use of two receive antennas at the base station, commonly called "Antenna Diversity".Receive antenna diversity is employed at the base site to improve the uplink by approximately 3 to5 dB. The gain obtained by spatial diversity is based on the assumption that the signals received bythe two separated antennas are not correlated or have a low degree of correlation, the affects of

AMPSRx

(Main)

CDMARx

(Main)

CDMARx

(Diversity)

AMPSRx

(Diversity)

CDMATx

AMPSTx

Notes: 1. Only 1 face of a 120° S/S implementation is shown here.



1 m min.verticalseparation


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fading on one path will therefore be independent from the second. The 3 to 5 dB improvement isalready incorporated into the equipment Eb/No receiver sensitivity specification. Note that ifhorizontal diversity is not utilized, the equipment performance may degrade.

6.3.2.1 Horizontal Antenna Diversity and Recommended Separation

The conventional method for determining the minimum separation for horizontal antennas toachieve non correlation is normally expressed as a factor of the wavelength (equal to the speed oflight/frequency). The recommendation for standard cellular implementation (800 MHz) hasgenerally been accepted as 10 times the wavelength (lambda). This figure should only beconsidered as an average distance as the level of correlation for horizontal diversity can also beaffected by a number of variables, for example; the height of the antennas, the type of surroundingclutter (i.e. the level of multipath) and the typical angular arrival of the signals (i.e. are the antennasmounted perpendicular to a highway).

As the wavelength of PCS frequencies is approximately half that of conventional cellular, it seemsfair to assume that the diversity antenna separation for PCS will effectively be half that of 800 MHzsystems. At this time, the antenna separation of 10 lambda at the base site is considered sufficientfor the non correlation of uplink signals within an urban environment (obviously greater than 10lambda will provide even less correlation).

Note that Lee’s equation utilizes the antenna height in addition to frequency to determine theminimum horizontal diversity separation. This equation can be used as a more accurate planningguideline where the antenna height is known.

Frequency: 1850 MHz Wavelength: 16 cm Diversity distance (x10): 1.6 m (5.3 ft.)

Lee’s Equation: d = 77.27*h/fWhere d = Rx antenna separation, h = Rx antenna height (ft.), f = frequency (MHz)

Example (1850 MHz @ 100 ft.)d = 77.27*100/1850d = 4.2 ft.

It is believed that the horizontal separation of 5.3 (ft.) is an achievable separation distance for PCScell site installations. Field trials and performance tests on PCS systems will determine if thisminimum separation can be reduced under certain conditions.

6.3.2.2 Vertical Antenna Diversity

The vertical separation of two diversity antennas could be an appealing alternative for CDMAoperators where the location of two horizontally separated antennas is hard to achieve.Unfortunately, the system engineer should be aware that the vertical separation of antennasprovides poor diversity performance. This is due to a higher degree of correlation for a givendistance compared to horizontal separation. In other words, the vertical separation distancerequired between two base site antennas is much larger than the horizontal separation required togain the same correlation coefficient of two received branches.


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The preferred method of implementing diversity at a base site is horizontal diversity. While verticalseparation of receive antennas will provide a degree of non correlation, the performance of verticaldiversity is not considered as effective as horizontal diversity.

6.4 CDMA Antenna Sharing

The following section discusses the various antenna sharing strategies that are currently availablewith respect to the Motorola CDMA BTS.

6.4.1 Multiple Frame Antenna Sharing with 800 MHz BTS Products

This section provides some of the multiple frame antenna sharing configurations for the MotorolaBTS product lines at 800 MHz that are currently supported.

Each 800 MHz SC4812T frame is capable of supporting up to two IS-95A/B or IS-2000 1X six-sector carriers or up to four IS-95A/B or IS-2000 1X three-sector carriers. The SC4812T starterframe can currently support one or two SC4812T expansion frames, depending on the frequencyof operation. External low-loss cavity combining for transmit antenna sharing is not supported. Anoptional duplexer can be used to share Tx and Rx antennas (see Figure 6-5). The SC4812T differsfrom the earlier SC4812 in that it contains Trunked LPAs in place of the dedicated per-sectorLPAs. The Trunked LPA contains 4 LPA modules and supports 1 CDMA RF carrier for all sectors.Its power output capacity is shared between all sectors proportional to the traffic on each sector.Internal 2:1 or 4:1 cavity combiners are used to combine the Trunked LPAs to increase the numberof CDMA RF carriers available.

Figure 6-5: SC4812T to SC4812T Expansion Frame

Note: m = main, div = diversity, exp = expansion

SC4812TExp. FrameSC4812T

Rx Exp.

Rx-m Tx

D

Tx

OptionalDuplexer

Rx-divD


6


The 800 MHz SC4812T expansion frame can also share Rx antennas with some of the existing 4-digit 800 MHz BTS products, which include the following.

• SC2450 STPA• SC2400 with ELPA• SC9600 with LPA or ELPA

There are three versions of the SC4812T frame, a starter frame, an expansion frame, and a modemframe. The general differences between the three different versions are as follows. A starter frameis a standard stand-alone BTS frame which is designed to amplify the Rx & Tx signals whileconnected directly to the antenna feed line jumpers. An expansion frame shares the Rx signals froma starter frame and thus it is designed with a lower Rx gain in the front end, since the starter frameprovides the first stage of amplification. The Tx signals of an expansion frame are independentfrom that of the starter frame and are typically connected to their own antenna (unless some sort ofexternal combining technique is used). An SC4812T modem frame is functionally similar to theSC9600 modem frame. In this case, the modem frame shares the Rx signals from another frame(typically a SIF) as well as providing a low level Tx output signal which requires furtheramplification from yet another frame (typically an LPA or ELPA frame). The following figuresprovide some of the antenna sharing configurations for the various SC4812T frame versions as itshares the Rx antennas from various 4-digit 800 MHz BTS products.

Figure 6-6: SC2450 to SC4812T Expansion Frame


Each SC2450 or SC2400 starter frame is capable of supporting as many as three expansion frames.The expansion frames can be of the SC24XX series or SC4812T expansion frames (three-sectorconfiguration only, see Figure 6-6 & Figure 6-7). There are no transmit antenna sharingconfigurations that are currently supported between these frames. For expansion kit ordering

SC4812TExp. FrameSC2450

Rx Exp.

Rx-m Tx

D

Tx

Optional Duplexer

Rx-div

10 dBPad

D


6


information refer to the latest version of the equipment planning guide or contact the ProductManagement group for more information.

Figure 6-7: SC2400 ELPA to SC4812T Expansion Frame


For the SC2400 frames using CDMA only, the Tx output from the ELPA can be duplexed with theRx antenna (this is not shown in Figure 6-7). Although it is typically not recommended, the outputsignals from the SC2400 ELPA frame can also be duplexed for mixed mode analog and CDMAframes onto the Rx antenna, but extreme care should be used in frequency planning to prevent IMproducts from effecting system performance.

Figure 6-8: SC9600 SIF to SC4812T Expansion Frame

The configuration in Figure 6-8 provides Rx antenna sharing between a SC9600 Site InterfaceFrame (SIF) and an SC4812T expansion frame (three-sector only). Up to two SC4812T expansionframes can be supported in this configuration. Each SC4812T expansion frame requires a separateTx antenna. For expansion kit ordering information refer to the latest version of the equipmentplanning guide or contact the Product Management group for more information.

SC4812TExp. Frame

SC2400

Rx Exp.

Rx-m TxRx-div

10 dBPadELPA

SC4812TExp. Frame

SC9600SIF

Rx Exp.

Rx Tx


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Figure 6-9: SC9600 SIF & LPA with SC4812T Modem Frame

The SC4812T modem frame in Figure 6-9 is comparable to the existing SC9600 modem frame.External combiners can be used for combining up to two SC4812T modem frames (or 8 carriers)in this configuration. For modem frame or expansion kit ordering information refer to the latestversion of the equipment planning guide or contact the Product Management group for moreinformation.

6.4.2 Multiple Carrier Cavity Combining With 1900 MHz BTS Products

Combining is considered desirable by PCS operators in order to support multiple carriers at cellsites with a minimum number of antennas. It is important to remember that the function ofcombining will inherently add loss to the forward link. The following section will therefore providethe system engineer with general guidelines on how combining will be implemented within theMotorola BTS architecture (at 1900 MHz).

6.4.2.1 Output Power Without Combining

The SC4812T will provide 22.4 Watts “top of cabinet” output power assuming that the RF powerdelivered to each sector is equal. For PCS applications, Motorola assumes that 13 Watts issufficient to balance the uplink and downlink paths. The combining and associated cablingsupplied by Motorola will therefore have to provide no greater loss than 2.4 dB in order to achieve13 Watts from a 22.4 Watt LPA input. Note that 22.4 Watts “top of cabinet” does not include the0.5 dB loss of the duplexer, which is external to the cabinet.

The SC300 1X will provide 10 Watts “top of cabinet” output power. The reduced output power ofthe SC300 1X will require a 1.14 dB (13 W to 10 W) offset in the link budget calculations in orderto balance the paths at 10 Watts. The SC300 1X may be expanded up to 4 carriers by the additionof Field Replaceable Units (FRUs).

6.4.2.2 Type of Combining

Motorola will provide multiple pole cavity filter combiners, utilizing conventional phasedtransmission line combining techniques, which are self contained within a “cast” housing. A

SC4812TModem

SC9600SIF

Rx Exp.

Rx-m

SC9600LPA or

Tx

Frame ELPA

Rx-div


6


maximum of 4 branch combining will be supported allowing up to a maximum of 4 alternate carrierchannels to be combined per antenna/per sector (with duplexers). The insertion loss of the cavitycombiners, duplexer, and associated cabling will not exceed 2.4 dB in order to maintain 13 Wattsoutput power for the SC4812T.

6.4.2.3 Multiple Carrier Scenarios

The SC4812T will support a maximum of 12 sector-carriers per site (i.e. 3 sectors with 4 RFcarrier, or 6 sectors with 2 RF carriers). The 22.4 Watts at the "top of the cabinet" for SC4812Tincludes the combining loss with the cabinet for either configuration, therefore 13 Watts of outputpower per each RF carrier on each sector can be provided through up to 2.4 dB of externalcombiner, duplexer, and cable loss.

The SC300 1X supports one carrier per FRU. Up to four carriers can be supported byinterconnecting four FRUs. Each FRU supports 10 Watts per carrier RF output power.

The following figures provide a high level outline of the combining required to support two andeight carriers with the SC4812T (note that a only a single sector is shown as all 3 sectors areidentical).

Assuming that the maximum number of antennas allowed at a cell site is 6 (2 per sector), Figure 6-10 shows that combining is not required for a two adjacent carrier configuration. If 6 duplexers areutilized, each antenna within each sector can be duplexed to either carrier 1 or carrier 2. Thisconfiguration will allow for balanced receive paths (i.e. no need for pads) and will allow forsufficient power (13 Watts) to balance the uplink. Provided that both carriers are duplexed in everysector, only 6 antennas will be required for a 3 sector site.

Figure 6-10: 2 Carrier Configuration

Alternatively, the SC4812T frame may include either 2:1 or 4:1 Tx cavity combiners. Adjacent RFcarriers cannot be combined using cavity combiners. Alternate adjacent carriers can be combinedwith the cavity combiners. In the single frame 3-sector 6 antenna case, only 1 duplexer per sectoris needed. This configuration will also allow for balanced receive paths (i.e. no need for pads) andwill allow for sufficient power (at least 13 Watts) to balance the uplink.

Tx1 Tx2

Antenna 1(Sector 1)

Antenna 2(Sector 1)

Duplexers

2 Carriers with 2 Duplexers (no combining)

Rx-m Rx-div


6


Figure 6-11 shows how the configuration of 8 carriers for the SC4812T may be combined onto 6antennas. Note the following applies to SC4812T:

1. Only a single stage of 4 branch cavity combining is required.2. The use of alternate (non adjacent) frequencies is required.3. Duplexers for each antenna are required.

The configuration of 8 carriers will require (2) SC4812T cabinets. The cavity combiners arecontained within the SC4812T cabinets, thus helping to minimize the cable lengths.

Figure 6-11: 8 Carrier Configuration

6.4.3 Duplexing

Duplexing is one of the options that can be used to reduce the number of antennas required tosupport a CDMA base station. The duplexer for the SC4812T, for example, is a standard, three-port device, which allows for the combination of transmit and receive signals onto one antenna.

Figure 6-12: Duplexer

Tx1 Tx2Tx3 Tx4

Tx5 Tx6Tx7 Tx8

Antenna 1(Sector 1)

Antenna 2(Sector 1)

DuplexerDuplexer

To Rx A To Rx B

4 BranchCavity Combiners

4 Branch Cavity Combining for 8 Carriers

ANT PORT

Rx PORT Tx PORT

Path 1 Path 2

Path 3


6


The duplexer does not incorporate a circulator. Therefore, port isolation is achieved through thephasing and stop band attenuation of the two bandpass filters. The following table outlines thefrequency response characteristics for a 1900 MHz duplexer.

Table 6-5: Duplexer Frequency Response Characteristics

The duplexer 3rd order intermodulation (IM) products between the Tx port and Rx port, for two(10) Watt carriers in the transmit band (1930 - 1990 MHz) will be below -100 dBm and the fifthorder (and higher) IM products will be below -120 dBm.

The duplexer is physically included within the SC4812ET/ET Lite (outdoor products) and theSC300 1X cabinet, but is not located within the SC4812T (indoor) product. Please refer to thecurrent Motorola “B1” document for full equipment specifications.

6.4.3.1 Pre-Engineered Kits

Note that Motorola will be offering pre-engineered RF kits as part of its equipment offering for theSC4812T, these kits will include items such as duplexers and directional couplers.

6.4.3.2 Duplexers and Intermodulation

The use of duplexed antennas will allow the combination of transmit and receive signals onto asingle antenna via a duplexer. This solution may be considered desirable by a number of PCSoperators in order to reduce the total number of antennas required per site. The Motorola PCSinfrastructure will be capable of supporting duplexed antenna configurations. The SC4812ET/ETLite (outdoor products) and the SC300 1X include internal duplexing equipment.

The use of duplexers implies zero isolation at the antenna port between transmit and receivecarriers. Under these conditions any transmit IM spurs created by non-linearities, in active orpassive components, in the common path, might produce significant interferers if they fall withinthe receive carrier band. Duplexers can be made to work, in some applications, under idealconditions; but any imperfections introduced by aging, lightning, thermal cycling, bi-metallicinteraction or other common stresses can reduce system performance to below acceptable levels.

With regard to duplexing at 1900 MHz, it is useful to look at the potential for TransmitterIntermodulation (IM) in duplexer equipped installations and to compare it to some of the existingcellular technology systems. The following table examines the operation of AMPS/GSM/CDMAand outlines the minimum Transmitter IM order required to generate IM products in the Rx band

Antenna Port to Receive Port

Transmit Portto Antenna Port

Transmit Port to Receive Port

Pass Band 1850 - 1910 MHz 1930 - 1990 MHz -Stop Band DC to 1770 MHz

& 1990-4000 MHz3860 - 5970 MHz 1850 - 1910 MHz

1930 - 1990 MHzPass Band Insertion Loss 0.5 dB max 0.5 dB max -Stop Band Isolation 30 dB 30 dB 40 dB minimum


6


of each technology. The minimum is calculated since the power generated by IM tends to fall offfairly quickly with increasing IM order. Therefore, the majority of interference is generated by thelowest order products.

Note that the IM orders presented in the following table for 1900 MHz refer to a single PCS bandcase, operation within multiple PCS bands at the same site may require further investigation.

Table 6-6: Minimum IM Orders.

It is clear from the table above that the 1900 MHz CDMA systems have a significant advantagefrom the combination of smaller channel grouping (no orphan extended bands) and the higher Txto Rx offset. Motorola believes that duplexers are a viable solution for PCS systems due to the factthat only high order IM products will fall within the PCS band.

In general, 11th order frequency separation is sufficient to maintain control of transmitter passiveintermodulation in duplexed systems if all equipment recommendations are followed.

6.4.3.3 Proper Installation and Maintenance of Duplexed Antennas

The comments below are intended to show proper installation and component selection in systemswhere duplexer use cannot be avoided.

6.4.3.3.1 Equipment Recommendations

All RF components in the cell site common receive/transmit path must be certified by theequipment manufacturer for IM performance. A typical (derived from GSM) IM specification isthat all transmit IM products appearing in the receive band should be less than -110 dBm for twoinput transmit carriers, at a power level of 25 Watts per carrier. In addition, a regularly scheduledPreventative Maintenance Inspection (PMI) plan should be developed to verify that system IMperformance has not been degraded and to ensure component integrity. Typical requirements for aPMI plan are described below.

The following components at the site would require IM certification:

Coax - Standard “Heliax” type coax is considered to have acceptable IM performance ifundamaged and unkinked. Other types of coax would have to be individually tested and certified.Cable installation should include visual inspections for cable damage and electrical measurementsto verify performance. Provisions for strain relief to minimize stress on cables and maintain proper

SystemOperator

BandwidthTx-Rx

SpacingMin IM Order

AMPS A side 22.5 MHz 45 MHz 5thAMPS B side 14.0 MHz 45 MHz 7thGSM (best case) 12.5 MHz 45 MHz 7th1900 MHz CDMA 15.0 MHz 80 MHz 11th1900 MHz CDMA 5.0 MHz 80 MHz > 30th


6


bend radii should be made. Cables should be mounted securely so as to prevent vibration andmovement per vendor specifications.

Connectors - The connectors in the common transmit/receive path are the most likely cause ofsystem IM problems. System planning should attempt to minimize the number of connections inthis path in order to prevent IM problems from occurring. Connectors with good IM propertieshave silver plating and mechanical rigidity. 7/16 type connectors have been optimized for IMperformance and should be used, if possible, in all paths with potential for IM problems. Assemblyand installation instructions should be provided by the manufacturer and should include torquespecifications. All connectors should be thoroughly cleaned, prior to installation, andwaterproofed, if exposed to outdoor elements. Care should be taken when mating and unmatingconnectors to prevent contamination and to maintain plating integrity. Connectors should beregularly inspected for damage and proper torque.

Lightning Arrestors - Certification of lightning arrestors is the same as that of connectors. Inaddition, lightning arrestor performance will degrade if a lightning strike has been taken by theantenna. Verification of component performance should be made regularly.

Duplexers - Considerable effort has been made by duplexer manufacturers to improve IMperformance of duplexers. A duplexer that has been certified for its IM performance should includeadequate silver plating of components and 7/16 type connectors. Accelerated life testing should beperformed as part of the certification process. Only IM certified duplexers should be used in aduplexed system.

Antennas - Each antenna installed in a cell site should be tested and certified for IM performance.This is due to the additional potential IM risk of contamination of the material used for the radiatingelements (no ferromagnetic materials). Proper care in installation should be used to preventantenna damage and to verify that there are no metallic objects in the radiation paths close enoughto reradiate back into the receiver (the “rusty bolt effect”). Mechanical stability should be providedto protect from exposure and wind effects. Inspection and electrical verification should be made ona regular basis, especially after a lightning strike or other unusual weather occurrence.

6.4.3.3.2 Installation Recommendations

Antennas - Care should be taken in installation to maintain proper distances from any otherradiators or other obstruction on the same tower.

Cable Lashing - All cables should be prevented from movement. A major source of IM is themovement of the cable at any connector. In addition, damage may result to the cable at a connectorfrom continued movement.

Cable Bends - Care should be taken to prevent any excessive bends in cabling. Slack and serviceloops should be provided in cable runs to prevent stress to cables.

Water Proofing - All external connectors should be waterproofed and regularly inspected forhermeticism. External components should be installed to prevent internal water capture.Components should be removed from any areas with potential standing water.


6


6.4.3.3.3 Maintenance

A Preventative Maintenance Inspection (PMI) plan should be developed and followed in order tomaintain the IM performance of a cell site. A PMI should include a complete visual inspection ofthe cell site for obvious component damage or misapplication and an RF two tone test to verifysystem performance is satisfactory. Figure 6-13: Two Tone IM Test Set Up (800 MHz) is adiagram of the two tone test setup and is shown below.

The low noise amplifiers combined with the spectrum analyzer in the above diagram should besensitive enough to measure IM products at -120 dBm or lower. The frequencies of the CW tonesshould be such that the spurious product of interest should fall within the passband of the receivepath. All measured IM products should be below -116 dBm (for 0.5 dB typical sensitivitydegradation).

If any anomalies are observed, a sweep of the transmit path using a Time Domain Reflectometer(TDR) or equivalent should be performed. A TDR will identify the existence and location ofsignificant RF discontinuity in the signal path.

Monitoring cell site received signal strength indicator statistics for consistent foreign carriers isalso a good indication of IM problems and should be part of a PMI plan. Monitoring the receiverport in the cell site with a spectrum analyzer for foreign carriers should also be performed. The portshould be monitored with the transmit carriers keyed and unkeyed to verify whether interferenceis internally or externally generated.


6


Figure 6-13: Two Tone IM Test Set Up (800 MHz)

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6


6.5 CDMA Antenna Sharing With Other Technologies

The following section discusses topics associated with the sharing of antennas which is sometimesrequired to support both CDMA and AMPS technologies in the 800 MHz spectrum. Variousmethodologies for implementing co-located AMPS and CDMA cell sites are provided. Issues ofmutual system interference and cell site equipment sharing are considered. Where appropriate, thisdiscussion could be extended to include other antenna sharing configurations, provided thatminimum isolation requirements are met.

While Motorola recommends that CDMA implementations not share equipment with existingAMPS systems, it is understood that zoning restrictions and other hard realities might make thesharing of some equipment a virtual requirement from the customer’s point of view. The guidelinesbelow are intended to assure the most efficient implementation of the CDMA system whileminimizing the risk to operation of the host AMPS system.

For this version of the CDMA RF Planning Guide it is assumed that the CDMA antennas will beco-located with existing AMPS antennas and will be sharing the same tower or roof top location.

For sites where the AMPS and CDMA systems are both omni-directional, it is assumed that thereceive antennas will be shared between the two systems. Motorola recommends that a separatetransmit antenna be installed for the CDMA system to simplify the system design. Motorola doesnot generally recommend the use of duplexers to allow the AMPS and CDMA systems to sharecommon antennas. Please refer to Section 6.4.3 and Section 6.5.2 for more details on the subjectof duplexed antennas.

For sites where the AMPS and CDMA systems will both be sectorized, Motorola recommends thatwhenever possible the CDMA system should have separate antennas from the AMPS system. Infact, there are several CDMA system requirements which can only be satisfied by the use ofseparate CDMA and AMPS antenna systems. For example, the coverages of the AMPS andCDMA systems at the site require different downtilt angles for their respective antennas, or theCDMA softer handoff considerations require a narrower horizontal beamwidth for the CDMAsector antennas than for the AMPS sector antennas. Refer to the tower specifications to balance theweight to height ratio (tower loading).

It should be understood that in order to even allow for the possibility of sharing, the antenna willneed to be able to operate in both of the frequency bands to be shared. For instance, an antenna thatoperates in the AMPS frequency band would not be acceptable to also share carriers assigned forthe PCS band. Another instance to consider is if the antennas are only specified for operation in thetransmit or receive portion of the band. An antenna of this type would not be acceptable to supportboth transmit and receive bands.

6.5.1 SC9600 BTS/HDII Shared Facilities

Sharing equipment virtually always implies sharing antennas. Three likely conditions for antennasharing might exist:


6


• Common transmit antenna• Common receive antenna(s) • Duplexed antennas

In all cases where equipment is shared between SC9600 BTS and HDII, a site-by-site evaluationof the changes to basic parameters (receive noise figure, receive input intercept point - IPi, receivesensitivity, transmit maximum power, transmit IM spur potential of the site, etc.) is required (inmost cases).

6.5.1.1 Common Transmit Antenna

Several possible cases of transmit antenna sharing are described in this section. In most cases, inorder to share a transmit antenna it will be necessary to combine all signals prior to the LPA input,unless the >3 dB loss resulting from post LPA wide-band hybrid combining is site engineered anddetermined to be acceptable.

6.5.1.1.1 Combining Configuration for the SC9600 LPA (Used by HDII Carriers)

This configuration is recommended for commercial deployment.

Figure 6-14: SC9600 LPA Used by HDII Carriers

Notes for Figure 6-14: SC9600 LPA Used by HDII Carriers:

1. HDII system coverage is not affected, if the SC9600 LPA has enough reserve power.2. Refer to Chapter 4 for the maximum total average power available from a single LPA.

6:1HDII

SC9600

SC9600 LPA

CDMAINTERFACE

HDIIINTERFACE

SC9600 SIF

FROM OTHERHDII BAYS

XCVR RACK

CDMA MF

PREAMP


6


6.5.1.1.2 Combining Configuration for the HDII LPA (Used by SC9600 BTS CDMA Carrier(s))

Two options are described below to properly configure the HDII LPA (used by the SC9600 BTSCDMA carriers). The first option uses the SC9600 Modem Frame. The second option uses theSC9600-D Modem Frame.

Option 1: SC9600 Modem Frame

This configuration requires an upgrade to the NAMPS LPA which contains a preamplifier. Theupgraded NAMPS LPA has two input ports, one for high level HDII signals, and the other for lowlevel CDMA signals. The optional LPA output filter which provides increased attenuation in thereceive band should also be ordered; this reduces the isolation needed between the transmit antennaand the receive antenna.

Figure 6-15: HDII LPA Used by SC9600 CDMA Carriers

Notes for Figure 6-15: HDII LPA Used by SC9600 CDMA Carriers:

1. HDII system coverage is not affected if the NAMPS LPA has enough reserve power.2. This system can handle multiple CDMA carriers. 3. This configuration is only applicable for the HDII 20 channel rack. It does not apply to

LD rack due to the lack of a wideband combiner/attenuator.4. Refer to Chapter 4 for the maximum total average power available from a single LPA.

6:1HDII

NAMPS LPA

PREAMP

CDMAINTERFACE

HDIIINTERFACE

SC9600 SIF

FROM OTHERHDII BAYS

XCVR RACK

(WITH OPTIONALPREAMPLIFIER)

SC9600CDMA MF


6


Option 2: SC9600-D Modem Frame

This configuration also requires the upgrade to the NAMPS LPA which contains a preamplifier andtwo separate input ports for HDII and CDMA signals. The optional LPA output filter whichprovides increased attenuation in the receive band should also be ordered; this reduces the isolationrequired between the transmit antenna and the receive antenna. The SC9600-D configurationprovides SC9600 CDMA capability into an existing HDII analog cell site that presently has enoughreserve power in the LPA(s) to support a CDMA carrier. Since the existing HDII filter rack andLPA frames are reused, this configuration provides a cost effective way of implementing a CDMAoverlay into an existing HDII system.

Figure 6-16: HDII LPA Used by SC9600-D CDMA Carriers

Notes for Figure 6-16: HDII LPA Used by SC9600-D CDMA Carriers:

1. HDII system coverage is not affected if the NAMPS LPA has enough reserve power.2. This system can handle multiple CDMA carriers. 3. This configuration is only applicable for the HDII 20 channel rack. It does not apply to

LD rack due to the lack of a wideband combiner/attenuator.4. Refer to Chapter 4 for the maximum total average power available from a single LPA.

6:1HDII

NAMPS LPA

CDMAINTERFACE

HDIIINTERFACE

RFDS

FROM OTHERHDII BAYS

XCVR RACK

(WITH OPTIONALPREAMPLIFIER)

(OPTIONAL)

PREAMP

SC9600-DCDMA MF


6


6.5.1.1.3 Unapproved Combining Configurations

Ring Combiners

Combining of CDMA transmit signals with AMPS signals using ring combiners is notrecommended. The constraints on the passband amplitude and phase characteristics for the widebandwidth CDMA signal, and the narrow transition region between the CDMA carrier and theAMPS carriers, results in a filter design that would be undesirable because of high insertion loss.Such a filter would have to be tuned for a specific frequency plan, and would change as additionalCDMA carriers are added. A wideband hybrid combiner (3 dB) would be smaller and lessexpensive, while still lossy.

Pseudo-Omni Cell Using Splitters/Combiners

It is possible to construct a unique AMPS cell site configuration using panel antennas with passiveTx splitters and Rx combiners to achieve a pseudo-omni pattern using an omni configuration BTS.While such a configuration would function for CDMA, the risk of performance degradation issignificant. The deliberate creation of a deeply faded field in the antenna overlap areas, without thebenefit of softer handoff, is likely to require increased average power per subscriber. The delayspread between these simulcast signals from each antenna can be less than 1 chip time. Forwardand reverse power control operation in this situation would be more highly taxed. How muchdegradation occurs would depend on the amount of multipath present. This configuration is notrecommended.

6.5.1.2 Common Receive Antenna(s)

Several possible cases of receive antenna sharing are described in the this section.

6.5.1.2.1 HDII Multicoupler (Receive Outputs Serving CDMA BTS)

Four options are available for the HDII multi-carrier. The first option uses the SC9600-D ModemFrame, the second option uses the SC9600 BTS Frame, the third option uses the SC2400 BTSFrame, and the fourth option uses the SC4812T 800 MHz Modem Frame.

Option 1: SC9600-D Modem Frame

The SC9600-D configuration provides SC9600 CDMA capability into an existing HDII analog cellsite that presently has enough reserve power in the LPA(s) to support a CDMA carrier. Since theexisting HDII filter rack and LPA frames are reused, this configuration provides a cost effectiveway of implementing a CDMA overlay into an existing HDII system.


6


Figure 6-17: SC9600-D CDMA-AMPS Configuration, Shared Sector HDII Multicoupler

Notes for Figure 6-17 and Figure 6-18:

1. Consult field/systems engineering for proper attenuators used in the CDMA receivepath. Values shown are typical.

2. No change to the HDII receive path is required.

XCVR20 CHANNEL

Rx

2:1

4:1

MULTI

3 dBPAD

HDII SITE FILTER RACK

6:1

SRF2140B

XCVR

10 CHANNEL XCVR BAY

Preselector

5dB

COUPLEREXTENDER

MATRIX

RxMATRIX

XCVR BAY

RxMATRIX

PAD

SRF2290C

PreselectorSGRF1009A

(OR 7 dBPAD)7dB

PAD

BBX

SC9600-D CDMA MF

MPC

2:12:1 2:1

3 dBPAD BBX

SC9600-D CDMA MF

MPC

2:1 2:12:1


6


Figure 6-18: SC9600-D CDMA-AMPS Configuration, Shared Omni HDII Multicoupler

Option 2: SC9600 BTS Frames

This implementation requires the use of a SC9600 SIF which accepts the CDMA receiver feeds(main and diversity) from available outputs of the HDII multicoupler. This assures no need toreoptimize the HDII receiver path, as well as balanced delay, noise figure, and RF levels forCDMA. This configuration is recommended for field trial systems. Identification of anydegradations to the performance of the CDMA system are to be exposed by site engineeringevaluation.

Eliminating redundant portions of the SIF (filters, etc.) suggests the use of a unique SIF frame (notavailable), and is not supported at this time.


6:1

6:1

SRF2140B

XCVR

20 CHANNEL

4:14:1

2:1

XCVR

4:1

4:1

PreselectorSGRF1009A XCVR BAY

10 CHANNEL XCVR BAY7 dBPAD

0-3 dBPAD

BBX

SC9600-D CDMA MF

MPC

2:1 2:1

BBX

SC9600-D CDMA MF

MPC

2:1 2:1

2:1

2:1

PreselectorSRF2290C

5 dBPAD


6


Figure 6-19: SC9600 CDMA-AMPS Configuration, Shared Sector HDII Multicoupler




Figure 6-20: SC9600 CDMA-AMPS Configuration, Shared Omni HDII Multicoupler

BBX

SC9600 CDMA MFPreselector

SC9600 SIF

5 dBPAD

XCVR20 CHANNEL

Rx

4:1

MULTI

5 dBPAD Multicoupler


6:1

SRF2140B

XCVR

10 CHANNEL XCVR BAY

2:1

2:1

2:1

COUPLEREXTENDER

MATRIX

RxMATRIX

XCVR BAY

RxMATRIX

(OR 7 dBPAD)

2:1

PreselectorSRF2290C


5 dBPAD


6:1

6:1

SRF2140B

BBX


2:1

2:1

2:1

SC9600 SIF

Multicoupler

XCVR

20 CHANNEL

4:14:1

XCVR

4:1

4:1

5 dBPAD

5 dBPAD

XCVR BAY

10 CHANNEL XCVR BAY

2:1


PreselectorSRF2290C

5 dBPAD


6


Option 3: SC2400 BTS Frame

Figure 6-21: SC2400 CDMA-AMPS Configuration, Shared Sector HDII Multicoupler




Figure 6-22: SC2400 CDMA-AMPS Configuration, Shared Omni HDII Multicoupler

BBX

SC2400 CDMA MFPreselector I/O

XCVR20 CHANNEL

Rx

4:1

MULTI

MPC


6:1

SRF2140B

XCVR

10 CHANNEL XCVR BAY

COUPLEREXTENDER

MATRIX

RxMATRIX

XCVR BAY

RxMATRIX

(OR 7 dBPAD)

2:1

2:1

2:1

2:1

2:1

7 dBPAD

2:1

PreselectorSRF2290C


5 dBPAD

3 dB

Option B

3 dBOption A


6:1

6:1

SRF2140B

XCVR

20 CHANNEL

4:14:1

XCVR

4:1

4:1

XCVR BAY

10 CHANNEL XCVR BAY

BBX

SC2400 CDMA MFPreselector I/O

MPC

2:1

2:1

2:1

2:1

2:110 dBPAD

2:1


PreselectorSRF2290C

5 dBPAD

Option B

Option A


6


Option 4: SC4812T 800 MHz Modem Frame

Figure 6-23: SC4812T CDMA-AMPS Configuration, Shared Omni HDII Multicoupler



2. No change to the HDII receive path is required.3. The SC4812T 800 MHz BTS is configured as a stand-alone product. This configuration

does not support Tx antenna sharing.

Figure 6-24: SC4812T CDMA-AMPS Configuration, Shared Sector HDII Multicoupler

HDII Site

Rx Exp.

Rx

TxFilter Rack

(Omni)

6:1

6:1

Rx Exp.

10 dBPad

SC4812TFrame

HDII Site

Rx Exp.

Rx

Tx

3 dBPad

Filter Rack(Sector)

6:1

4:1

Rx Exp.

10 dBPad

SC4812TFrame

MulticouplerExtender


6


6.5.1.2.2 SC9600 SIF (Receive Outputs Serving HDII)

Figure 6-25: CDMA-AMPS Config., Shared SC9600 SIF frame, AMPS/NAMPS Sector Rx


1. Consult field/systems engineering for proper attenuators used in the analog receive path.2. Reoptimization is required for analog operation.

Figure 6-26: CDMA-AMPS Config., Shared SC9600 SIF Frame, AMPS/NAMPS Omni Rx

4:1

Rx M/C

4:1

4:1

SC9600 SIF

4:1

Multicoupler

BBX


XCVR20 CHANNEL

XCVR

2:1

2:1

2:1

EXTENDER

7 dBPAD

XCVR BAY

RxMATRIX

RxMATRIX

PreselectorSRF2290B

7 dBPAD

7 dBPAD

3 dBPAD

2:1

RxMATRIX

10 CHANNEL XCVR BAYPreselectorSRF2290B

SC9600 SIF

Multicoupler

4:1

BBX

SC9600 CDMA MF

Preselector

4:1

4:1

XCVR

20 CHANNEL

XCVR

4:1

2:1

2:1

2:1

Rx M/CEXTENDER 3 dB

PAD 7 dBPAD

2:1

7 dBPAD

7 dBPAD 4:1

XCVR BAY

4:14:1

4:1

10 CHANNEL XCVR BAY

PreselectorSRF2290B

PreselectorSRF2290B


6


6.5.2 Duplexed AMPS/CDMA Antennas

The use of duplexers implies zero isolation between a family of transmit carriers and a family ofreceive carriers. Under these conditions, any transmit IM spurs created by non-linearities, in activeor passive components, in the common path might produce significant interferers in the receiveband. Duplexers can be made to work in some applications under ideal conditions; but anyimperfections introduced by aging, lightning, thermal cycling, bi-metallic interaction or othercommon stresses can reduce system performance to below acceptable levels.

Motorola does not recommend the use of duplexers for AMPS/CDMA systems at 800 MHz;however, certain situations may require their use. Intermodulation products introduced by theduplexed antenna system may degrade either the CDMA or the analog system depending upon theduplexing scheme implemented. For further clarification, refer to Figure 6-27 and theaccompanying text.

Duplexing a 800 MHz CDMA system has been broken down into three options. These are the onlyoptions that are considered to be acceptable at this time. Any duplexing configurations that aredifferent from what is shown below would require evaluation of its acceptability. The followingtable and figure illustrate three possible configurations where duplexers could be used with CDMAand AMPS carriers and the acceptability of each:

Figure 6-27: CDMA Duplexing Options

Table 6-7: Possible Duplexed Configurations

CDMA Tx AMPS Tx CDMA & AMPS Tx

CDMA&

AMPSRx

Option #1: Unconditionally acceptable for one CDMA carrier. Conditionally acceptable for multiple CDMA carriers.

Option #2: Unconditionally acceptable for SIG only. Conditionally acceptable for multiple AMPS carriers. NOT acceptable for multiple AMPS carriers including SIG.

Option #3: Conditionally acceptable for one or multiple CDMA and AMPS SIG only. NOT acceptable for CDMA and multiple AMPS voice carriers.

Option #1 Option #2 Option #3

CDMATx

Tx

Rx

Tx

Rx

Tx

Rx

CDMA& AMPS SIG

CDMA&

RxAMPS

CDMA&

RxAMPS

CDMA&

RxAMPS

AMPSVoice or SIG


6


Option 1: Duplexing One CDMA Transmit Carrier with CDMA and/or AMPS Receive.

This is the recommended implementation. Duplexing multiple CDMA transmit carriers withCDMA and/or AMPS receive may be acceptable if the proper IM prevention site engineering,frequency planning, and maintenance techniques are employed.

Option 2: Duplexing AMPS Voice or One AMPS SIG Channel (control channel) with CDMA and/or AMPS Receive.

This is an acceptable configuration. Duplexing multiple AMPS voice transmit carriers with CDMAand/or AMPS receive may be acceptable with proper IM prevention site engineering, frequencyplanning, and maintenance techniques. This is the least desired option due to the complexity ofimplementing and maintaining the proper IM frequency planning techniques for the multipleAMPS carriers. Duplexing multiple AMPS voice and SIG carriers with CDMA and/or AMPSreceive is not acceptable.

Option 3: Duplexing One or Multiple CDMA and AMPS SIG Carriers with CDMA and/or AMPS Receive

This may be an acceptable configuration if the proper IM prevention site engineering, frequencyplanning, and maintenance techniques are employed. Duplexing one or multiple CDMA andmultiple AMPS voice carriers with CDMA and/or AMPS receive is not acceptable.

The only inherently acceptable application of a duplexed CDMA system is to duplex the Tx of oneCDMA carrier or one AMPS SIG carrier with the Rx of CDMA and/or AMPS. This is alwaysacceptable because there is no transmitter generated receive band IM for one carrier.

Configurations that are inherently not acceptable are multiple AMPS carriers, including signallingchannels, combined with CDMA carriers. These configurations are considered unacceptablebecause there is a potential problem of in-band intermodulation generation with difficult spuriousfrequency location prediction. The IM frequency planning mentioned above refers to planning thetransmit frequencies into the duplexer such that high energy, low order IM products, do notinterfere with the planned receive frequencies of the duplexer. The potential for interference anddifficulty in spurious location prediction increases significantly when using EAMPS and NAMPSchannels due to the increased number of carriers used in such configurations. The increase offrequency spacing of EAMPS channels also allows IM products, as low as fifth order for non-wireline systems, and seventh order for wireline systems to potentially exist (non-expanded AMPSsystems only had potential for eleventh order IM products and higher).

Combined analog and CDMA systems, that are considered conditionally acceptable, require siteengineering and preventative maintenance in order to provide acceptable system performance.Some of the guidelines for site engineering and preventative maintenance are presented inSection 6.4.3.3.


6


6.6 GPS AntennasThe installation of a GPS antenna and associated cabling is discussed later in this document. As therecommendations for GPS antenna mounting (etc.) are common for both 800 MHz and 1900 MHzno further guidelines will be proposed here.

6.7 Ancillary Antenna System Components

In addition to a duplexer, there are other RF components that are considered part of the antennasystem. Some of the more common components will be highlighted next.

6.7.1 Directional Couplers

A directional coupler is a power "sampler" with selective directivity. It is a relatively simplewaveguide device that is used to sample the power on a transmission line, both in the forward andreverse directions. The sampling (or coupling) performed by the directional coupler is attenuatedat a level (typically 30 dB) as to not affect the power on the transmission line, (i.e) it is samplingrather than splitting. In the Motorola antenna system, directional couplers are used for theconnection of the RFDS (see Section 6.8 for more information). For PCS applications thedirectional couplers are connected in line with the transmission coax and may be mounted eitherat the waveguide (cable entry window) or within a 19" rack.

6.7.2 Surge (Lightning) Protectors

To complement the existing internal and external grounding system (Please Reference:"Motorola’s Grounding Guideline for Cellular Radio Installations" - 68P81150E62), alltransmission cables entering the cell site must be protected by devices such as "grounding kits" andtube or MOV protectors, commonly called "Surge or Lightning Protectors". Surge protectors arerequired in order to dissipate surge energy that can be generated from a local lightning strikes orother energy sources on the transmission lines.

A single surge protection unit is required (in addition to sufficient grounding equipment) for everytransmission cable entering the site (Tx/Rx/GPS). The following description outlines the Motorolarecommended surge protection unit. Please contact Motorola ancillary (dropship) for specificproduct part numbers.

The Huber and Suhner 3400 Series protector consists of a coaxial transmission line and anoptimized 1/4-wave shorting stub which is located between the center conductor and outerconductor. These protectors are designed as coaxial feedthroughs. A V-groove washer made of softcopper ensures that a low contact resistance between protector body and the mounting wall isachieved.


6


6.7.3 Transmission Line

The standard type of transmission line used for antenna systems is coaxial cable. There are anumber of factors that must be considered in the choice of coaxial cable both in terms of RFperformance and physical application.

6.7.3.1 RF Performance of Transmission Lines

For RF performance, the most important parameters in the choice of coaxial cable include,attenuation loss for a given frequency/ambient temperature, the VSWR (Voltage Standing WaveRatio), return loss, power rating and insulation properties of the cable.

The loss of a coaxial cable will vary with frequency. Generally, the higher the frequency, thegreater the loss for a fixed distance. Transmission line losses are incorporated into link budgetcalculations to determine the total loss of a RF transmission path. As this "path loss" will impactcell radius, the loss associated with the transmission cable should be kept to a minimum. Differenttypes of coaxial cable are available and those with superior electrical properties (lower loss) arenormally both larger (thickness) and more expensive (per meter).

The VSWR rating of a cable is the additional load allowed due to the mismatch of impedance. Thesystem engineer should ensure that a cable with a VSWR rating between 1.01:1 and 1.15:1 isordered. A cable which allows higher VSWR and hence load (due to reflected power) will increasethe attenuation of the transmission line. Note that a VSWR of 1.15:1 equates to 23 dB return loss.

The return loss of a cable can be directly related to the VSWR rating. The return loss of atransmission cable can be considered as the difference in power in the forward and reversedirections when measured into a well matched load. All other things being equal, the higher thereturn loss the better the cable. The system engineer should choose a transmission cable with areturn loss of 23 dB or better.

Please refer to the antenna parameter Section 6.2.5 for an explanation on how to convert VSWR toreturn loss.

The peak power rating of a coaxial cable refers to the maximum amount of power that can be safelysent over the coax. The power rating is determined by the type of insulation material and thestructure between the inner and outer conductors of the cable (dielectric).

Power rating is not expected to be a problem for low powered CDMA PCS applications, asstandard cable power ratings are rarely reached even for multiple carrier cellular configurations.

6.7.3.2 Physical Characteristics

The physical characteristics of coaxial cable should not be overlooked in the choice of transmissionline. Although from a system perspective, the goal may be to limit loss, site specific installationcriteria may limit the type of coaxial cable that can be used. The system engineer should consider;the cable length required, minimum bending radius allowed, the weight of multiple cables, the


6


effects of wind loading, the ability to correctly mount/ground the cables and the cost of installationand expansion.

Generally, thicker cables allow less loss over a given distance but require more substantialhardware for mounting and grounding. The system engineer should plan for an achievabletransmission line loss during initial system planning, bearing in mind both the optimum cableperformance and the physical limitations of the cell site. During preliminary planning, it isrecommended that the system engineer plans for approximately 2-3 dB total transmission line loss(including transition cables).

6.7.3.3 Choice of Transmission Line

The recommended type of transmission line in terms of performance versus cost, is foam dielectriccoaxial cable. The dielectric material used is a closed-cell, low density polyethylene foam whichprevents water penetration and allows for repeated bending. A solid corrugated outer conductorresults in low loss, high power handling and continuous RF/EMI shielding. The combination ofboth a solid inner and outer conductor minimizes the potential for intermodulation generation. Thefollowing table gives an example of typical foam dielectric cables and their respective attenuationper 100 ft. at an operating frequency of 1850 MHz. At lower operating frequencies the attenuationvalues would be lower.

Table 6-8: Transmission Line Performance.

6.7.4 Transition Feeder Cables (Jumper Cables)

While the system engineer is considering the transmission line loss within the link budget, the lossof transition cables or “Jumpers” that may be required both at the antenna and equipment hardwarealso need to be included. These jumpers will generally be required due to the physical limitationsof low loss thicker cable (i.e. the bending radius). The length of these jumper cables should be keptto within a few meters and the associated loss of both the cable and connectors should becalculated. The following table outlines a typical jumper cable type, Andrews 1/2" Superflexoperating at 1850 MHz. Different characteristics would result if the operating frequency waschanged.

CharacteristicAndrews

LDF5-50A (7/8")

Andrews LDF6-50 (1-1/4")

AndrewsLDF7-50(1-5/8")

Attenuation dB/100ft @ 1850 MHz 1.88 dB 1.38 dB 1.19 dBImpedance (Ohms) 50 50 50Peak Power Rating @ 1850 MHz (kW) 1.45 2.20 2.96DC Breakdown volts 6000 9000 11000Diameter over jacket (mm) 28 39.4 50Minimum bending radius (mm) 250 380 510Cable Weight (kg/m) 0.49 0.98 1.36


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Table 6-9: Transition Cable Characteristics.

6.8 RF Diagnostic System

The Motorola RF Diagnostic System (RFDS) is a self contained unit within the BTS architecturethat monitors and tests the RF paths of the BTS site. The aim of the unit is to identify faults ordeteriorated conditions that are sufficient to impair the performance of the cell site RF channels.For the SC4812T (indoor) product, the RFDS is 19" rack mountable. The RFDS for the SC4812ET/ET Lite is incorporated into the product (within the cabinet).

The RFDS connects to the RF paths of the cell site via pre-installed directional couplers (see above)and the RFDS itself is comprised of the following equipment:

• Directional Couplers• Controller Card• A Test Subscriber Unit• Up to 2 Antenna Selector Units

The RFDS measurement unit consists of directional couplers which sense and couple test signalsto and from the RF system, an RF switch that connects "test equipment" to the RF path under testand a controller which is used to setup/execute tests via the RGLI card. Access points are providedto allow external measuring instruments to be connected, this means that tests not performed bythe RFDS may be conducted. Examples are transmitter frequency, in-band transmit spuriousoutput, transmit occupied bandwidth and adjacent channel leakage.

The RFDS will allow remote testing through interface connections to the Operations andMaintenance Centre-Radio (OMC-R) and/or the Local Maintenance Facility (LMF). The firstphase of RFDS implementation (with initial BTS installations) will support call terminationloopback and the following phases will include test features such as: call origination withsubscriber status reports, forward (Tx) pilot channel power, Tx/Rx antenna VSWR, and forwardFER rate.

The RFDS can improve system performance by providing a quick and efficient method ofdetecting faults and it will provide the operator with the earliest notification of degraded equipmentperformance.

Characteristic Andrews FSJ4-50B

Attenuation dB/100ft @ 1850 MHz 5.17 dBImpedance (Ohms) 50Peak Power Rating @ 1850 MHz (kW) 0.625DC Breakdown volts 2500Diameter over jacket (mm) 13.2Minimum bending radius (mm) 32Cable Weight (kg/m) 0.21



Table of Contents

7.1 Dual Polarized Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 37.1.1 Fundamental Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 3

7.1.1.1 Dual Polarization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 37.1.1.2 Diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 47.1.1.3 Diversity Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 57.1.1.4 Cross-Correlation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 7

7.1.2 Isolation Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 117.1.3 Performance Impacts - Industry and Motorola Findings . . . . . . . 7 - 127.1.4 Antenna Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 14

7.1.4.1 Dual Polarized Antennas versus Singularly Polarized Antennas . . 7 - 147.1.4.2 Antenna Selection Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 15

7.1.5 Transmission at 45° . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 157.1.6 Incorporation of Dual Polarized Antennas into a Link Budget . . 7 - 167.1.7 Dual Polarized Antenna Summary . . . . . . . . . . . . . . . . . . . . . . . . 7 - 17

7.2 In-Building Distributed Antenna Systems . . . . . . . . . . . . . . . . . . . . . . . 7 - 187.2.1 In-Building System Architecture Overview. . . . . . . . . . . . . . . . . 7 - 197.2.2 Coaxial Cable System Design Using A Link Budget. . . . . . . . . . 7 - 20

7.2.2.1 Design Procedure Flow Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 207.2.2.2 Gathering Building Information . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 217.2.2.3 Determining the Base Station Location. . . . . . . . . . . . . . . . . . . . . . 7 - 237.2.2.4 Estimating the Antenna Placement within the Building . . . . . . . . . 7 - 247.2.2.5 Selecting the Antenna Type: Omni vs. Directional . . . . . . . . . . . . . 7 - 247.2.2.6 Choosing the Base Station Type . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 257.2.2.7 Choosing the Cable Topology: Splitters, Couplers, and Taps . . . . . 7 - 257.2.2.8 Estimating Cable Lengths from the Base Station to the Antennas . 7 - 307.2.2.9 Selecting the Coaxial Cable Type . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 307.2.2.10 Link Budgets For In-Building Design. . . . . . . . . . . . . . . . . . . . . . . 7 - 327.2.2.11 Evaluating the First Pass and Iterating the Design . . . . . . . . . . . . . 7 - 38

7.2.3 Active Coaxial Cable System Design. . . . . . . . . . . . . . . . . . . . . . 7 - 387.2.3.1 Downlink Amplifier Design Considerations . . . . . . . . . . . . . . . . . . 7 - 397.2.3.2 Uplink Amplifier Design Considerations . . . . . . . . . . . . . . . . . . . . 7 - 407.2.3.3 Optimizing Amplifier Placement . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 45

7.2.4 Fiber Optics for In-Building Systems. . . . . . . . . . . . . . . . . . . . . . 7 - 477.2.4.1 Fiber Optic Distribution System Architecture. . . . . . . . . . . . . . . . . 7 - 477.2.4.2 When To Use Fiber Optics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 477.2.4.3 Fiber Optic System Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 48

7.2.5 In-Building Antenna Systems Summary . . . . . . . . . . . . . . . . . . . 7 - 49

7.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 50

Chapter

7 RF Antenna Systems -Advanced Topics


7

CDMA/CDMA2000 1X RF Planning GuideChapter 7: RF Antenna Systems - Advanced Topics

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7.1 Dual Polarized Antennas

The availability of sufficient antenna tower/platform space to house required cellular/PCSantennas is becoming more and more of an issue in recent years with the addition of new wirelesstechnologies, both cellular and non-cellular. As a result, operators are looking for ways to reducethe amount of physical equipment that is required to be mounted on the antenna tower or platform.The use of dual polarized antennas offers one such solution, provided that the technology beingsupported by them does not suffer a significant impact in performance as a result.

It is the goal of this section to present the fundamental concepts associated with dual polarizedantennas, discuss any potential performance impacts and provide guidelines that can be used toassist the system engineer in deciding which dual polarization antenna design is optimum, if any,for a particular CDMA application. The performance impacts provided in this section were madefrom general observations taken from several different industry and Motorola studies that werefound on this subject.

7.1.1 Fundamental Concepts

In order to be able to make an educated decision as to which base station antenna polarizationscheme to use (single vs. dual, horizontal/vertical vs. slant 45°, etc.), it is important to understandthe various fundamental concepts associated with polarization diversity. Some key concepts arediscussed below.

7.1.1.1 Dual Polarization

Conventional cellular and PCS antennas are typically 1/2 wavelength dipoles designed for vertical(usually) or horizontal polarization. Recall that a dipole produces a linearly polarized signal. Thepolarization itself is achieved by the specific placement of the elements within the antenna stack.If the alignment produces an E vector (electric field vector) which is vertical with respect to theearth, the antenna is considered vertically polarized. In contrast, if the alignment produces an Evector which is horizontal with respect to the earth, the antenna is considered horizontallypolarized.

In a dual polarized antenna, the elements within the antenna housing are alternately placed. Asdepicted in Figure 7-1 Dual Polarization Antenna Element Configurations, some antenna modelsalternate the polarization from horizontal to vertical, others set the elements such that thepolarization is crossed at 45° (sometimes referred to as slant polarization).


7


Figure 7-1: Dual Polarization Antenna Element Configurations

PCS and cellular dual polarized antennas are orthogonally polarized (horizontal/vertical or slant45°). As will be discussed in more detail below, the antenna isolation and antenna crosspolarization suppression (antenna coupling effects) need to be considered. Orthogonally polarizedantennas have their polarizations ideally isolated and the cross polarization suppression is mostdistant.

Much like a singularly polarized antenna, a dual polarized antenna is capable of handling multiplefrequencies. If so desired, a duplexer can be used with the dual polarized antenna to combinetransmit and receive signals onto one set of elements, although there are issues associated with thisconfiguration, as discussed in Section 7.1.2 and Section 7.1.5.

7.1.1.2 Diversity

In communication systems, diversity is used to increase the probability of receiving a given signal(message), which improves the ability of interpreting that signal (message). ‘Distinct parts’ areneeded so that if one ‘part’ alone fails to deliver the message, perhaps a second ‘part’ will succeed.However, diversity is not simply a backup. Diversity is used to increase the probability ofreceiving a good signal, whether two signal components are combined or the stronger of the twosignal components is selected. The use of the phrase ‘signal components’ here is meant toemphasize that one message or signal is transmitted, then split into separate components by variousmeans (such as reflection, refraction, scattering, etc.). The components of the message are thenused individually, or combined, to recompose the original message.

Examples of diversity being utilized in CDMA can be seen throughout the infrastructure. Thefollowing is a brief list, differentiated by the type of diversity that is offered.

Y

X

V1V2

x-y plane

Y

X

V1

V2

(front view)

Slant 45°

x-y plane

(front view)

Horizontal/Vertical


7


• Time Diversity: Error Control Coding, Data Repeat Schemes, Interleaving

• Frequency Diversity: Carrier Bandwidth versus Coherence Bandwidth of the Channel

• Path Diversity: Soft Handoff/Multipath Diversity

• Spacial Diversity: Receive Antenna Diversity (as provided by the physical separationof antennas)

• Polarization Diversity: Receive Antenna Diversity (proposed topic of this section)

Spacial and polarization diversity are techniques used in what is commonly referred to as ‘antennadiversity’. This section focuses on base station receiver antenna diversity, specifically that whichcan be provided by dual polarization. Antenna diversity is approached with the hope that if oneradio path experiences deep fading, then a second independent path may have a signal with areasonable probability of not being in a fade at the same time.

Presently, commercial CDMA systems typically use two antennas at the base station for diversityon the reverse link (subscriber to base station signals). As was mentioned in Chapter 6, the twoantennas are separated (normally a horizontal separation) by at least 10 wavelengths at 800 MHzand at least 20 wavelengths at 1800 MHz. In this situation, the engineer assumes the signalcomponents into each antenna will have a polarization identical to the receive polarization1.However, if a transmitted signal scatters, and one of the scatter components undergoes additionalscattering, eventually some signal components may change polarization. Polarization diversitycould then take advantage of this change. A system engineer could use a diversity antenna whichhas a polarization which is unique as compared to the primary antenna. A dual polarized antennais, in fact, two antennas in a single housing with one antenna polarized orthogonal to the second.

7.1.1.3 Diversity Gain

Diversity gain measures the improvement in signal reception due to the utilization of a diversitypath. It is the difference in signal level between one reference signal and the signal received at theoutput of the diversity combiner for a given probability or signal reliability. Signal reliability is theprobability that the signal is adequate for a given period of time under the conditions encountered(usually measured between a 90% and 99% level)2.

Diversity gain can be measured as improvement in the signal-to-noise ratio (SNR) or Eb/No inCDMA. It is not a difference in SNRs, but rather a comparison between the final received SNR andwhat that SNR would have been without diversity. In real-world conditions, it may be difficult tomeasure the SNR, so measurements are typically taken of the signal plus the noise.

When a system engineer chooses to use antenna diversity, the type of diversity selected is based on

1. In CDMA, the base station transmit and receive antennas normally utilize linear vertical polarization.

2. Wahlberg, Ulrik. 1997. “Polarization Diversity for Cellular Base Stations at 1800 MHz.” Revision 1.0.Allgon.


7


the probability of receiving an uncorrelated3 signal. Generally speaking, in clean, high power, line-of-sight paths, diversity may be unnecessary. However, in CDMA systems, receive diversity ishighly recommended to achieve desired capacity and performance. If the probability of the signalto undergo a fade is high, then some type of diversity is normally used. [Note: In CDMA, even ifthe signals are correlated, the diversity gain has been found to improve uplink capacity since thesubscriber’s transmit power required is reduced (see Section 7.1.1.4.1). CDMA also uses othertechniques such as convolutional encoding to help capture enough information from the signal tounderstand the message.]

Diversity gain is affected directly by the correlation of the signal envelopes, branch imbalance andalso by the combining technique4. The greatest gain is achieved when two uncorrelated signals arereceived with equivalent energy (balanced branches) and combined.

Two branches (of a dual polarized or spacial diversity antenna system) can be individually selectedor combined to improve the single branch performance. In a two branch selection diversity system,it has been found that the potential savings in power offered is equal to approximately 10 dB (at99% reliability, see Figure 7-2) as compared to a single branch. In a two branch combiningdiversity system, the power savings (at 99% reliability) is equal to approximately 11.5 dB ascompared to a single branch, or a 1.5 dB improvement over selection diversity5. In CDMA, thecombining diversity method is used.

3. Correlation of signals literally means the “same-ness” of those signals.

4. There are four general methods used in selecting or combining signals in a diversity system:- Selection Diversity- Maximum-Ratio Combining (a.k.a. Maximal Ratio Combining)- Equal-Gain Combining- Switched Combining

5. Jakes, William C. 1974. “Microwave Mobile Communications.” New York. American Telephone andTelegraph Company. Reissued in Cooperation with IEEE Communications Society. pp. 309-324.


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Figure 7-2: Probability Distribution SNR for M-branch Selection Diversity System

7.1.1.4 Cross-Correlation

Cross-correlation is used to measure the correlation between two signal envelopes. In general, theliterature shows that diversity gain is best realized when the signal envelope cross-correlationcoefficient is under 0.7. If the signal envelope cross-correlation coefficient, on the other hand, isequal to 1.0, then the system is identical to a system without diversity. This is a key concept toremember. For CDMA systems utilizing spacial diversity, (at 1800 MHz) 20 wavelengthsseparation is used between the main Rx and the spacial diversity Rx antennas. This separation isnecessary to achieve a signal envelope cross-correlation coefficient of less than or equal to 0.7.

Signal correlation is dependent on the path loss and fading conditions encountered as the signaltransverses space. The type of fading depends on the environment and has both small scale andlarge scale characteristics.

Small scale fading (or fast fading) is that which creates deep and rapid amplitude fluctuations.These deep fades are created by summing multiple signals, with random phases and amplitudes, ina highly reflective environment. Normally, fast fading implies a Rayleigh fading distribution.

10 dB

Probability Distribution SNR γs for M-BranchSelection Diversity System.Γ=SNR on one Branch.


7


The Rayleigh probability density function (pdf) is shown in Figure 7-3. If statistically independentsamples are considered, the reception of a weak signal from a Rayleigh pdf infers that theprobability of receiving a stronger signal (shaded area) with the next sample is quite good.

Figure 7-3: Rayleigh Probability Density Function

Large scale fading (slow fading) is used to describe fading which occurs over long distances(several hundred or even thousands of meters apart). Large scale fading is normally due toshadowing in both the terrain profile and the nature of the surroundings. This type of fading is log-normally distributed and in urban environments has a standard deviation of approximately 10 dB.

While signals normally undergo large scale fading, it is in the small scale fading environmentswhere signal components are found to be uncorrelated, and therefore diversity combining makes asignificant impact.

The following examples show the difference in diversity gain if two correlated signals are receivedas opposed to two uncorrelated signals.

7.1.1.4.1 Reception of Highly Correlated Signals and Their Effect on Diversity Gain

Consider a system with a spatially diversified pair of antennas, each of which is verticallypolarized. If a subscriber transmits a signal in an unobstructed environment (line-of sight) towardsthe antenna pair, then the signal undergoes free-space path loss (assuming no reflection) and isreceived, highly correlated, at each antenna branch (see Figure 7-4).

Figure 7-4: Reception of Highly Correlated Signals

Received signal envelope voltage r (volts)

Weak RxSignal

Probability of Receivinga Stronger Signal

Two Vertically Polarized Antennas(front view)

Original Signal Faded Received SignalHighly Correlated at Each Branch


7


If the system used a selection method, the gain achieved by utilizing diversity is zero since thebranches have identical received signals.

If the system combines the identical received signal energy using a maximum ratio combiningmethod, then the maximum gain achieved is 3 dB (i.e. doubling the power of a single branch). Thegain achieved will never exceed 3 dB for correlated signals. This also applies to equal gaincombining.

7.1.1.4.2 Reception of Uncorrelated Signals and Their Effect on Diversity Gain

Diversity gain is at its highest value when the signals received at the spatially separated Rxantennas are uncorrelated. In this case, the received signals have different amounts of fading (seeFigure 7-5 Reception of Uncorrelated Signals). If the system uses selection or sampling methods,then the signal with the greatest SNR (lowest FER) is chosen. For example, assume the signalenergy in branch A is four times as strong as that of branch B. In this example, diversity providesa 6 dB gain over a system without the diversity antenna. Although in this example the mean signallevels of each branch are not balanced, it is important to know that diversity gain is greatest whenthe mean signal levels of the two branches are balanced.

If the system receives uncorrelated signals using a combining method, the maximum gain achievedcan vary significantly.

Figure 7-5: Reception of Uncorrelated Signals

To emphasize the importance of uncorrelated signals, assume the minimum receive level requiredis set at Level RCV as shown in Figure 7-6. If the signals are correlated and a diversity combiningmethod is assumed, then the greatest improvement would be a 3 dB signal gain. If the originalsignal was received below the minimum requirements, it is possible that the improvement due todiversity combining may not be sufficient to provide a minimum number of good frames. In thiscase, the frame erasure rate (FER), or SNR would be poor.6

6. Here the assumption is that the signal portion doubles, but it is important to note that the noise also doubles.

Two Vertically Polarized Antennas(front view)

Original SignalFaded Received Signal

Uncorrelated at Each Branch

A B


7


Figure 7-6: Correlated Signal Diversity Gain

In Figure 7-7, two uncorrelated signals are combined. In this example, the system samples eachsignal and the combined signal exceeds the minimum required receive level.

Figure 7-7: Uncorrelated Signal Diversity Gain

As a subscriber travels in dense clutter, such as urban and suburban environments, its transmittedsignal is reflected and undergoes various degrees of fading. Sometimes the base station antenna isline-of-sight with the subscriber and sometimes it is shadowed. It is in these fading conditions thatthe benefit of the diversity gain is intended to capture enough energy to interpret the message (seeFigure 7-8).

Level RCV (minimum)

Original Signal Correlated Signal Diversity Gain

Bad Frames

3 dB

Level RCV

Original Signal Uncorrelated Signal Diversity GainUncorrelated Signal

(minimum)


7


Figure 7-8: Uncorrelated Signal Diversity Gain

7.1.2 Isolation Considerations

As was discussed in Section 6.3.1, there are isolation requirements that exist between both Tx andRx antennas and between main and diversity Rx antennas that are primarily provided by thephysical separation. However, since both Rx antenna elements and possibly a third Tx antennaelement occupy the same dual polarized antenna housing, physical isolation requirements arereplaced by port-to-port isolation requirements. Port-to-port isolation is measured at the input ofthe base station equipment between the bottom jumpers of the antenna.

As with physically separated base station antennas, if the isolation requirements are not met withinthe antenna specifications, then the system engineer will need to consider using external band passfilters (for the Rx band at the Rx ports) or duplexers.

Note that antenna isolation is not dependent on the angles α and β, as shown in Figure 7-9.7

Figure 7-9: Theoretical Model for Base Station Polarization Diversity

7. Kozono, S. 1985. “Base Station Polarization Diversity Reception for Mobile Radio.” IEEE Transactionson Vehicular Technology. Vol. VT-33. No. 4. pp. 301-306.

Signal A

Signal A’

Fade Regionof

Signal A

As the subscriber travels, its transmitted signal is received with varying fades. If a signal is undergoing a deep fade, thenan uncorrelated signal can save the call (even if its mean energy level is weaker). Intuitively, when the signal is in a fade, the slower the subscriber speed, the higher the probability of continued signal fading.

Minimum RequiredRx Signal Strength

Y

X

V1V2 α

β

Z

X

x-y plane x-z plane

Multipath

Main Beam

(front view) (top view)


7


However, cross polarization suppression, or cross coupling, is dependent on α and β. It can beshown8 that because of this dependence, orthogonally polarized dual pole antennas are ideallyisolated. This is why dual polarized antennas are designed with orthogonal branches.

The orthogonality of a dual polarized antenna is specified by the antenna cross polarizationdiscrimination. This is the ratio of the outputs from the co-polarized and cross-polarized portswhen an antenna receives a signal from one plane (i.e. co-planar). As an example, if a horizontal/vertical dual polarized antenna receives a signal which is vertically polarized, then the antenna isconsidered to have good orthogonality if a very small portion of the signal is received at thehorizontal port. Likewise, a large portion of the signal should be received at the vertical port. Goodorthogonality has an antenna cross polarization discrimination value of about +20 dB (or greater).Poor orthogonality can push the antenna cross polarization discrimination value down to 0 dB (orless). Antenna cross polarization discrimination is generally required to be greater than +15 dB9.[Note: The term antenna cross polarization discrimination (AXPD) differs from the term crosspolarization discrimination (XPD). AXPD is the measure of orthogonality of the antenna. XPD isthe power ratio of the antenna branches.]

7.1.3 Performance Impacts - Industry and Motorola Findings

Many studies on the performance of a polarization diversity system utilizing dual polarizedantennas have been performed throughout the industry. A consolidation of various findings isprovided below. For more detailed information, consult the provided references (see Section 7.3).

NOTE: Most of the studies observed were completed on systems other than CDMA. All studiesnot done on CDMA systems focused on the signal envelope and therefore, focused on the signaldecorrelation and received signal strength.10 In a cellular CDMA system, power control willdirectly effect the received signal strength, making it a nearly impossible task to measure anychange from one diversity scheme to another. It is precisely because of the power control issues inCDMA that Motorola chose to study the received Eb/No requirements. Branch imbalance andsignal correlation were included in the study. Branch imbalance, rather than the signal correlation,showed a greater impact to the quality of the diversity scheme (the greater the branch imbalance,the smaller the diversity gain). It is unclear at this time as to the impact polarization diversity mayhave on CDMA specific issues such as power control. The power control is both an open andclosed loop process which relies on measured signal strength and Eb/No (for correction). If the loopbecomes imbalanced, the impact on capacity or quality could be significant.

8. Wahlberg, Ulrik. 1997. "Polarization Diversity for Cellular Base Stations at 1800 MHz." Revision 1.0.Allgon.

9. This number may vary per antenna manufacturer. Motorola recommends a minimum 34 dB isolationrequirement between the Tx and Rx branches, therefore if the separation is rated to be 15 dB, the systemengineer will need to insert a duplexer to ensure at least 34 dB separation.

10. This is often referred to as continuous wave (CW) testing.


7


The effect of surrounding clutter type:

It has been shown11 that clutter type greatly effects the ability of the signal to change polarizationsufficiently enough to be received decorrelated at the base station antennas. The denser the clutter,the higher the probability of receiving a decorrelated signal at each polarization. This finding wasconsistent throughout the studies. However, there appeared to be a greater branch imbalance ifhorizontal/vertical polarizations were used as opposed to slant 45° polarizations, and it follows thatdue to the large branch imbalance, diversity gain degrades.

The effect of subscriber unit antenna tilting:

Several studies transmitted signals utilizing varying degrees of subscriber transmit antennainclination. Some studies tested performance at several different angles; however, only tests at 0°and 45° subscriber inclinations were common in each study. Reviewing this aspect of the data, itappeared that larger values in diversity gain were achieved when the subscriber was inclined at 45°.For example, a study provided in Vaughan’s paper showed that a subscriber transmitting at 45° hada 1.7 dB improvement in diversity gain over a subscriber transmitting at a 0° inclination. In thisstudy, a horizontal/vertical polarized base station antenna was used and the data was collected froman urban clutter environment. Similarly, if a slant 45° dual polarized base station antenna was used,then a 0.3 dB improvement was shown for the subscriber transmitting at an inclination of 45°versus 0°. The results from the latter study also shows that the slant 45° dual polarized base stationantenna performs more consistently than the horizontal/vertical polarization.

It is important to note that in all of the studies, the improvement of using polarization diversityversus spacial diversity NEVER exceeded a 1 dB improvement (base station received power). Inmost cases, the polarization diversity performed worse than spacial diversity. Although the worstcase results showed a 2.7 dB degradation, the polarization diversity was normally within 1 dB ofthe spacial diversity results (base station received power).

The effect of branch imbalance and correlation:

The Motorola lab study12 examined Rayleigh distributed signal envelopes. The test verified thatbranch imbalance decreased diversity gain. The test also seemed to show that correlated signalsachieved greater gain than uncorrelated signals. This result seemed to counter the common findingin diversity systems; however, the data was calculated using a combined-minus-maximum-received-signal-strength equation and not the standard diversity gain equation. Diversity gain wasmeasured as the combined Eb/No into the system, less the maximum of the Eb/No received in eitherbranch. The maximum 3 dB gain achieved agrees with the maximum 3 dB gain of combining twoidentical (correlated) signals (discussed in Section 7.1.1.4). The greatest input from the Motorolastudies was the observation that Eb/No and power control issues also needed to be addressed whenstudying antenna diversity systems for CDMA technology.

11. Vaughan, Rodney G. 1990. “Polarization Diversity in Mobile Communications.” IEEE Transactions onVehicular Technology. Vol. 39. No. 3. (August): 177-186.

12. Tobin, Joe, Rob Nikides, Devesh Patel, Edward Golovin. 1997. “CDMA Dual Pole Antenna Testing -Arlington Heights, IL.” Version 1.0. Motorola.


7


Table 7-1 shows data Motorola collected in a field trial test in Israel13. It confirms that the branchimbalance was a greater issue than the correlation. Remember, branch imbalance refers to theamount of energy received at each branch, where correlation refers to the “sameness” of the signalcomponents received. This table goes on to show that the Eb/No requirement was larger for the dualpolarized antenna system (albeit very slightly), which also translates into a slight degradation ofperformance. And finally, Motorola shows little change in diversity gain between the two diversitytechniques. This data was collected in an urban clutter environment.

7.1.4 Antenna Selection

The following sections provide additional information to consider before selecting a dual polarizedantenna.

7.1.4.1 Dual Polarized Antennas versus Singularly Polarized Antennas

The most obvious advantage with using a dual polarized antenna, is the elimination of a secondreceive antenna unit (and possibly a third transmit antenna unit, if a duplexer or 3-port dualpolarized antenna is used). This saves on real estate and mounting hardware.

Due to the fact that elements are alternated, and the number of elements per pole are reduced,antenna gain is typically decreased in a dual polarized antenna (or the length of the antenna isincreased to accommodate the extra elements). Therefore, improved diversity gain may beachieved at the expense of antenna gain (for like-sized units). This may be an acceptable trade off,if the diversity gain is sufficient and range is not an issue. Otherwise, the loss of signal due toantenna gain may be intolerable. Therefore, dual polarized antennas should not be utilized to solverange problems. If the longer unit is selected for improved gain, tower loading issues will need tobe readdressed.

13. Golovin, Edward. 1998. “A Comparison of CDMA Reverse Link Performance with Base Station Spatialand Polarization Diversity Reception (Motorola Israel Measurement Campaign in Urban Area at 900 MHz)”Version 2.0. Motorola.

Table 7-1: Motorola Data Table

Parameters (average over all locations)

Spacial Diversity (two vertically polarized antennas)

Polarization Diversity (dual polarized antenna)

Diversity Scheme & CDMA Reverse Link Degradation

Branches Imbalance & XPD (median)

1.15 dB 2.16 dB 1.01 dB

Cross Polarization Correlation (XPC) (median)

0.19 0.25 0.06

Mean Eb/No

Measured Results

8.22 dB 9.08 dB 0.86 dB

Diversity Gain (median)

4.89 dB 4.68 dB 0.21 dB


7


The front-to-back ratio is typically decreased in a dual polarized antenna as compared to anoptimized vertical antenna (this varies with antenna vendor). For CDMA systems, this translatesinto a slight reduction in capacity due to an increase of interference seen from the adjacent sectors.

Some manufacturers have solved the size, gain, and front-to-back ratio issues by layering theantenna elements on top of one another. This keeps the antenna parameters consistent withsingularly polarized antennas.

Due to the fact that multiple antenna elements share the same antenna housing, dual polarizedantennas are also particularly susceptible to intermodulation distortion.

If the antenna is experiencing problems, with only one antenna at a given site, there is noopportunity to “hot swap” a line (i.e. no backup).

Dual polarized antennas, though seen as one antenna, will still require two separate transmissionlines (one for each polarization).

7.1.4.2 Antenna Selection Criteria

It is recommended that the system engineer consider three main polarization specifications whenchoosing an antenna14:

• Tracking of the radiation patterns radiated through two polarizations. Verifyingthat the antenna radiation patterns (relative amplitudes) of the two branches are similar.Unbalanced branches can impede diversity performance and create unequal coveragefootprints.

• Antenna cross-polarization discrimination (XPD). In dealing with 3-sector sites,orthogonality needs to be controlled over an angle of +60° off of bore sight. Cross-polarization discrimination is generally required to be higher than +15dB. Due toisolation requirements, Motorola recommends port-to-port isolation of at least 34 dB(Tx-Rx).

• Isolation. For details on antenna isolation requirements, please refer to Section 7.1.2.

7.1.5 Transmission at 45°

Currently, the effect of transmitting the base station signal from an antenna which is polarized 45°from vertical needs further analysis. The emphasis on dual polarization antenna studies has beenon the receive signal only; however, Motorola recognizes that in CDMA, the open and closed looppower control are of key importance. Figure 7-10 Tx, Rx and Diversity Rx Antenna Configurationsprovides various examples of the transmitting techniques involved with the different diversityantenna configurations.

14. Xiang, Jun. 1996. “Diversity Antenna Systems for GSM900/GSM1800/PCS1900 Networks.” Issue A.Motorola.


7


Figure 7-10: Tx, Rx and Diversity Rx Antenna Configurations

If a horizontal/vertical polarized antenna is employed, then the vertical polarization element can beused for both transmit and receive, and the horizontal polarization element can be used for diversityreceive. However, if a slant 45° polarized antenna is used, then regardless of which polarizationelement is chosen, the signal will be transmitted at 45° from the vertical.

In many cases, the maximum capacity is limited by the forward link. Therefore, any degradationto the forward link will typically impact the performance (i.e. coverage, capacity, and quality) ofthe entire site. An analysis of how large an impact to system performance is introduced by theforward link transmission of a 45° polarized signal is needed. Some believe if the clutter issufficient to induce scattering such that the reverse link variance in polarization is adequate toutilize a dual polarized diversity scheme, then the forward link should also be sufficient. Thisassumption cannot be readily made without testing, since path fading characteristics are normallydetermined by the near field clutter.

It has been shown that in given situations (see Section 7.1.3), slant 45° polarization diversity issuperior to horizontal/vertical polarization diversity (although neither is as good as spacialdiversity). In order to leverage the advantages of slant 45° polarization and also minimize the risksof transmitting with a 45° polarization, an alternate solution is to use an antenna designed withthree separate polarizations. An example of this type of antenna is shown in Figure 7-10. With thistype of 3-port polarization antenna, one port is polarized at +45° from the vertical, a second port ispolarized at -45° from the vertical, and a third port is vertically polarized.

Other considerations include the size of the antenna unit and the gain. A 3-port polarization antennawould be even longer than a 2-port slant 45° antenna.

7.1.6 Incorporation of Dual Polarized Antennas into a Link Budget

Utilizing dual polarized antennas as a means of diversity may have an impact on the CDMA RFlink budget. The CDMA base station receiver sensitivity is comprised of several components, oneof which is the required Eb/No to meet a specified performance (FER). The benefit of diversity gainis typically accounted for within the Eb/No value. Therefore, if a different diversity gain value is

Note: The arrows represent the direction of polarization.

Tx/Rx (main) Rx (diversity)

Spacial Diversity Slant 45° Horizontal/

Slant 45° &vertical in asingle unit

Dual Polarization Diversity

Tx/Rx (main)

Rx (diversity)

(either branch)

(either branch)

Tx/Rx (main)

Rx (diversity)

Tx

Rx (main)Rx (diversity)

(either branch)

Vertical


7


obtained from the various antenna diversity schemes, then a different Eb/No value will be required.This change in Eb/No will thereby impact the base receiver sensitivity and ultimately the maximumreverse link path loss. One of the Motorola field tests (discussed in Section 7.1.3) shows that thereverse Eb/No requirements are increased when using a polarization diversity scheme.

For the downlink, should a provider choose to use a 2-port slant 45° dual polarized antenna, thebase station transmit antenna would radiate with a 45° polarization. As stated in Section 7.1.5,further studies are needed which analyze the effect that transmit inclination at 45° could have onthe forward link, and (specifically from a CDMA perspective) how this may effect the Eb/Noperformance.

When inputting the value for antenna gain, the system engineer should use the gain value given bythe antenna vendor.

7.1.7 Dual Polarized Antenna Summary

Unfortunately, the majority of the case data analyzed for this document was derived from fieldexperiments and not from well controlled laboratory settings. Consequently, conclusions drawnfrom this data should be treated with a degree of skepticism, knowing that the environment inwhich each test was conducted and the test performed, may have had an impact on the result.

With the exception of the Motorola test cases, data was collected with continuous wave (CW)testing. For a CDMA system, CW testing may not be sufficient. Due to the power control inCDMA, Eb/No measurements are preferred. This makes data comparison between studies (CDMAvs. CW) extremely difficult.

In the past, most of the subscriber unit antennas were mounted onto the vehicle and theirtransmission was assumed to be vertically polarized. Today, most of the subscriber units arehandheld and are subjected to “hand-tilting”. With the introduction of non-vertically polarizedsignals, polarization diversity is assumed to be a potential option to improve signal reception. Infact, it has been found that the tilt of the subscriber has less to do with the effectiveness of thediversity scheme than the environment in which the subscriber and base station are located.

It is understood that scattering is required to change the polarization. Thus, dense urbanenvironments lead to more scattering and a higher probability of creating decorrelated signals withrespect to polarization (as seen by the base station antenna system).

In the proper environment (dense urban), polarization diversity performed well. Surprisingly, it didnot perform as well as a spacial diversity scheme, but was normally within 1 dB. (The worst caseshown was 2.7 dB which was seen in a suburban environment.) Taking into consideration thelosses incurred in transmission lines, connectors, duplexers and combiners, the loss in diversitygain may be offset dependent on the quality of the antenna system. Decisions would need to bemade as to whether or not an estimated 1 dB degradation would be acceptable.

Diversity gain could be offset in a CDMA system by a capacity degradation taken by utilizing adual polarized antenna. There are two main issues around which dual polarized antennas may


7


effect capacity. The first is the effect it may have on the Eb/No performance. Reverse pole capacityequations depend directly on target Eb/No values. Secondly, dual polarized antennas have smallerfront-to-back ratios than singularly polarized antennas which means they tend to introduce morenoise into the system (reducing capacity).15 How significant a degradation on capacity is yet to bedetermined.

Although the findings show that a dual polarized antenna with a slant 45° configuration performsbetter than a horizontal/vertical configuration, a significant concern lies in what may happen to theforward link and power control by transmitting with a 45° polarization. The horizontal/verticalpolarization configuration would at least leave one variable constant as compared to the presentspacial diversity scheme (the base station transmit antenna would continue to be vertically,linearly, polarized). However, to achieve the same level of decorrelation in branches would requirea more dense clutter environment, and even then, studies show that horizontal/vertical polarizedantennas tend to have a large branch imbalance with the vertical branch being most dominant.Ideally the choice would be to use the 3-port antenna model presented earlier which uses threepolarizations (vertical and slant 45°). The cost and extra weight added (for identical antenna gain)would need to be determined, and factored into the decision process.

Finally, the Motorola field tests found that the greatest factor to impact the diversity gain wasbranch imbalance (more so than signal correlation). In measuring Eb/No requirements of apolarization diversity system as compared to a spacial diversity system, it was found that there waslittle change to the gain between the systems. The polarization diversity scheme showed a slight(less than 1 dB) degradation in performance. This study was performed in an urban environment.

Whether or not to use polarization diversity is left to the system engineer. The recommendation isto use this scheme if real estate is not available for spacial diversity, and the environment cluttertype is urban or dense urban. Isolation between ports needs to be strictly adhered to and Motorolarecommends a minimum of 34 dB between Tx and Rx ports. It is unknown how transmission at45° may effect the forward link, and until further studies are performed, the system engineer shouldbe cautious in using this approach.

7.2 In-Building Distributed Antenna Systems

With the proliferation of portable cellular phones, wireless subscribers not only require service onroadways, they also desire CDMA cellular service within buildings. Typical in-buildingapplications include:

• Office Buildings• Airports• Hospitals• Shopping Malls• Hotels & Convention Centers• Sports Arenas• Colleges & Universities

15. This is dependent on antenna manufacturer.


7


Improving indoor coverage is an important step towards meeting the customer’s expectation. Bychoosing the proper design philosophy, an indoor system will increase system capacity andimprove call quality. One approach to meeting the customer requirement for in-building coverageis to increase the ambient power of the outdoor macro-cellular system, allowing signals topenetrate outer walls and provide coverage within buildings. This method is used with limitedsuccess due to the wide variation of building materials and their respective penetration loss. Inorder to provide high quality in-building cellular service, it may be necessary to place the coveragewithin the building through the use of Micro sites and distributed antenna systems.

Several methods of in-building coverage solutions exist including passive coax, active coax, fiberoptics, leaky feeder, Micro RF heads and hybrid combinations of these types. Each approach hasa unique set of attributes, which makes it most suited for a particular application.

7.2.1 In-Building System Architecture Overview

The goal of in-building system design is to distribute the RF signal uniformly throughout all of theareas to be covered. The system should be easy to install, inexpensive, unobtrusive, and highlyreliable. Distributing antennas within the building, using coaxial cable, fiber optics cable or PicoRF heads, can meet these requirements. Figure 7-11 illustrates a typical coaxial cable designapproach.

Figure 7-11: Coaxial Cable Design Approach

The coaxial cable approach uses splitters, directional couplers, or taps to direct the RF signal tovarious locations within the building.

Current fiber optic distribution systems employ a star architecture. In large buildings, the fiber runsmay be reduced by distributing the fiber control units as in Figure 7-12.

RF BaseStation

Splitter, Tap, orDirectional Coupler Coaxial Cable

Antenna

Ceiling


7


Figure 7-12: Fiber Optic Design Approach

Passive coaxial cable systems typically offer the most cost effective implementation solution forsmall building applications. The term passive coax is used to describe a coaxial cable system thatdoes not have any active devices, such as in-line amplifiers. Coaxial cable systems that do employamplifiers are referred to as active coax systems. Because of their low cost, passive coax systemsshould be used to distribute the RF signal whenever practical. The limitation of passive coax is thatthe cable loss increases as the cable run length increases. Higher cable loss results in lowerdownlink power and degrades the system uplink performance. For larger buildings, it may not bepossible to meet the coverage goals using only passive coax. For these larger applications fiberoptic distribution systems, active coaxial cable or Pico-Cell systems can be employed.

7.2.2 Coaxial Cable System Design Using A Link Budget

The following section (Section 7.2.2.1) provides a flow chart with the steps involved withdesigning an in-building antenna system using a passive coaxial cable system design. Theremaining sections provide a brief description of the various steps provided in the flow chart.

7.2.2.1 Design Procedure Flow Chart

The flow chart shown in Figure 7-13 describes a process that can be used for estimating the designof an in-building RF distribution system.

Details on each of the flow chart steps are given in the following sections.

Fiber Optic Cable

RF Base Station

Ceiling

Fiber Antenna Unit

Fiber Base Unit


7


Figure 7-13: Coax Design Flow Chart

7.2.2.2 Gathering Building Information

Before the design of the distributed antenna system can begin, some basic information about thebuilding, equipment locations and areas requiring coverage must be obtained. With thisinformation, the system planner can begin to construct the details of the design, such as the numberof antennas required throughout the building.

Phase I: Education

Motorola recommends training be provided for as many key people as possible, especially theindividuals who will be participating in the installation, optimization and trial stages.

Gather The Building Information

Determine The Base Station Location

Estimate The Antenna Placement

Select The Antenna Types

Choose The Base Station Type

Choose The Cable Topology

Estimate The Cable Run Lengths

Select The Coaxial Cable Type

Link Budget Design

Meet CoverageRequirements

Estimated Design Is Complete

NO

YES


7


Phase II: System Requirements

Clear specifications and requirements are a key to any project. In-building antenna systems are noexception. Motorola recommends extensive training and design sessions due to the specialrequirements of in-building systems.

Phase III: Building Design Information

Building design information in the area of traffic requirements, coverage area, and building detailsare needed.

Traffic requirements:

• The number of subscribers for the system (this will be necessary to size the finalequipment)

• The Average Holding time including Erlang studies of the call duration on the PBX orlandline

• Peak traffic periods during the day

• Desired Grade Of Service (GOS)

• The type of back-haul spans should also be determined (i.e. Microwave, T1 or E1, etc.)

Coverage Area:

Floor plans, including a scale, are required. The plan dimensions should be clearly legible andshould detail the layout of the floor. The height of each floor and clearance above the ceilingsshould also be detailed. In consultation with the customer and using the floor plans, the number offloors and areas within the building requiring coverage can be determined. This decision can bemade by examining the probability that a call will be made (or received) in a particular area.Locations that can be expected to see activity, such as an office space or conference room, shouldbe adequately covered. Locations where call activity will be minimal, such as storage rooms andmechanical sectors, may not need to be covered. There will be a trade-off when determining thecoverage requirement. As an example, a design for 90% area coverage may be significantly lessexpensive than a design for 100% area coverage. The coverage goal should be established prior tobeginning the system design and implementation.

Building Details:

Details on the building construction will help with the system design. An arrangement to ensurecomplete building access must be agreed upon with the customer. Table 7-2 provides examples ofbuilding topology that should be discussed to give a more detailed description of the areas to becovered:


7


A second marked-up copy of the floor plans can be used to illustrate and describe where thesematerials or obstacles are located.

The vertical elevator shafts, stairwells, fire escapes and any vertical duct or passageway should beillustrated on the plan or cross-sectional diagram. Any in-building parking facilities should also bedescribed.

Photographs and/or video would also be helpful for more complex implementations.

A brief review should be done to see if the size of the passageways will be sufficient to transfer theequipment from the delivery truck to the installation area. The equipment may need to be un-cratedbefore moving it into the building. The Telco rooms and PBX rooms should be clearly marked aswell. Considerations should be given to the provisioning of back-haul transmission connections.

A list of contacts from the customer, designating key individuals to support the project, must alsobe defined. Individuals to address building code, electrical, plumbing, duct work, and structuralquestions should also be identified. These individuals should be readily available to answer any on-site questions, especially questions pertaining to cable runs and locations.

With the above information, a spreadsheet design procedure can be used to determine the amountof equipment, cable and antennas required for the desired coverage area. Additionally, preliminaryplans for cable runs, equipment locations and antenna placement can be formulated.

7.2.2.3 Determining the Base Station Location

A survey of the building should be carried out to determine the equipment room location and checkthe cable routing options. Using the floor plan drawings and inputs from the customer, an estimateof the base station location(s) can be made. The base station should be located as centrally aspossible within the building. This will minimize the coaxial cable lengths and cable losses thereby

Table 7-2: Building Topology Examples

• glass content • open areas• re-bar • sky lights• metal • atriums• struts • mezzanines• wire mesh • fiberglass insulation• metal-skin walls • steel beams• partial walls • asbestos• full walls • cubicles• floor thickness • basements• floor materials • tunnels• duct work • ceiling plumbing


7


providing the best possible downlink and uplink performance. If there are multiple floors to becovered, the base station should be located on the middle floor if possible. All design informationshould be drawn on the building floor plans.

7.2.2.4 Estimating the Antenna Placement within the Building

The coverage (ERP) from an antenna is dependent on the cable loss from the base station to theantenna. Therefore, RF distribution design is an iterative process. In order to start the process, anestimate of the number of antennas and antenna placement within the building is required. Table7-3 can be used to determine a first pass estimated coverage radius for each antenna.

Using this estimated coverage radius as a starting point, first pass antenna locations can be derivedand drawn on the building floor plans. In a future step, the drawing is used to calculate the cableruns.

A concern with antenna placement is the maximum allowable received power at the subscriber. Aswith any active device, the subscriber receiver is only designed to operate over a range of inputpower levels. If the maximum input power level is exceeded, distortion will occur. The input powerlevel received at the subscriber is a function of the distributed antenna system ERP and theminimum distance between the subscriber and the distributed antenna. As a rule of thumb, for lowgain, ceiling mounted antennas, the power into the antenna should not exceed 10 dBm. In general,the antenna ERP should be set to a level that will result in no higher than -30 dBm at the subscriber.If these design guidelines are not followed, distortion may occur when a subscriber is used in closeproximity to an antenna. This distortion will rapidly decrease as the subscriber moves away fromthe antenna.

7.2.2.5 Selecting the Antenna Type: Omni vs. Directional

After estimating the antenna placement, the type of antenna(s) to be used must be selected. Ingeneral, there are two types of antennas to choose from: omni-directional (omni) and directionalantennas. Omni antennas provide a uniform field pattern in 360° in the horizontal.

Directional antennas have increased gain in one or more directions at the expense of reducing thegain in other directions. There are a number of directional antennas available for indoor use with avariety of gain patterns.

Omni antennas can be employed in most cases. Directional antennas are useful when covering anarea that is shaped similar to the antenna gain pattern. For example, a long hallway might best becovered by a "bow tie" antenna as in Figure 7-14 "Bow Tie" Antenna.

Table 7-3: Estimated Coverage Radius

Area Type Estimated Coverage Radius (Feet)Office 200Factory 350Store 350


7


Figure 7-14: "Bow Tie" Antenna

7.2.2.6 Choosing the Base Station Type

There are several parameters that need to be considered when choosing the base station type to beused. The primary variables are:

• Channel capacity

• Maximum downlink power

• Physical size

• Antenna system complexity

• Installation and maintenance

• Cost

For applications requiring only a few traffic channels and minimal forward power, a smallmicrocell product (limited capacity) may prove to be both economical and easy to install.

For applications requiring greater capacity or higher RF penetration, a larger BTS product, forinstance a macro site BTS, can be used.

The system designer will need to weigh the attributes of each BTS product to determine the bestBTS for their design. For instance, if passive coaxial cable is used to distribute the RF to antennas,it may be preferable to use more BTS products to limit the length of transmission run and therebyminimize cable loss (BTS is placed closer to area to be covered). If fiber optic transmission is beingused to distribute the RF, line loss is not as much an issue and therefore, the BTS can be locatedfurther from the area to be covered.

7.2.2.7 Choosing the Cable Topology: Splitters, Couplers, and Taps

There will inevitably be a need to split a single coaxial cable branch into multiple branches. Forexample, a main feeder run may have to be split into two branches to feed two separate antennas.

Bow Tie Antenna


7


There are several different approaches to accomplish this signal division:

• RF taps

• Power splitters or dividers

• Directional couplers

Each method has benefits and limitations that must be considered.

7.2.2.7.1 RF Tap

An RF tap acts like a pin hole in a water hose. As the water (RF) flows past the hole, some leaksout. The RF tap is basically a small antenna that is inserted into the main coaxial line which drainsa small portion of energy from the tapped branch into the new branch (see Figure 7-15 SchematicDiagram of a Power Tap). The drained or coupled energy propagates down the new line.

Figure 7-15: Schematic Diagram of a Power Tap

Standard taps are available from commercial sources and provide a relatively inexpensive way tobranch from a main feeder.

The coupling loss indicates how much of the signal will enter the new branch. For example, if thesource line is at 0 dBm and the tap has a coupling loss of 12 dB, then the power in the new branchwill be -12 dBm. The majority of the energy continues to propagate down the main branch. Atypical application for an RF tap would be to branch several antennas off of a main branch. Forinstance, RF taps could be used to provide an antenna for a meeting room with its own local branch(see Figure 7-16 Typical Tap Application).

T h r u P o r t - 0 . 5 d B

T a p P o r t - 1 2 d B

C o a x .

T a p


7


Figure 7-16: Typical Tap Application

7.2.2.7.2 Power Splitter or Divider

The power divider uses a resistive network (or similar approach) to break one input into two ormore outputs of equal power. For instance, a two-way splitter may typically have a loss of 3.5 dB,so a 0 dBm signal entering a 2-way splitter will exit as two -3.5 dBm signals (see Figure 7-17Diagram of a Power Splitter).

Figure 7-17: Diagram of a Power Splitter

There are two components to the splitter loss. The first is the loss associated with actually splittingthe signal into multiple outputs, and the second is the insertion loss due to resistive loss. This iswhy a two way splitter has 3.5 dB of loss rather than 3 dB. There are usually a large selection ofcommercial power splitters available for use. A brief sample of various output ports and theirassociated loss values are presented in Table 7-4.

Main Branch

Antenna

Antenna

Meeting Room

0 d B m I n

- 3 . 5 d B mO u t

- 3 . 5 d B mO u t


7


7.2.2.7.3 Directional Coupler

With a directional coupler, most of the signal is transmitted to the through port while a smallportion of the signal is diverted to the coupled port. This is similar to a tap; however, the methodused to couple the signal is different and, in general, more efficient (see Figure 7-18).

Figure 7-18: Schematic of a Directional Coupler

The directional coupler can be used in situations where a small amount of power needs to be drawnoff of a main branch with minimal disturbance. Directional couplers also come in a multitude ofvalues.

7.2.2.7.4 Cable System Distribution Examples

When selecting splitters, taps or directional couplers, there is a choice between parallel or seriespower distribution. A parallel method would use a splitter to branch the main run into local runs.A series method would use directional couplers or RF taps to divert power from the main cable runto local runs. Both methods work equally well for short runs. However, as cable runs, antennas andbranches increase, the series method can provide increased power levels at antennas locatedfurthest from the base station. The benefit of series distribution can be seen in Figure 7-19 andFigure 7-20.

Table 7-4: Typical Values for Power Splitters

# of Output ports Total Loss (dB)

2 3.53 5.84 7.08 10.0

I n

O u t P o r t

C o u p l e d P o r t

5 0 O h m T e r m i n a t i o n

- 0 . 5 d B

- 1 0 d B

1 0 d B C o u p l e r


7


Figure 7-19: Parallel Power Distribution Using a Power Splitter

In the case of parallel power distribution, the power reaching the antenna closest to the insertionpoint (250 ft.) has 22 dB more power than the antenna furthest (1000 ft.) from the insertion point.The non-uniform distribution of power will cause an increased coverage area for the antennaclosest to the insertion point and a decreased coverage area for the antenna farthest from theinsertion point.

Figure 7-20: Series Power Distribution Using Directional Couplers

In the case of series power distribution using directional couplers, three directional couplers willbe required: 15 dB, 10 dB and 6 dB. With directional couplers, the power delivered to each antennais more uniform than with splitters. In addition, there is an 8.5 dB improvement at the final antennausing the series method as opposed to the parallel method. Overall, series distribution may be usedwhen a power improvement is required at a distant antenna, or when multiple cable runs becomescost prohibitive.

Often, a combination of parallel and series power distribution methods may be used. For example,a power splitter can be used to divide a main branch into several sub-branches; then, directionalcouplers or RF taps can be used to distribute power from the sub-branch to the antennas.

0 ft 250 ft 500 ft 750 ft

20 dBminput

1000 ft

(-5 dB)(-5 dB)

(-5 dB)(-5 dB)

2-way Splitter

ERP = 11.5 dBm 3 dBm-5.5 dBm

-10.5 dBm

0 ft 250 ft 500 ft

15 dB Coupler10 dB

1000 ft750 ft

6 dB

ERP =0 dBm 0 dBm -1 dBm

20 dBminput

-0.4 dB -0.5 dB -1.4 dB

-2 dBm

(-5 dB) (-5 dB) (-5 dB) (-5 dB)


7


7.2.2.8 Estimating Cable Lengths from the Base Station to the Antennas

Once the base station and preliminary antenna locations are marked on the floor plans, estimatesfor the cable lengths, number of directional couplers, splitters, and taps can be made. The cableruns should be located in standard cable areas within the building. If the standard cable locationsare not known, a good rule of thumb is to assume that the cable will run down the hallways. Theestimated cable runs and network components (couplers, splitters, and taps) should be drawn onthe building floor plans.

7.2.2.9 Selecting the Coaxial Cable Type

There are several alternatives to be considered when selecting the media for delivering the RFsignal from the base station to the antenna, and vice versa. Ideally the distribution media shouldhave the following characteristics:

• Low loss

• Flexible

• Durable

• Light weight

• Fire resistant

• Low cost

• Minimum space requirement

There are several varieties of coaxial cable that can meet the above requirements for distributedantenna applications. Each variety of cable has its own advantages. However, there are trade-offsinvolved in selecting a cable type. For example, cable runs that do not require many turns and bendscan utilize typical foam dielectric coaxial cable. This type of cable has low loss, light weight andexcellent durability. The cable comes in a variety of sizes, with loss decreasing as diameterincreases. However, the larger sizes are less flexible, cost more and suffer from increased weightand space requirements.

A large building with minimal turns and bends can use a larger diameter cable with lower loss. Insome cases, the standard low loss cable may not have enough flexibility for the particularapplication. If the system has numerous turns, or sharp bends, a super-flexible cable may berequired. This type of cable trades increased loss for increased flexibility.

If the cable is to be placed in or near air handling spaces, the use of plenum rated cable may berequired. The plenum rating specifies that the cable meets certain fire resistance and smokeproducing specifications. Although most coaxial cables have a fire retardant option, a plenumrating may be necessary (check local code requirements).

Low loss 7/8" coax may be a good choice for in-building applications. However, because of thehigher price of 7/8" coax, 1/2" coax may be desired.


7


7.2.2.9.1 Designing With Radiating (Leaky) Coax

Radiating (also known as leaky) cable is a type of coaxial cable which has holes milled in the outerconductor as shown in Figure 7-21.

Figure 7-21: Radiating Cable

A small portion of the RF energy that is transmitted down the radiating cable leaks out from theholes, hence the term "leaky" coax.

Radiating cable can be used in place of point source antennas to provide coverage within buildingsas shown in Figure 7-22.

Figure 7-22: Radiating Cable Implementation

Some of the advantages of radiating coax are that the coverage is more uniform and the radiatedpower levels are low, which improves signal containment and reduces the risk of overloading thesubscriber unit. Although radiating cable can be used most anywhere, typical applications havebeen for elevator shafts, long tunnels and for hallways.

A radiating coax system design is similar to a conventional coaxial cable design. A link budget canbe used to tabulate all of the system losses up to the radiating cable. Coupling loss and cable lossper unit distance factors, which can be obtained from vendor data sheets, are used to determine thepower level radiated by the cable. The coupling factors are typically specified for a 20 foot distanceon either side of the cable as shown in Figure 7-23.

S C 6 0 1 orS C 6 0 4

S pl i t t er , T ap, orDi r ect i onal Coupl er

R adi ax Cabl e

Cei l i ng

BTS

Splitter, Tap, or Directional Coupler

Radiating Cable


7


Figure 7-23: Radiating Cable Coverage

In this example, the input power is 10 dBm and the radiating cable loss per 100 feet is assumed tobe 5.0 dB. The power remaining at the end of the cable is 0 dBm. The power received at a distanceof 20 feet from the radiating cable is the power remaining at the end of the cable less the couplingloss, which is assumed to be 66 dB for this type of cable.

An indoor propagation model can be used to estimate the path loss between the 20’ mark and theedge of the building to determine the worst case receive signal level.

If the cable is to be placed in or near air handling spaces, the use of plenum rated cable may berequired. Although most coaxial cables have a fire retardant option, a plenum rating may benecessary (check local code requirements).

7.2.2.10 Link Budgets For In-Building Design

The link budget provides a means to determine the maximum allowable path loss between the basestation and the subscriber unit. The path loss ultimately determines the coverage area, whichequates to the amount of equipment necessary to meet the system performance goals. The actualenvironment of the area to be covered can greatly influence the range to which a site will propagate.The link budget analysis technique takes these environmental characteristics into account. The linkbudget is an important part of the detailed design which must be done to ensure coverage qualityand reliability.

The link budget can be used for passive coax systems or active coax systems. The active designparameters can be included in a spreadsheet tool, although it is more complex than a simple passivedesign. However, with a combined passive and active design, "what-if" scenarios can be tested tosee if using amplifiers will improve system performance.

Motorola recommends that a passive design be considered first, due to its lower cost.

Figure 7-24 shows a block diagram of the components that enter into the link budget calculationfor both the passive and active cases.

Radiating Cable

10 dBMInput Power

20 Feet

200 Feet

-66 dBm

0 dBm

-66 dBm


7


Figure 7-24: Link Budget Block Diagrams

For the passive coax system, the downlink received signal strength at the subscriber is calculatedby subtracting the network and propagation losses from the base station transmit power. The uplinkreceived signal strength at the base station is calculated by subtracting the propagation and networklosses from the subscriber transmit power. In both directions, the received signal level should beat or above the receive threshold for satisfactory system performance.

With active systems, the amplifier gain must also be included in the link budget. The uplink noisepower changes due to the active components and must also be considered when analyzing thesystem.

The propagation path loss is used to determine the maximum coverage radius from each antennaas shown in Figure 7-25.

AmplifierLossy

Network

Base

PropagationLoss

LossyNetwork

Active Coax

BasePortable

LossyNetwork

Passive Coax

PropagationLoss

Portable

Downlink

Base TxPower

+AmplifierGain

-NetworkLoss

-PropagationLoss

>= PortableRx Threshold

-NetworkLoss

Uplink

+AmplifierGain

-NetworkLoss

-PropagationLoss

-NetworkLoss

PortableTx Power

>=Base RxThreshold

Uplink

Downlink

Base TxPower

-NetworkLoss

-PropagationLoss

>= PortableRx Threshold

PortableTx Power

-PropagationLoss

-NetworkLoss

>=Base RxThreshold

Base Station

Base Station


7


Figure 7-25: Maximum Coverage Distance

A floor penetration loss component may also be included as part of the propagation loss within thelink budget analysis. Depending on the floor construction materials, it may be possible to coverseveral floors using one antenna as shown in Figure 7-26. The additional propagation loss due topenetrating the floors must be included in the link budget calculation when using this approach.Suggested floor penetration loss factors are presented in Section 7.2.2.10.1.

Figure 7-26: Multiple Floor Coverage

7.2.2.10.1 Estimating In-Building Path Loss Using Statistical Models

Due to the existence of many variables in an indoor propagation environment, accurate path lossprediction becomes difficult. These variables include floor/ceiling materials and various wallconstruction materials and geometry, in addition to numerous obstacles between the transmitterand receiver. Presently, there are several methods for predicting path loss for indoor environments.Among these methods are deterministic models, such as ray tracing, site specific diffraction, andwall/material loss models. All of these methods describe the path loss for a variety ofcircumstances, with a fair amount of accuracy. Their major drawback is computational complexitysince they need to account for a large number of variables (such as wall size and material, locationof furniture, light fixtures, etc.). In addition, these methods are time consuming and costly.

200 FeetAntenna #1 Antenna #2

Maximum Coverage

Distance=160 Feet

500 Feet

Base

Floor Loss

Floor Loss


7


Another method is statistical modeling, which has proven to be effective in predicting path loss forindoor environments. Statistical models are based on measurements recorded in various differentbuilding types. The main advantage of using statistical models is the simplicity of representing thepath loss between the transmitter and a receiver. These path loss calculations are easilyimplemented in a spreadsheet design tool. All equations in Table 7-5 express path loss as a functionof distance only. The path loss equations express the path loss in dB in terms of distance in feet.Included in these models are linear regression methods based on measurements taken in twoMotorola facilities16.

Figure 7-27 shows the plots of the logarithmic models in Table 7-5.

Figure 7-27: Logarithmic Path Loss Models

Table 7-5: Path Loss Models

Model Name Path Loss Equation (dB)

Retail Store PL(d) = 22 Log(d) + 20.1

Suburban Office Bldg.open plan

PL(d) = 24 Log(d) + 19.1

Suburban Office Bldg.soft partition

PL(d) = 28 Log(d) + 17.0

Suburban Office Bldg.hard partition

PL(d) = 30 Log (d) + 16.0

Motorola Cluttered PL(d) = 0.18(d) +71

Motorola Uncluttered PL(d) = 0.11(d) +55

University PL(d) = 0.19(d) + 63

Free Space @ 894 MHz PL(d) = 20 Log(d) + 21.1

Free Space @ 1900 MHz PL(d) = 20 Log(d) + 27.7

16. These measurements, except for the Free Space models, were made at cellular frequencies.

Logarithmic Path Loss Models

Distance (Feet)

0.0

20.0

40.0

60.0

80.0

100.0

0 50 100 150 200 250

Retail Store

Open Office

Soft Wall Office

Hard Wall Office

Free Space


7


Figure 7-28 shows the plots of the linear models, based on measurements at Motorola facilities andat a college university. Free space path loss is included in both figures as a reference. The Motorolacluttered model is based on measured data from a Motorola office facility. The office area wascomprised of both hard metallic walls and soft walled cubes. The Motorola uncluttered model isbased on path loss measurements that were taken in open factory and distribution areas.

Figure 7-28: Linear Path Loss Models

The path loss curves represent the average path loss as a function of distance for a large number ofdata points. Some areas within the building will have higher path loss and some areas will havelower path loss than the average. The distribution of path loss values around the mean has beenfound to approximate a log-normal (bell shaped) curve with a standard deviation in the range ofabout 5 to 10 dB. A fade margin can be added in the link budget, if desired, to account for this log-normal variation of received signal level. The fade margin can be adjusted to achieve the desiredpercent area coverage.

In addition to these path loss models, floor attenuation factors (FAFs) have been developed by S.Y.Seidel and T. S. Rappaport based on thousands of signal strength measurements taken in twomultiple floor buildings. A summary of their experimental results is listed in Table 7-6. The valuesin Table 7-6 are the average floor attenuation factors with their respective standard deviations.

Table 7-6: Average Floor Loss Attenuation Factors

Location FAF(dB) σ (dB)Office Building 1Through 1 floor 12.9 7.0Through 2 floors 18.7 2.8Through 3 floors 24.4 1.7Through 4 floors 27.0 1.5Office building 2Through 1 floor 16.2 2.9Through 2 floors 27.5 5.4Through 3 floors 31.6 7.2

Linear Path Loss Models

Distance (Feet)

0

20

40

60

80

100

120

0 50 100 150 200 250

Motorola Cluttered

Motorola Uncluttered

University (CMU)

Free Space


7


The model that most closely resembles the particular area to be covered should be used. Eachantenna can have a different path loss model associated with it, depending on the area type that itwill cover.

Rather than using one of the statistical path loss models, it is possible to make on-sitemeasurements for the purpose of determining the path loss characteristics of a particularenvironment.

7.2.2.10.2 Measuring In-building Path Loss

Signal strength measurements can be performed on-site, so that the transmit power requirementscan be evaluated and established. This information can be used to decide very accurately how manyantennas will be needed to provide adequate coverage throughout the building.

A test transmitter is set up in the area to be covered. An antenna is connected to the test transmitterand signal strength measurements are recorded systematically within the expected coverage area.These measurements may be taken manually with a measuring receiver or automatically with acommercially available data collection system.

The data collection system produces coverage plots to determine the signal strengths within thebuilding. Since this is a downlink coverage measurement, care must be taken to insure that theuplink coverage will also be adequate. A link budget tool can be used in conjunction with themeasured coverage data to insure that both the downlink and uplink coverage requirements aremet.

Figure 7-29: Measurement System Test Setup

This design approach is more costly due to the required on-site visit. Approximately one day isrequired at the building location to view the equipment room, likely cable routes, and antennalocations. A test transmitter can be set up in representative areas and coverage data can be collectedusing a portable data collection system, or other test receiver. Using the on-site test results, anaccurate system design can be developed to meet the coverage requirements.

Computer orData Storage

Battery orPower Source

Data CollectionSystem

Rx Antenna

SignalGenerator

8 - 10 ft.

Tx Antenna

Portable Unit Fixed Unit


7


7.2.2.11 Evaluating the First Pass and Iterating the Design

After all of the antenna link budget information has been calculated and the propagation path lossdetermined using a path loss model or by actual measurements, the results can be compared to thecoverage goals. If the design does not meet the coverage requirements, a second pass should becompleted. The design may be improved by adding antennas, using lower loss cable and/orchanging the cable topology. Several iterations may be necessary to reach a point where all of thecoverage objectives are met.

If the analysis shows that the coverage margins are excessive, some antennas should be removedto reduce the system cost. Depending on the implementation method and building structure, it mayonly be necessary to use one antenna for every two or three floors of coverage.

If after several iterations, the coverage objectives cannot be reached using a simple passive coaxdesign, two alternatives can be investigated. These alternatives are:

• Fiber optic distribution

• Active coax distribution using bi-directional or uni-directional amplifiers to overcomecable losses

The use of in-line amplifiers must be considered carefully because of the higher cost andimplementation and maintenance complexity. Employing lower loss coaxial cable and locating thebase station as near as possible to the center of the coverage area is recommended. If the systemcannot be designed using passive coax, then in-line amplifiers or fiber optics must be considered.

7.2.3 Active Coaxial Cable System Design

The following sections discuss the technical issues and design alternatives for active coaxial cablesystem planning.

Bi-directional or uni-directional amplifiers can be used to overcome the cable and network lossesin an RF distribution system. Bi-directional amplifiers provide amplification in both the uplink anddownlink direction as shown in Figure 7-30.

Figure 7-30: Bi-Directional Amplifier

Downlink

Uplink

Bi-Directional Amplifier


7


This is in contrast to a uni-directional amplifier that only provides amplification in one direction.A possible implementation for an uplink uni-directional amplifier is shown in Figure 7-31.

Figure 7-31: Uni-Directional Uplink Amplifier

In general, the bi-directional amplifier can be used when the uplink and downlink are nearlybalanced. A uni-directional amplifier can be used to improve performance when the system isuplink limited, possibly due to the use of high power LPAs on the downlink.

7.2.3.1 Downlink Amplifier Design Considerations

The main concerns when using downlink amplification are the amplifier’s maximum compositeoutput power, gain, and intermodulation performance. The amplifiers that are used in RFdistribution systems have a maximum composite output power that must be shared among all ofthe carriers. In order to keep the intermodulation product levels within specification, the poweroutput per carrier must be limited to a maximum value based on the amplifier’s specifications.

The downlink parameters related to an active system can be described as follows:

In-Line Amplifier Gain: The amplifier gain is usually adjustable within a given range.

If the calculated required gain is lower than the minimum amplifier gain setting, then an attenuatormust be used in front of the amplifier, as shown in Figure 7-32, to reduce the input signal level.

Uni-Directional Uplink Amplifier

Duplexer


7


Figure 7-32: Downlink Amplifier Gain

Power Out of In-line Amplifier: The power out of the in-line amplifier is calculated as the inputpower plus the amplifier gain. The calculated output power of the amplifier should not exceed themanufacturer’s specification for the amplifier.

The amplifier gain is typically adjustable, thus the gain of the amplifier must be set at a level thatwill insure that the maximum composite output power specification is not exceeded.

7.2.3.2 Uplink Amplifier Design Considerations

In order to fully understand the uplink performance characteristics of an active coaxial cablesystem, it is necessary to understand some of the fundamentals of receiver system design. Thesereceiver system design basics are discussed as follows.

7.2.3.2.1 Receiver System Fundamentals

Noise Figure: By definition, noise figure (NF) is the difference between the input signal-to-noiseratio and the output signal-to-noise ratio in dB.

NF = (S/N)in - (S/N)out (dB)

Minimum Amplifier Gain = 30 dB Maximum Amplifier Output = 17 dBm Per Channel

Base- 20 dB

27 dBm 7 dBm 37 dBm

+30 dB

Power =

Network Loss

Base- 20 dB

27 dBm 7 dBm 17 dBm

+30 dB

Power =

Network Loss

-20 dB

Pad

Too High

In Spec.-13 dBm


7


Figure 7-33 illustrates the effect of a 10 dB noise figure amplifier with 10 dB Gain.

Figure 7-33: Effect of a 10 dB Noise Figure Amplifier

The input signal and noise is amplified by 10 dB and the output noise is also increased by the noisefigure of 10 dB. Therefore, the total increase in the noise floor is 20 dB.

Noise Figure of a Lossy Device: The noise figure of a lossy device, such as a length of a coaxialcable, filter, splitter, or attenuator is equal to the loss of the device. Figure 7-34 illustrates thisconcept.

Figure 7-34: Noise Figure of a Lossy Device

The term kTB in this figure is used to represent the thermal noise in dBm. The thermal noise levelis the same at the input as it is at the output of a lossy device. However, the signal level has droppedby the amount equal to the device loss. Therefore, the signal-to-noise ratio at the output of the lossydevice is lower than that at the input by an amount equal to the device loss. Hence, the noise figureis equal to the device loss.

Cascaded Noise Figure: When two or more system blocks are cascaded together as in Figure 3.20,the cascaded noise figure formula can be used to determine the total system noise figure.

System NF(dB) =

10 dB Noise Figure

10 dB Gain

Input Output

Noise = -127 dBm

Signal = -87 dBm

Power

Input S/N = 40 dB

40 dBNoise = -107 dBm

Signal = -77 dBmPower

30 dB

Output S/N = 30 dB

NF = 40 dB - 30 dB = 10 dB

30 dB Cable Loss

Input Noise = kTBInput Power = Pin

Output Noise = kTBOutput Power = Pin - 30 dB

NF =(Pin - kTB) - (Pin - 30 dB - kTB)NF = 30 dB

10Log10 F1F2 1–

G1---------------- F3 1–

G1 G2⋅------------------- F4 1–

G1 G2 G3⋅ ⋅-------------------------------- …+ + + +


7


Where F1, F2, F3, F4.... are the stage noise figures in linear terms, and G1, G2, G3, G4.... are thestage gains (the gains will be less than one for lossy system blocks), also in linear terms.

Figure 7-35: Cascaded System Noise Figure

As seen in the network drawing, the blocks that are cascaded can be active devices or lossy networkdevices such as coaxial cable, splitters, couplers, attenuators, or filters.

Sensitivity: The receiver sensitivity is defined as the minimum allowable receive signal level thatwill result in a given audio quality, as specified by audio signal-to-noise ratio or audio SINAD.SINAD is similar to signal-to-noise, and is defined as the ratio of the Signal plus Noise plusDistortion to Noise plus Distortion. This can be related to a statistical number called the Bit ErrorRate or BER for digital systems.

SINAD = (S + N + D)/(N + D)

System sensitivity can be calculated as follows:

Where:k Boltzmann’s constant = 1.38 x 10-23 W/(Hz K)

T Room temperature of 290° Kelvin

B Bandwidth of the carrier in Hz

NF Noise figure of the equipment

Eb/No Energy bit density over noise

R Information bit rate

The value kTB is the noise power at the receiver input due to thermal noise in dBm. For CDMA,the thermal noise power is -113 dBm.

Base

NetworkLoss

NetworkLossAmplifier

F4G4 F3

G3F1G1

F2G2

System NF

SensitivitydBm kTB( )dBm NF( )dB Eb No⁄( )dBBR---

dB

–+ +=


7


As a point of reference, the SINAD for land line call quality ranges between 25 dB and 40 dB. Inorder to have acceptable call quality in a fading environment, a higher minimum signal strength isrequired.

When amplifiers are used, the uplink noise figure is increased and therefore the receive thresholdmust also be increased by the same amount to maintain the same call quality.

7.2.3.2.2 Uplink Design Parameters

The main parameters of concern for an uplink amplifier are noise figure, gain and 3rd orderintermodulation performance.

The amplifier gain is typically adjustable within a specified window. Since the amplifier gainenters into the cascaded noise figure it must be set as part of the design procedure. It is customaryto set the amplifier gain equal to the cable and network losses between the amplifier and the basestation as shown in Figure 7-36.

Figure 7-36: Uplink Amplifier Gain Setting

There is no advantage to increasing the amplifier gain above the level of the network losses. In fact,raising the gain will degrade the system intermodulation performance because both the receivedsignal and the input noise are amplified equally. As such, there is no improvement in the outputsignal-to-noise ratio when increasing the amplifier gain above the network losses.

7.2.3.2.3 Uplink Link Budgets For Active Coax Systems

The uplink parameters related to an active coax system can be described as follows:

Amplifier Noise Figure: The amplifier noise figure, which can be obtained from themanufacturer’s data sheet is entered in dB.

Amplifier Gain: The amplifier gain is set equal to the network losses between the amplifier andthe base station.

Base Station Noise Figure: The noise figure for the Motorola base station is entered in dB. Amaximum value of 6 to 7 dB is normally used for the estimated design. Typical base station noisefigure values are approximately 4.5 dB.

-35 dB Cable Loss

-3.5 dB Splitter Loss

-1.5 dB Duplexer Loss

Uplink amp. gain is set to

(1.5+3.5+35+1.5)=41.5 dB

Base

TXRX

-1.5 dB


7


Noise Summing Degradation: When two or more amplifiers are used in parallel within a network,the noise power from each amplifier adds together. The end result is to raise the system noise floor.Figure 7-37 illustrates this concept.

Figure 7-37: Noise Summing

Receiver Noise Rise: To determine the noise rise, which is the amount by which the uplink receivethreshold should be increased, both the cascaded noise figure and the noise summing degradationsare taken into account.

System Noise Figure Without Amplifiers: It is important to determine if the addition of uplinkamplifiers is actually improving uplink performance. The uplink system noise figure is calculatedfor the case where amplifiers are not used and compared to when amplifiers are used. The noisefigure for the system, excluding amplifiers, is simply the sum of all of the uplink network lossesand the base station noise figure.

System Noise Figure With Amplifiers: The cascaded noise figure equation is used to determinethe system noise figure with in-line amplifiers. The noise summing degradation is also added in thesystem noise figure calculation.

Amplifier Uplink Improvement: The amplifier uplink improvement is the difference between thesystem noise figure without amplifiers (passive system) and the system noise figure withamplifiers. Since uplink amplifiers can only overcome losses between the amplifier and the basestation, the addition of an in-line amplifier may actually degrade system performance. If the resultof an amplifier uplink improvement calculation is negative, then the amplifier has actuallydegraded the system uplink performance.

System Level Receive Threshold: Assume that the uplink amplifier gain has been set to be equalto the loss between the amplifier and the base station. The receive threshold is being increased toovercome the noise added by the amplifiers. At first glance, it may appear that the amplifiers arenot improving system performance since the receiver noise is increased. However, the receivernoise is likely increased by a few dB, while the uplink amplifier can overcome 30 to 40 dB of cable/network loss, when properly located in the system.

Base

NFA

NFA

NFA

NFB

Path 1

Path 2

Path 3

Noise

Noise

Noise


7


7.2.3.3 Optimizing Amplifier Placement

Once it has been determined that an amplifier is necessary, the next step is to decide where theamplifier should be located in the network. In general, the most improvement in coverage will beobtained by placing the amplifier as near to the antenna as possible. On the downlink side, this willreduce the line loss between the amplifier output and the antenna. On the uplink side, this willprovide the best improvement in system noise figure and sensitivity. There will usually be a trade-off between how close the amplifiers are located to an antenna and the number of amplifiers neededin the system. Figure 7-38 illustrates this idea.

Figure 7-38: Amplifier Location

In Configuration 1, the amplifier is placed after the splitter so that only one amplifier is requiredfor two antennas. In Configuration 2 the maximum improvement in system performance isachieved by placing two amplifiers before the splitter/combiner.

Splitter

Splitter

Configuration 1

Configuration 2

Uplink Signal Direction


7


Figure 7-39 illustrates the performance trade-off associated with moving the amplifier furtheraway from the antenna.

Figure 7-39: Amplifier Performance vs. Location

-40 dB-5 dB

NF=10 dBGain = 40 dB

Gain = 0 dB For Amplifier + Network

Base

NF = 7 dB

System Noise Figure = 16 dB


-5 dB-40 dB

NF=10 dBGain = 40 dB

Gain = 0 dB For Amplifier + Network

Base

NF = 7 dB

-45 dBBase

NF = 7 dB

Scenario 1: No Amplifier

Using the Cascaded Noise Figure Equation


Scenario 2: Amplifier Near The Antenna

Scenario 3: Amplifier Far From The Antenna




7


For Scenario 1: There is no amplifier and the system noise figure is simply the base station noisefigure plus the cable loss (NF = 52 dB).

For Scenario 2: An uplink amplifier is placed relatively near the antenna. This improves the uplinknoise figure by 36 dB (from 52 dB to 16 dB). The improvement is nearly equal to the loss betweenthe amplifier and the base station (Loss = 40 dB).

For Scenario 3: The amplifier has been located too close to the base station producing a systemnoise figure of 51 dB. Only a 1 dB improvement in the system noise figure and sensitivity isprovided for this configuration. Scenario 3 demonstrates that there is no advantage to using anuplink amplifier close to the base station.

In summary, placing the uplink amplifier close to the antenna is analogous to using tower mountedamplifiers in a macro-cellular system. The amplifier gain compensates for the coaxial cable lineloss, thereby increasing performance.

7.2.4 Fiber Optics for In-Building Systems

The following sections provide information regarding fiber optic system architecture and design.

7.2.4.1 Fiber Optic Distribution System Architecture

A fiber optic distribution system employs a fiber optic base unit along with a number of fiber opticantenna units to distribute RF throughout a building. Figure 7-40 illustrates the star architecture.

Figure 7-40: Fiber Optic Star Architecture

7.2.4.2 When To Use Fiber Optics

Fiber optic systems for distributing RF in buildings offer a number of advantages over coaxialcable as follows:

Fiber Optic Cable

SC 614 or SC 611

Ceiling

Fiber Antenna Unit

Fiber Base Unit

RF Base Station


7


Low Cable loss: The attenuation of fiber cable is on the order of 1.5 dB per mile. For in-buildingapplications, the cable loss is negligible. This significantly eases the system design andimplementation tasks.

Installation flexibility: Since the fiber optic cable loss is negligible, deviations from the plannedcable route during the installation process will not affect the system performance. In coax systemsdeviations from the designed cable route can result in more cable loss and degraded systemperformance. Deviations from the planned cable route are common because the building drawingsused to lay out the cable runs are not always complete or up to date.

Reduced Interference: Optical cable does not radiate, which eliminates any electromagneticinterference concerns for the optical cables.

Installation Ease: Optical cable is flexible and light weight, which simplifies the systeminstallation.

The main drawback to fiber optics is the relative expense. The fiber optic cable itself is generallyless expensive than coaxial cable; however, the cost of the active fiber base unit and the active fiberantennas add to the system expense.

Fiber optic systems in general will not make good economic sense for smaller implementations,where low cost coaxial cable can be employed to provide good system performance. For largerfacilities, where very long cable lengths may be required, either active coax systems or fiber opticsmay need to be employed. For larger implementations, the cost of a fiber optic system isapproximately the same as an equivalent active coaxial cable system. Fiber optic systems haveseveral advantages over active coaxial systems:

• Easier to engineer

• Less sensitive to installation variations

• Easier to install

• Easier to maintain

7.2.4.3 Fiber Optic System Design

Fiber optic distribution systems are less complicated to design than active coax systems. Thedownlink ERP and uplink receive threshold are essentially the same for every antenna unit. Itdoesn’t matter whether the antenna is located near to the base unit or at a great distance from thebase unit. If the propagation environment within the building is somewhat uniform, then thecoverage radius for each fiber antenna will be the same. If there are different propagationenvironments, such as factory and office areas, then a different coverage radius would be expectedfor each area type; however, within a given area type, the coverage radius from each antenna unitwould be approximately the same.


7


Estimated Number of Antenna Units

With the assumption that the uplink coverage is noise limited, the number of antenna units usedwill govern the uplink coverage. This is because each fiber optic antenna unit and base transceiverpair have active devices that contribute noise in the uplink direction as depicted in Figure 7-41.

Figure 7-41: Fiber Uplink Noise Summing

The noise sums together at the RF combiner. The total noise power increases and the coverage areadecreases as more antenna units are used. The reduced coverage radius is due to the increase inuplink noise associated with adding more fiber links.

A good starting point for the fiber optic design is to assume that at least ten fiber antenna units willbe employed. Between one and ten antennas, the uplink coverage radius decreases very rapidly.Above ten antennas, the uplink coverage radius decreases at a much more gradual rate. Even if onlya few antennas are expected for the initial implementation, it is preferable to design the systemusing the coverage radius associated with ten antennas. In this way, there will be little impact onsystem performance if additional antennas are required at a later date to expand the system.

7.2.5 In-Building Antenna Systems Summary

A number of in-building distribution system alternatives have been presented. Because the cost ofpassive coaxial RF distribution systems is typically lower, it should be used whenever practical.For larger facilities, fiber optics can be used to distribute the RF signal. Fiber offers the keyadvantage of negligibly low cable loss, which eases system design and implementation. Anotheralternative for larger buildings is to employ active coaxial cable systems. Care must be taken whenusing in-line amplifiers to insure that amplifier gain and noise are properly accounted for.

The design process discussed here can be used to obtain an estimate of the in-building systemrequirements. For larger, more complex buildings, or when a firm quotation is required, a moreaccurate site survey method should be used.

Fiber Antenna 1

Fiber Base Transceiver 1 Fiber Optic

Cable RF Signal + Noise

Noise

Noise

PortableFiber

Antenna 2

Fiber Antenna N

Fiber Base Transceiver 2

Fiber Base Transceiver N

To Base Station

Fiber Base Unit

RF Combiner


7


7.3 References

1. Wahlberg, Ulrik. 1997. “Polarization Diversity for Cellular Base Stations at 1800MHz.” Revision 1.0. Allgon.

2. Jakes, William C. 1974. “Microwave Mobile Communications.” New York. AmericanTelephone and Telegraph Company. Reissued in Cooperation with IEEECommunications Society. pp. 309-324.

3. Kozono, S. 1985. “Base Station Polarization Diversity Reception for Mobile Radio.”IEEE Transactions on Vehicular Technology. Vol. VT-33. No. 4. pp. 301-306.

4. Vaughan, Rodney G. 1990. “Polarization Diversity in Mobile Communications.” IEEETransactions on Vehicular Technology. Vol. 39. No. 3. (August): 177-186.

5. Tobin, Joe, Rob Nikides, Devesh Patel, Edward Golovin. 1997. “CDMA Dual PoleAntenna Testing - Arlington Heights, IL.” Version 1.0. Motorola.

6. Golovin, Edward. 1998. “A Comparison of CDMA Reverse Link Performance withBase Station Spatial and Polarization Diversity Reception (Motorola IsraelMeasurement Campaign in Urban Area at 900 MHz)” Version 2.0. Motorola.

7. Xiang, Jun. 1996. “Diversity Antenna Systems for GSM900/GSM1800/PCS1900Networks.” Issue A. Motorola.

8. Rappaport, Theodore S., and Sandhu, Sandip, "Radio-Wave Propagation for EmergingWireless Personal-Communication Systems". IEEE Antennas and PropagationMagazine, Vol. 36, No. 5, October 1994.

9. Fennick, John, Quality Measures and the Design of Telecommunications Systems.Artech House, Inc., 1988.



Table of Contents

8.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 3

8.2 Base Station Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 3

8.3 Synchronization Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 58.3.1 Global Positioning System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 58.3.2 Low Frequency Receiver (LFR). . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 68.3.3 High Stability Oscillator (HSO) . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 7

8.4 Synchronization Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 7

8.5 Synchronization Source Antenna Planning and Installation . . . . . . . . 8 - 88.5.1 GPS Antenna/Preamplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 9

8.5.1.1 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 98.5.1.2 Cabling Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 108.5.1.3 Multiple Frame GPS Cabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 10

8.5.2 Remote GPS Antenna/Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 118.5.2.1 RGPS Receiver Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 138.5.2.2 Cabling Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 148.5.2.3 Multiple Frame RGPS Cabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 15

8.5.3 LFR Antenna / Preamplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 168.5.3.1 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 17

8.5.3.2 Cabling Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 17

Chapter

8 Synchronization of theCDMA System


8

CDMA/CDMA2000 1X RF Planning GuideChapter 8: Synchronization of the CDMA System

NOTES

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8


8.1 Introduction

CDMA is based on a 1.2288 MHz per second chip rate. If this rate is offset by even a single chip,code translation will be impossible. Synchronization is, therefore, the basis of a CDMA system.This chapter emphasizes the reliance CDMA has on the GPS system and what backup timingtechnology is available. Signal delays are accounted for by the software, mainly by awaiting framesand counting chips. Timing is truly the heartbeat to CDMA.

A CDMA spread spectrum digital cellular system requires a much higher degree ofsynchronization between base stations than other cellular technologies. As defined in theWideband Spread Spectrum Cellular System standard (EIA/TIA/IS-95), CDMA base stations mustcontain a time base reference from which all time critical transmissions, including pilot PNsequences, frames, and Walsh functions, must be derived. This time base reference must be time-aligned to CDMA system time and must provide a means to maintain time alignment in the eventthat the external source of system time is lost. CDMA system time is defined to begin on January6, 1980 00:00:00 Universal Coordinated Time (UTC), which coincides with the start of GPS time,but does not incorporate UTC leap second corrections to system time clocks (i.e. GPS time).

This chapter describes the clock / synchronization sub-system specifically developed to achieve therequired level of synchronization and provide a high degree of redundancy for the MotorolaCDMA Base Station product.

8.2 Base Station Synchronization

The following items are the key specifications which influence the design of the clock /synchronization sub-system for CDMA base stations. They originate from the EIA/TIA/IS-95standard entitled “Mobile Station - Base Station Compatibility Standard Dual-Mode WidebandSpread Spectrum Cellular System" and the EIA/TIA/IS-97D "Recommended MinimumPerformance Standards for Base Stations Supporting Dual-Mode Wideband Spread SpectrumCellular Mobile Stations".

CDMA System Time• Origin: IS-95 Specification, Section 1.2

• Requirement: All base station digital transmissions shall be referenced to a commonCDMA system-wide time scale that uses the Global Positioning System(GPS) time scale, which is traceable to and synchronous with UTC.

Frequency Tolerance• Origin: IS-95 Specification, Section 7.1.1.2

• Requirement: The RF spectrum allocation shall not exceed + 0.05 ppm of the CDMAfrequency assignment.


8


Timing Reference Source• Origin: IS-95 Specification, Section 7.1.5.1

• Requirement: Time-aligned to CDMA system time shall maintain time alignment whenthe external source of system time is lost

Base Station Transmission Time• Origin: IS-95 Specification, Section 7.1.5.2

• Requirement: Generation of the pilot PN sequence with respect to CDMA system timeshall not exceed + 1 µs for CDMA channels from same base station,should not exceed + 3 µs between base stations (i.e. GPS Operational),and shall not exceed + 10 µs between base stations (i.e. GPS Failure).

IS-95 Section 7.1.5.2 specifies that all CDMA base stations should transmit their pilot sequencewithin + 3 µs of CDMA system time. CDMA system time is equivalent to GPS time. The primarymethod of providing this degree of synchronization and absolute time information is through theuse of the GPS satellite network using a GPS receiver. To maintain system synchronization, shouldthere be a GPS failure, an alternative source must be available at all base stations in the network.This source must keep a site within the + 10 µs specified to restrict the maximum window size overwhich a subscriber must search. Depending upon geographical location, Low FrequencyNavigational Broadcasts are an excellent source which can be used to provide indefiniteredundancy for a GPS failure. A “free running” rubidium oscillator is an option which provideslimited redundancy, since a base station will eventually drift out of synchronization due totolerances. These sources are graphically depicted in Figure 8-1, which shows the synchronizationarchitecture for a CDMA cell site.


8


Figure 8-1: CDMA Cell site Synchronization Architecture

8.3 Synchronization Sources

There are three (3) types of synchronization sources currently supported by the ClockSynchronization Manager (CSM) card which offer various degrees of base station synchronization.The supported reference sources are the Global Positioning System Receiver (GPSR), LowFrequency (LORAN-C) Receiver (LFR) and High Stability Oscillator (HSO).

8.3.1 Global Positioning System

The Global Positioning System (GPS) is a radio-navigation system that employs RF transmittersin twenty-four (24) satellites. The satellite configuration when completed will guarantee that a GPSreceiver located anywhere on earth can receive RF signals from at least four (4) satellites 24 hoursa day (with unobstructed visibility). For commercial use, each satellite transmits unique bi-phasepseudo-random-noise codes on the L-band carrier frequency of 1.57542 GHz. A GPS receiver

Spanline Interface

CDMA base station 1

LFReceiver

GPSReceiver

Spanline Interface

CDMA base station 2

LFReceiver

GPSReceiver

GPSSat.

1

GPSSat.N

fc = 1.57 GHz N = 8 MAX

fc = 100 kHz M = 6 MAX

LFBROADCAST

TRANSMITTER

LFBROADCAST

TRANSMITTER

RubidiumOscillator

RubidiumOscillator

MSC


8


decodes the spread spectrum modulations and uses triangulation techniques on the signals tocalculate precise latitude, longitude, altitude and timing information from a position on earth. GPS,officially known as the NAVSTAR GPS (NAVigation System with Timing and Ranging GlobalPositioning System) is operated by the Department of Defense (DoD). It consists of twenty-one(21) operational satellites and three (3) spares circling the earth approximately once every 12hours.

The GPSR, when used as a synchronization source for a CDMA cell site, offers several significantadvantages over the other alternatives. The system provides world-wide coverage, absolute systemtime information, excellent accuracy, and all at a relatively low cost.

There are, however, some limitations associated with the use of GPS which prevent it from beingthe total system solution for base station synchronization. The requirement for an unobstructedview of the satellite orbits forces several restrictions on antenna placement and cabling at a cell site(see Section 8.5). Several environmental factors (i.e. snow, sleet, debris, RF interference) canseverely degrade receiver performance. Field tests have shown that some receivers can be jammedby intentional or non-intentional low power interference sources over a fairly wide range (1 Wattup to 14 miles). Since the entire network is under DoD control and has important militarysignificance, the uninterrupted availability of the system can also be cause for concern. Theintentional introduction of clock jitter to the GPS timing signal commonly referred to as SelectiveAvailability (SA) was until recently used to limit the use of the GPS for hostile purposes. With thecessation of SA other means of preventing the hostile use of the GPS may be employed such asjamming or temporary interruptions of service.

8.3.2 Low Frequency Receiver (LFR)

Transmissions within the Low Frequency (LF) radio band are primarily ground based waves whichare not affected by changes in the ionosphere level. This is why LF radio frequencies (30 kHz to300 kHz) exhibit only minor phase variations over time. For this reason, the LF band has beenprimarily used for standard time and navigation broadcasts. There are many LF broadcasts(LORAN-C, WWVB, MSF) which could be considered suitable for a synchronization source.

LORAN-C (LOng RAnge Navigation-C) is perhaps the most practical LF broadcast for thispurpose. This is due to the wide coverage and accurate timing signals transmitted by LORAN-C.There are currently more than fifty (50) transmitters throughout the world, providing coverage overmost of the northern hemisphere. A LORAN-C transmitter’s coverage can extend fromapproximately 1,500 to 2,000 miles. The domestic transmitters are run off of three (3) Cesiumclocks at each transmitter site, with eighteen (18) transmitters organized into six (6) chains acrossthe continental U.S (some transmitters are dual rated).

While LORAN-C does not broadcast UTC information, its signal is traceable to UTC. The use ofthis transmission requires that initial synchronization be achieved by some other means (GPS).LORAN-C does provide much greater coverage and is less prone to atmospheric disturbances ascompared to other LF sources which are UTC based (i.e. WWVB).

A precisely timed interval is broadcast by LORAN-C stations that is within + 200 ηs of itsprescribed time. By measuring this period with an operational GPS receiver and correlating it to


8


current GPS time, LORAN-C provides a widely available central synchronization source that caneasily maintain base station synchronization for a CDMA cellular network. While there is presentlylittle coverage in the southern hemisphere, plans are being considered for South America and otherpotential CDMA markets.

By phase locking to the pulse train transmitted by a LORAN-C station, it is possible to synthesizea clock having a stability of 1 X 10-12. The LFR can maintain a cell site’s synchronization to IS-95 levels indefinitely while receiving LORAN-C transmissions.

8.3.3 High Stability Oscillator (HSO)

The High Stability Oscillator (HSO) is an optional card that provides backup for the GPSR. Itcontains a highly stable timing reference when there is a loss of the GPS signal, a GPSR failure, ora primary CSM failure. The outputs of the HSO card are routed to each of the CSM cards in amodem frame (CSM 1 and CSM 2). For the HSO to provide the specified performance, a minimumoperational period of 24 hours is required for oscillator stabilization and numerical compensation.After the oscillator is stabilized, the HSO is capable of maintaining the synchronization initiallyestablished by the GPS reference signal for a period of 24 hours with a maximum temperaturedeviation of + 10°C during the backup interval.

8.4 Synchronization Redundancy

As has been previously stated, the GPSR acts as the primary synchronization reference source forthe Motorola CDMA product line. Either an LFR or HSO can be employed as a backup timingreference to the GPSR. The following list summarizes the strengths and limitations of the primaryand redundant timing reference sources. Because LORAN-C transmissions are synchronous toUTC and GPS time, the LFR can provide extended backup intervals in the event of a GPS or GPSRfailure. The LFR is useful in sites that are difficult to reach for service or where extreme reliabilityis required.

The HSO does not depend on the reception of a transmitted timing signal and therefore does notrequire the installation of an external antenna and is also immune to external jamming. However,the HSO only provides a limited backup interval.


8


The following provides a general comparison of strengths and limitations of the threesynchronization sources.

8.5 Synchronization Source Antenna Planning and Installation

This section is intended to provide some initial guidance for the system engineering activitieswhich will be required to properly install the synchronization antennas at a cell site. These aregeneral suggestions and should not be considered absolute requirements (unless so indicated).

It is recommended that the GPS and LFR antennas be rooftop mounted. For optimum performance,both antennas should have a clear view within 20° of the horizon in all directions. It is alsorecommended that the GPS and LFR antennas be located as far as possible from the main cell siteantenna tower. This will minimize tower shadowing, potential damage due to lightning strike andfalling ice, and reduce the possibility of receiver overload due to the strong fields present in closeproximity to the transmitter antennas. At cell sites employing the LFR backup, care should be taken

GPS Strength:

• World-wide coverage• System time information

accurate to within + 1µS• Signal unaffected by electrical

storms• Unaffected by Low Frequency

jamming sources

LORAN-C Strength:

• Non-military system• Line of site view of transmitter

is not required• Reception is not affected by

snow, sleet or heavy rain• Unaffected by High Frequency

jamming sources• Capable of maintaining

network synchronization indefinitely

HSO Strengths:

• No antenna required• Immune to external jamming

sources• World-wide use

GPS Limitations:

• Military significance (and control)• Unobstructed view of satellites required• Signal may be significantly attenuated by

snow, sleet or heavy rain• Jamming on carrier frequency possible

LORAN-C Limitations:

• Poor coverage in southern hemisphere• Synchronous to UTC but no encoded

time standard• Signal may be affected by extreme

electrical storms.

HSO Limitations:

• limited 24 hour backup


8


to physically separate the LFR and GPS antennas to reduce the possibility of common modefailures (e.g. both antennas being damaged by lighting, falling ice, etc.).

While the above antenna installation configuration is optimum, variations are still possible for aparticular site. A site survey may be the most practical means for determining if a particularlocation with questionable surroundings will provide acceptable performance.

8.5.1 GPS Antenna/Preamplifier

The GPS Antenna/Preamplifier unit is an active micro-strip patch which obtains power through aDC bias on the coaxial cable. It is recommended that the GPS antenna be pole mounted to helpreduce shadowing and signal attenuation due to potential snow buildup or blown debris. Thesurface of the antenna, must be mounted parallel with the horizon. For optimum performance, aclear view to within 20° of the horizon is desirable. Any reduction in the view may result in reducedsatellite coverage, degraded receiver performance, and in extreme cases, temporary loss of the GPStiming signal.

For an antenna location to be considered acceptable for cell site synchronization, a 24 hour surveyshould be performed while noting the number of GPS satellites being tracked by the CSM. Antennainstallations which demonstrate the reception of less than four (4) GPS satellites during any part ofthis 24 hour survey period may suffer from a high number of GPS Reference Source FailureTrouble Notifications or increased BTS initialization periods. Attempts to improve the visibility ofthe a GPS antenna should be made when less than four (4) satellites are tracked during the 24 hoursurvey period.

8.5.1.1 Specifications

The Motorola Position and Navigation Systems Business (PNSB) Timing 2000 GPS Antenna isthe recommended GPS antenna for use with the CSM card in SC96/48/24xx CDMA Base Stationsdue to its superior RF performance. The Timing 2000 GPS antenna is available from the MotorolaWireless Networks Products (WNP) group with the following part number: 242884A. CompleteGPS antenna kits (including all necessary mounting hardware, weatherproofing materials,lightning arrestor, etc.) are also available with the following part numbers: CGDSAWGPSKIT12,CGDSAWGPSKITV5 or CGDSAWGPSKITV5A.

Note: The part numbers provided in this document are subject to change. Contact theappropriate Motorola product/program manager for updates to the product part numbers.

The GPS antenna used with the CSM card should meet or exceed the following specifications:

• Power Requirements: 5 VDC + 0.25 V @ < 30 mA (DC bias supplied via coax by GPSR)• Gain: 10dB minimum, 25 dB typical, 26 dB maximum at 1.57542 GHz + 1.024 MHz• Noise Figure: < 2.5 dB• Altitude: < 5 km• Operating Temperature: -40οC to +85οC• Humidity: 0-85% non condensing 0οC to +60οC (when properly mounted)


8


8.5.1.2 Cabling Requirements

Selection and installation of the cable for the GPS antenna should be handled in the same manneras the other external RF cabling required at a cell site. The following items should help guide theselection of the RF cable type and connectors which will be needed for a particular cell siteinstallation. For additional information in determining the proper cable type, length, andinstallation requirements, please consult Chapter 4, Antenna Description of the Motorola"ONCORE USER’S GUIDE", June 1998, Revision 3.2 and "Guidelines for JCDMA GPS Multi-frame Antenna Splitting", Issue 1.1, October 14, 1997 by Richard Dickens, Motorola, Inc.

• Impedance: 50Ω Coaxial Cable

• Maximum receive system noise figure: < 4.0 dB loss @ 1575 MHz including all cableloss, receiver noise figure, antenna LNA noise figure and in line amplifier noise figures

• Antenna and cabling signal gain: 10 dB min., 26 dB max.

Note: The Clock Synchronization Manager (CSM) located in the Motorola modem frame hasthe capability to compensate for the time delays introduced by the cable propagationcharacteristics. For sites requiring long cable runs it may be desirable to compensate forthis delay, so the installer should record total cable length and the propagation factor forthe cable type used.

Additional lightning protection may be required at the cable entry point into the building if localcodes or operator policies warrant. (If used, this additional lightning protection device must beincluded in the loss calculation). A protection device should be selected using the followingguidelines:

• Carrier Frequency: 1575 MHz

• Bandwidth: > 2.05 MHz + DC

• Clamping Voltage: > 7 VDC

8.5.1.3 Multiple Frame GPS Cabling

For most applications, one (1) RF GPS antenna can feed up to four (4) BTS frames with a 4:1distribution amplifier (see Figure 8-2). It is recommended that a splitter have all output ports DCcoupled to the RF GPS antenna input, so that there is no dependency on the operation of a singleframe. By using a DC coupled GPS antenna splitter, any one (1) frame can provide the necessaryDC operating voltage to the RF GPS antenna.

When using an RF GPS signal splitter, it will be necessary to only use version SGLN1145DE andlater CSM cards. The SGLN1145DE CSM employs a GPS receiver which is capable of sourcingan 80 mA GPS antenna current. A typical GPS signal splitter requires as much as a 50 mAoperational current. A signal splitter and GPS antenna configuration should be selected that doesnot exceed a total operational current of 80 mA.


8


Care should be taken to insure that the overall GPS antenna system noise figure and gainrequirements specified in Section 8.5.1.2 are met when utilizing GPS signal splitters or in lineamplifiers. Please consult the "Guidelines for JCDMA GPS Multi-frame Antenna Splitting", Issue1.1, October 14, 1997 by Richard Dickens, Motorola, Inc. document for system guidelinesregarding the proper use of GPS signal splitters.

Figure 8-2: Single and Multi-Frame RF GPS Configurations


8.5.2 Remote GPS Antenna/Receiver

The Remote Global Positioning System (RGPS) receiver is an alternative to the RF GPS receiverwhich allows great installation flexibility. Because the RGPS receiver provides a digital interfaceto the Base Station Equipment, RF cabling losses are not a factor in installation.

The RGPS receiver consists of a GPS antenna, GPS receiver, and a digital interface enclosed in an

LightningArrestor

RF GPSAntenna

EarthGroundIN

OutA OutB

OutC OutDCGDSHP58536A 1:4Active GPS signal

splitter

GPSAntenna Port


8


outdoor rated enclosure. The function of the RGPS head is to receive the GPS satellite signals,process them, and output accurate timing information (GPS & UTC). The major differencebetween a RGPS installation and a traditional GPS installation is the interface that is used to spanthe distance between the antenna and the target equipment (either a BTS or pilot beacon). In atraditional RF GPS setup, the distance is spanned with coax connecting the GPS antenna to theGPS receiver. With Remote GPS, the distance is spanned with a digital interface between the GPSreceiver and the target equipment. The digital interface is less distance sensitive than the coaxialinterface. The overall function of the RGPS head is the same as that of a traditional RF GPSinstallation, but the RGPS receiver has an additional feature to measure and compensate for thegreater cable lengths (delays) possible with RGPS. This circuit can be used to automaticallydetermine the time delay of the cable between the RGPS head and the target equipment. Cablelengths of as great as 1 km can be used between the RGPS receiver and BTS connection. With theuse of a Remote GPS Distribution (RGD) card, multiple co-located frames can share one (1) RGPSreceiver. The various RGPS receiver installation configurations are depicted in Figure 8-3: Singleand Multi-Frame Remote GPS Configurations.

It is recommended that the RGPS head be pole mounted to help reduce shadowing and signalattenuation due to potential snow buildup or blown debris. The surface of the antenna must bemounted parallel with the horizon. For optimum performance, a clear view to within 20° of thehorizon is desirable. Any reduction in the view may result in reduced satellite coverage, degradingreceiver performance, and in extreme cases, temporary loss of the GPS timing signal.

For an antenna location to be considered acceptable for cell site synchronization, a 24 hour surveyshould be performed while noting the number of GPS satellites being tracked by the CSM. Antennainstallations which demonstrate the reception of less than four (4) GPS satellites during any part ofthis 24 hour survey period may suffer from a high number of GPS Reference Source FailureTrouble Notifications or increased BTS initialization periods. Attempts to improve the visibility ofthe a GPS antenna should be made when less than four (4) satellites are tracked during the 24 hoursurvey period.


8


Figure 8-3: Single and Multi-Frame Remote GPS Configurations


8.5.2.1 RGPS Receiver Specifications

The following is a list of RGPS receiver specifications:

• Power Requirements: Voltage Range +36 to +8 VDC @ 2.0 Watts

• Altitude: < 5 km

• Operating Temperature: -40οC to +75οC

RG

D

Expansion FramesStarter Frame

Lightning ArrestorWNP CGDS0971017AA1

CellsiteGround

30-86433H02

30-86433H02

30-86433H02

30-8

6433

H02

01-86012H03(Symmetricom Z3827A)

RGPS

RGPS Connetor(See Note 2)

RGPS Receiver Cable30-87465C0x or 30-86039Hxx

(See Note 1)

12 pin DeutschConnectorRGPS Interface Cable

30-87465C0x or 30-86433Hxx(See Note 1)15 pin

Subminature "D"Connector

RGDSGLN5684AA


8


• Humidity: 5% to 95% R.H., < 0.024 pounds of water per pound of air, non-condensingper Telcordia standard

• Physical Dimensions: 6.00" diameter, 6.38" height (excluding cable)

• Weight: 24oz. (without mounting hardware)

• Mounting: Threaded Pole Mount (3/4" standard pipe thread)


The RGPS receiver employs a six (6) twisted pair cabling interface which provides all necessarypower, data transmit, data receive and timing signals. As is shown in Figure 8-3, two (2) basiccable assemblies are available for connection to the RGPS receiver. The 30-87465C0x assemblyis a fully terminated cable consisting of a twelve (12) pin "Deutsch" connector which connects tothe RGPS receiver and a fifteen (15) pin subminiature "D" connector which connects to the modemframe or RGD card RGPS connector. An additional cable assembly is available for those BTSswhich employ a punch block RGPS cabling interface. The 30-86039Hxx cable assembly isterminated on only one end with a twelve (12) pin "Deutsch" RGPS connector. The un-terminatedend of the 30-86039Hxx cable consists of individual 22 gauge wires for direct connection to apunch block. The 30-86039Hxx cable assembly is typically used with SC3xx and SC4812ET typeframes.

The RGPS receiver cabling shall meet the following requirements:

• Conductors: Six (6) 22 gauge twisted pairs (12 conductors) with overall foil shield

• Characteristic Impedance: 120Ω + 20%

• DC Resistance: < 7Ω/100 m

• Temperature Range: -40οC to +75οC

• Near End Crosstalk Attenuation: > 56 dB at 1 MHz

• Jacket Material: FEP Teflon

• Insulation: FEP Teflon

• Cable Drain Wire: 22 gauge

Connector:

The twelve (12) pin connector attached to the pigtail of the RGPS head is a Deutsch MMP21C-2212P1. The twelve (12) pin connector attached to the cable which connects the RGPS head to theBTS/shelter is a Deutsch MMP26C-2212S1. A diagram of the BTS to RGPS cable matingconnector is shown in Figure 8-4.


8


BTS to RGPS Cable:

• Conductors: Six (6) twisted pair (12 conductor), 22 gauge, solid conductor

• Maximum cable length: 1 km (3,280 feet)

The BTS to RGPS cable wiring definitions (pin out, wire colors, and signal description) areprovided in Table 8-1.

Figure 8-4: BTS to RGPS Cable Connector Diagram

Table 8-1: BTS to RGPS Cable Wiring Definitions

8.5.2.3 Multiple Frame RGPS Cabling

The Remote GPS Distribution (RGD) card allows a single RGPS receiver to provide timing to asmany as four (4) co-located CDMA modem frames. A typical RGD installation can be seen inFigure 8-3. The RGD card provides individually buffered copies of the RGPS timing and receivedata signals to each of the connected modem frames. The RGD includes a Master Frame arbiter

1

2

3

45

6

7

8

910

11 12Pin 1

BTS Connector(15 Pin Subminature D)

(Plug)

RGPS Connector(Deutsch MMP26C-2212S1)

(Socket)

BTS Connector(15 Pin Subminiature D)

(Plug)

RGPS SignalDescriptions

RGPS CableColor Code

(wire/stripe)

BTS ConnectorPin Number

RGPS_Tx+

RGPS_Tx-

1_PPS+

1_PPS-

Reserved

Spare

Green

Green/Black

Brown

Brown/Black

Red

Red/Black

1

9

2

10

No Connection

No Connection

RGPSConnector

Pin Number

5

4

11

12

7

6

RGPS_Rx+

RGPS_Rx-

+28V_B

Power_RTN_B

+28V_A

Power_RTN_A

White

White/Black

Yellow

Yellow/Black

Blue

Blue/Black

4

12

7

14

8

15

3

2

10

8

1

9

Cable Drain - 13No Connection


8


which selects one (1) frame to act as the RGPS controller. Should the selected Master Frame failor otherwise go off line, the RGD will select another active frame to act as the RGPS controller.There are no dependencies on any single modem frame for proper RGD and RGPS operation. TheRGD supports a maximum cable length of 1 km (3,280 feet) between the RGPS receiver and aBTS. See Figure 8-5 for a diagram and the following notes for additional requirements associatedwith this configuration.

Figure 8-5: Remote GPS Distribution Box Diagram

Notes for Figure 8-5:

• The maximum distance from the RGPS head to the BTS is 1 km (3,280 feet) (i.e. A + B4above).

• The maximum recommended difference between BTSs (i.e. B4 - B1 above) is less than15.2 meters (50 feet) for the CSM to automatically compensate for all cable delays. Ifthe difference is greater than 50 feet, then a delay parameter will need to be configuredin the MM data base for each BTS.

• The SC4812T has an RGD function incorporated into the top of the frame. Thus, themaximum cable length for an expansion BTS is 50 feet for automatic delaycompensation.

• Surge protection is required at the building entry point for the cable of the remote GPShead prior to the connection of the remote GPS distribution box.

8.5.3 LFR Antenna / Preamplifier

It is important to select an antenna location which will not degrade the performance of the LowFrequency Receiver. Since line of sight reception is not required for satisfactory performance atLORAN frequencies, the installation of the antenna and preamplifier can be accomplished quiteeasily, provided some basic concerns are addressed.

BTS-1

RemoteGPSHead

RemoteGPSDist.Box

BTS-2

BTS-3

BTS-4

B1

B2

B3

B4

A

1 km (3,280 feet) Max.

15.2 m Max. (see notes below)


8


The ideal location for the LFR antenna/preamplifier unit should be free of very large obstructionsat an angle of 30° above the horizon. For best performance, it is recommended to mount the LFRantenna at least 10 feet above ground level and approximately 50 feet away from any co-locatedhigh tension power distribution lines. The unit should be near an earth referenced metal structure(building framework) which can be used to provide proper antenna grounding. A four (4)conductor shielded cable connects the LFR antenna/preamplifier unit to the modem frame's MFIOpanel within the cell site building.

A site survey which measures performance levels can be a useful way to determine whether aspecific location will provide acceptable performance. The following performance criteria can beused in such s survey:

• Primary Station: Signal Strength > -8 dB (as measured by the LFR)

• Alternative Stations: Signal Strength > -8 dB (minimum of two (2) additional as measured by the LFR)

8.5.3.1 Specifications

The following is a list of LFR antenna/preamplifier unit specifications:

• Power Requirements: 12 VDC @ 10 mA (DC bias supplied via differential pair by LFR)

• Altitude: < 5 km

• Operating Temperature: -40°C to +85°C

• Humidity: 0-100%

• Physical Dimensions: 3.5" X 3.24" base; 26.25" overall height

• Weight: 52 oz. (including mounting bracket & hardware)


The cabling requirements for the LFR antenna are much simpler due to the low frequency natureof this signal. The differential signal requires one twisted pair connection. A DC bias on this pairprovides power to the preamplifier unit. A second twisted pair connection allows preamplifiercalibration and fault detection capability. While the standard LFR kit includes a 150’ terminatedcable assembly, the following information is provided in case variations are necessary forparticular installations.


8


Cable Requirements

The following is a list of LFR cable requirements:

• Impedance: ~100Ω differential

• Conductors: Two (2) twisted pairs 24 AWG with individual shields

• Belden Cable Type: 9729

• Maximum Length: 300 feet

Wiring Definitions

The following information provides the wiring definitions for LFR cable connectors:

• To Modem Frame: Nine (9) pin Sub-miniature D Plug (male pins) (i.e. AMP 747952-1)

• To Antenna / Preamplifier: Five (5) pin circular (i.e. TAJIMI TC1108-12A10-5M(8.6))

Grounding Guidelines

In order to insure a dependable ground path for proper signal reception, a corrosion resistantconnection must be attached to a conductive metal structure leading to a common earth ground. Incases where metal structures at the antenna site may be struck by lightning, Motorola groundingguidelines (“Grounding Guidelines for Cellular Radio Installations”) must be followed to assure

Pin Number Wire Color Signal Description

1 Red Antenna+ (Power & Signal)

6 Black (paired with Red) Antenna- (Power & Signal)

5 White Calibrator+

9 Black (paired with White) Calibrator-

3 Bare Drain (from shield)

Pin Number Wire Color Signal Description

D Red Antenna+ (Power & Signal)

E Black (paired with Red) Antenna- (Power & Signal)

A White Calibrator+

B Black (paired with White) Calibrator-

C Bare Drain (from shield)


8


maximum safety of personnel and equipment. The following wire size is recommended fordifferent grounding lengths.

• 14 gauge for runs < 40 feet

• 12 gauge for runs < 100 feet

Additional lightning protection may be added at the cable entry point into the building if localcodes mandate it. A protection device should be selected using the following guidelines:

• Carrier Frequency: 100 kHz

• Bandwidth: >> 35 kHz + DC

• Differential Signals: 2

• Clamping Voltage: > 15 VDC


8


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Table of Contents

9.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 3

9.2 Cellular/PCS Inter-System Interference. . . . . . . . . . . . . . . . . . . . . . . . . 9 - 39.2.1 Intra-Band Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 4

9.2.1.1 AMPS Cells to CDMA Subscribers . . . . . . . . . . . . . . . . . . . . . . . . 9 - 69.2.1.2 AMPS Subscribers to CDMA Cells . . . . . . . . . . . . . . . . . . . . . . . . 9 - 99.2.1.3 CDMA Cells to AMPS Subscribers . . . . . . . . . . . . . . . . . . . . . . . . 9 - 99.2.1.4 CDMA Subscribers to AMPS Cells . . . . . . . . . . . . . . . . . . . . . . . . 9 - 9

9.2.2 Inter-Band Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 109.2.2.1 Preventative Measures: BS-to-BS Interference. . . . . . . . . . . . . . . . 9 - 139.2.2.2 Preventative Measures: Subscriber-to-Subscriber Interference . . . 9 - 27

9.3 PCS and Microwave Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 289.3.1 PCS to Microwave Interference . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 28

9.3.1.1 Coordination Distances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 299.3.1.2 Propagation Models. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 309.3.1.3 Power Aggregation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 349.3.1.4 Microwave Receiver Interference Criteria . . . . . . . . . . . . . . . . . . . 9 - 359.3.1.5 PCS to Microwave Interference Summary . . . . . . . . . . . . . . . . . . . 9 - 37

9.3.2 Microwave to PCS Interference . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 389.3.2.1 General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 389.3.2.2 Calculation of Nominal Noise Floor . . . . . . . . . . . . . . . . . . . . . . . . 9 - 389.3.2.3 Calculation of Effective Interference Power . . . . . . . . . . . . . . . . . . 9 - 399.3.2.4 Calculation of Effective Noise Figure . . . . . . . . . . . . . . . . . . . . . . . 9 - 399.3.2.5 Microwave to PCS Interference Summary . . . . . . . . . . . . . . . . . . . 9 - 40

9.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 40

Chapter

9 Inter-SystemInterference (ISI)


9

CDMA/CDMA2000 1X RF Planning GuideChapter 9: Inter-System Interference (ISI)

NOTES

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9


9.1 Introduction

The purpose of this chapter is to provide systems engineers/planners with a basic understanding ofseveral inter-system interference issues that can adversely affect CDMA system deployments. Inthis chapter, CDMA is defined as being a general term that applies not only to 2nd generation (2G)digital cellular, as defined in IS-95A/B, but also to 3G digital cellular, as defined in IS-2000.Currently covered in this chapter are cellular/PCS inter-system interference, as well as 1900 MHzCDMA and Microwave interference. For this discussion, there are no material differences between2G and 3G-1X that would have to be dealt with for Intra-band and Inter-band interference issues.In the future, any additional inter-system interference scenarios that arise will be addressed in laterversions of this document, as necessary.

9.2 Cellular/PCS Inter-System Interference

In real world situations, frequency spectrum is the most limited resource for implementing orexpanding cellular radio telecommunications systems. As cellular service continues to migratefrom the use of analog technologies to digital technologies such as CDMA, operators are oftenfaced with choosing one of two options:

• Spectrum clearing, when deploying a CDMA system into an existing frequency band, byclearing spectrum that was formerly used by other cellular technologies. Examples ofsuch deployments could include the clearance of AMPS analog spectrum for use withco-existing 800 MHz CDMA systems and the clearance of TACS analog spectrum foruse with co-existing 900 MHz CDMA systems.

• Spectrum Reassignment, when deploying a CDMA system in an alternate frequencyband previously unallocated for cellular use. Examples of this deployment strategycould include the use of the AMPS band for CDMA in an area already using TACS and/or GSM spectrum, and the use of the PCS 1900 MHz band for CDMA in an area alreadyusing DCS 1800 MHz spectrum.

Associated with each of the above deployment options is the potential for interference between thesystem being introduced and the currently existing, co-located cellular system(s). The severity ofthis interference, and its impact, will depend mainly on how frequency spectrum is assigned to allcellular systems that are required to co-exist in a given coverage area. The interference can bedivided basically into two categories that will be referred to here as intra-band and inter-band.Intra-band interference corresponds to interference between co-existing systems that share thesame cellular frequency band allocations, such as AMPS and TACS. Inter-band interferencecorresponds to interference between co-existing systems that utilize multiple cellular frequencyband allocations, such as:

• AMPS with TACS and GSM, or• DCS 1800 with PCS 1900


9


9.2.1 Intra-Band Interference

Many cellular operators are installing, or have already installed, CDMA digital technology thatallows them to continue the process of expanding capacity in their currently existing AMPS, orTACS, analog markets. These cellular operators may now be at the point where they want to install,or are installing, the next phase of CDMA, namely IS-2000 1X technology having the samespectral bandwidth of 1.23/1.25 MHz, but twice as many Walsh codes (128). For purposes of thisnext step in technology migration, which enables greater throughput and data services, there are nomaterial differences between 2G and 3G-1X that would have to be dealt with for Intra-band andInter-band interference issues. In these markets, both CDMA and the currently operating analogsystem must exist simultaneously and in some cases even share the same spectrum. As a result, inaddition to the possibility of increased blocking on the existing analog cellular system (due tospectrum clearing), there exists the potential threat of inter-system interference between the co-existing, co-frequency-band-allocation systems. This interference, referred to as intra-band inter-system interference, exists typically between the base stations of one system and the subscriberstations of the other, co-existing system (Figure 9-1).

Figure 9-1: Intra-Band Interference

Here, the interference arises as a consequence of the near-far effect, an example being created whena nearby base station transmitter, serving one system, captures the receiver of a subscriber unitbeing served by another system base station that is significantly farther away. The closer,interfering base station transmitter is able to capture the victim subscriber unit receiver because ofthe small propagation path loss between them. This interference phenomenon can have asignificantly greater effect on a new system being deployed with fewer cell sites than the other pre-existing, co-band system. This is because the new system, with its fewer cell sites, creates greaterdifferences in the signal levels seen either in the Forward (downlink), or Reverse (uplink), RFchannels. Practically, this situation can be avoided by system planners if they strive to keep the cellsite ratio (B:A) as close to (1:1) as possible, where "B" indicates the number of new cell sites, forsystem B, relative to "A," the number of old cell sites already existing in system A. Anotherimportant aspect regarding the relationship between B and A is that the cell site base stations forsystem A and B should be located very near each other, or co-located, as close as possible.

An example of an unbalanced situation, reflecting a cell site (B:A) ratio of (1:3), is depicted inFigure 9-2. Here, a subscriber being served by system B could potentially be threatened with intra-band interference to its receiver from cell site transmitters in the co-existing system A. System Bsubscribers could potentially experience their worst operating performance at the edges of cells insystem B that lie close to the centers of the cells from system A.

System A System B System BCell Subscriber Cell


9


Similarly, if the system A subscriber is close enough to a non-co-located system B cell site, thesystem A subscriber’s transmitter could also potentially cause interference to the system B cell sitereceiver if the subscriber is transmitting at a high enough power level.

Figure 9-2: Example of a (1:3) Overlay

Depending on the actual overlay of the two co-existing systems, there exists the potential for fourdifferent interference scenarios:

• System A subscriber(s) interfering with System B base station• System A base station interfering with System B subscriber(s)• System B subscriber(s) interfering with System A base station• System B base station interfering with System A subscriber(s)

The above four scenarios are discussed in more detail in the following four sub-sections, using aco-located AMPS and 800 MHz CDMA system as an example. Note that intra-band interferenceis not a problem unique to CDMA, as it is a radio-systems issue. The same issues will occur witha GSM system if overlaid on a TACS system in the same frequency band. All technologies havethe same set of contributing factors. Some key variables for the interfering transmitter are: ERP(Effective Radiated Power, which is RF power directed towards the receive antenna), transmitnominal power, and sideband emissions. A few key variables for a potential victim receiver are:IM (Intermodulation) intercept point of the receiver, filter protection available, and gain of thereceive antenna system.

After the potential for interference has been assessed, corrective action can then be taken, ifrequired. Corrective action can be in the form of improving the filtering at the site. Or, it can berelated to any of the other variables noted above: improving Tx sideband emissions, adjusting ERP,doing frequency planning, etc. In all cases, the potential for interference, and the best correctiveaction, is site specific. There is no generic solution, so site engineering is required.Recommendations for corrective action are addressed, where appropriate, in later paragraphs ofthis section.

System B

System A

X

XX

X

XX

X - Potential InterferenceAreas

X

X

X

X

X

X

XX

X

X

XX

X

XX

X

X

X


9


One additional note that cannot be overlooked has to do with Rogue transmitters, which areunauthorized and illegal transmitting units. Even though the existence of Rogue transmitters arerare, the operation of just a single Rogue transmitter can cause problems for one or more sectors ofa CDMA system, if this Rogue unit has a relatively high RF power output. A common symptomthat is observed when a Rogue unit is transmitting is that the impacted CDMA cells will exhibit adecrease in coverage area due to the elevated interference noise rise caused by the Rogue unit.

9.2.1.1 AMPS Cells to CDMA Subscribers

There are several potential inter-system interference mechanisms, but the dominant problem is aninterference product resulting from strong AMPS base station signals mixing in the front end of asubscriber receiver, thereby creating unwanted signals that land inside the CDMA subscriberreceiver passband. The subscriber receiver intermodulation (IM) performance is essentiallyidentical for all technologies.

In order for this phenomena to occur, three things must happen simultaneously. First, the CDMAsubscriber unit must be physically close to the AMPS base transmitter site. Second, the AMPStransmitter frequencies must create a third order mix. Third, the desired CDMA received signalmust be relatively weak.

Anything that can be done to overcome or inhibit any combination of the above mechanisms willhelp in preventing an interference problem. For example, one of the easiest ways to prevent thisparticular interference problem is to make sure that there is a CDMA base station located at eachone of the AMPS transmitter sites. Such a configuration was described earlier and is termed a (1:1)one-to-one overlay. In this arrangement, the undesired mix products will still occur, but becausethe desired CDMA signal from the local transmitter is always stronger than the mix products, theproblem is prevented. Hence, the first and third mechanisms are no longer contributors.

Usually, the problem will appear when an operator tries to deploy CDMA at fewer sites than everyAMPS site (usually during the initial phase of introducing CDMA into a market). The operator maytry to put CDMA base stations into fewer AMPS sites, to save initial system deployment costs. Ifthis ratio is about one-third of the AMPS sites, then it would be called a (1:3) overlay, reflectingthe (B:A) ratio. (See Figure 9-3).


9


Figure 9-3: AMPS System with a Larger CDMA Site Overlay(cells marked “a” are potential CDMA sites)

In this case, it would be possible for the CDMA subscribers to be exposed to strong local AMPSsignals while trying to receive a weak CDMA signal from a great distance, because two-thirds ofthe AMPS sites would lack a co-located CDMA transmitter. In fact, if the system is laid out on aregular grid, with a (1:3) overlay, the AMPS base sites that lack co-located CDMA transmitterswill be exactly halfway between the CDMA base sites, thereby allowing the areas having theweakest CDMA signals to have AMPS base sites located there.

It should be noted that a (1:1) deployment is a “fix” for reducing the interference between anoperator’s AMPS base stations and his own CDMA system, but this does not totally eliminate theinterference. There is still the possibility that a CDMA subscriber could experience interferencewhen in the vicinity of the other operator’s cell site in an area having a weak CDMA desired signal.As a practical matter, high traffic areas will attract cells from both operators. As a result, the hightraffic areas will usually have CDMA base stations deployed in the same area which will producea strong CDMA signal in order to overcome these problems.

When there is an AMPS site without a co-located CDMA site, a subscriber may or may notexperience noticeable interference, depending on the number, level, and frequency of the AMPScarriers, and the CDMA signal strength itself. Using a few simplifying assumptions, Figure 9-4shows the relationship between the signal levels at which the interference will appear for an un-modified IS-98 subscriber receiver, and for a subscriber receiver having either of two proposedsubscriber changes, namely a switchable attenuator, or a continuously variable attenuator.


9


Figure 9-4: Required CDMA Signal Strength vs. Interfering AMPS Signal Strength

As can be seen from the graph, the interference can be mitigated by reducing the AMPS signallevel, or by raising the CDMA signal level. The most likely way of increasing CDMA signal levelswould be to add one or more CDMA transmitter sites in the immediate vicinity of any potentialinterfering AMPS transmitters.

Recently, a specification change for IS-98A has been proposed that addresses the need forimproved IM performance in the subscriber receiver. As the graph above clearly shows, theproposed change allows for a wider front end dynamic range in the subscriber, either by utilizinga variable attenuator, or a switchable attenuator, in the front end. The use of either of theseattenuators introduces approximately 20 dB of loss so that the subscriber can operate in a strongsignal environment (for example, if the received CDMA signal strength were greater than -79dBm). The operator will still have to manage a minimum CDMA signal strength in accordancewith the anticipated interference levels that may be potentially encountered.

-120

-100

-80

-60

-40

-20

0

-45 -40 -35 -30 -25 -20 -15 -10 -5

IS-98 spec (1% FER)

IS-98A spec (1% FER) w/ variable attenuator

IS-98A spec w/ step attenuator

A signal strength

Interfering AMPS signal Strength (per carrier for 2 carriers)

JSR 2/7/96

IS-98A; Step Attenuator

IS-98 Spec Level

IS-98A; Variable attenuator

Req

uir

ed C

DM

A S

ign

al S

tren

gth

Interfering AMPS Signal Strength(per carrier for 2 carriers)


9


To facilitate assessing the impact of any potential inter-system interference, the Motorola CDMASimulator has been modified to include an interference zone simulation and prediction.

As for the potential for inter-system interference at 1900 MHz, this type of interference is notexpected to be a serious issue because the power levels are generally lower, the path losses arehigher, and the environment will not be one of an unbalanced overlay. Still, there may have to besome engineering to provide interference control at the 1900 MHz band edges, where two differentoperators meet on different site grids. This situation will not be unique to CDMA, as the subscriberreceiver intermodulation performance is essentially identical for all technologies.

In summary, the most desirable way to design a CDMA overlay is as a (1:1) deployment, althoughit will still be necessary to review AMPS site placement in weaker CDMA coverage areas. If theoperator chooses to initially implement a lower density deployment, with something less than a(1:1) deployment, then the design of both the A and B sides will need to be very carefullyengineered for interference control. If a lower initial cost is desired, then a system utilizing a (1:1)deployment with omni cells is preferred over a system using (1:3) or higher deployments. Thiswould result in a system with the same number of sectors deployed, but not susceptible to the sameamount of system interference.

9.2.1.2 AMPS Subscribers to CDMA Cells

Narrowband AMPS subscribers are not viewed as posing a problem to CDMA cells. Out-of-bandAMPS subscriber Tx sideband emissions are not significant across the recommended 9 AMPSchannels comprising the CDMA guard band. In-band AMPS subscribers must be geographicallyseparated by a guard zone of sufficient path loss.

9.2.1.3 CDMA Cells to AMPS Subscribers

Although CDMA cells will have a lower Tx ERP, CDMA cells may still interfere with AMPSsubscribers that are far from an AMPS cell. The interference is caused by CDMA cell Tx sidebandemissions, which do not roll off as fast as those associated with a narrow band AMPS transmitter.Note that this should not cause the same amount of system interference since the CDMA sites willbe co-located with the same AMPS system sites.

9.2.1.4 CDMA Subscribers to AMPS Cells

The CDMA subscriber Tx power is typically low, so low sideband emission power results.However, a (1:3) overlay will significantly increase the probability of interference from CDMAsubscribers because all AMPS-only cells are located near the edge of the CDMA cells. CDMAusers near the AMPS sites will be at the higher power levels and offset in frequency by as little as900 kHz from the center of the CDMA channel. Depending on the path loss from the CDMAsubscribers to the AMPS Rx cell sites, the CDMA subscribers might cause interference to theAMPS receive signal.


9


9.2.2 Inter-Band Interference

Some cellular system operators who want to introduce digital cellular technologies into theirexisting systems may prefer, instead, to deploy such digital systems like CDMA in an alternatefrequency band previously not allocated for cellular use in a given country. Examples of this typeof deployment strategy can involve the following:

• Use of the AMPS band for CDMA, in an area already using TACS or GSM spectrum• Use of the TACS band for CDMA, in an area already using AMPS spectrum• Use of the PCS 1900 band for CDMA, in an area already using DCS 1800 spectrum

While implementing any one of the above examples might allow a new cellular system to bedeployed more readily (i.e. with little to no effect on the traffic performance of the existing analogsystems), there may be an increased threat of inter-system interference depending on whatoperating spectrum is being used for the new and the existing cellular systems. To say this anotherway, inter-band interference typically occurs between the base stations and/or between thesubscriber stations of two or more co-existing systems (see Figure 9-5), unlike the aforementionedintra-band interference.

Figure 9-5: Inter-Band Interference

Thus, while inter-band interference is a radio-systems issue that is not unique to a particularcellular technology and has been dealt with previously, what may be different with currentdeployments is how eager some operators are in trying to co-locate multiple-band cellulartechnologies affected by these issues. Such ambitious system deployments result in:

1. Less guard band than is recommended between two systems that must co-exist2. Smaller antenna separation (along with less isolation between systems), due to high

system densities3. More aggressive antenna sharing requirements between different technologies through

the use of combiners, duplexers, etc.

As a result, it is imperative to give proper consideration to the threat of these interferencephenomena and to take proper measures to prevent any potential system performance degradation,such as a reduction in system capacity or RF link quality/reliability. It is the goal of this section toprovide such consideration.

System B System A System B System ACellSubscriber SubscriberCell


9


As was mentioned previously, the threat and severity of inter-band interference between two ormore co-existing cellular systems using multiple frequency bands will depend on what spectrum isassigned to each system. Table 9-1 shows how the AMPS/TACS/GSM spectrum has been assignedby the EIA/TIA/ANSI standards organization, for AMPS spectrum, and by the ETSI standardsorganization, for TACS/GSM spectrum.

In the 800/900 MHz band, extended bands EAMPS and ETACS overlap by as much as 22 MHz.The end of the standard AMPS band at 890 MHz is also the beginning of the standard TACS band(Figure 9-6).

Figure 9-6: AMPS/TACS/GSM Spectrum

Likewise, the DCS 1800 band overlaps the PCS 1900 spectrum by as much as 30 MHz (seeFigure 9-7).

Table 9-1: Cellular Spectrum Allocation

StandardsBody

Cellular BandBS Tx / Sub. Rx Operating Band

(MHz)

Sub. Tx / BS Rx Operating Band

(MHz)

ANSI/ AMPS 869-894 824-849

EIA/TIA PCS 1900 1930-1990 1850-1910

TACS/ETACS 917-960 872-915

ETSI GSM 935-960 890-915

DCS 1800 1805-1880 1710-1785

869

870

880

890

891.

589

4

917

925

935

942.

5

950

960

872

880

890

897.

5

905

915

824

825

835

845

846.

584

9

B’A’A”

AM

PS

A

AM

PS

B

ET

AC

S B

TA

CS

B/

TA

CS

A/

ET

AC

S A

AM

PS

A

AM

PS

B

B’A’A”

TA

CS

Res

erve

d/

GSM

GSM

GSM

ET

AC

S B

TA

CS

B/

TA

CS

A/

ET

AC

S A

TA

CS

Res

erve

d/

GSM

GSM

GSM

BASE Rx/Subscriber Tx

BASE Tx/Subscriber Rx


9


Figure 9-7: DCS 1800 and PCS 1900 Spectrum

Table 9-2 provides a summary of the various interference scenarios that can result when attemptingto utilize these different spectrum allocations.

While the use of overlapping operating bands in co-existing systems would be unacceptable due tothe threat of co-channel interference, use of adjacent operating bands has already beenimplemented in or is being considered for some markets. Due to the typical wide band nature ofcellular base station and subscriber station receivers, inter-system interference is also a threat inthis scenario.

Table 9-2: Inter-Band Interference Scenarios

Interferer Victim

AMPS-Band Base Station

TACS/GSM-Band Base Station

TACS/GSM-Band Subscriber Station

AMPS-Band Subscriber Station

DCS 1800-Band Base Station

PCS 1900-Band Base Station

PCS 1900-Band Subscriber Station

DCS 1800-Band Subscriber Station

D EF

1930

1990

1850

1910

A B C

A B C

1880

1805

1785

1710

D EF

DCS 1800

DCS 1800

PCS 1900

PCS 1900 BASE Rx/Subscriber Tx

BASE Tx/Subscriber Rx


9


There are four predominant inter-band interference mechanisms:

• Interfering transmitter sideband emissions landing on-channel in a victim receiver’s Rx frequency band.

• Interfering transmitter intermodulation (IM) products landing in a victim receiver’s Rx frequency band.

• Victim receiver desensitization from an interfering transmit carrier.• Victim receiver intermodulation from two or more interfering transmit carriers.

9.2.2.1 Preventative Measures: BS-to-BS Interference

There are several options available to help prevent the occurrence of inter-band interferencebetween base stations. Some examples include:

1) Providing ample guard band between the co-existing systems. In this case, base stationtransmitter equipment specifications for the interfering system and base station receiver equipmentspecifications for the victim system would provide enough protection from potential interference.

2) Separating interfering and victim base station antennas as much as possible, both horizontallyand vertically, to provide the necessary isolation.

3) Providing adequate filtering of the interfering base station transmitter and/or the victim basestation receiver to achieve additional isolation.

• Tx Filters would aid in attenuating transmitter intermodulation and/or sidebandemissions to levels low enough so that they would not cause interference to, and/ordesensitization of, the victim receiver.

• Rx Filters would aid in attenuating off-channel signals that pose a threat of eitherreceiver desensitization or receiver intermodulation.

4) Modifying the frequency plan of either the interfering system or the affected system, on a site-by-site basis, to minimize the possibility of interference.

5) Reducing interfering base station RF power.

9.2.2.1.1 BS-to-BS Interference Analysis Procedure

There are two steps involved in a BS-to-BS interference analysis procedure.

Step 1.

The first step in the analysis procedure is to determine the minimum isolation required between co-existing base stations when just considering the relevant equipment specifications. The minimumrequired isolation between an interfering base station Tx antenna and a victim base station Rxantenna can be approximated by using some simple calculations that take into account varioustransmitter and receiver specifications (as provided in Section 9.2.2.1.3), antenna gains, free space


9


path loss, etc. Typically, up to four such calculations are required, one with respect to each of theaforementioned potential interference scenarios: interfering transmitter sideband emissions,interfering transmitter IM, receiver desensitization, and receiver IM. See Section 9.2.2.1.2 forfurther information regarding radio equipment interference mechanisms.

Which calculations to use for a given interference analysis will depend on what type of interferenceis possible and where the potential interference may fall with respect to the victim base stationreceiver’s operating spectrum. For example, if it is determined that no interfering Tx carrierfrequencies fall within or near the wide passband of a victim cellular receiver, then the receiverdesensitization calculation may not be required. Furthermore;

• IF an interfering system utilizes just a single Tx carrier (as is possible with CDMA),AND

• IF there are no other interfering Tx carriers present to mix with it to create IM productspotentially falling within a victim receiver’s passband

• THEN the transmitter IM and the receiver IM calculations would NOT be required1

Step 2.

The second step in the analysis procedure is to take the largest isolation requirement and determineif it is reasonable to achieve it solely through antenna separation. Required antenna separation fora given isolation value can be approximated using free space path loss equations:

SH =[10 ((PLmin - 32.44-20*(log(f)))/20)]*1000 [EQ 9-1]

SV =10 (PLmin - 28)/40 * 300/f [EQ 9-2]

Where:SH Minimum horizontal antenna separation, in meters, for use with non-co-located

sites

SV Minimum vertical antenna separation, in meters, for use with co-located sites2

PLmin Minimum required isolation

f Interfering base station transmit frequency, in MHz

1. Where appropriate, it is recommended that consideration be given to the possibility for future expansionof the interfering system (resulting in the allocation of additional Tx carriers) when determining isolationrequirements in order to prevent any future interference scenarios.

2. NOTE: The vertical spacing decoupling equation (Equation 9-2) provides a rough estimate of requiredantenna separation and does not consider near-field effects that can alter the actual isolation provided. It isstrongly recommended that appropriate on-site testing be completed to verify the actual isolation achieved byvertical antenna separation.


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Note that while other path loss models can be used to approximate antenna separation (such asHata, Okumura, etc.), it is recommended to use the above path loss equations as a worst-casescenario.

If it turns out that the required antenna separation requirements are not reasonable between the co-existing systems (e.g. too large), then appropriate filtering may be considered to provide theremaining isolation. The amount of isolation provided from filtering will depend on the amount ofguard band available between interfering systems and the amount of attenuation needed in thefilter’s stop-band. The transmitter sideband emission and transmitter IM isolation calculations areto be used with respect to any Tx filter requirements. The receiver desensitization and receiver IMisolation calculations are to be used with respect to any Rx filter requirements.

If required, filter quantities should be ordered as follows. As a guide, order one set of Tx filters perinterfering base station, where the quantity of filters in a set would depend on the number ofinterfering base station antennas present at the site. If Rx filters are required, order one set of Rxfilters for each affected base station that is either co-located or directly adjacent to an interferingbase station. Note that the need for Rx filters at a given affected base station may need to bedetermined on a site-by-site basis considering actual antenna separation distances and the amountof path loss between them.

9.2.2.1.2 Radio Equipment Interference Mechanisms

Inter-system interference scenarios addressed in this section are the result of several commoninterference mechanisms that can occur either in the transmitter or receiver of a radiocommunications system. The following radio equipment interference mechanisms are discussedbelow:

• Transmitter Sideband Emissions• Intermodulation (Tx IM, Rx IM, External IM)• Receiver Desensitization

1. Transmitter Sideband Emissions

Transmitter sideband emissions occur primarily in either the speech amplifier, oscillator and/ormodulator of the transmitter. Sideband emissions are created by the infinite bandwidthcharacteristics of white noise modulating the Tx carrier. Most transmitter equipment specificationsrequire a minimum of 60 dB attenuation of sideband emissions with respect the mean power levelof the transmitter (see Figure 9-8).


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Figure 9-8: Transmitter Spectral Mask

When sideband emissions fall within the passband of a sensitive communications receiver, itcreates interference. This can happen when transmitters operate near receivers with adjacentpassbands. The effect on the victim receiver is that of a reduction to the usable sensitivity fordesired channel performance. With this type of interference, no particular “sound” is created at thereceiver, just receiver noise (see Figure 9-9).

Figure 9-9: Interfering Transmit Carrier and Sideband Emission Spectrum

Emission profiles vary between different transmitter designs but, in general, have an energy(depicted in the above figure as Isideband), that is some specified level below the carrier’s powerlevel, (Iout). Table 9-4 and Table 9-5 in the following section provide Tx sideband emissionspecifications for relevant technologies, listed both as defined values and as a function of Iout. Thetransmit sideband emission level must be received at the victim base station receiver below amaximum allowable interference level (VINT), which results in a certain tolerable degradation inreceiver sensitivity. For example, most cellular/PCS receiver equipment specifications allow for amaximum degradation in receiver sensitivity of 3 dB, which corresponds to a maximum on-channel interference level equal to that of the receiver’s thermal noise floor (kTBF). In this case,interfering transmit sideband emission levels would then need to be received by a victim receiver

-10

-70

-20

-30

-40

-50

-60

0

f

60 dB

Iout = Interfering BS RF equipment Tx

Interfering BS Tx Sideband Emissions Performance (dBc)

Isideband (dBm)

FTx FRx

output power level (top of frame) in dBm


9


at a level below its thermal noise floor (e.g. VINT = kTBF). For example, tolerating a 3 dBsensitivity degradation, a GSM receiver having a noise figure (F) of 4 dB and a channel bandwidth(B) of 200 kHz would have a maximum tolerable interference level of -117 dBm:

VINT,GSM = GSM Rx thermal noise floor = kTBFGSM

= -174 dBm/Hz + 10 * log(200 * 103) dB-Hz + 4 dB = -117 dBm

In addition to Isideband and VINT, the following must also be accounted for in order to determine theisolation required to avoid sideband emissions interference to a victim base station receiver:

• Interfering base station feeder loss (Ifeeder) and antenna gain (Iant, which is equal to 0dBi if co-located w/victim base station antenna)

• Victim base station antenna gain (Vant, which is equal to 0 dBi if co-located withinterfering base station antenna), feeder loss (Vfeeder), receiver multicoupler/preselectorloss/gain3 (VRMC), receiver bandwidth adjustment factor4 (VBWA), and receiversensitivity (Vsens)

The following relationship shows the minimum isolation, PLmin,Sideband, required between aninterfering base station transmit antenna and a victim base station receive antenna to preventsideband emission interference:

[EQ 9-3]

2. Intermodulation (IM)

Intermodulation, or IM, can occur anywhere in the transmission path from the transmitter to thereceiver. IM is caused by non-linearities in transmitter circuitry, receiver circuitry, and/or along theRF path from the transmitter to the receiver. Severity of the IM process will depend on the numberof IM products involved, their signal strengths, and bandwidths.

IM can be detected as either a distinctive sound or as noise. For example, with 3rd-order, FM-modulated IM, an analog receiver hears two voices, one loud and distorted and the other normal.On the other hand, IM produced by two or more signals, where at least one of them is a CDMAsignal, would be detected by the user of analog receiver as noise.

3. The amount of available multicoupler/preselector loss (VRMC) will depend on the amount of guardbandbetween the two systems. It is expected that for most cases this loss will be minimal considering the verygradual roll-off attributed to these normally wideband filters. In fact, some multicouplers and preselectorscontain LNA’s that may have gain rather than loss in-band. In those cases, VRMC would have a negative value.

4. The VBWA term is necessary to adjust the sideband emission power specification, Isideband (listed in Table9-4 and Table 9-5 in units of dBm/30 kHz), to that of the channel bandwidth of the victim receiver. Forexample, VBWA for a CDMA receiver would be equal to 10*log(1228800/30000) = 16.12 dB.

PLmin Sideband dB( ), Isideband dBm 30kHz⁄( ) Ifeeder dB( )– Iant dBi( ) Vant dBi( )+ +=

Vfeeder dB( )– VRMC dB( )– VBWA dB( ) VINT dBm( )–+


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For this discussion, the IM types will be divided into three categories:

• Transmitter IM• Receiver IM• External IM

While the three categories of IM are distinctly separate matters, which are subject to differentengineering considerations, the frequency relationships applying to IM products are common.Frequencies of IM products can be defined in the following manner:

• Fundamental Frequencies - referring to the center frequencies of the signals from which IM products are derived.

• Harmonics - corresponding to the whole number multiples of a fundamental frequency.• Order - corresponding to the classification of IM products according to the sum of the

harmonics of the constituent frequencies (e.g. 2nd, 3rd, 4th,... Nth).

For example, a 3rd order IM signal centered at frequency C could result from the combination ofthe 2nd harmonic of a signal whose fundamental center frequency is A and a second signal whosefundamental center frequency is B:

C = 2A + (1)B (where order = 2 + 1 = 3)

Some examples of 2nd through 5th order intermodulation products are provided in Table 9-3.

Some generalizations can be made concerning IM products. First, the signal strength level ofharmonic decreases rapidly with its order (e.g. 3A would be weaker than 2A). Second, higher orderIM products may require too many different transmitters to be keyed simultaneously (e.g.A+B+C+2D+2E) for the IM to occur. Lastly, even order IM products almost always fall out of thelocal systems’ operating bands. For these reasons, the third and fifth order intermodulationproducts are the more prevalent and therefore more prone to cause IM interference.

Table 9-3: Example IM Products

Order Intermodulation Products

2nd A+B, A-B

3rd 2A+B, 2A-B, 2B+A, 2B-A, A+B+C

4th 2A+2B, 2A-2B, 3A+B, 3A-B

5th A+4B, A-4B, 4A+B, 4A-B, 2A+3B, 2A-3B...


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The following sections discuss the three categories of IM.

Transmitter Intermodulation (IM)

There are at least two distinctive types of Transmitter IM:

• Multi-carrier LPA IM• Transmitter-to-Transmitter IM

Multi-carrier LPA IM can occur as a result of the amplification of different RF carriers by acommon linear power amplifier. In this case, any resulting transmitter IM products that fall insideof the Tx frequency band or close to it cannot be attenuated by RF filtering, and thus tend to all beof approximately the same power level. Any transmitter IM products that fall well outside of theTx frequency band could be attenuated by RF filtering.

Transmitter-to-Transmitter IM can occur inside the transmitter circuitry if two or more transmittersare installed closely together (and thus offering low isolation). Conducted transmit intermodulationis the effect of frequency mixing in the final amplifier stage of one interfering carrier transmitterwith the outputs of others. The non-linear final amplifier circuit generates the IM and the antennaradiates it. The result is that unwanted channel power may be generated in the interferingtransmitter and land in the victim receiver’s Rx band (see Figure 9-10).

Figure 9-10: Transmitter IM

When transmitter IM products fall within the passband of a sensitive communications receiver, itcreates interference. The effect on the victim receiver is that of a reduction to the usable sensitivityfor desired channel performance.

Reradiated signals are subject to a mixing loss in the IM-producing transmitter, which can bedefined by the dB difference between the power of the incoming signal and outgoing

Tx AFreq.870.57MHz

Tx BFreq.892.89MHz

870.57 and also 848.25

892.89 and also 915.21

MHz radiated

* IM Products are formed in

transmitter final amplifier and

* ReceiverFreq. = 848.25or 915.21 MHz

MHz radiated

are radiated.

LOWISOLATION


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intermodulation. A typical value for this loss is 60 dB. Most transmitter equipment specificationsrequire a minimum of 60 dB attenuation of IM signals with respect to the mean power level ofeither transmitter, equivalent to this mixing loss.

Power levels of potential transmitter IM products vary between different transmitter designs but,in general, have an energy (depicted in Figure 9-11 as IIM), that is some specified level below theTx carrier’s power level (Iout).

Figure 9-11: Interfering Transmit Carriers and Intermodulation Spectrum

As with transmitter sideband emissions, all transmitter IM products falling within a victim basestation receiver’s passband must be received at a level below a maximum allowable interferencelevel (VINT), which results in a certain tolerable degradation in receiver sensitivity. Table 9-4 andTable 9-5 in the following section provide Tx IM specifications for relevant technologies, listedboth as defined values and as a function of Iout.

In addition to IIM and VINT, the following must also be accounted for in the calculation:

• Interfering base station feeder loss (Ifeeder) and antenna gain (Iant, which is equal to 0dBi if co-located w/victim base station antenna)

• Victim base station antenna gain (Vant, which is equal to 0 dBi if co-located withinterfering base station antenna), feeder loss (Vfeeder), and receiver multicoupler/preselector loss/gain (VRMC)

The following relationship shows the minimum isolation, PLmin,TxIM, required between aninterfering base station transmit antenna and a victim base station receive antenna to prevent TxIM interference:

[EQ 9-4]

Receiver Intermodulation (IM)

Receiver IM occurs when two or more off-channel signals enter and drive a receiver’s RF amplifieror 1st mixer stage. The nonlinear nature of the electronic devices commonly used in receiver

IIM (dBm)

F3Tx

X X =

F1Tx F2Tx FRx

Iout = Interfering BS RF equipment Tx output power level (top of frame) in dBm

Interfering BS Tx IM Performance (dBc)

PLmin TxIM dB( ), IIM dBm( ) Ifeeder dB( )– Iant dBi( ) Vant dBi( ) Vfeeder dB( )– VRMC dB( )– VINT dBm( )–+ +=


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amplification and mixing circuits leads to the production of undesired responses, such as IM, inaddition to the desired response (see Figure 9-12). The closer to saturation that an amplifier orstage is driven, the worse (higher in level) the IM products become.

Figure 9-12: Receiver IM

If one or more of the victim receiver-produced IM products falls on or near a frequency to whichthe victim receiver is tuned, the effect is that the product will be an interferer to the desired receivechannel. Since the receiver is most sensitive to this in-band product, the IM must be reduced at thispoint by signal level reduction of one or more of the mixing frequencies.

Tolerance to receiver IM will vary between different receiver designs. In general, performance willbe limited by a maximum allowable interfering (e.g. receiver IM-producing) signal level asreceived at the victim receiver (depicted in Figure 9-13 as VIMR), which is some specified levelabove the receiver’s Rx sensitivity, Vsens.

A given receiver’s ability to combat receiver IM, is quantified by its intermodulation rejectionspecification, or IMR. To prevent receiver IM, interfering signal(s) must be received at a signalstrength lower than a level as determined by the receiver’s reference sensitivity and IMRspecifications:

FRx < (Vsens + VIMR)

Tx AFreq

870.57MHz

Tx BFreq

892.89MHz

870.57 MHz

892.89 MHz

only radiated

* IM Products are formed in

receiver amplifier or mixer.

* ReceiverFreq. = 848.25or 915.21 MHz

only radiated

HIGHISOLATION


9


Figure 9-13: Victim Receiver Out-of-Band Intermodulation

Table 9-6, Table 9-7 and Table 9-8 in the following section provide receiver IM specifications forrelevant technologies, listed both as a defined value and as a function of Vsens.

In addition to VIMR and Vsens, the following must be taken into account in the calculation:

• Interfering BS RF equipment Tx output (top of frame) power level (Iout), feeder loss(Ifeeder), and antenna gain (Iant, which is equal to 0 dBi if co-located w/victim basestation antenna)


The following relationship shows the minimum isolation, PLmin,RxIM, required between aninterfering base station transmit antenna and a victim base station receive antenna to preventreceiver IM:

[EQ 9-5]

The resulting isolation requirements can be achieved through both antenna separation and filteringof the interfering transmitter(s) and affected receiver(s).

External Intermodulation (IM)

External IM is created by passive, non-linear elements in the transmission path from transmitter toreceiver such as antennas, combiners, duplexers, cables, connectors, etc. and other elements in theimmediate vicinity of the transmission line, such as guy wires, tower joints, anchor rods, etc. Here,signals are picked up by these elements and reradiated as IM products (see Figure 9-14).

X =

F1Tx F2Tx FRx

VIMR = BS Max Allowable Out-of-band, Receiver

Victim BS Receiver IM Rejection Performance (dB)

Vsens = Victim BS Receiver Sensitivity (dBm)

= kTBF + S/N - Processing Gain*

* if applicable

IM-Producing Rx Signal Level (dBm)

PLmin RxIM, dB( ) Iout dBm( ) Ifeeder dB( ) I+ant dBi( )

– Vant dBi( ) Vfeeder dB( )– VRMC dB( )– VIMR dBm( )–+=


9


Figure 9-14: External IM

Locating the actual source of external IM may be very difficult. There are really no preventativemeasures with respect to external IM other than to conduct thorough periodic maintenance ofelements in and around the transmission path. However, while low-order external IM created in theantenna path system can easily cause interference to base station receivers that share the sameantenna, resulting IM signal levels are usually low enough that they won’t create interference tosubscribers or other base stations.

3. Receiver Desensitization

Receiver desensitization, also known as receiver blocking, is usually caused by strong off-channelinterfering signals that fall within or just outside the often wide passband of the receiver. If theinterference is strong enough, bias conditions can be changed on certain receiver stages, causingthem to lose gain. This makes the receiver less sensitive to any desired signals. The ability of areceiver to receive an intended signal in the presence of these interfering signals is measured by itsdesensitization or blocking level specification. Associated with this level, is an allowabledegradation in Rx sensitivity, usually 3 dB.

While its negative effects might not be immediately noticeable in a desired received signal,receiver desensitization could result in an increased susceptibility to fading and a reduction inchannel capacity. Example causes of receiver desensitization are interfering Tx carrier power level,transmitter sideband emissions and transmitter IM products.

Desensitization levels vary between different receiver designs but, in general, have an energy(depicted in Figure 9-15 as Vblock), that is some specified level above the receiver’s Rx sensitivity,Vsens. Off-channel interfering signal(s) must be received at the victim base station receiver at alevel below Vblock.

ANELECTRICALLY

NON-LINEAROBJECT

Rx

Tx1

Tx2

IM INTERFERENCE


9


Figure 9-15: Victim Receiver Out-of-Band Desensitization

The Rx sensitivity level, Vsens, is a certain number of dB above or below the receiver’s thermalnoise floor (kTBF) and is a function of the receiver’s required S/N ratio (Eb/No, C/I, etc.) andprocessing gain (CDMA only). Processing gain is equivalent to the receiver’s channel bandwidthin Hz (B) divided by the Rx data rate in Hz (R). An example calculation for 8 kbps CDMA withan Eb/No (S/N) of 7 dB and a receiver noise figure (F) of 6 dB is provided below:

Vsens,CDMA = kT (dBm/Hz) + 10*log(BCDMA) (dB) + F (dB) + S/NCDMA (dB) - 10*log(BCDMA/RCDMA) (dB)

= -174 + 10*log(1.2288*106) + 6 + 7 -10*log(1.2288*106/9600) = -121.2 dBm

Table 9-6, Table 9-7 and Table 9-8 in the following section provide desensitization specificationsfor relevant technologies, listed both as defined values and as a function of Vsens.

In addition to Vblock and Vsens, the following must also be accounted for in the calculation:

• Interfering BS RF equipment Tx output (top of frame) power level (Iout), feeder loss(Ifeeder), and antenna gain (Iant, which is equal to 0 dBi if co-located w/victim basestation antenna)


The following relationship shows the minimum isolation, PLmin,Desense, required between aninterfering base station transmit antenna and a victim base station receive antenna to preventreceiver desensitization as a result of the presence of strong off-channel signals:

[EQ 9-6]

Vblock = Victim Max Allowable BS Receiver

Vsens = Victim BS Receiver Sensitivity (dBm)

FTx FRx

Blocking/Desense Level (dBm)

= kTBF + S/N - Processing Gain*

* if applicable

PLmin Desense dB( ), Iout dBm( ) Ifeeder dB( ) I+ant dBi( )

– Vant dBi( ) Vfeeder dB( )– VRMC dB( )– Vblock dBm( )–+=


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9.2.2.1.3 Equipment Specifications

Isideband, IIM, Vblock and VIMR will vary with equipment type. Typical values, based on standardequipment specifications are provided in Table 9-4 through Table 9-8 below.

Table 9-4: Partial Example of Base Station Transmitter Specifications

Technology (Specification)

Maximum Transmitter Sideband Emission Level, Isideband

(dBm/30 kHz)

Maximum Transmitter IM Power Level, IIM

(dBm)

AMPS(IS-20A)

< Larger of -31 or (Iout - 78) @ |f-fc| > 90 kHz

< (Iout - 60 dB)

800 MHz CDMA

(IS-97A)

< (Iout - 45)@ 1.98 > |f-fc| > 0.75 MHz

< (Iout - 60) @ |f - fc| > 1.98 MHz

< (Iout - 45)@ 1.98 > |f-fc| > 0.75 MHz

< (Iout - 60) @ |f - fc| > 1.98 MHz

Table 9-5: DCS 1800 Base Station Transmitter Specifications (GSM 05.05)

Offset Range From Tx Carrier

(kHz)

Maximum Transmitter Sideband Emission Level, Isideband

(dBm/30 kHz)

Maximum Transmitter IM Power Level, IIM

(dBm)

200 < (Iout - 30) < (Iout - 30)

250 < (Iout - 33) < (Iout - 33)

400 < (Iout - 60) < (Iout - 60)

600 to <1200 < -27 <-27

1200 to <1800 < -30 <-30

1800 to <6000 < -37.2a

a. AMPS IS-20A lists a sideband emission level in dBm/300 Hz. GSM 05.05 lists sideband emission levelsin dBm/100 kHz for frequency offset ranges > 1800 kHz. A conversion to dBm/30 kHz is used here to beconsistent with units used for other specification values.

<-32

> 6000 (Iout - 85.2)a < Larger of -36 or (Iout - 70)


9


Table 9-6: Partial Example of Base Station Receiver Specifications

Technology(Specification)

Maximum Receiver IM Level, VIMR

(dBm)

Maximum Receiver Desense/Blocking Level, Vblock

(dBm)

TACS > (Vsens + 65)

> -50 (for signals falling within TACS A band)

> -23 (for signals falling within TACS B band)

900 MHz GSM(GSM 5.05)

> - 43 (See Tables 3-6 and 3-7)

900 MHz CDMA(China IS-97A) > (Vsens + 72)

> (Vsens + 50)@ 0.9 > |f-fc| > 0.75 MHz

> (Vsens + 87)@ |f-fc| > 0.9 MHz

PCS 1900 CDMA(J-STD-019) > (Vsens + 72)

> (Vsens + 50)@ 0.9 > |f-fc| > 0.75 MHz

> (Vsens + 87)@ |f-fc| > 0.9 MHz

Table 9-7: In-Band GSM Base Station Receiver Blocking Specifications (GSM 05.05)

Offset Range From Intended Rx

Carrier(kHz)


(dBm)

600 to <800 > -26

800 to <3000 > -16

Table 9-8: Out-of-Band GSM Base Station Receiver Blocking Specifications (GSM 05.05)

Frequency Band(MHz)


(dBm)

0.1 to <915 > 8

980 to <12750 > 8


9


Note that the values in the previous tables are worst case and are based solely on the methods ofmeasurement as outlined in each technology’s specification documentation. Actual values mayvary according to both base station equipment manufacturer and desired quality of service(SINAD, Eb/No, BER, FER, data rate, etc.). With this in mind, vendor-specific documentation andsystem design constraints should be obtained to determine more accurate and/or appropriate datafor a given interference analysis.

9.2.2.2 Preventative Measures: Subscriber-to-Subscriber Interference

The severity of interference between subscribers will depend on the subscriber densities of eachsystem involved and the distances between them, because both the interfering transmitters and theaffected receivers are moving with respect to one another and are in random positions relative toone another. The likelihood of experiencing interference will also depend on the power controlcapabilities of the interfering subscriber transmitter(s) and the affected subscriber stationreceiver(s).

As Table 9-9 illustrates, interference between subscriber stations is generally less of a problem thanbetween base stations.

Since intermodulation requires two or more interfering signals at precise frequency spacing, theprobability of any resulting product causing interference could therefore be very low. Therefore, it

Table 9-9: Inter-Band Interference Comparison

Subscriber Station-to-Subscriber Station

Base Station-to-Base Station

Antenna Separation Distance

Variable Fixed

Path Loss Variable Fixed

# of Distinct Tx Frequencies-

FDMA/TDMA Systems

1 per subscriber (narrow-band carrier)

> 1 per Base Station

# of Distinct Tx Frequencies-

CDMA Systems

1 per subscriber (wide-band carrier)

> 1 per Base Station

Power/channel Low High

Antenna Cross Polarization Loss

Variable Fixed


9


is reasonable to conclude that most Subscriber-to-Subscriber interference is typically caused by Txsideband emissions. In areas subject to a high density of pedestrian subscriber traffic (for example,in a shopping mall, subway station, etc.), this interference could be significant enough to affect callquality or cause a dropped call.

Unfortunately, there is little that can be done to prevent Subscriber-to-Subscriber interference otherthan to address the potential for interference in the actual physical design of both the interferingand victim subscriber units so that sufficient isolation is provided. This, however, seems to be anunlikely possibility as subscriber performance requirements (again, generated by distinctlydifferent standards bodies: ANSI/EIA/TIA and ETSI) typically do not address inter-bandinterference issues of this nature.

Note that frequency plans could also be modified to help prevent interference in certain areas,depending on the technologies involved. However, in high-traffic areas which are of the mostconcern, frequency plan flexibility may be limited.

9.3 PCS and Microwave Interference

Within the US 1900 MHz band, there are over 4,500 microwave links, the majority of which are 5MHz (300 channel) or 10 MHz (600 channel) analog FM-FDM systems. The chart belowillustrates where these links are centered with respect to the PCS MTA and BTA license bands.

Figure 9-16: The PCS Spectrum

9.3.1 PCS to Microwave Interference

PCS license requirements essentially dictate that any PCS system may not cause any harmfulinterference into incumbent microwave systems. Detailed interference analysis is needed todetermine the interference potential of PCS into microwave systems.


9


Recommendations and guidelines for analyzing potential interference into microwave systems areprovided in the Telecommunications Industry Association’s (TIA) Bulletin, TSB-10-F. The fourmain considerations detailed in Bulletin TSB-10-F are:

• Coordination Distances• Propagation Models• Power Aggregation• Microwave Receiver Interference Criteria

These considerations must incorporate interference from all system sources and subscriber units.As a result, the term PCS transmitter can refer to a base station or a subscriber unit. Please refer tothe Bulletin for more information. The following sections will summarize the four mainconsiderations.

9.3.1.1 Coordination Distances

It is necessary to determine a search area around each PCS transmitter within which the process ofinterference analysis needs to be undertaken. This is known as the Coordination Distance. Theprimary factors governing the coordination distance for a PCS transmitter are its antenna heightand EIRP. In general, the PCS base station transmitter will define the coordination distance. Theminimum Coordination Distance is calculated by using the following formula set:

; [EQ 9-7]

[EQ 9-8]

[EQ 9-9]

[EQ 9-10]

[EQ 9-11]

Where:D Coordination distance

P EIRP (dBm)

HT Transmitting antenna height above average terrain (m)

DL Free Space distance (km)

DD Diffraction distance (km)

DLT Distance to horizon (km)

DLT 2.56 HT( )=

DL 1051.87 P+

20-----------------------

=

DD65 1.85DLT P+ +

0.106 DLT 33.6+( ) 0.899+log------------------------------------------------------------------------=

DS19.9– 0.12 DLT P+×+

0.1156 5.65–×10 DLT×–

-----------------------------------------------------------=

D min DL max D DS,( ),( )=


9


For example, a typical PCS BTS with an antenna height of 30 meters and an EIRP of 100 Wattsrequires a coordination distance of 275 km.

The following graph shows the coordination distances for a PCS transmitter with 30 and 90 meterantenna heights, over a wide range of EIRP values.

Figure 9-17: Example Coordination Distances

As can be seen, the distances involved are substantial and may even extend beyond the MTA/BTA(Major Trading Area / Basic Trading Area) license boundary.

9.3.1.2 Propagation Models

To determine the level of interference into a microwave system, it is necessary to calculate thesignal strength of the PCS signal at the microwave receiver. In traditional microwave systems, thefree space path loss calculation is used in link planning. However, with the lower antenna heightsof PCS transmitters, the effects of local clutter must be considered. For this reason, the Hata modelwith suburban correction is used as the base propagation model. In addition, because of the largecoordination distances, propagation beyond the transhorizon (the point at which line of sightcommunications between two fixed antennas is no longer possible) must also be considered. Theforward scatter loss model is used for propagation beyond the horizon.

The Hata and forward scatter loss models are used for both the subscriber unit and the base stationpath loss calculations. However, different correction factors are set to account for differences inantenna heights.


9


9.3.1.2.1 Basic Propagation Models

Free Space Path Loss

The free space path loss calculation is represented by the following equation:

[EQ 9-12]

Where:d distance (km)

f frequency (MHz)

Hata Model

The Hata based propagation model (suburban area) is represented by the following equation:

[EQ 9-13]

Where:Lpcs Loss between PCS and MW antennas using the modified Hata model.

PCS antenna height correction factor

Forward Scatter Loss (Troposcatter) Model

The actual distance to the transhorizon is calculated by using the smooth earth transition method,which specifies the receiver and transmitter antenna heights above the average elevation along thepath. Assuming no clutter or terrain obstacles, the smooth earth transition distance (transhorizon)is represented by the following formula:

[EQ 9-14]

Where:dh Transition distance (km)

hpcs PCS antenna height above average terrain (m)

hmw Microwave antenna height above average terrain (m)

The recommended equation for forward scatter loss, adjusted for hourly median loss, is as follows:

[EQ 9-15]

Lfs 32.44 20 d( )log 20 f( )log+ +=

Lpcs 69.5 26.16 f( ) 13.82 hmw( ) 44.9 6.55 hmw( )log–[ ] d( ) α hpcs( )– 2f

28------

log2

– 5.4–log+log–log+=

α hpcs( )

dh 4.123 hpcs hmw+( )×=

L50 29.73 30 f( ) 10 d( ) 30 θ( ) N H h,( )+log+log+log+=


9


Where:L50 Hourly median transmission loss 50% of the time (dB)

f Frequency (MHz)

d Path length (km)

dh Smooth Earth Transition Distance

[EQ 9-16]

Where:

H

h

9.3.1.2.2 PCS Base Station Correction Factors

The same basic Hata model is used for path loss calculations for both subscriber unit and basestation sources. However, a correction set is applied to account for differences in antenna heights.The Hata model from above and the following correction factors should be used for microwaveantennas below 180 m and PCS antennas below 60 m.

For PCS antennas below 9 m (ground level subscriber unit sources), the following Hata suburbancorrection factor equation is used:

[EQ 9-17]

For PCS antennas between 9 m and 60 m (base station sources), the Hata large city correctionfactor equation is as follows:

[EQ 9-18]

Outside of these ranges, the free space path loss formula should be used to predict the propagationloss to the transhorizon. The following graph shows the relationship between the three propagationmodels at both PCS downlink frequencies. As previously mentioned, the local clutter has the effectof increasing the propagation loss above that of free space path loss. This in turn results in thetransition from the Hata model to the troposcatter model occurring further out than the transhorizondistance.

θ d dh–( )8.5

------------------- milliradian( )

N H h,( ) 20 5 γh+( ) 4.343γh+log=

θd4000------------

1.0633–×10 θ2×

γ 0.27

α hpcs( ) 1.1 f( )log 0.7–[ ] hpcs 1.56 f( )log 0.8–[ ]–×=

α hpcs( ) 3.2 11.75 hpcs×( )log[ ] 2× 4.97–=


9


Figure 9-18: Propagation Curves for High PCS Antennas

Downlink PCS Frequency = 1960 MHz

9.3.1.2.3 PCS Subscriber Unit Correction Factors

Subscriber transmissions will be a significant factor in the interference analysis as, unlike the basestation, the subscriber unit is not fixed and will try to access the PCS system in various locations.For PCS subscriber units on the street, the recommended loss model is the mean Hata suburbanmodel, Equation 9-7, with the suburban correction factor as stated in Equation 9-15. Refer to thefollowing figure.

Figure 9-19: Propagation Curves for Low PCS Antennas

Uplink PCS Frequency = 1880 MHz

Transition Point

Transition Point


9


One of the most significant issues of interference into microwave systems is line of sight situations.The most common occurrence of this will be from a subscriber unit located in a high rise buildingor on a balcony. In this case, path loss figures approaching free space loss may be experiencedbetween the subscriber unit and microwave antennas.

It is possible for this situation that the subscriber unit’s interfering signal will be stronger than theaggregated powers of many base station transmissions at the microwave receiver. In urbanenvironments, the probability of an elevated subscriber unit is greater. Thus, the impact of thesubscriber unit interference sources on the microwave receiver will be more substantial than inresidential areas.

TSB-10-F, Section F-4.4.1.1 provides statistical adjustments to the mean Hata suburban model toaccount for the above effects.

9.3.1.3 Power Aggregation

When considering the interference level into a microwave receiver, the combined effect of all thePCS transmitters in a service area must be considered. The aggregated power will be a function ofthe total number of PCS transmitters (both base station and subscriber units) included within theservice area.

Figure 9-20: Example Aggregated Service Area

Statistical methods for aggregating the PCS transmitter powers may be used to determine theexpected spatial PCS distribution within the service area. As a default, uniform distribution ofpowers should be assumed. From the specified distribution, the aggregated interference signal canbe determined by using either analytical techniques or Monte Carlo simulation methods.

Micr

owav

e Main

Bea

m

Microwave Site

Angle Theta


9


9.3.1.4 Microwave Receiver Interference Criteria

Three interference criteria are used to determine if a PCS system will interfere with microwave:

1. Carrier to Interference2. Threshold Degradation3. Reliability

All three forms of interference criteria should be assessed utilizing the analysis procedure in orderto determine which microwave systems require relocation because they are vulnerable tointerference, as well as to demonstrate non-interference into other microwave systems situatedwithin the coordination distance.

9.3.1.4.1 Carrier to Interference

The Carrier to Interference criteria is used to specify the threshold at which an unwanted signal willcause harmful interference upon the wanted signal. For single frequency transmission systems, asingle C/I ratio may be quoted for the receiver. However, with multi-channel microwave systems,the C/I criteria is expressed in terms of a curve representing the allowable C/I ratio at a specificfrequency separation of an unwanted signal from the center of the microwave carrier.

The C/I curves are calculated based on the transmit power spectral densities of both the microwaveand PCS systems, as well as the receiver selectivity of the microwave system. The power spectraldensity, the number of channels, the modulation type, and the bandwidth play an important role indetermining the shape of the curve. The following graph is an example of such a curve for bothGSM and CDMA carriers as interferers.

Figure 9-21: Example C/I Curves for a 10 MHz Microwave Receiver


9


9.3.1.4.2 Threshold Degradation

Threshold degradation is the reduction in the microwave receiver sensitivity caused by aninterfering PCS signal. Bulletin TSB-10-F states that the maximum interfering signal level foranalog receiver threshold degradation in Bulletin TSB-10-F links can be represented by thefollowing equation:

[EQ 9-19]

Where:Imax Maximum interfering signal level, dBm

Rt Receiver threshold, dBm

Fα The difference between the operating fade margin and that required to meet theoutage objective, dB

Se Effective selectivity of the victim receiver to the interfering signal, dB

(fs) Interfering signal frequency at which Se is defined, MHz

For example, if the microwave receiver sensitivity is -80 dBm, then the co-channel interfering PCSsignal must be -90 dBm or less to avoid degrading the sensitivity of the receiver (assuming nodegradation due to fade margin).

9.3.1.4.3 Reliability

Reliability is an all-encompassing term that describes how well the microwave link guaranteescommunications. In general, because link failures are mostly attributable to fading having veryshort durations, the microwave link reliability measures can be expressed in either of two mainforms:

• Availability, quoted as a percentile, such as 5 nines (99.999%) or 6 nines (99.9999%)• Annualized outage time (seconds)

For most microwave links, the operator defines a minimum required reliability. Reliability withina microwave link is, in fact, a function of the fade margin allocated for the link. A reduction in thefade margin will reduce the availability and increase the outage time per year. It is not uncommonfor the microwave link to have been over-engineered, which means that the fade margin allocatedis in excess of the reliability required. Thus, a 1 dB degradation or more caused by a PCS interferermay not always compromise the minimum required reliability.

Imax Rt Fα Se fs( ) 10–+ +=


9


Calculating Outage Time:

[EQ 9-20]

Where:T Annual outage time (seconds)

r Fade occurrence factor

To (t/50)(8*106) = length of fade season (seconds)

t Average annual temperature in oF

CFM Fade Margin (dB)

Io Space Diversity Improvement Factor = 1 for non-diversity, > 1 for diversity

Calculating Availability:

[EQ 9-21]

Where:A Annual availability (%)

T Annual outage time (seconds)

9.3.1.5 PCS to Microwave Interference Summary

The methods and procedures required to perform microwave interference analysis are complex.Thus, this section serves to demonstrate the fundamental aspects of the process. A full guidedetailing all scenarios is beyond the scope of this document. Therefore, it is recommended thatBulletin TSB-10-F be used as a reference when considering any in-depth PCS to Microwaveinterference analysis.

Note: Detailed analysis is best performed with the use of an automated microwave interferenceanalysis tool.

TrTo

CFM10

------------- –

×10Io

-----------------------------------=

A31.4496

6×10 T–

31.44966×10

----------------------------------------

100×=


9


9.3.2 Microwave to PCS Interference

In contrast to PCS to microwave interference, there are no recommendations or guidelinespresented by the TIA for the calculation of microwave interference into PCS systems. The PCSsystem supplier must therefore determine the appropriate method and levels.

The relocation of microwave links degraded by the PCS systems will naturally remove the majorityof sources of microwave to PCS interference. However, it should not be assumed that nointerference will occur.

9.3.2.1 General Considerations

Interference to PCS base stations is best characterized as a degradation to the receiver noise figure.The degradation to the noise figure produces an effective noise figure, which must then be used inthe link budget for the affected cell or sector. The reason interference can be treated as noise is thatthe de-spreading following the receiver filtering will result in widening of the interferer’s spectrumsuch that it is seen as a noise rise.

The procedure for calculating the effects of microwave interference on the PCS base stations(BTSs) can similarly be applied in calculating the effects of microwave interference on the PCSsubscriber units. However, it must be remembered that the subscriber unit receiver has a highernoise figure, and its selectivity is different from that of the base station. Hence, the calculationsshould reflect these differences.

9.3.2.2 Calculation of Nominal Noise Floor

The nominal noise floor is set by the bandwidth of the receiver and its noise figure. For example,the noise figure of some base station receivers is designed to be 6 dB. The corresponding noisebandwidth of these base station receivers is approximately 1.25 MHz.

Given:Nominal Noise = Nnom

Thermal Noise = Nth(dB) = -174 dBm/Hz

Noise Figure = NF(dB) = 6 dB

Noise Bandwidth = fnb = 1.25 MHz

The nominal noise is the linear sum of these three parameters, in dB:

Nnom(dB) = Nth(dB) + NF(dB) + 10 Log (fnb)

= -174 dBm/Hz + 6 dB + 61 dB Hz

= -107 dBm


9


To calculate the nominal noise floor in a subscriber unit receiver, the appropriate noise figure forthe particular unit type must be substituted for the noise figure quoted for the base station receiver.All compliant subscriber units guarantee a noise figure of 10 dB, which compares to a 6 dB noisefigure for the base station. The net result is that the subscriber unit receiver has a noise floor thatis 4 dB higher than that for the base station.

9.3.2.3 Calculation of Effective Interference Power

The receiver filtering and the spectrum of the interferer establishes the effective interferencepower. The receiver filtering can be determined by the receiver desense curve. Since the desensespecification includes the effects of processing gain and receiver Eb/No, these must be removed asthe first step in the process. This is easy to do, as their effect is equal to the desense at 0 Hz channeloffset, which is nominally 14 dB. Define the following:

Receiver Filtering = |H(f)| = - (Desense(f) - Desense(0)),

Where:f Frequency offset from the carrier frequency in Hz

Note, the minus sign in the above equation is due to the fact that desense is a positive quantity. Thespectrum of the interfering signal must also be known,

Interferer Power = G(f)

Effective interference power is calculated as the integrated product:

Effective Interference Power = Ieff

=

Performing rectangular integration is adequate in most cases, allowing the calculation to becompleted by using a summation of the products.

9.3.2.4 Calculation of Effective Noise Figure

The effective noise in the receiver’s bandwidth is the sum of the nominal noise power and theeffective interference power, i.e.

Effective Noise = N eff

= Nnom + Ieff

H f( )2G f( ) fd∫


9


Expressed in dB:

Effective Noise (dB)= Neff (dB)

= 10 log (Nnom + Ieff)

The ratio of the effective noise and the nominal noise is the effective noise figure:

Effective NF = NFeff

= Neff /Nnom

Expressed in dB:

Effective NF (dB) = 10 log [(Nnom + Ieff) / Nnom]

If Ieff = Nnom, the Effective NF is increased by 3 dB.

9.3.2.5 Microwave to PCS Interference Summary

Any interference in-band to the 1.25 MHz channel will directly add to the nominal noise power ofeither the base station or the subscriber unit. Therefore, with a 4 dB higher receiver noise floor, thesubscriber unit is less sensitive than the base station. If it is assumed that an interfering signal 10 dBbelow the receiver sensitivity will cause a 1 dB increase in the signal to noise ratio, then theinterfering signal at the subscriber unit must be 4 dB greater than that at the base station to causean equivalent effect.

Whether either the base station receiver or the subscriber unit receiver is more severely degradedby a microwave interferer is determined on an individual basis. This determination includesdependencies such as the location of the microwave transmitter relative to the PCS systemcoverage area, and also the heights of both the base station antenna and the subscriber unit antenna.

9.4 References

1. ANSI IS-20A, Recommended Minimum Standards for 800-MHz Cellular LandStations, May, 1988, Sections 3.4.1 and 3.4.4.

2. ANSI J-STD-019, Base Station Compatibility Requirements for 1.8 to 2.0 Ghz CodeDivision Multiple Access (CDMA) Personal Communications Systems, August, 1995.

3. Clapp, Scott (Motorola), “Inter-band Interference Control”, August 15, 1998.

4. EIA/TIA IS-97-A, Recommended Minimum Performance Standards for Base StationsSupporting Dual-Mode Wideband Spread Spectrum Cellular Mobile Stations, June,1996, Sections 9.4.3, 9.4.4 and 10.5.1.


9


5. ETSI/GSM 05.05, Digital Cellular Telecommunications System Radio Transmissionand Reception, July, 1996, Sections 2, 4.2.1, 4.7.2, 5.3 and 6.2.

6. Leonard, Terry (Motorola), “CDMA to GSM Base Station Interference Control”, May 5,1997.

7. Tajaddini, Mohammad (Motorola), “Analysis of AMPS B Band and GSM SystemsInterference in Co-Located Sites”, December 15, 1993.

8. United Kingdom Total Access Communication System Mobile Station - Land StationCompatibility Specification, Issue 4, Amendment 2, February, 1995, Sections A.7 andA.8.

9. Wilcox, Gordon (Motorola), “Radio Frequency Interference in Two-Way RadioSystems”, November, 1975.

10. TIA/EIA IS-97-D, Recommended Minimum Performance Standards for cdma2000Spread Spectrum Base Stations, March 30, 2001. (See http://www.3gpp2.org/Public_html/specs/index.cfm for more information.)


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I - 1CDMA/CDMA2000 1X RF Planning GuideMar 2002


Table of Contents

I.1 Terms and Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I - 3

Appendix

I Terms and Acronyms

I - 2 CDMA/CDMA2000 1X RF Planning Guide Mar 2002

I

CDMA/CDMA2000 1X RF Planning GuideAppendix I: Terms and Acronyms

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I.1 Terms and Acronyms• AGC - Automatic Gain Control

• AMR - Alarm, Monitoring and Reporting Card

• AMPS - Advanced Mobile Phone System/Service

• ARP - Average Rated Power

• ATCH - Actual Traffic CHannels (including SHO)

• BBX - Broad Band Transceiver card

• BBX-R - BBX Redundant

• BBX I/O - BBX Input Output card

• BDC - Baseband Distribution Card

• BHCA - Busy Hour Call Attempts, the number of call attempts during the busiest hour of the day

• BSC - See CBSC

• BSS - The Base Station System consists of one BSC and its associated BTSs

• BTA - Basic Trading Area

• BTS - The Base Transceiver Sub-System includes the equipment necessary to implement a CDMA DigitalCellular Base Station

• BTS Cluster - A group of BTSs controlled by a single BSC

• BTS Site - The location where a particular BTS resides

• CCP - CDMA Channel Processor

• CDMA - Code Division Multiple Access

• CBSC - The Centralized Base Site Controller consists of the Mobility Manager and Transcoder

• CCITT - International Consultative Committee for Telegraph and Telephony is a standards committee thatrecommends specific implementations of various communication protocols

• CPU - Central Processing Unit

• CSM - Clock Synchronization Module

• C7 - CCITT #7 or Signaling System #7 (SS7)

• CW - Continuous Wave

• dBc - Decibels below carrier

• dBd - Decibels referenced to a half wave dipole

• dBi - Decibels referenced to an Isotropic radiator

• dBm - Decibels referenced to a milliWatt

• DDC - Duplexer with integrated Directional Coupler

• DoD - Department of Defense

• EAMPS - Extended Advanced Mobile Phone System/Service

• Eb - Energy per Bit

• Ec - Energy per Chip


I


• EIRP - Effective Isotropic Radiated Power

• ELPA - Enhanced Linear Power Amplifier

• EMI - Electro-Magnetic Interference

• ERP - Effective Radiated Power

• ETCH - Effective Traffic CHannels

• F - Noise Factor

• FER - Frame Erasure Rate

• Frame - an enclosed rack of equipment

• FWT - Fixed Wireless Terminal

• GHz - Giga-Hertz (109 Hz)

• GLI - Group Line Interface

• GOS - Grade Of Service, the blocking probability.

• GPS - Global Positioning Satellite system used to synchronize Sites around the System

• GSM - Global System for Mobile communications (at 900 MHz) - Previously known as Groupe SpecialMobile (Pan-European digital cellular standard). GSM900 is used only when necessary to differentiate itfrom DCS1800.

• HDII - High Density Analog Base Station

• HSO - High Stability Oscillator

• IM - InterModulation

• IPi - InPut intercept point

• ISI - Inter-System Interference

• ISO - International Standards Organization

• Io - Total interference density

• kbps - kilo bits per second

• kHz - kilo-Hertz (103 Hz)

• km - kilometers

• kTB - Thermal noise calculated from the product k x T x B, where k = Boltzmann’s constant (1.38x10-23

W/HzK), T = room temperature in degrees Kelvin (290 K), and B = bandwidth (in Hz)

• LFR - Loran Frequency Receiver card

• LMF - Local Maintenance Facility

• LNA - Low Noise Amplifier

• LORAN-C - LOng RAnge Navigation Low Frequency Broadcast

• LOS - Line-Of-Sight

• LPA - Linear Power Amplifier amplifies multiple carriers

• LTMS - Laboratory Test-oriented Mobile Station

• MAWI - Motorola Advanced Wideband Interface


I


• Mbps - Mega bits per second

• MCC - Multiple Channel CDMA card

• MF - 1. Multifrequency 2. Modulated Frequency 3. Modem Frame

• MHz - Mega-Hertz (106 Hz)

• MPC - Multicoupler Preselector Card

• MS - Mobile Station

• MSC - Mobile Switching Center

• MSF - European Low Frequency Broadcast of Standard Time

• MSI/O - The physical termination card for the RF Modem Frame (similar to the BIB)

• MTA - Major Trading Area

• NAMPS - Narrowband Advanced Mobile Phone Service

• NF - Noise Figure

• OH - OverHead Channels

• O & M - Operations and Maintenance

• PA - Power Amplifier

• PCM - Pulse Code Modulation

• PCS - Personal Communication System

• POTS - Plain Old Telephone Service

• PSTN - Public Switched Telephone Network

• PTCH - Physical Traffic CHannels (including SHO+OH)

• PN - Pseudo-random Noise spreading sequence

• QoS - Quality of Service

• RF - Radio Frequency

• RFMF - RF Modem Frame

• RFDS - The Radio Frequency Diagnostic Sub-system monitors the performance of the BTS

• RGD - Remote GPS Distribution box

• RGPS - Remote Global Positioning Satellite

• RL - Return Loss

• Rx or RX - Receive

• RXDC - Receiver Distribution Card

• SBN - Side Band Noise

• Sector - An RF coverage area segment

• Shelf - Generic name used to describe a mechanical enclosure, included in several types of BSS Frames

• SHO - Soft HandOff

• SIF - Site Interface Frame


I


• SNR - Signal to Noise Ratio

• Span Line - A T-1 (1.544 Mbps) or E-1 (2.048 Mbps) transmission link

• TCH - A Traffic CHannel is a single voice or data channel. Normally considered to be on the BTS side ofthe BSC and/or on the air interface.

• TDA - Time Difference of Arrival

• TDMA - Time Division Multiple Access

• TDR - Time Domain Reflectometer

• TIB - Telco Interconnect Board

• Trunk - A Trunk is a single 64 kbps voice or data channel (DS-0) on a given span line between the BSCand MSC.

• Tx or TX - Transmit

• TRX - Transceiver

• TTA - Tower Top Amplifier

• USDC - United States Digital Cellular, based upon the IS-136 specification

• UTC - Universal Coordinated Time

• VSWR - Voltage Standing Wave Ratio

• WiLL - Wireless Local Loop

II - 1CDMA/CDMA2000 1X RF Planning GuideMar 2002


Table of Contents

II.1 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II - 3

Appendix

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CDMA/CDMA2000 1X RF Planning GuideAppendix II: Glossary

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II.1 Glossary

Active SetThe pilots associated with the Forward Traffic Channels assigned to the subscriber. It is the basestation that assigns all active set pilots to the subscribers.

AttenuatorA device for reducing the energy level of a signal without introducing distortion. Also called a pad.

BlockingThe inability of the calling subscriber to be connected to the called subscriber because either allpaths are busy, or because idle paths in the calling group cannot be accessed by idle paths in thecalled group.

Candidate SetThe pilots that are not currently in the Active Set but have been received by the subscriber withsufficient strength to indicate that the associated Forward Traffic Channels could be successfullydemodulated. As a property of the Mobile Assisted HandOff (MAHO), the subscriber promotes aNeighbor Set or Remaining Set pilot to the Candidate Set when certain pilot strength criteria aremet, and then recommends the pilot to the base station for inclusion in the Active Set.

Channel1) A particular member of a group, that is associated with a unique time slot. Each member isassociated with one port in the switch; either an RF channel, a land trunk, a three-party conferencecircuit, or a tone signalling port. 2) A particular member of an RF group that has a uniquefrequency. 3) For a TDMA air interface, it describes the unique frequency and time slot allocationfor a single call. 4) For a CDMA air interface, it describes the Walsh code assignment allowed forthe subscriber unit.

Directional CouplerA bi-directional coupler carrying Tx and Rx RF signals to and from the antennas. It includes a portwhich allows the signals to be routed to the RFDS for direct measurement of in-band forward (Tx)signals without service interruption.

ErlangA measure of telephone traffic intensity equivalent to the average number of simultaneous calls.Alternatively, it is the total circuit usage in an interval of time divided by that interval. Thus, 1Erlang equals 3600 call seconds per hour or 36 CCS per hour.

EAMPSExtended Advanced Mobile Phone System - Refers to additional voice channels defined as anextension to the AMPS systems. Analogous to ETACS in TACS systems.


II


Neighbor SetThe pilots that are not currently in the Active Set or the Candidate Set, but are likely candidates forhandoff. Neighbor Set pilots are identified by the base station via Neighbor List and Neighbor ListUpdate messages.

PILOT_ARRIVALThe pilot arrival time is the time of occurrence of the earliest arriving usable multipath componentof a pilot relative to the subscriber’s time reference.

PILOT_INCThe pilot PN sequence offset index increment is the interval between pilots, in increments of 64chips. Its valid range is from 1 to 15. The subscriber uses this parameter in only one manner, todetermine which pilots to scan from among the Remaining set. Only valid pilots (i.e. those pilotsthat are multiples of PILOT_INC) will be scanned. For the subscriber, PILOT_INC impacts onlythe scanning rate applied to Remaining pilots. It accomplishes this by reducing the number ofRemaining pilots that need to be scanned.

For the base station, the effect of the PILOT_INC is different. In the base station, it is used inproperly translating pilot phase back into pilot offset index. The consequence is that the operatormay artificially increase the separation between valid time offsets. By selecting a PILOT_INC of2, for instance, an operator chooses to limit the number of valid offsets to 256 (i.e. 0, 2, 4,..., 508,510) instead of 512. The increased separation means that the pilot arrival must be larger beforeadjacent offset ambiguity is possible and consequently the likelihood of a strong adjacent interfereris reduced.

PILOT_PNThe pilot PN sequence offset (index), in units of 64 PN chips. It ranges from 0 to 511. Everytransmit sector will have an offset assigned to it. This parameter is set for each sector.

PILOT_PN_PHASEThe subscriber reports pilot strength and phase measurements for each active and candidate pilotin the Pilot Strength Measurement Message (PSMM) when recommending a change in the handoffstatus (i.e. mobile assisted handoff). The subscriber computes the reported PILOT_PN_PHASE asa function of the PILOT_ARRIVAL and the PILOT_PN. The pilot arrival component representsthe time delay of the pilot relative to the time reference or, in other words, how skewed the pilot isfrom the subscriber’s concept of system time. Note also that the subscriber does not identify pilotsby their offset index directly, but by their phase measurement. If the pilot arrival was larger than32 chips (1/2 of a pilot offset or 4.8 miles), then this could undermine the ability of the base stationto properly translate pilot phase into pilot offset index (given a PILOT_INC of 1).

Remaining SetThe set of all possible pilots in the current system on the current CDMA frequency assignment,excluding pilots in the other sets. These pilots must be integer multiples of PILOT_INC (definedabove).


II


Reuse PatternThe minimum number of cells required in a pattern before channel frequencies are reused, toprevent interference. Varies between cell configuration type (omni, sector, etc.) and channel type(traffic, control). The pattern shows assignments of adjacent channels to minimize interferencebetween cells and sectors within the pattern area. In CDMA, reuse pattern refers mainly to thepattern of the pilot assigned to each sector in the system.

SRCH_WIN_AThis parameter represents the search window size associated with the Active Set and Candidate Setpilots. The subscriber centers the search window for each pilot around the earliest arriving usablemultipath component of the pilot. Note that in contrast to the neighbor or remaining set searchwindows, the active/candidate search windows "float" with the desired signals. That is to say thatthe center position of the search window is updated every scan to track the new location of theearliest arriving multipath component.

SRCH_WIN_N, SRCH_WIN_RThese parameters represent the search window sizes associated with Neighbor Set and RemainingSet pilots. The subscriber centers the search window for each pilot around the pilot’s PN sequenceoffset using timing defined by the subscriber’s time reference.

In general, a neighbor search window, SRCH_WIN_N, will be sized so as to encompass thegeographic area in which the neighbor may be added (a soft handoff “add” zone or “initialdetection area”). The largest a neighbor search window need be is such that it is sufficient to coverthe distance between the neighbors, , plus an accommodation of the time-of-flight delay(approx. 3 chips).

To illustrate these relationships better, consider the following scenario. A subscriber monitors aneighbor pilot. The neighbor search window is centered on the neighbor pilot offset. This centeringis relative based on timing derived from the time reference. When the pilot strength of a neighborpilot recommends promotion to the candidate set, then the search window will be tightened to theactive search window size. The active search window is sized to compensate for delay spread onlyand is therefore smaller than the neighbor search window. In addition, the active search windowlocks onto and tracks the candidate pilot.

System TimeAll base station digital transmissions are referenced to a common CDMA system-wide time scalethat uses the Global Positioning System (GPS) time scale, which is traceable to and synchronouswith Universal Coordinated Time (UTC).

Time ReferenceThe subscriber establishes a time reference which is used to derive system time. This timereference will be the earliest arriving multipath component being used for demodulation. Thisreflects the assumption that the subscriber’s fix on system time is always skewed by delayassociated with the shortest active link.

3R


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III - 1CDMA/CDMA2000 1X RF Planning GuideMar 2002


Table of Contents

III.1 Watts to dBm Conversion Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III - 3

Appendix

III Watts to dBmConversion Table

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III

CDMA/CDMA2000 1X RF Planning GuideAppendix III: Watts to dBm Conversion Table

NOTES

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III - 3CDMA/CDMA2000 1X RF Planning GuideMar 2002

III


III.1 Watts to dBm Conversion Table

The following table provides a conversion from Watts to dBm.

Table III-1: Watts to dBm Conversion Table

Watts dBm Watts dBm Watts dBm Watts dBm Watts dBm

200 53.010 174 52.405 148 51.703 122 50.864 96 49.823

199 52.989 173 52.380 147 51.673 121 50.828 95 49.777

198 52.967 172 52.355 146 51.644 120 50.792 94 49.731

197 52.945 171 52.330 145 51.614 119 50.755 93 49.685

196 52.923 170 52.304 144 51.584 118 50.719 92 49.638

195 52.900 169 52.279 143 51.553 117 50.682 91 49.590

194 52.878 168 52.253 142 51.523 116 50.645 90 49.542

193 52.856 167 52.227 141 51.492 115 50.607 89 49.494

192 52.833 166 52.201 140 51.461 114 50.569 88 49.445

191 52.810 165 52.175 139 51.430 113 50.531 87 49.395

190 52.788 164 52.148 138 51.399 112 50.492 86 49.345

189 52.765 163 52.122 137 51.367 111 50.453 85 49.294

188 52.742 162 52.095 136 51.335 110 50.414 84 49.243

187 52.718 161 52.068 135 51.303 109 50.374 83 49.191

186 52.695 160 52.041 134 51.271 108 50.334 82 49.138

185 52.672 159 52.014 133 51.239 107 50.294 81 49.085

184 52.648 158 51.987 132 51.206 106 50.253 80 49.031

183 52.625 157 51.959 131 51.173 105 50.212 79 48.976

182 52.601 156 51.931 130 51.139 104 50.170 78 48.921

181 52.577 155 51.903 129 51.106 103 50.128 77 48.865

180 52.553 154 51.875 128 51.072 102 50.086 76 48.808

179 52.529 153 51.847 127 51.038 101 50.043 75 48.751

178 52.504 152 51.818 126 51.004 100 50.000 74 48.692

177 52.480 151 51.790 125 50.969 99 49.956 73 48.633

176 52.455 150 51.761 124 50.934 98 49.912 72 48.573

175 52.430 149 51.732 123 50.899 97 49.868 71 48.513

III - 4 CDMA/CDMA2000 1X RF Planning Guide Mar 2002

III


Watts = [10(dBm/10)] / 1000

dBm = 10 Log(Watts * 1000)

dBm = dB + 30

70 48.451 46 46.628 22 43.424 0.94 29.731 0.46 26.628

69 48.388 45 46.532 21 43.222 0.92 29.638 0.44 26.435

68 48.325 44 46.435 20 43.010 0.90 29.542 0.42 26.232

67 48.261 43 46.335 19 42.788 0.88 29.445 0.40 26.021

66 48.195 42 46.232 18 42.553 0.86 29.345 0.38 25.798

65 48.129 41 46.128 17 42.304 0.84 29.243 0.36 25.563

64 48.062 40 46.021 16 42.041 0.82 29.138 0.34 25.315

63 47.993 39 45.911 15 41.761 0.80 29.031 0.32 25.051

62 47.924 38 45.798 14 41.461 0.78 28.921 0.30 24.771

61 47.853 37 45.682 13 41.139 0.76 28.808 0.28 24.472

60 47.782 36 45.563 12 40.792 0.74 28.692 0.26 24.150

59 47.709 35 45.441 11 40.414 0.72 28.573 0.24 23.802

58 47.634 34 45.315 10 40.000 0.70 28.451 0.22 23.424

57 47.559 33 45.185 9 39.542 0.68 28.325 0.20 23.010

56 47.482 32 45.051 8 39.031 0.66 28.195 0.18 22.553

55 47.404 31 44.914 7 38.451 0.64 28.062 0.16 22.041

54 47.324 30 44.771 6 37.782 0.62 27.924 0.14 21.461

53 47.243 29 44.624 5 36.990 0.60 27.782 0.12 20.792

52 47.160 28 44.472 4 36.021 0.58 27.634 0.10 20.000

51 47.076 27 44.314 3 34.771 0.56 27.482 0.08 19.031

50 46.990 26 44.150 2 33.010 0.54 27.324 0.06 17.782

49 46.902 25 43.979 1 30.000 0.52 27.160 0.04 16.021

48 46.812 24 43.802 0.98 29.912 0.50 26.990 0.02 13.010

47 46.721 23 43.617 0.96 29.823 0.48 26.812 0.01 10.000

Table III-1: Watts to dBm Conversion Table

Watts dBm Watts dBm Watts dBm Watts dBm Watts dBm

IV - 1CDMA/CDMA2000 1X RF Planning GuideMar 2002


Table of Contents

IV.1 Complementary Error Function Table . . . . . . . . . . . . . . . . . . . . . . . . . . IV - 3

Appendix

IV Complementary ErrorFunction Table

IV - 2 CDMA/CDMA2000 1X RF Planning Guide Mar 2002

IV

CDMA/CDMA2000 1X RF Planning GuideAppendix IV: Complementary Error Function Table

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IV - 3CDMA/CDMA2000 1X RF Planning GuideMar 2002

IV


IV.1 Complementary Error Function Table

The following Complementary Error Function Table is supplied for the reader’s reference. Notethat the value of x within Q(x) is the sum of value in the first column of a specific row plus the valuegiven in the top row. For example, Q(0.76) corresponds to 0.2236 and Q(2.42) corresponds to0.0078.

Table IV-1: Complementary Error Function, Q(x)

Q(x)

x 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

0.0 0.5000 0.4960 0.4920 0.4880 0.4840 0.4801 0.4761 0.4721 0.4681 0.4641

0.1 0.4602 0.4562 0.4522 0.4483 0.4443 0.4404 0.4364 0.4325 0.4286 0.4246

0.2 0.4207 0.4168 0.4129 0.4090 0.4052 0.4013 0.3974 0.3936 0.3897 0.3859

0.3 0.3821 0.3783 0.3745 0.3707 0.3669 0.3632 0.3594 0.3557 0.3520 0.3483

0.4 0.3446 0.3409 0.3372 0.3336 0.3300 0.3264 0.3228 0.3192 0.3156 0.3121

0.5 0.3085 0.3050 0.3015 0.2981 0.2946 0.2912 0.2877 0.2843 0.2810 0.2776

0.6 0.2743 0.2709 0.2676 0.2644 0.2611 0.2579 0.2546 0.2514 0.2483 0.2451

0.7 0.2420 0.2389 0.2358 0.2327 0.2297 0.2266 0.2236 0.2207 0.2177 0.2148

0.8 0.2119 0.2090 0.2061 0.2033 0.2005 0.1977 0.1949 0.1921 0.1894 0.1867

0.9 0.1841 0.1814 0.1788 0.1762 0.1736 0.1710 0.1685 0.1660 0.1635 0.1611

1.0 0.1586 0.1562 0.1539 0.1515 0.1492 0.1468 0.1446 0.1423 0.1401 0.1378

1.1 0.1357 0.1335 0.1313 0.1292 0.1271 0.1251 0.1230 0.1210 0.1190 0.1170

1.2 0.1151 0.1131 0.1112 0.1093 0.1075 0.1056 0.1038 0.1020 0.1003 0.0985

1.3 0.0968 0.0951 0.0934 0.0917 0.0901 0.0885 0.0869 0.0853 0.0838 0.0823

1.4 0.0807 0.0793 0.0778 0.0764 0.0749 0.0735 0.0721 0.0708 0.0694 0.0681

1.5 0.0668 0.0655 0.0643 0.0630 0.0618 0.0606 0.0594 0.0582 0.0570 0.0559

1.6 0.0548 0.0537 0.0526 0.0515 0.0505 0.0495 0.0485 0.0475 0.0465 0.0455

1.7 0.0446 0.0436 0.0427 0.0418 0.0409 0.0401 0.0392 0.0384 0.0375 0.0367

1.8 0.0359 0.0352 0.0344 0.0336 0.0329 0.0322 0.0314 0.0307 0.0301 0.0294

1.9 0.0287 0.0281 0.0274 0.0268 0.0262 0.0256 0.0250 0.0244 0.0239 0.0233

2.0 0.0228 0.0222 0.0217 0.0212 0.0207 0.0202 0.0197 0.0192 0.0188 0.0183

2.1 0.0179 0.0174 0.0170 0.0166 0.0162 0.0158 0.0154 0.0150 0.0146 0.0143

2.2 0.0139 0.0136 0.0132 0.0129 0.0126 0.0122 0.0119 0.0116 0.0113 0.0110

2.3 0.0107 0.0105 0.0102 0.0099 0.0097 0.0094 0.0091 0.0089 0.0087 0.0084

IV - 4 CDMA/CDMA2000 1X RF Planning Guide Mar 2002

IV


2.4 0.0082 0.0080 0.0078 0.0076 0.0074 0.0072 0.0070 0.0068 0.0066 0.0064

2.5 0.0062 0.0060 0.0059 0.0057 0.0056 0.0054 0.0052 0.0051 0.0049 0.0048

2.6 0.0047 0.0045 0.0044 0.0043 0.0042 0.0040 0.0039 0.0038 0.0037 0.0036

2.7 0.0035 0.0034 0.0033 0.0032 0.0031 0.0030 0.0029 0.0028 0.0027 0.0026

2.8 0.0026 0.0025 0.0024 0.0023 0.0023 0.0022 0.0021 0.0021 0.0020 0.0019

2.9 0.0019 0.0018 0.0018 0.0017 0.0016 0.0016 0.0015 0.0015 0.0014 0.0014

3.0 0.0014 0.0013 0.0013 0.0012 0.0012 0.0011 0.0011 0.0011 0.0010 0.0010

3.1 0.0010 0.0009 0.0009 0.0009 0.0008 0.0008 0.0008 0.0008 0.0007 0.0007

3.2 0.0007 0.0007 0.0006 0.0006 0.0006 0.0006 0.0006 0.0005 0.0005 0.0005

3.3 0.0005 0.0005 0.0005 0.0004 0.0004 0.0004 0.0004 0.0004 0.0004 0.0004

3.4 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0002

3.5 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002

3.6 0.0002 0.0002 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001

3.7 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001

3.8 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001

3.9 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

Table IV-1: Complementary Error Function, Q(x)

Q(x)

x 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

rf planning guide

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