8)cdma 1x capacity planning

Wireless Curriculum Development SectionWireless Curriculum Development Section

ISSUEISSUE

0RG004601 CDMA1X Capacity 0RG004601 CDMA1X Capacity planningplanning

2.22.2

Capacity Planning Procedure

Calculate the sector carrier throughput and subscriber throughput according to the interference analysis and traffic model

Calculate the number of CFMR , BCPM/CCPM to configure the BTS

Configure the CEVC and CPPU according to the channel type and the number of each type of channel

The coverage and capacity planning are combined with the calculation of the number of carriers and BTSs

Capacity planning

Course Contents

Characteristics of CDMA NetworkCharacteristics of CDMA Network

Interference analysis Interference analysis

Reverse link capacity analysisReverse link capacity analysis

Forward link capacity analysisForward link capacity analysis

Capacity planningCapacity planning

Capacity Analysis

In CDMA system, all cells shares the same spectrum, which increases the capacity of a CDMA system. However the use of same frequencies may cause for multi-address interference. This kind of interference can restricts the system capacity.

The capacity of a radio system is determined by both the forward and reverse links. During the capacity planning. The analysis should be based upon both the forward and reverse links.

Because of distributed sources, in general we concentrate on the reverse link capacity more.

Characteristics of CDMA network

Basic Capacity Model

Limited interference model ITOT=Iown+Iother+PN+T

Iown Interference from subscribers in the local cell

Iother Interference from subscribers in the neighboring cells

PN Background noise of receiver

T External interference

Limited power model PTOT=Ppil+Psync+Ppag+Ptraf+Pother

Ppil Power of pilot channel

Psync Power of synchronous channel

Ppag Power of paging channel

Ptraf Power of traffic channel

Pother Power of other channel

Characteristics of CDMA network

Course Contents

Characteristics of CDMA NetworkCharacteristics of CDMA Network Interference analysisInterference analysis Reverse link capacity analysisReverse link capacity analysis Forward link capacity analysisForward link capacity analysis Capacity planningCapacity planning

Interference at reverse link

I own Interference from subscribers in the local cell

Interference each subscriber should overcome: ITOT - Pj Pj is the receiving power of jth subscriber , Vj is the voice activation facto

r Provided that the power control is ideal, then:

The value of Pj can be obtained:

The interference of the subscribers in the local cell is equal to the sum of all other subscribers power reaching the receiver:

Interference analysis

Interference due to the neighboring cell subscribers It is difficult to conduct theoretical analysis of the interference contr

ibuted by the neighboring cell subscribers, which is closely related to the subscriber distribution, actual cellular layout, load of neighboring cell, antenna pattern, etc.

f is adjacent cell interference factor and it is the ratio between the intercell interference to the intra cell interference, i.e.

If the subscribers are distributed uniformly, The typical value of f is 0.55 for an omini-directional cell The typical value of f is 0.65 for 3-sectors directional cell

Interference at reverse linkInterference analysis

Let

We can write

Since


Where is uplink load factor:

The two main components of the reverse interference depends upon the cell load When the load factor is equal to 1, ITOT reaches infinite. In this case, the correspon

ding capacity is called the limit capacity

Supposing： Power control is ideal Interference from subscribers in neighbor cells is constant

From last equation we get


Relationship between load factor and reverse interference

50% load -- 3dB

60 % load -- 4dB

75 % load -- 6dB


Iown from subscribers in the local cell (Very few interference due to Rake receiver) Forward coherent demodulation of the local cell, the interference originates from multipa

th, and defining the multipath factor. In the following graph, the horizontal axis indicates the number of multipath components and the vertical axis indicates the ratio of the co-channel interference to the total power spectrum in the same cell. The distribution of multipath energy has a certain rule, according to it, 87% of the energy is distributed into three strongest multipaths. The Rake receiving technology is adopted to compesate this effect and achieve the 2-3dB demodulation gain.

Interference at forward linkInterference analysis

Interference from the neighboring cell subscribers The interference from the neighboring cell is closely related to the subscri

ber distribution. At the center of BTS, the interference from the neighboring cell is very small, while at the edges of the cell, the interference is very large

The horizontal axis indicates the distance from the mobile station to the BTS, and the vertical axis indicates ratio of the forward link interference from other cells to the forward link power received by the local BTS (Ioc/S).

Interference at forward linkInterference analysis

How to Control Interference

Influence of interference upon the network Successful handoff rate

Access efficiency

Call drop rate

Conversation quality

How to control interference Improve power control

Improve the Rake receiving efficiency

Reasonable network planning

Interference analysis

Course Contents

Characteristics of CDMA NetworkCharacteristics of CDMA Network Interference analysis Interference analysis Reverse link capacity analysisReverse link capacity analysis Forward link capacity analysisForward link capacity analysis Capacity planningCapacity planning

According to the interference analysis, the pole capacity model

could be obtained:

Reverse Capacity Model – Pole Capacity ModelReverse Capacity Model – Pole Capacity ModelReverse link capacity analysis

11

1max

dGN

Nmax: The maximum users could be supported by 1 carrier simultaneously

:Voice activity factor

:Neighbor cell Interference factor d :Demodulation Threshold

G :Processing gain which means W/R

When the cell load is given, the actual capacity could be obtained:N=Nmax*X, where X is the cell load

Reverse Capacity Model – Soft Blocking ModelReverse Capacity Model – Soft Blocking Model

))1(

)1((

22

22

222

21

0

eM

eMXRW

QBcdma

dtexQ t

x

2/2

21)(

0X : Indicating the permitted cell load, determined by factors such as cell coverage, etc.

10/)10(ln,)/( tb NEe

2、 : First order and second order factors for speech activation

、 : First and second order interference factor

: Power control covariance

M : Cell capacity (Erlang)

RW / : Spread frequency gain

CDMAB : Soft blocking possibility

Reverse link capacity analysis

Typical values of reverse capacityReverse link capacity analysis

1X9.6K voice

Service demodulation threshold

5.08 5.57 6.34 7.13 6.78

Throughput of omni-directional BTS (Kbps)

117.2 103.1 84.2 68.2 74.9

Throughput of directional TRX (Kbps)

99.6 87.6 71.5 57.9 63.6

1X19.2K data


3.4 4.11 4.96 5.96 5.37


138.5 113.0 88.1 65.4 78.0


117.7 96.0 74.9 55.6 66.3

1X38.4K data


2.59 3.01 3.64 4.78 4.26


145.7 128.4 105.9 74.2 87.4


123.8 109.1 90.1 63.1 74.3


1X76.8K data


2.15 2.47 3.01 4.28 3.57


131.5 118.7 99.5 65.1 82.7


111.8 100.9 84.6 55.4 70.3

1X153.6Kdata


1.54 1.98 2.51 3.8 2.68


118.8 102.1 84.8 53.4 79.9


101.0 86.8 72.1 45.4 67.9


According to the traffic model provided by Zhengzhou Research Institute and

the subscriber proportion, the calculated TRX capacity of embedded omni-dir

ectional cell is 110kbps in reverse link 300kbps and in forward link. For 120º

sector site, it is 94kbps in reverse link and 255kbps in forward link.

Reverse Capacity at Different Rates and SpeedsReverse Capacity at Different Rates and SpeedsCapacity planning

Application rate proportion Static 3km/h 8km/h 30km/h 100km/h

Data subscriber 90% 5% 3% 2% 0%

Voice subscriber 60% 20% 14% 5% 1%

Access rate proportion 9.6kbps 19.2kbps 38.4kbps 76.8kbps 153.6kbps

Data subscriber 85% 8% 6% 1% 0%

Proportion of subscriber

service type

Voice subscribers

Data subscribers

Mixed service subscribers

90% 0% 10%

Course Contents


Forward Link Capacity ModelForward Link Capacity Model

].)(

.10[

..)(

max

max10/)(

maxpag

pagp

sync

syncpil

fTm

dBM

traftraf

traf

PGN

PGPKRLNP

KPG

PM

)( maxPM : Forward capacity )(dBM : Demodulation threshold allowance maxP : Maximum permitted power of BTS : Speech activation factor (being 0.4 generally) trafPG : Processing gain of traffic channel; syncPG : Processing gain of synchronous channel; pagPG : Processing gain of Paging channel traf : Demodulation threshold of traffic channel; pil : Demodulation threshold of pilot channel; sync : Demodulation threshold of synchronous channel; pag : Demodulation threshold of paging channel pN : Number of paging channels in the cell mN : Thermal noise trafK : Subscriber distribution factor fK : Forward integrated interference factor (including interference inside and outside the cell) )(RLT : Forward link attenuation (corresponding to the cell radius actually)

Forward link capacity analysis

Typical Value Of Forward Capacity

　　 static 3km/h 8km/h 30km/h -105Basic Parameter thermal noise -105 -105 -105 -105 -105

forward link attenuation 130 130 130 130 130

forward link interference factor 2 2 2 2 2

subscriber distribution factor 0.4 0.4 0.4 0.4 0.4

BTS maximum transmission power (W) 20 20 20 20 20

pilot channel demodulation threshold (dB) -15 -15 -15 -15 -15

sync channel demodulation threshold (dB) 6 6 6 6 6

paging channel demodulation threshold (dB) 6 6 6 6 6

CDMA 1X 9.6k Voice service service demodulation threshold 6.8 7.46 8.49 9.54 9.08

　 cell throughput (Kbps) 285.7 245 193 152 169

CDMA 1X 19.2k Data service service demodulation threshold 4.8 5.8 7 8.41 7.58


CDMA 1X 38.4k Data service service demodulation threshold 4.5 5.23 6.32 8.31 7.4





　 cell throughput (Kbps) 654.46 530 411 221.76 379.21


Forward Capacity Test Results of Pilot ProjectForward Capacity Test Results of Pilot Project

Background noise (dBm) -105

Path loss (dB) 130

System interference index 1.4

Geographic distribution coefficient of subscribers 0.4

Maximum transmitting power (W) 20

Demodulation threshold of pilot channel (dB) -15

Demodulation threshold of synchronous channel (dB) 6

Demodulation threshold of paging channel (dB) 6

Demodulation threshold of traffic channel (dB) 7

Throughput of omni-directional station (Kbps) 401

Throughput of traffic channel in 120º sector (Kbps) 341

Throughput of S111 BTS in 3-sector cell (Kbps) 1024

Forward Capacity Characteristics of the System

For different service type, the total capacity of equipment is different

The movement speed has great influences on the system capacity

In the central area of a cell, the forward interference is mainly because of multipath

At the borders of a cell, the forward interference is mainly because of the neighboring cells

The capacity of forward link depends upon the total transmitting power of the cell and the distribution of the transmitting power in the traffic channel and other additional channels

The subscriber distribution has direct influence upon the forward capacity of the BTS.


Reverse capacity The coherent demodulation of reverse pilot is adopted for traffic

channels and the Turbo code is used for the data service so that the

reverse demodulation performance is improved. The reverse capacity

of the CDMA-1X is 2 to 3 times that of the IS-95

Forward capacity The quick power control technique is used for the forward channel so

that the power control accuracy is improved and the mean forward

transmitting power is decreased. Moreover turbo code is used for the

data service. The forward capacity of the CDMA-1X is 1.5 to 2 times

that of the IS-95

Comparison of Capacity Characteristics Comparison of Capacity Characteristics between IS-95 and CDMA-1Xbetween IS-95 and CDMA-1X

Course Contents


CDMA 1X Capacity Planning

Data-Voice Traffic Model

Configuration of TRXs and Channel Resources in the System

Voice Service ModelVoice Service Model

For voice service, the 2G and 3G systems do not differ with

respect to subscriber behavior, service type and resource

occupation. A standard model is available for the 2G voice

service in the telecom industry, so the analysis results of the

model are directly quoted.

Voice service model

Service blocking rate 2%

Primary channel rate (Kbps) 9.6

Traffic (Erl) 0.02

Soft handover proportion 30%

Capacity planning

For voice services, the fixed rate channel is adopted and Erl is us

ed to describe the processing capability of equipment. Once the d

ata service is imported, different services lead to different mean s

ubscriber rates, in such case it is difficult to describe the occupatio

n in Erl. To describe this, Huawei uses throughput, which is

Throughput = Traffic strength*Data rate*Activation factor

Voice Capacity Described in ThroughputVoice Capacity Described in Throughput

rAvS

Capacity planning

Data Service Model Data Service Model Capacity planning

Data service rate Grade Statistic proportion of distribution(%) for high end user

Statistic proportion of distribution(%) for high low end user

9.6kbps R1 24 100

19.2kpbs R2 40 0

38.4kbps R3 30 0

76.8kbps R4 4 0

153.6kpbs R5 1 0

Mean data service rate (kbps)

R 26.21 9.6

Selection of communication rate for high and low end subscriber

3600321 RMMMTnSM1: Centralized coefficient on busy day N: Access service count T: Mean communication time M2:Centralized coefficient on busy hours M3: duty cycle R: Mean data service rate , ,26.21 for high end user

Capacity planning

Information query

WWW browse & WAP

E_mail

FTP Voice & video multimedia flow service

E-commerce

Others

Monthly use times 60 60 60 60 5 20 15

Centralized coefficient on busy day(M1)

0.05 0.05 0.05 0.05 0.05 0.05 0.05

Centralized coefficient on busy hours(M2)

0.1 0.1 0.1 0.1 0.1 0.1 0.1

Mean use time (s) 120 300 15 30 300 120 60

Duty cycle (M3) 0.1 0.1 0.75 0.8 0.8 0.1 0.1

Throughput (bps) 26.21 65.53 24.57 52.42 43.68 8.74 3.28

Estimated action of high-end users in the early phase of network

Through put at busy hours:

The throughput of high-end subscribers is 250 bps The uplink and downlink proportion is 1:4, the uplink throughput is 50bps

and the downlink throughput is 200bps Mean length of information frame is 200 byte

Data Service Model Data Service Model

The throughput of the low-end subscribers is 35 bps The uplink and downlink proportion is 1: 4, the uplink throughput is 7bps and the downlink throughput is 28bps. Mean length of information frame is 200 Byte.

Capacity planning

Information query

WWW browse & WAP

E_mail FTP Voice & video multimedia

E-commerce Others

Monthly useage 30 30 20 30 0 10 10

Centralized coefficient on busy day

0.05 0.05 0.05 0.05 0 0.05 0.05

Centralized coefficient on busy hours

0.1 0.12 0.1 0.1 0 0.1 0.1

Mean use time (s)

120 300 15 30 0 120 60

Duty cycle 0.1 0.1 0.75 0.8 0 0.1 0.1

Throughput (bps)

4.80 14.40 3.00 9.6 0 1.60 0.8

Classification and Definition of Subscriber BehaviorClassification and Definition of Subscriber Behavior Capacity planning

rv AvS 9600

Service allocation and value of voice subscribers (reverse channel)

Subscriber type Proportion

Traffic of single subscriber (Erlang)

Data service throughput of single subscriber (bps)

Voice 100% 0.02 ＝ 76.8

Pure voice subscriber service model

SS d

SS d

Service allocation and value of voice subscribers (reverse channel)

Subscriber type Proportion Data service throughput of single subscriber (bps)

Low-end pure data subscriber

80% ＝ 7

High-end pure data subscriber

20% ＝ 50

Pure data subscriber service model

Capacity planning

lltt

rdv

PSPSAvS

9600,

Allocation and value of mixed service (reverse channel)Subscriber type

ProportionTraffic of single su

bscriber (Erlang)

Data service throughput of single

subscriber (bps)

Mixed service throughput of single subscriber

(bps)

voice 100% 0.02 76.8

=92.4

High-end data 20% - 50

Low-end data 80% - 7

Mixed service model

Classification and Definition of Subscriber BehaviorClassification and Definition of Subscriber Behavior

CDMA 1X Capacity Planning

Data Voice Traffic Model

Configuration of TRXs and Channel Resources in the System

Um interface channel (FCH with soft handoff + SCH without soft handoff + Common channel ）

Characteristics of the CSM5000 chip:In forward direction 64 CEs, each CE can demodulate a 9.6k FCH/SCHIn reverse direction 32 CEs, each CE can demodulate a 19.2k SCH/FCH

Characteristics of DSP chip:The voice FCH channel is equivalent to a 9.6k channelThe data FCH channel is equivalent to a 9.6k channelThe data SCH channel is equivalent to multiple 9.6K channels

Abis interface (including soft handoff branch)

Voice Data

BCPM/CCPM

CFMR

CPRS/CPMS CEVC

(Not including soft handoff branch)

Voice channelData channel

Capacity planning

Flow Diagram

Characteristics of Equipment

In the CDMA-1X system, different channel boards have different processing capabil

ity. Therefore, analysis the processing capability of each channel processing unit be

fore configuration.

CCPM/BCPM (BTS): At present, several types of boards are available

1: With four CSM5000 chips. Each CMS5000 chip process the 64 forward CEs and 3

2 reverse CEs.

2: With two CSM5000 chips.

FMR board (BSC): Each board provides 450 channels demodulation resources. Ea

ch demodulation resource can process an FCH channel or a 9.6k SCH channel.

EVC board (BSC): Each board provides 192 voice channels processing units.

PPU board (BSC): Each PPU board provides data throughput of 20Mb and each C

PMS can provide 2500 activated PPP connections.

Capacity planning

Suppose the subscribers in Area 1 are 800000

The subscriber service behavior: Number of pure voice subscribers Pv=90%，Number of pure data service subscribers Pd=0%，Number of mixed service subscribers Pv,d=10%。Plan according to the 50% mean load

The blocking rate of the system is 2%

The voice traffic is 0.02Erl.

The mean throughput of high-end subscribers is 250bps.

The mean throughput of low-end subscribers is 35bps.

The proportion of forward and reverse subscriber data is 4:1.

A case studyA case studyCapacity planning

TRX & CE ConfigurationCapacity planning

Mean subscriber throughput in the coverage area = Sv × Pv + Sd × Pd + Sd,v × Pd,v = 76.8*90%+92.4*10%=78.36bps

Number of subscribers a single TRX can accommodate = Mean throughput of a single TRX

Mean subscriber throughput in the coverage area

=94*1024/78.36=1229Number of TRXs needed = Number of subscribers in the coverage area

Number of subscribers a single TRX can accommodate

= 800000/1229=651

TRX Type Number of subscriberss, a single TRX can accomodate

Minimum number of TRXes needed

S1 1229 651

O1 1437 557

BTS Type Number of subscriberss, a single BTS can accomodate

Minimum number of BTSs needed

S1/1/1 3687 217

O1 1387 557

BTS channel board, the forward and reverse CEs process the forward and reverse channels independently. Each forward CE can demodulate an FCH or a 9.6k SCH channel, while a reverse CE can demodulate an FCH channel or a 19.2k SCH channel. In one BTS, multiple sectors share the same CE resources. Please configure the CEs based upon the subscriber services in the coverage area of each BTS

In actual application, common channels should be reserved for the cells. For each reverse channel, a reverse CE should be reserved. While three forward CEs should be reserved for each sector for the processing of forward pilot, synchronous and paging channels

Soft handoff branches of the CDMA system occupy the CE processing resources. Currently only FCH takes part in the soft handoff while the SCH does not take part in the soft handoff. During the data service analysis, carefully consider which data are transferred by the FCH channel and which data are transferred by the SCH channel

In a BTS, currently two types of channel boards are provided

Capacity planning

TRX & CE Configuration

In our example, the voice subscribers are 90%, so we consider the reverse limitation i.e. configure the channels in reverse way. From observations, when the data subscribers reach 70% then there will be the forward limitation on resources. The reverse configuration method is as follows:

Voice channel resource = Voice subscriber throughput Voice flux/Voice activation factor

FCH channel resource = FCH data throughput(Primary rate of FCH data*Utilization ratio of data demodulation resource)

SCH channel resource= SCH data throughput(Primary rate of SCH data* Utilization ratio of data demodulation resource)

The SCH channel does not take part in the soft handoff. Total channel resource after soft handoff = (Voice channel resource + FCH channel resource)

(1 - Soft handoff proportion) Consider configuring a common access channel for each sector. Number of channels to be configured = ErlB_B (Basic channel resource of BTS, service blocking rate) Voice subscriber throughput = Planned number of subscribers a single TRX can accommodate* （ Pro

portion of pure voice subscribers + Proportion of mixed service subscribers ） * Voice subscriber throughput

Capacity planning


+SCH Channel Resource

The detailed configuration of channels and CSM5000 chips should be based upon the coverage of the BTS and the number of subscribers a single TRX can accommodate. For the initial planning, we can configure according the approximate estimation of the traffic coverage:

The number of subscribers a single TRX can accommodate according to the analysis results of the model developed by Zhengzhou research institute: 1229

Voice throughput =1229*(90%+10%)*76.8=94387.2bps Data FCH throughput =1229*10%*80%*7+1229*10%*20%*50*36.6%=1674.13bps Data SCH throughput =1229*10%*20%*50*63.4%=243.11bps Number of voice channel resources =94387.2/(9600*0.4)=24.58 Number of data FCH resources =1674.13/9600=0.17 Number of data SCH resources =243.11/(9600*1.5)=0.02 Considering 30% soft handoff =[(24.58+0.17)/(1-30%)+0.02]=35.4 Number of common channel per sector =1 Number of CEs per BTS =ErlB_B(36.4*3,0.02)=122 Number of channels needed for 800, 000 subscribers =122*217=26474

Capacity planning


Note: The numbers in red indicate “exceeding the throughput of single TRX”, which is solved by adding more TRXs.

TRXs & CE Configuration in the System (S1/1/1)Capacity planning

Number of subscribers per sector

Voice service flux (kbps)

Channels needed for voice service

Data service flux (kbps)

Channels needed for data service

100 7.68 2 0.15 0.01

250 19.2 5 0.38 0.03

550 42.24 11 0.84 0.06

1150 88.32 23 1.75 0.12

1750 134.4 35 2.67 0.19

The real project planning should be based on the detailed subscriber configuration according to the coverage planning and the subscriber distribution. The subscriber distribution is relatively sparse in suburb areas, a small number of channels can meet the requirements, while in dense urban areas, the subscribers are distributed densely, so more channels are needed to meet the capacity requirements. The typical configuration is given below:

TRXs & CE Configuration in the System (S1/1/1)Capacity planning

The following results can be obtained from the above analysis:

Number of subscribers per BTS

Basic configuration

Considering soft handover

Considering access channel

Actual configured channels considering the blocking rate

100*3 S2/2/2 S3/3/3 S4/4/4 S7/7/7

250*3 S6/6/6 S8/8/8 S9/9/9 S12/12/12

550*3 S12/12/12 S16/16/16 S17/17/17 S21/21/21

1150*3 S24/24/24 S31/31/31 S32/32/32 S36/36/36

1750*3 S36/36/36 S47/47/47 S48/48/48 S52/52/52

Note: The numbers in red indicate “exceeding the throughput of single TRX”, which is solved by adding more TRXs.

Number of voice FCH channels = Number of subscribers*Proportion of voice subscribers*Voice subscriber traffic =800000*(90%+10%)*0.02=16000Number of data FCH channels =(Number of subscribers* Proportion of data subscribers*Proportion of low-end subscribers*Throughput of low-end subscribers*Forward proportion+ Number of subscribers* Proportion of data subscribers* Proportion of high-end subscribers* Throughput of high-end subscribers*Forward proportion*FCH data proportion)/FCH processing capability =(800000*(0%+10%)*80%*35*80%+800000*(0%+10%)*20%*250 *80%*36.4%)/9600=309Number of data SCH channels =(Number of subscribers * Proportion of data subscribers * Proportion of high-end subscribers * Throughput of high-end subscribers * Forward proportion *SCH data proportion)/SCH processing capability =800000*(0%+10%)*20%*250*80%*(1-36.4%))/9600=212Number of FMR channels to be configured =Number of FCH channels/(1- soft

handoff proportion) + Number of data SCH channels =(16000+309)/(1- 30%)+212=23510

Calculation of BSC Processing ChannelCalculation of BSC Processing ChannelCapacity planning

Number of voice channels in the TC frame = 800000*0.02=16000

Reverse data traffic flow in the PM frame=(800000*10%*15.6/1024/1024)=1.2M

The forward and reverse proportion is 4:1, so the data traffic in the PM frame is =1.2*5=6Mbps

Provided that the subscribers are averagely distributed, then the hardware resources to be configured are as follows:Number of FMR boards =[23510/450]=53 piecesNumber of EVC boards =[16000/192]=84 piecesNumber of PPU boards =[6/20]=1 piece

Calculation of BSC Processing ChannelsCalculation of BSC Processing ChannelsCapacity planning

8)cdma 1x capacity planning

Documents

zhengzhou

ce configurationcapacity

reverse linkinterference

subscriber

data demodulation

data service

6k sch channel

voice traffic