lte qualcom

UMTS/WCDMA Technical Overview

MAY CONTAIN U.S. EXPORT CONTROLLED INFORMATION



Student Guide

80-W1447-1 Rev A

Viettel Telecom Training, May 7-9, 2008, Hanoi, Vietnam

Material Use RestrictionsThese written materials are to be used only in conjunction with the associated instructor-led class. They are not intended to be used solely as reference material.

No part of these written materials may be used or reproduced in any manner whatsoever without the written permission of QUALCOMM Incorporated.

Copyright © 2007 QUALCOMM Incorporated. All rights reserved.

QUALCOMM Incorporated5775 Morehouse DriveSan Diego, CA 92121-1714U.S.A.

This technical data may be subject to U.S. export, re-export or transfer ("export") laws. Diversion contrary to U.S. law prohibited.

QUALCOMM is a registered trademark of QUALCOMM Incorporated in the United States and may be registered in other countries. Other product and brand names may be trademarks or registered trademarks of their respective owners. QUALCOMM CDMA University is a registered trademark of QUALCOMM Incorporated. QUALCOMM University is a trademark of QUALCOMM Incorporated.

CDMA2000® is a registered certification mark of the Telecommunications Industry Association, used under license. ARM is a registered trademark of ARM Limited. QDSP is a registered trademark of QUALCOMM Incorporated in the United States and other countries.


UMTS/WCDMA Technical Overview 80-W1447-1 Rev ATable of Contents

© 2007 QUALCOMM Incorporated MAY CONTAIN U.S. EXPORT CONTROLLED INFORMATION



About Qualcomm University

Qualcomm University (“QU”) offers the advanced technology training solutions you need to stay on the cutting edge of wireless technology.

Visit the QU website for more information about individual training products, international training centers, and distance learning opportunities, along with a complete list of classes—all developed by QUALCOMM Incorporated, the pioneers of CDMA.

Qualcomm University: www.qualcommuniversity.comQUALCOMM Incorporated: www.qualcomm.com

Notes

iii






Where Can I Learn More?

UMTS/WCDMA Physical Layer and Radio Interface Protocols for Rel 99 (2 days)

WCDMA HSDPA: Protocols and Physical Layer (1 day)

WCDMA HSUPA: Protocols and Physical Layer (1 day)

Want to learn more?Qualcomm University offers additional in-depth technical training related to this course. To learn more about this or related topics, sign up for the following courses.

To check out the schedules for these courses and enroll, go to:

www.qualcommuniversity.com

Notes

iv



© 2007 QUALCOMM Incorporated MAY CONTAIN U.S. EXPORT CONTROLLED INFORMATION v



CDMA Courses from CDMA University

CDMA University training is offered by the CDMA Development Group (CDG) in association with Qualcomm. For the latest information on all CDMA University courses, visit http://www.cdmauniversity.com/.

Notes



© 2007 QUALCOMM Incorporated MAY CONTAIN U.S. EXPORT CONTROLLED INFORMATION vi



UMTS Courses from Qualcomm University

For the latest information on all Qualcomm University courses, visit www.qualcommuniversity.com.

Notes



© 2007 QUALCOMM Incorporated MAY CONTAIN U.S. EXPORT CONTROLLED INFORMATION vii

Table of Contents Section 1: Introduction.......................................................................... 1-1 Course Overview ..................................................................................... 1-2 Course Learning Objectives..................................................................... 1-3 Reference Documentation........................................................................ 1-4 Section 2: 3G and UMTS/WCDMA ..................................................... 2-1 Section Learning Objectives .................................................................... 2-2 From GSM to UMTS............................................................................... 2-3 What is 3G or IMT-2000?........................................................................ 2-4 What is UMTS? ....................................................................................... 2-5 What is WCDMA?................................................................................... 2-6 UMTS Network ....................................................................................... 2-7 UMTS-WCDMA Allocated Frequency Bands........................................ 2-8 UMTS-WCDMA Spectrum Bandwidth .................................................. 2-9 Who defines the UMTS/WCDMA Standards?...................................... 2-10 3GPP Releases and Features.................................................................. 2-11 Some UMTS Standards to Explore........................................................ 2-12 From GSM to WCDMA Data Services ............................................................................. 2-13 Data Rate Evolution................................................................... 2-14 UMTS Network Architecture ................................................................ 2-15 User Equipment (UE) ............................................................................ 2-17 Universal Terrestrial Radio Access Network (UTRAN) ....................... 2-18 Core Network (CN) ............................................................................... 2-19 UMTS Network Topology – Network Planning.................................... 2-20 3G and UMTS/WCDMA – What Did We Learn?................................. 2-21 Exercises ........................................................................................ 2-22 Answers...................................................................................... 2-24 Section 3: WCDMA Protocol Layers and Channels........................... 3-1 Section Learning Objectives .................................................................... 3-2 UE Signaling Protocol Stack ................................................................... 3-3 Protocol Stack Circuit Switched Control Plane ................................................... 3-4 Packet Switched Control Plane.................................................... 3-5 Circuit Switched User Plane ........................................................ 3-6 Packet Switched User Plane......................................................... 3-7 Access Stratum......................................................................................... 3-8 Protocols ...................................................................................... 3-9 Layer 3 – Radio Resource Control (RRC)............................................. 3-10



© 2007 QUALCOMM Incorporated MAY CONTAIN U.S. EXPORT CONTROLLED INFORMATION viii

Layer 2 PDCP and BMC......................................................................... 3-11 Radio Link Control (RLC)......................................................... 3-12 Medium Access Control (MAC)................................................ 3-13 Layer 1 – Physical Layer ...................................................................... 3-14 Significant Channels .............................................................................. 3-15 UMTS Channel Terminology ................................................................ 3-16 Channel Mapping R99 Logical Channels................................................................ 3-17 R99 Transport Channels ............................................................ 3-18 R99 Physical Channels .............................................................. 3-19 R99 Physical Only Channels ................................................................. 3-20 Dedicated Channels – AMR Call Mapping Example ............................ 3-21 WCDMA Protocol Layers and Channels – What Did We Learn? ........ 3-22 Exercises ........................................................................................ 3-23 Answers...................................................................................... 3-24 Section 4: Key WCDMA Radio Concepts and Procedures................ 4-1 Section Learning Objectives .................................................................... 4-2 WCDMA Basic Radio Concepts ............................................................. 4-3 Multiple Access Methods ........................................................................ 4-4 Interference Between Cells ...................................................................... 4-5 Frequency Reuse...................................................................................... 4-6 The “CDMA Cocktail Party”................................................................... 4-7 WCDMA Code Types.............................................................................. 4-8 Example of Spreading with Three Users ................................................. 4-9 De-spreading Example........................................................................... 4-10 OVSF Tree ........................................................................................ 4-11 Scrambling Codes .................................................................................. 4-12 Secondary Scrambling Codes (SSC) ..................................................... 4-13 WCDMA Power Control ....................................................................... 4-14 The Near-Far Problem ........................................................................... 4-15 Closed Loop Power Control................................................................... 4-16 R99 Closed Loop Power Control........................................................... 4-17 R99 Uplink Power Control ................................................................... 4-18 R99 Downlink Power Control ............................................................... 4-19 Open Loop Power Control ..................................................................... 4-20 WCDMA Mobility Procedures .............................................................. 4-21 Cell Reselection versus Handover ......................................................... 4-22 Types of Cell Reselection and Handover............................................... 4-23 Soft Handover ........................................................................................ 4-24 Softer Handovers ................................................................................... 4-25 Inter-RAT Hard Handover..................................................................... 4-26 UMTS/WCDMA Key Concepts – What Did We Learn?...................... 4-27 Exercises ........................................................................................ 4-28 Answers...................................................................................... 4-30



© 2007 QUALCOMM Incorporated MAY CONTAIN U.S. EXPORT CONTROLLED INFORMATION ix

Section 5: Basic UE Call Flow Procedures and Operations............... 5-1 Section Learning Objectives .................................................................... 5-2 Life of a Phone......................................................................................... 5-3 What Happens When the Phone is Turned On?....................................... 5-4 Initial PLMN and Cell Selection.............................................................. 5-5 NAS Registration Procedure – RRC Connection Establishment and NAS Attach.................................................................................. 5-6 UMTS Security Overview Security Procedures and Messages .............................................. 5-7 Features ........................................................................................ 5-8 Call Establishment – Mobile Originated/Terminated Calls..................... 5-9 Mobile Originated Voice Call Flow ...................................................... 5-10 Packet Switched Data Call Flow............................................................ 5-11 Mobile Terminated Voice Call Setup .................................................... 5-12 Call Release ........................................................................................ 5-13 UE Procedures at Power Off.................................................................. 5-14 NAS/AS Interaction and QoS ................................................................ 5-15 NAS CS and PS Logical Connections ................................................... 5-16 UTRA RRC States ................................................................................. 5-17 Relationship Between NAS and AS States............................................ 5-18 Quality of Service .................................................................................. 5-19 PS Quality of Service Architecture........................................................ 5-20 QoS – UMTS Traffic Classes Delay and Error Tolerance......................................................... 5-21 UMTS Bearer Service Attributes............................................... 5-22 QoS Negotiation in CS and PS Domain ................................................ 5-23 Basic UE Call Flow Procedures and Operations – What Did We Learn? ................................................................. 5-24 Exercises ........................................................................................ 5-25 Answers...................................................................................... 5-26 Section 6: High Speed Downlink Packet Access (HSDPA) ................ 6-1 Section Learning Objectives .................................................................... 6-2 High Speed Downlink Packet Access (HSDPA) ..................................... 6-3 UMTS Network Architecture with HSDPA and HSUPA ....................... 6-4 Packet Data in Release 99........................................................................ 6-5 HSDPA Basic Concepts........................................................................... 6-6 High Speed Downlink Shared Channel (HS-DSCH)............................... 6-7 Node B Transmit Power Allocation......................................................... 6-9 Multi-Code Operation............................................................................ 6-10 HARQ Protocol...................................................................................... 6-11 Retransmissions ..................................................................................... 6-12 Adaptive Modulation and Coding (AMC)............................................. 6-13 AMC versus Power Control................................................................... 6-14



© 2007 QUALCOMM Incorporated MAY CONTAIN U.S. EXPORT CONTROLLED INFORMATION x

HSDPA Scheduling and Retransmissions ............................................. 6-15 Functional Overview of Fast Scheduling............................................... 6-16 HSDPA Functional Overview................................................................ 6-17 HSDPA Channels................................................................................... 6-18 MAC-hs for HSDPA.............................................................................. 6-19 Change of Serving Node B – Repointing .............................................. 6-20 Overall Comparison Summary .............................................................. 6-21 HSDPA Performance Summary ............................................................ 6-22 HSDPA Fundamentals – What Did We Learn?..................................... 6-23 Exercises ........................................................................................ 6-24 Answers...................................................................................... 6-25 Section 7: High Speed Uplink Packet Access (HSUPA) .................... 7-1 Section Learning Objectives .................................................................... 7-2 High Speed Uplink Packet Access (HSUPA).......................................... 7-3 Applications Requiring an Improved Uplink (UL).................................. 7-4 Release 99 Uplink Limitations................................................................. 7-5 Enhancements Provided by HSUPA........................................................ 7-6 How are HSUPA Enhancements Achieved? .......................................... 7-7 Theoretical HSUPA Maximum Data Rate............................................... 7-8 New UL Transport Channel – Enhanced Uplink Dedicated Channel (E-DCH)....................................................................................... 7-9 New Uplink Physical Channels ............................................................. 7-10 New Downlink Physical Channels......................................................... 7-11 New Channels in HSUPA Operation..................................................... 7-12 HSUPA Channels Mapping .................................................................. 7-13 HSUPA Features HARQ Operation ....................................................................... 7-14 Hybrid ARQ............................................................................... 7-15 Resource Control ....................................................................... 7-16 Load Control .............................................................................. 7-17 HSUPA versus Release 99 Data Transmission ..................................................................... 7-18 Rate Adaptation ......................................................................... 7-19 HSUPA vs. HSDPA............................................................................... 7-20 HSDPA Fundamentals – What Did We Learn?..................................... 7-21 Exercises ........................................................................................ 7-22 Answers...................................................................................... 7-23




Acronyms and Abbreviations 16-QAM 16-Quadrature Amplitude Modulation 1G 2nd Generation 2G 2nd Generation 3G 3rd Generation 3GPP 3rd Generation Partnership Project AICH Acquisition Indicator Channel AM Acknowledged Mode AMC Adaptive Modulation and Coding AMPS Advanced Mobile Phone System/Service (ubiquious analog network in US)ARFCN Absolute Radio Frequency Channel Number ARIB Association of Radio Industries and Businesses (Japan) ARIB Association of Radio Industries and Businesses (Japan) ARPANET Advanced Research Projects Agency NETwork ARQ Automatic Repeat Request AS Access Stratum AuC Authentication Center BCCH Broadcast Control Channel BCH Broadcast Channel BLER Block Error Rate BMC Broadcast/Multicast Control BMP Broadcast Multicast Protocol CC Call Control CCCH Common Control Channel CCSA China Communications Standards Association (China) CCTrCh Coded Composite Transport Channel CD Compact Disk CDMA Code Division Multiple Access CM Connection Management CN Core Network CO Central Office CPC Continuous Packet Connectivity CPCH Common Packet Channel (Transport Channel) CPICH Common Pilot Channel CQI Channel Quality Indicator CRC Cyclic Redundancy Check CTCH Common Traffic Channel (Logical Channel) CWTS Chinese Wireless Telecommunication Standard D-AMPS Digital AMPS dB Decibel DCCH Dedicated Control Channel DCH Dedicated Channel DECT Digital European Cordless Telecommunications DL Downlink DPCCH Dedicated Physical Control Channel

xi




DPCH Dedicated Physical Channel DPDCH Dedicated Physical Data Channel DRX Discontinuous Reception DSCH Downlink Shared Channel (Transport Channel) DTCH Dedicated Traffic Channel E1 The European format for digital transmission. Carries signals at 2 Mbps

(32 channels at 64 Kbps) E-AGCH Enhanced Absolute Grant Channel E-DCH Enhanced Dedicated Channel EDGE Enhanced Data rates for GSM Evolution E-DPCCH Enhanced Dedicated Physical Control Channel E-DPDCH Enhanced Dedicated Physical Data Channel E-HICH Enhanced Hybrid ARQ Indicator Channel E-RGCH Enhanced Relative Grant Channel ETSI European Telecommunications Standards Institute EUL Enhanced Uplink E-UTRAN Evolved UTRAN FACH Forward Access Channel FBI Feedback Information FDD Frequency Division Duplex FDMA Frequency Division Multiple Access FEC Forward Error Correction FM Frequency Modulation FTP File Transfer Protocol GERAN GSM/EDGE Radio Access Network GGSN GPRS Gateway Support Node GMM GPRS Mobility Management GMSC Gateway Mobile Switching Center GPRS General Packet Radio Service GRX GPRS Roaming eXchange GSM Global System for Mobiles (European standard). Based on TDMA, uses

SIM cards for subscriber identity HARQ Hybrid Automatic Repeat Request HLR Home Location Register HPA High Power Amplifier HSDPA High Speed Downlink Packet Access HS-DPCCH High Speed Dedicated Physical Control Channel HS-DSCH High Speed Downlink Shared Channel (Transport Channel) HSPA High Speed Packet Access HS-PDSCH High Speed Physical Downlink Shared Channel (Physical Channel) HS-SCCH High Speed Shared Control Channel (Transport Channel) HSUPA High Speed Uplink Packet Access IMT-2000 International Mobile Telecommunications-2000 Inter-RAT Inter-Radio Access Technology IP Internet Protocol IR Incremental Redundancy

xii




ISDN Integrated Services Digital Network ITU International Telecommunications Union kbps Kilobits Per Second KHz Kilo Hertz L1 Physical Layer LA Location Area LCS Location Services LP Long Play(ing) (record) LTE Long Term Evolution MAC Media Access Control (protocol layering context) MAP Mobile Application Part MBMS Multimedia Broadcast/Multicast Service Mcps Megachips per second ME Mobile Equipment MHz Mega Hertz (unit of frequency, 1,000,000 cycles per second) MIMO Multiple Input Multiple Output MM Mobility Management OR Multimedia MP3 MPEG-1/2 Audio Layer 3 ms Millisecond MS Mobile Station MSC Mobile Switching Center (Switches mobile-oriented or -terminated traffic.

Connects the PSTN to the Base Station.) MT Mobile Terminated NAK Negative AcKnowledgement NMT Nordic Mobile Telephone Node B Base Station NTT Nippon Telephone & Telegraph OFDM Orthogonal Frequency Division Multiplexing OLPC Open Loop Power Control OVSF Orthogonal Variable Spreading Factor PACH Paging Channel PCCH Paging Control Channel PCCPCH Primary Common Control Physical Channel PCH Paging Channel (Transport Channel) PCS Personal Communication Services/System (amalgam of multiple,

competing technologies (TDMA, CDMA, GSM) in the 1,900 MHz band) PDA Personal Digital Assistant PDCP Packet Data Convergence Protocol PDF Portable Document Format PDP Packet Data Protocol PI Paging Indicator PICH Paging Indicator Channel PN Pseudorandom Noise PRACH Physical Random Access Channel PSC Primary Scrambling Codes P-SCH Primary Synchronization Channel

xiii




PSTN Public Switched Telephone Network QoS Quality of Service QPSK Quadrature Phase Shift Keying RA Routing Area RAB Radio Access Bearer RACH Random Access Channel RAN Radio Access Network RF Radio Frequency RLC Radio Link Control RNC Radio Network Controller RNS Radio Network Subsystem RRC Radio Resource Control SAE System Architecture Evolution SAW Stop-And-Wait SCCPCH Secondary Common Control Physical Channel S-CCPCH Secondary Common Control Physical Channel SCH Synchronization Channel SDMA Space Division Multiple Access SF Spreading Factor SGSN Serving GPRS Support Node SIR Signal-to-Interference Ratio SM Session Management SMS Short Message Service SSC Secondary Scrambling Codes T1 Trunk Level 1, total signaling speed of 1.544 Mbps. One of the basic

signaling systems (24 channels at 64 Kbps). TB Transport Block TDD Time Division Duplex TDMA Time Division Multiple Access TD-SCDMA Time Division Synchronous Code Division Multiple Access TFCI Transport Format Combination Indicator TM Transparent Mode TPC Transmit Power Control TTA Telecommunications Technology Association (Korea) TTC Telecommunications Technology Committee (Japan) TTI Transmission Time Interval UARFCN UTRA Absolute Radio Frequency Channel Number UE User Equipment (mobile, fixed station, data terminal, etc.) UICC Universal Integrated Circuit Card UL Uplink UM Unacknowledged Mode UMB Ultra Mobile Broadband UMTS Universal Mobile Telecommunications Systems USIM Universal Subscriber Identity Module UTRA Universal Terrestrial Radio Access UTRAN Universal Terrestrial Radio Access Network

xiv



© 2007 QUALCOMM Incorporated MAY CONTAIN U.S. EXPORT CONTROLLED INFORMATION xv

VLR Visitor Location Register VoIP Voice over Internet Protocol VSF Variable Spreading Factor WCDMA Wideband Code Division Multiple Access WLAN Wireless Local Area Network WWW World Wide Web



© 2007 QUALCOMM Incorporated MAY CONTAIN U.S. EXPORT CONTROLLED INFORMATION xvi

This page left blank intentionally.



Section 1: Introduction80-W1447-1 Rev A

1-1© 2007 QUALCOMM Incorporated MAY CONTAIN U.S. EXPORT CONTROLLED INFORMATION


Section 1-1


Section 1:Introduction

1SECTION

Introduction

Notes






Section 1-2


Course Overview

1. Introduction2. 3G and UMTS/WCDMA3. WCDMA Protocol Layers and Channels 4. Key WCDMA Radio Concepts and Procedures5. Basic UE Call Flow Procedures and Operations6. High Speed Downlink Packet Access (HSDPA)7. High Speed Uplink Packet Access (HSUPA)

Notes






Section 1-3


Course Learning Objectives

Describe the main UMTS/WCDMA requirements. List the major releases of the UMTS standard and what they support.List the major components in a UMTS Network and their functions.Explain the UMTS radio interface Protocols and channels.Describe the main radio interface concepts and procedures.Explain the basic UMTS call flows and the main NAS concepts.Illustrate the main HSDPA/HSUPA concepts and principles.

Notes






Section 1-4


Reference Documentation

Course R

eferences

Course R

eferences

Course R

eferences

Course R

eferences

Course R

eferences

964AB_00_revD.emf

Reference Documentation

[1] 3rd Generation Partnership Project Technical Specifications, ftp://ftp.3gpp.org/Specs

[2] Harri Holma and Antti Toskla, editors, WCDMA for UMTS; Radio Access for Third Generation Mobile Communications, Third Edition, John Wiley & Sons, 2004 (ISBN 0470870966)

[3] Juha Korhonen, Introduction to 3G Mobile Communications, Artech House, 2001 (ISBN 10: 158053287X)

[4] Christophe Chevallier, Christopher Brunner, Andrea Garavaglia, Kevin P. Murray, and Kenneth R. Baker, editors. WCDMA (UMTS) Deployment Handbook, Wiley & Sons, Ltd., 2006. (ISBN 13: 978-0-470-03326-5) (ISBN 10: 0-470-03326-6)

[5] H. Holma and A. Toskala: HSDPA/HSUPA, Wiley and Sons Ltd, 2006 (ISBN 10: 0-470-01884-4).

[6] R. Tanner and J. Woodard: WCDMA Requirements and Practical Design, Wiley and Sons Ltd, 2004.

[7] Andrew Richardson: WCDMA Design Handbook, Cambridge University Press, 2005. (ISBN 10: 0521828155)



2-1

Section 2: 3G and UMTS/WCDMA80-W1447-1 Rev A



Section 2-1


Section 2:3G and UMTS/WCDMA

2SECTION

3G and UMTS/WCDMA

Notes



2-2




Section 2-2


Section Learning Objectives

Understand the main requirements for UMTS/WCDMA.

Name the standards organization that produces WCDMA/UMTS standards.

List the WCDMA (UMTS) standard releases and their main features.

List the main evolutional drivers from GSM to UMTS and beyond.

Understand the main UMTS network entities and functions.

Notes



2-3




Section 2-3


From GSM to UMTS

From GSM to UMTS

Notes



2-4




Section 2-4


What is 3G or IMT-2000?

The International Telecommunications Union (ITU) defined the key requirements for International Mobile Telecommunications 2000 (IMT-2000) services, more commonly known as…

ITU approved family of standards that meet IMT-2000 criteria*

3G requirements• Improved system capacity, backward compatibility with Second Generation (2G) systems,

multimedia support, and high speed packet data services meeting the following criteria:– 2 Mbps in fixed or in-building environments

– 384 kbps in pedestrian or urban environments

– 144 kbps in wide area mobile environments

* ITU approved IMT-2000 terrestrial radio interfaces

3G3G

What is IMT-2000?

Two different standards bodies developed and proposed two families of standards:

3rd Generation Partnership Project 2 (3GPP2) – CDMA2000 family of standards

3rd Generation Partnership Project (3GPP) – WCDMA (UMTS) family of standards

The International Telecommunications Union (ITU) accepted both the CDMA2000 and WCDMA proposals as the basis for a global and unified International Mobile Telecommunications-2000 (IMT-2000) specification. The IMT-2000 specification was designed to deliver advanced 3G mobile services such as high-speed data services, video, and other feature-rich multimedia applications.

Subsequently, the IMT-2000 standard accommodated several different modes, three of which are based on CDMA technology:

IMT-2000 CDMA Direct Spread (WCDMA) – CDMA-based

IMT-2000 CDMA Multi-Carrier (CDMA2000) – CDMA-based

IMT-2000 CDMA Time Division Duplex (TDD) Time Division-Synchronous CDMA (TD-SCDMA) – CDMA-based; China deployments expected in 2007

IMT-2000 TDMA Single carrier (UWC-136) and FDMA/TDMA (DECT); not expected to be widely deployed



2-5




Section 2-5


What is UMTS?

What is Universal Mobile Telecommunications System (UMTS)?

• An IMT-2000 standard – 3G mobile wireless solution.

• Designed to be deployed reusing most parts of the GSM/GPRS (General Packet Radio Service) corenetwork (a key driver in standardization!)

• UMTS uses a totally new CDMA-based Radio Access technology in the form of WCDMA.

• Supports multiple services, better quality of service (QoS) differentiation and higher data rates (up to 14 Mbps).

UMTS Overview

Universal Mobile Telecommunications System, or UMTS, is a CDMA-based technology standardized by the Third Generation Partnership Project (3GPP) and first deployed in 2003. UMTS meets the goals of IMT-2000.

UMTS provides an evolutionary path for GSM to achieve high speed data and higher capacity. Although UMTS reuses most of the GSM core network, it uses a different technology (WCDMA) with a larger channel size (5 MHz vs. 200 kHz for GSM) and will be deployed on its own frequency band. UMTS is presumed to have economies of scale by deploying it under the GSM/GPRS MAP network. Also, the standard allows easy handovers to and from GSM and GPRS radio access.

UMTS supports multiple services, better Quality of Service (QoS) differentiation, and higher data rates. The UMTS maximum packet-switched data rate is 14 Mbps, while the maximum circuit-switched rate is 384 kbps.

For packet data users, UMTS supports HSPDA, which currently offers a high speed Downlink, and HSUPA, which is designed to provide high speeds on the Uplink.



2-6




Section 2-6


What is WCDMA?

WCDMA = Wideband Code Division Multiple Access

• WCDMA (also known as UTRA-FDD) has separate 5-MHz wide channels dedicated to communications in both Uplink and Downlink.

• WCDMA is a Radio Access Network (RAN) technology in the UMTS standard.

• Many use the terms UMTS and WCDMA interchangeably.

• This course uses WCDMA to refer to the radio interface technology used within UMTS, and UMTS to refer to the complete system.

• This course focuses on the WCDMA radio interface.

WCDMA Overview

Although WCDMA and UMTS are often used interchangeably in the wireless industry, strictly speaking WCDMA is one of three access technologies that are part of the larger UMTS Network. In some parts of the world, when people say WCDMA, they are referring to a non-3GPP version deployed by NTT DoCoMo in Japan. In this class, however, we use WCDMA to mean the FDD radio access mode of UMTS, as defined by the current 3GPP specifications.



2-7




Section 2-7


UMTS Network

WCDMA

UMTS Network

UMTS networks consists of 2 stratums, the Non-access stratum (the “Core Network”) and the Access stratum (the “radio access network”).

The Non-Access stratum deals with switching and routing of circuit-switched and packet-switched traffic while the Access stratum deals with providing radio access and controlling the radio resources. The Access Stratum consists of three different Access Network technologies:

UMTS Terrestrial Radio Access – Frequency Division Duplex (UTRA-FDD). UTRA-FDD is commonly referred to as Wideband Code Division Multiple Access (WCDMA). WCDMA is the primary focus of this course.

UMTS Terrestrial Radio Access – Time Division Duplex (UTRA-TDD) 1.28 Mcps and 3.84 Mcps. This technology is not widely deployed. However, a version of this technology, UTRA-TDD 1.28 Mcps, commonly known as Time Division-Synchronous CDMA (TD-SCDMA) is being pursued in China.

Global System for Mobile Communications (GSM)/General Packet Radio Service (GPRS). GSM/GPRS networks are widely deployed with over 2 billion GSM subscribers worldwide. For this reason, the UMTS Core Network reuses most of the existing GSM/GPRS Core Network.



2-8




Section 2-8


UMTS-WCDMA Allocated Frequency Bands

1749.9 -1784.9

830 - 840

824 - 849

1710 - 1755

1850 - 1910

880 - 915

1710 - 1785

2500 - 2570

1920 - 1980

UL Range (MHz)

No400 MHz2110 - 21552 x 45IVUMTS-1700-2100

Yes80 MHz1930 - 19902 x 60IIUMTS-1900

Japan

IX

VI

V

VIII

III

VII

I

Band Number

2 x 35

2 x 10

2 x 25

2 x 35

2 x 75

2 x 70

2 x 60

Size (MHz)

1844.9 -1879.9

875 - 885

869 - 894

925 - 960

1805 - 1880

2620 - 2690

2110 - 2170

DL Range (MHz)

95 MHz

45 MHz

45 MHz

45 MHz

95 MHz

120 MHz

190 MHz

Separation (MHz)

UMTS-1700

UMTS-800

UMTS-850

Americas

UMTS-900

UMTS-1800

Europe/GSM

UMTS-2600

UMTS-2100

Multiple Regions

Band Names

No

No

Yes

No

Yes

No

Yes

Deployed*

* Spectrum deployed as of November 2007

UMTS Frequency Allocations

It would have been desirable to have a unique worldwide frequency allocation for all 3G systems. However, individual regulatory agencies control spectrum allocations and no universally clear spectrum is available.

Thus, different frequency bands have been assigned to UMTS in different regions and/or countries.

UMTS FDD systems are currently specified to operate in the above paired bands, although only a few are currently deployed. UMTS-900 deployments are expected in Europe beginning in 2008.



2-9




Section 2-9


UMTS-WCDMA Spectrum Bandwidth

UMTS 2100 band (I)

UMTS Bandwidth

Channel Spacing

The nominal channel spacing is 5 MHz, but this can be adjusted to optimize performance in a particular deployment scenario.

Channel Raster

The channel raster is 200 KHz, which means that the center frequency must be an integer multiple of 200 KHz.

Channel Number

The carrier frequency is designated by the UTRA Absolute Radio Frequency Channel Number (UARFCN), where:

Fcenter = UARFCN * 200 KHz

Uplink to Downlink Separation

The frequency separation between Uplink and Downlink varies by band (see the slide titled “Commonly Used UMTS Frequency Allocations” earlier in this section). There must be sufficient separation between the bands to permit filtering of out of band emissions from the Node B transmitter and an interfering Node B receiver and between the UE Transmitter and the UE Receiver. TDD uses the same frequencies for Uplink and Downlink, so Uplink to Downlink frequency separation does not apply.



2-10




Section 2-10


Who Defines the UMTS/WCDMA Standards?

3GPP (3rd Generation Partnership Project )

3GPP Technical Bodies/Groups

Project Co-ordination Group(PCG)

TSG RANRadio Access Networks

RAN WG1Radio Layer 1 specification

RAN WG2Radio Layer2 spec &

Radio Layer3 RR spec

RAN WG3lub spec lur spec lu spec &UTRAN O&M requirements

RAN WG4Radio Performance &

Protocol Aspects

RAN WG5Mobile Terminal

Conformance Testing

TSG RANRadio Access Networks

RAN WG1Radio Layer 1 specification

RAN WG2Radio Layer2 spec &

Radio Layer3 RR spec

RAN WG3lub spec lur spec lu spec &UTRAN O&M requirements

RAN WG4Radio Performance &

Protocol Aspects

RAN WG5Mobile Terminal

Conformance Testing

TSG SAServices &

System Aspects

SA WG1Services

SA WG2Architecture

SA WG3Security

SA WG4Codec

SA WG5Telecom Management

TSG CTCore Network& Terminals

CT WG1MM/CC/SM (lu)

CT WG3Interworking with External Networks

CT WG4MAP/GTP/BCH/SS

CT WG5OSA

Open Service Access

CT WG6Smart Card

Application Aspects

TSG GERANGSM EDGE

Radio Access Network

GERAN WG1Radio Aspects

GERAN WG2Protocol Aspects

GERAN WG3Terminal TestingGERAN WG3Terminal Testing

TSG GERANGSM EDGE

Radio Access Network

GERAN WG1Radio Aspects

GERAN WG2Protocol Aspects

GERAN WG3Terminal TestingGERAN WG3Terminal Testing

April 2007

WCDMA/UMTS Standards – 3GPP

The 3rd Generation Partnership Project (3GPP) is a collaboration agreement that was established in 1998. The collaboration agreement unites a number of telecommunications standards bodies. The current Organizational Partners are ARIB, CCSA, ETSI, ATIS, TTA, and TTC.

ARIB – Association of Radio Industries and Businesses (Japan)CCSA – China Communications Standards Association (China)ETSI – European Telecommunications Standards Institute (Europe)TIA – Telecommunications Industry Association (North America)TTA – Telecommunications Technology Association (Korea)TTC – Telecommunications Technology Committee (Japan)

The original scope of 3GPP was to produce globally applicable Technical Specifications and Technical Reports for the evolved GSM core network and the new radio access technologies (i.e., Universal Terrestrial Radio Access [UTRA] for both Frequency Division Duplex [FDD] and Time Division Duplex [TDD] modes).

The scope was subsequently amended to include the maintenance and development of the Global System for Mobile communication (GSM) Technical Specifications and Technical Reports including evolved radio access technologies (e.g., General Packet Radio Service [GPRS] and Enhanced Data rates for GSM Evolution [EDGE]).

3rd Generation Partnership Project



2-11




Section 2-11


3GPP Releases and Features

UMTS and WCDMA Releases and Features

Release 99 – Improvements over GSM/GPRS/Edge include improved voice capacity and higher data rates. Includes Location Services (LCS).

Release 4 – Mainly introducing CS split architecture, TDD at 1.28 Mcps, Tandem/Transcoder Free operation, PS Streaming.

Release 5 – HSDPA provided significantly higher Downlink data rates compared to R99. Added support for All IP transport and IP Multimedia Subsystem.

Release 6 – High Speed Uplink Access (HSUPA) provided higher Uplink data rates over R99 and R5. Added Multimedia Broadcast Multicast Service (MBMS) and Rich Multimedia Services based on IMS (PTT, Presence, Conferencing, Video Share).

Release 7 – HSPA+ (HSPA Evolution) provides enhanced radio interface features: Downlink Multiple Input-Multiple Output (MIMO) and 64/16 QAM in DL/UL for higher data rates. It also employs Continuous Packet connectivity (CPC), which includes DPCCH gating, CQI reporting reduction, and reduced High Speed-Shared Control Channel (HS-SCCH) operation to reduce power consumption required to maintain connectivity.

Release 8 – Looking even further into the future, Long Term Evolution (LTE) will be OFDM-based, employing scalable bandwidths from 1.25 MHz to 20 MHz.



2-12




Section 2-12


Some UMTS Standards to Explore

34.xxxUE Conformance

22.xxx, 23.xxx, 24.xxxNAS Layer (CC, SS, SMS, MM)

22.060, 23.060Packet Switched Data Services

23.910Circuit Switched Data Services

25.2xxPhysical Layer

25.3xxLayer 2 and Layer 3

25.4xxUTRAN

26.xxxVoice Service

25.1xxRF Performance

LTE

USIM

Topic

36.xxx

31.xxx

Specifications Series Number

Specifications are segmented by layers and are available at:

http://www.3gpp.org/specs/numbering.htm

For a complete list of UMTS specifications, see 21.101.

For a list of acronyms, see 21.905.

UMTS Standards

The 3rd Generation Partnership Project (3GPP) is responsible for writing and maintaining the UMTS specifications. The standards for UMTS are continuously evolving within 3GPP.



2-13




Section 2-13


GPRS GPRS

EDGEEDGE

WCDMA (R99)WCDMA (R99)

HSDPA / HSUPA(Rel 5 / Rel 6)

HSDPA / HSUPA(Rel 5 / Rel 6)

Peak Data Rate

Sp

ectr

al E

ffic

ien

cy

Video StreamingVideo TelephonyHigher data rate services

Wireless Broadband AccessRich Multi-media applicationsInteractive GamingVoIP

Text Messaging GSM GSM

Push-to-TalkCustomized InfotainmentMultimedia Messaging

Data ServiceEvolution

Source: UMTS Forum/QUALCOMM Incorporated

Voice & Limited Data

Medium Speed Data

Voice & High Speed Data

From GSM to WCDMA – Data Services

HSPA(Rel 7)HSPA(Rel 7)

LTE(Rel 8)LTE

(Rel 8)

384 kbps160 kbps

WCDMA Data Services

WCDMA provides higher data rates and spectral efficiency than earlier technologies such as GSM, GPRS, or EDGE. Later Releases of WCDMA, HSDPA (Release 5), HSUPA (Release 6) provide even higher data rates on the Downlink and Uplink respectively. Future releases, HSPA (Release 7) and LTE (Release 8) will provide even higher data rates and spectral efficiency (i.e., higher data rates per Hz of spectrum) along with lower latency.



2-14




Section 2-14


From GSM to WCDMA – Data Rate Evolution

Theoretical maximum achievable peak data rates: Downlink = 14.4 Mbps / Uplink = 5.76 Mbps

Downlink Peak Data Rate (Typical Deployment)

Uplink Peak Data Rate (Typical Deployment)

GSM 9.6 kbps (CS) 9.6 kbps (CS)GPRS 40 kbps 20 kbpsEDGE 120 kbps 60 kbps

WCDMA Release 99 384 kbps 64 kbpsHSDPA - Release 5 7.2 Mbps 384 kbpsHSUPA - Release 6 7.2 Mbps 1.4 Mbps (early deployment)

Data Rate EvolutionTypical data rates offered by GSM, GPRS and EDGE were not much improved over dialup modem speeds (~56 kbps). Assumptions for Typical Downlink Peak Data Rates for GPRS and EDGE:

1. GPRS: Coding Scheme 2 (CS2), 4 Time Slots at 10 kbps per slot. Assumed C/I=15 dB.

2. EDGE: Modulation CS6 (MCS6), 4 Time Slots at 30 kbps per slot. Assumed C/I=15 dB.

The lack of high peak data rates for 2-2.5G cellular technology was major driver for the development of 3G networks. The goal of 3G was to provide a minimum speed of 384 kbps. The chart on the slide shows the evolution of WCDMA from GSM, GPRS, and EDGE to the presently deployed Release 99. HSDPA is included in Release 5 of the specifications. Following Release 5, whose enhancements provide benefits for the Downlink, Release 6 introduces the High Speed Uplink Packet Access (HSUPA) or Enhanced Uplink (EUL), which will provide faster data services for the Uplink.



2-15




Section 2-15


UMTS Network Architecture


Notes



2-16




Section 2-16




A UMTS system consists of three major subsystems:

User Equipment (UE) – May be a mobile, a fixed station, a data terminal, etc. Includes a USIM, which contains all of a user’s subscription information.

Access Network – Includes all of the radio equipment necessary for accessing thenetwork. It may be either Universal Terrestrial Radio Access Network (UTRAN) or GSM/EDGE Radio Access Network (GERAN).

Core Network – Includes all of the switching and routing capability for connecting to either the PSTN (circuit-switched calls) or a Packet Data Network (packet-switched calls), for mobility and subscriber location management and for authentication services.

In a WCDMA system, the functionality of the Core Network equipment is essentially unchanged from a GSM/GPRS system, but a new interface to UTRAN is required. The Access Network and User Equipment are entirely new.



2-17




Section 2-17


User Equipment (UE)

UserEquipment

MobileEquipment

USIM

Universal Subscriber Identity Module (USIM)

• Application that manages UE subscription information and authentication functions.

Mobile Equipment• All other UE functions.

UMTS User Equipment

The specifications sometimes make a distinction between the mobile equipment (ME), which does not include USIM functionality, and the User Equipment (UE), which does include the USIM. Specifications that were originally defined for GSM/GPRS and have been updated to include UMTS functionality often refer to the Mobile Station (MS), which is equivalent to the UE.

The USIM is the application that runs in a Universal Integrated Circuit Card (UICC), which is typically a removable card. The card itself is commonly referred to as a USIM.



2-18




Section 2-18


Universal Terrestrial Radio Access Network (UTRAN)

Universal Terrestrial Radio Access Network (UTRAN)

UTRAN is the Radio Access Network portion of a WCDMA system. It consists of one or more Radio Network Subsystems (RNS). Each RNS consists of a Radio Network Controller (RNC) and one or more Node Bs. The main purpose of the UTRAN is to provide a connection between the UE and the Core Network. In this respect, the UTRAN isolates the Core Network from radio-related details of providing this connection.

The UTRAN offers a Radio Access Bearer (RAB) to establish a call connection between the UE and the Core Network. The characteristics of the RAB differ depending on the kind of information or service that is being transported. RABs are characterized by Quality of Service parameters such as latency and data rate.

The Node B handles the radio transmission and reception to/from the UE over the Uu radio interface. The Node B is controlled by the RNC over the Iub interface. The Node B covers at least one and usually three cells. The Radio Network Controller is the entity that controls all UTRAN functions. It connects the UTRAN to the Core Network through the Iu interface.

UTRAN Network Interfaces

The following interfaces are used between different nodes:

UMTS core network and WCDMA radio access network (WCDMA RAN / UTRAN / radio network subsystem – RNS) – Iu, bridging the Core Network and the radio access network

RNC and Node B – Iub, providing signaling and data links

RNC and RNC – Iur, providing signaling and data links for inter-RNC soft handover or transition

Node B and UE – Uu, providing signaling and data links through the over-the-air radio frequency transmissions



2-19




Section 2-19


Core Network (CN)

Access Networks

External Networks

Core Network (CN)

UMTS supports both circuit-switched (CS) and packet-switched (PS) operation. The MSC/VLR and GMSC are referred to as the CS domain, while the Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN) are referred to as the PS domain. Both domains share a common Home Location Register (HLR) and Authentication Center (AuC).

UMTS core networks may be connected to both GERAN and UTRAN access networks. In a geographic area where both GSM/GPRS and WCDMA systems are deployed, coordination between the access networks allows a dual-mode UE to operate in either system, and perform inter-system handovers between GSM/GPRS and WCDMA.

The GSM/GPRS access network uses the existing A/Gb interface to communicate with the Core Network. The UTRAN access network uses the new Iu interface to communicate with the Core Network.

In Rel5, two main changes have been introduced to the above architecture:

The CN CS domain can be split between Signaling and User Plane, replacing a MSC with a MSC Server (signaling) and MGW (Media Gateway, on the user plane)

GERAN Iu mode can be used (in addition to the A/Gb mode): GERAN BSCs can connect to the CN via Iu-CS and Iu-PS interfaces, similar to UTRAN.



2-20




Section 2-20


UMTS Network Topology –Network Planning

Cells, Location Areas, Routing Areas, and UTRAN Registration Areas

The cell is an area of radio coverage identified by a Base Station identification: PSC (Primary Scrambling Code) in UTRAN, BSIC (Base Station Identity Code) in GERAN.

Each Node B controls a group of cells. A traditional configuration would be three cells per Node B.

In the circuit-switched domain, a collection of cells controlled by multiple Node Bs is called a Location Area (LA). Mobility management for circuit-switched operations is based on Location Areas.

In the packet-switched domain, mobility management for packet-switched operations is based on Routing Areas (RA).

Cell, LAs, and RAs are also grouped into UTRAN Registration Areas (URA). These are used to manage the location of the UE in the UTRAN while it is operating in UTRA connected mode.

The only standard requirement on the relationships between LAs, RAs, and URAs is that an RA shall be a subset of one and only one LA (a RA cannot span more than one LA). A Routing Area may be identical to a Location Area, or there may be multiple Routing Areas within a given Location Area. A UTRAN Registration Area will probably be smaller than an LA or RA, though this is not required. Up to eight URAs may be identified within a cell. The organization of cells, LAs, RAs, and URAs is part of the UMTS network planning effort.



2-21




Section 2-21


3G and UMTS/WCDMA –What Did We Learn?

What are the main requirements for WCDMA and UMTS?

What standards organization produces WCDMA/UMTS standards?

What are the WCDMA (UMTS) standard releases and what are their main features?

What are the main evolutional drivers from GSM to UMTS and beyond?

What are the main UMTS network entities and functions?

Notes



2-22




Section 2-22


Exercises

1. Is WCDMA FDD or TDD?

2. How wide (in MHz) is a WCDMA Channel?

3. What is another name for WCDMA?

4. What standard body is responsible for UMTS specifications?

5. What are the main Rel5 and Rel6 radio features?

Exercises



2-23




Section 2-23


Exercises (continued)

6. Draw a network diagram from the UE to the Internet. Label the required network elements.

7. Use the Internet to find what companies manufacture UEsNode Bs, RNCs, and other network elements.

8. Use the Internet to find a Node B spec sheet. What are the differentiating features?

9. Use the Internet to find RNC specifications. What are the differentiating features?

Exercises



2-24




Section 2-24


Exercises – Answers

1. Is WCDMA FDD or TDD? Answer: WCDMA is FDD (Frequency Division Duplex)

2. How wide (in MHz) is a WCDMA Channel? Answer: WCDMA has a 5 MHz wide channel.

3. What is another name for WCDMA? Answer: UMTS Terrestrial Radio Access (UTRA-FDD)

4. What standard body is responsible for UMTS specifications? Answer: 3rd Generation Partnership Project (3GPP)

5. What are the main Rel5 and Rel6 radio features?Answer: HSDPA (Rel5) and HSUPA (Rel6)




2-25




Section 2-25


Exercises – Answers (continued)

6. Draw a network diagram from the UE to the Internet. Label the required network elements.Answer: Refer to slides 2-18 & 2-19.

7. Use the Internet to find out who makes UE’s Node Bs, RNC, etc.Answer: List and discuss the various vendors.

8. Use the Internet to find a Node B spec sheet. What are the differentiating features? Answer: There are many Node B specifications. List and compare them. Discuss which are the most important.

9. Use the Internet to find RNC specifications. What are the differentiating features? Answer: There are many RNC specifications. List and compare them. Discuss which are the most important.




2-26



Comments/Notes



3-1

Section 3: WCDMA Protocol Layers and Channels80-W1447-1 Rev A


UMTS /WCDMA Technical Overview

Section 3-1


Section 3: WCDMA Protocol Layers and Channels

3SECTION

WCDMA Protocol Layers and Channels

Notes



3-2




Section 3-2



Describe the UMTS Release 99 AS/NAS Protocol Stack.

Explain the difference between the Control Plane and the User Plane.

Describe the main Access Stratum protocol functions.

Explain the main Rel99 channel functions and their mapping.

Notes



3-3




Section 3-3


UE Signaling Protocol Stack

Mobility Management (MM)

Radio Resources Control (RRC)

Supplementary Services (SS)

Short Message Services (SMS)

Layer 2

Physical Layer (L1)

Non-Access Stratum

Access Stratum

GPRS Mobility Management (GMM)

Session Management

(SM)

Radio Link Control (RLC)

Medium Access Control (MAC)

Connection Management (CM)

Call Control (CC)

Short Message

Services (SMS)

Circuit Switched Packet Switched

UE Signaling Protocol Stack

The UE signaling protocol stack is divided into Access Stratum (AS) and Non-Access Stratum (NAS). The Non-Access Stratum architecture evolved from the GSM upper layers and includes:

• Connection Management – includes sublayers responsible for:

– CS services: Call Control (e.g., call set-up and release), supplementary services(e.g., call forwarding, 3-way calling), and short message service (SMS).

– PS services: Session Management (e.g., PS connection set-up and release), SMS.

• Mobility Management – Handles location updating and authentication for circuit-switched calls.

• GPRS Mobility Management – Handles location updating and authentication for packet-switched calls.

Because the UMTS Non-Access Stratum layer is essentially the same as GSM, this coursetouches only briefly on its functions and services.

The Access Stratum architecture is new for WCDMA and is the focus of this course.



3-4




Section 3-4


Protocol Stack –Circuit Switched Control Plane

Circuit Switched

Circuit Switched Control Plane Protocol Stack

The control plane protocol stack illustrates how signaling protocols are terminated. This example shows a circuit-switched call operating on dedicated physical channels.

Non-Access Stratum (NAS)

• Call Control (CC) protocols are defined between UE and MSC to handle call setup and release functions.

• Mobility Management (MM) protocols are defined between UE and MSC to handle UE mobility functions.

Access Stratum (AS)

• The Radio Resource Control (RRC) protocol is defined between UE and RNC to handle establishment, release, and configuration of radio resources.

• The Radio Link Control (RLC) protocol is defined between UE and RNC to provide segmentation, re-assembly, duplicate detection, and other traditional Layer 2 functions.

• The Medium Access Control (MAC) protocol is defined between UE and RNC to multiplex user plane and control plane data.

• The Physical Layer protocol is defined between UE and Node B to transfer data over the radio link. The interface between UE and RNC at the Physical Layer handles macro-diversity combining and splitting functions.



3-5




Section 3-5


Protocol Stack –Packet Switched Control Plane

Packet Switched

Packet Switched Control Plane Protocol Stack

The control plane protocol stack illustrates how signaling protocols are terminated. This example shows a packet-switched call operating on dedicated physical channels.


• Session Management (SM) protocols are defined between UE and SGSN to handle packet session establish and release procedures.

• GPRS Mobility Management (GMM) protocols are defined between UE and SGSN to handle UE mobility functions.

Access Stratum (AS)

The control plane Access Stratum is identical for packet and circuit switched operations.



3-6




Section 3-6


Protocol Stack –Circuit Switched User Plane

Circuit Switched

Circuit Switched User Plane Protocol Stack

The user plane protocol stack illustrates how user protocols are terminated. This example shows a circuit-switched voice call operating on dedicated Physical Channels.


• An application can consist of several layers. For example, in the case of voice, the topmost layer corresponds to the actual acoustic signals heard by users on both ends, whereas a lower layer carries the vocoded bits. In this protocol architecture, vocoders reside at the UE and at the MSC to translate digitized voice between the format transmitted over the air and that sent over digital wirelines (e.g., T1/E1).

Access Stratum (AS)

• The RLC, MAC, and Physical Layer protocols for the user plane are the same as for the control plane.

• RRC does not participate in user plane protocols. It is responsible for setting up the radio bearers and channels, but does not touch the data.



3-7




Section 3-7


Protocol Stack –Packet Switched User Plane

Packet Switched

Packet Switched User Plane Protocol Stack

The user plane protocol stack illustrates how user protocols are terminated. This example shows a packet-switched call operating on dedicated Physical Channels.


• The application layer could be Web browsing, FTP, email, etc.

• When the Session Management layer activates a Packet Data Protocol (PDP) context, it identifies the type as Internet Protocol (IP) or Point to Point Protocol (PPP).

Access Stratum (AS)

• The Packet Data Convergence Protocol (PDCP) provides protocol transparency for higher-layer protocols, such as IPv4, PPP, and IPv6, and performs protocol control information compression.

• The RLC, MAC, and Physical Layer protocols for the user plane are the same as for the control plane.

• RRC does not participate in user plane protocols. It is responsible for setting up the radio bearers and channels, but does not touch the data.



3-8




Section 3-8


Access Stratum

cont

rol

cont

rol

cont

rol

cont

rol

Access Stratum

The Access Stratum consists of the following layers:

• Radio Resource Control (RRC)

• Packet Data Convergence Protocol (PDCP)

• Broadcast/Multicast Control (BMC)

• Radio Link Control (RLC)

• Medium Access Control (MAC)

• Layer 1 or Physical Layer (L1 or PHY)

Each of these layers is covered in more detail later in this section.

Data flow between layers is represented by:

• Radio Bearers – carry signaling between RRC and RLC or carry user data between application layers and Layer 2.

• Logical Channels – carry signaling and user data between RLC and MAC.

• Transport Channels – carry signaling and user data between MAC and PHY.

• Physical Channels – carry signaling and user data over the radio link.

Note: In practice, most R99 data is circuit switched, and thus PDCP and BMC are not usually used. However, both are used in HSDPA and HSUPA.



3-9




Section 3-9


Access Stratum Protocols

• Layer 3 – Radio Resource Control (RRC)

• Layer 2:– Packet Data Convergence Protocol (PDCP)

– Broadcast/Multicast Control (BMC)

– Radio Link Control (RLC)

– Medium Access Control (MAC)

• Layer 1 – Physical Layer

Notes



3-10




Section 3-10


Layer 3 – Radio Resource Control (RRC)

Radio Resource Control (RRC)

• Access Stratum control

• Paging and notification

• Measurement control & reporting

• RRC connection management

• Radio Bearer management

• Broadcasts system information

Access Stratum Overview – Layer 3

The Radio Resource Control (RRC) protocol (Layer 3) controls the UE from the RNC and is the main Access Stratum control protocol. The RRC controls physical channels and user plane connections also known as Radio Access Bearers (RABs). RABs transport user plane information (e.g., voice or packet data) across the radio interface from the UE to the CN.

The RRC also handles the mapping of different channel types, handover, measurement, and other procedures associated with mobility. RRC is responsible for the establishment, modification and release of radio connections (commonly referred to as “RRC connections”) between the UE and the UTRAN.



3-11




Section 3-11


Layer 2 – PDCP and BMC

Packet Data Convergence Protocol (PDCP) • IP header compression

• Not used for CS Services

Broadcast/Multicast Control (BMC)• Supports Cell Broadcast Messages, including:

– Transmission of BMC messages to UE

– Delivery of Cell Broadcast messages to upper layer (NAS)

Layer 2 – PDCP and BMC

Packet Data Convergence Protocol (PDCP) – deals mostly with header compression, which is important because the IP header of a voice packet can be quite large without compression. This protocol is only defined for use with the packet switched (PS) domain and is not used for circuit switched services (e.g., R99 CS data).

Broadcast Multicast Protocol (BMP) – supports broadcast and multicast messaging.



3-12




Section 3-12


Layer 2 – Radio Link Control (RLC)

Radio Link Control (RLC) provides:

• Segmentation, reassembly, concatenation, padding

• Retransmission control, flow control

• Duplicate detection, in-sequence delivery

• Error correction

• Ciphering

Layer 2 – Radio Link Control (RLC)

Radio Link Control (RLC) provides segmentation and retransmission service for both the RRC signaling (the Signaling Radio Bearer) and for the user data (the Radio Access Bearer). RLC operates in one of three modes:

Transparent Mode (TM) – In this mode, the RLC layer adds no overhead. AMR speech uses transparent mode.

Unacknowledged Mode (UM) – In this mode, there are no RLC layer retransmissions. This is used by applications that can tolerate some loss of packets and/or cannot tolerate the variations in delay that retransmission would produce. Voice over IP uses unacknowledged mode.

Acknowledged Mode (AM) – Employs RLC layer retransmissions to provide assured delivery of packets.

There are usually several RLC instances. In most cases, there will be one RLC instance per service. Exceptions to the rule include voice and signaling where there are sometimes multiple RCL entities per service. Each RLC entity can be configured differently, with the configuration of an individual RLC entity depending on the Quality of Service (QoS) specified for that service.



3-13




Section 3-13


Layer 2 – Medium Access Control (MAC)

Medium Access Control (MAC)

• Maps logical channels to transport channels

• Prioritizes data flows

• Addresses common channel to individual users

• Provides Ciphering for (RLC) Transparent Mode Channels (e.g., speech calls)

Layer 2 – Medium Access Control (MAC)

The MAC protocol provides dynamic resource allocation under the control of the RRC layer. This includes using relative priorities between services to control access to the radio interface transmission resources. Specifically, the MAC layer provides priority handling, transport format selection as well as scheduling and mapping of logical channels onto transport channels found in the Physical Layer. MAC also provides addressing to common channels so that individual users can distinguish their data from that of other users.



3-14




Section 3-14


Layer 1 – Physical Layer

Physical Layer (PHY or L1)

• Multiplexing and channel coding

• Spreading and scrambling

• Modulation

• Handover

• Compressed Mode

• Power control

• Measurements

Layer 1 – Physical Layer

Layer 1 is also referred to as the Physical Layer or Level 1 (L1). Functions of the Physical Layer include RF processing, chip rate processing, and symbol rate processing, as well as transport channel combination.

In the transmit direction, the Physical Layer takes blocks of data from the MAC layer contained in transport channels and multiplexes them onto a physical channel.

In the receive direction, the Physical Layer receives and then processes the multiplexed data from the physical channels and delivers it to the MAC Layer.



3-15




Section 3-15


Significant Channels

Important R99 Channels:

– Logical Channels

– Transport Channels

– Physical Channels

Notes



3-16




Section 3-16


UMTS Channel Terminology

User A, User B, User C, …Common Channel

Dedicated Channel User A only

Some Common UMTS Channel Terminology

• Downlink – transmitted by UTRAN, received by UE.

• Uplink – transmitted by UE, received by UTRAN.

• Common – carries information to/from multiple UEs.

• Dedicated – carries information to/from a single UE.

• Logical – defined by what type of information is transferred, e.g., signaling or user data and whether it is dedicated or common. Logical channels are between the RLC and the MAC.

• Transport – defined by how data is transferred over the air interface; e.g., multiplexing of logical channels. The transport channel provide a mechanism for the MAC to send messages via the Physical Layer. Transport channels span between the MAC and the Physical Layer. Transport channels generally map to specific physical channels.

• Physical – defined by physical mappings and attributes used to transfer data over the air interface; e.g., spreading rate. Most physical channels have a very specific purpose.



3-17




Section 3-17


Channel Mapping – R99 Logical Channels

Channel Mapping

This diagram shows possible mappings of logical, transport, and physical channels in the control and user planes for UMTS Release 99. Mapping for UMTS Release 5 and Release 6 appear later in this course. Not all mappings would be defined at the same time for a given UE, and multiple instantiations of some mappings may occur simultaneously. For example, a voice call uses three DTCH logical channels mapped to three DCH transport channels.

Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM) indicate the mode in which RLC is configured for a logical channel.

Some channels exist only in a Physical Layer context (e.g., CPICH, SCH, DPCCH, AICH, PICH). These channels carry no upper layer signaling or user data. Their contents are defined at the Physical Layer.

R99 Logical Channels

Logical channels carry signaling and user data between the RLC and MAC layer and are defined by what type of information is transferred, e.g., signaling or user data. Some important logical channels include:

Broadcast Control Channel (BCCH) [DL] – broadcasts information to UEs relevant to the cell, such as radio channels of neighboring cells, etc.

Paging Control Channel (PCCH) [DL] – is associated with the PICH and is used for paging messages andnotification information.

Common Control Channel (CCCH) [UL and DL] – transfers control information in both directions.

Dedicated Control Channel (DCCH) [UL and DL] – carries dedicated control information in both directions.

Dedicated Traffic Channel (DTCH) [UL and DL] – a bidirectional channel carrying user data or traffic.



3-18




Section 3-18


Channel Mapping – R99 Transport Channels

R99 Transport Channels

Transport channels carry signaling and other user data between the MAC and physical layers and are defined by how data is transferred over the air interface, e.g., multiplexing of logical channels. Some important transport channels include:

Broadcast Channel (BCH) [DL] – broadcasts information to the UEs in the cell to enable them to identify the network and the cell.

Paging Channel (PCH) [DL] – carries messages that alert the UE to incoming calls, SMS messages, data sessions or required maintenance such as re-registration.

Forward Access Channel (FACH) [DL] – carries data or information to the UEs that are registered on the system. A FACH may carry packet data and there may be more than one FACH per cell.

Random Access Channel (RACH) [UL] – carries requests for service from UEs trying to access the system

Dedicated Transport Channel (DCH) [UL and DL] – used to transfer data to a particular UE. Each UE has its own DCH in each direction.



3-19




Section 3-19


Channel Mapping – R99 Physical Channels

R99 Physical Channels

The physical channels carry signaling and user data over the radio link and are defined by physical mappings and attributes used to transfer data over the air interface, e.g., spreading rate.Some important Physical Layer channels include:

Primary Common Control Physical Channel (PCCPCH) [DL] – continuously broadcasts system identification and access control information.

Secondary Common Control Physical Channel (SCCPCH) [DL] – carries the Forward Access Channel (FACH) providing control information, and the Paging Channel (PACH) with messages for UEs registered on the network.

Physical Random Access Channel (PRACH) [UL] – enables the UE to transmit random access bursts to access a network.

Dedicated Physical Data Channel (DPDCH) [UL and DL] – used to transfer user data.



3-20




Section 3-20


R99 Physical Only Channels

R99 Physical Only Channels

DPCCH (UL/DL) – Dedicated Physical Control Channel. DPCCH carries control information associated to the DPDCH (e.g., Pilot signal used for DPCH synchronization, Transmit Power Control [TPC] commands, Transport Format Combination [TFCI]). On the DL, DPCCH is time-multiplexed with DPDCH, while on the UL they are two separate physical channels.

SCH (DL) – Synchronization Channel. P-SCH and S-SCH are transmitted simultaneously during the DTX of the P-CCPCH. Their role is to time-synchronize UEs within the cell. The P-SCH is used for the UE’s initial acquisition of the WCDMA system. The S-SCH provides frame timing, and reduces the Primary Scrambling Code (PSC) search space from 512 to 8.

CPICH (DL) – Common Pilot Channel. The CPICH provides an in-cell timing reference. There are two types of Common Pilot Channels, the primary CPICH (P-CPICH) and the secondary CPICH (S-CPICH). In addition, P-CPICH is used for cell signal quality estimation for HO and cellreselection purposes, open loop power control.

PICH (DL) – Paging Indicator Channel. The PICH carries page indicators (PIs). PIs signal the UE that there is a message for it on the transport PCH mapped to an SCCPCH. The PICH is used for efficient UE sleep operation.

AICH (DL) – Access Indicator Channel. The AICH carries acquisition indicators (AIs). AIs notify the UE that the preamble on the Random Access Channel (RACH) was heard and that the RACH message can now be transmitted



3-21




Section 3-21


Dedicated Channels –AMR Call Mapping Example

DCH DCH DCH

DL DCCH

DL DCCH

Dedicated Transport Channels

DL DCCH

DL DCCH

Dedicated Logical Channels

DL DTCH

DL DTCH

DL DTCH

DCH

Coded Composite Transport Channel (CCTrCh)

Dedicated Physical Channel

Dedicated Channels – Mapping Example

This diagram is an example of mapping dedicated logical channels to a dedicated transport channel. This example is a typical configuration for an AMR voice call.

• DCCH to DCH – Four logical Dedicated Control Channels (DCCH) are allocated to carry signaling messages. Two are used by the NAS Layer, and two are used by the RRC Layer. All four logical channels are mapped to a single Dedicated Transport Channel (DCH).

• DTCH to DCH – Three logical Dedicated Traffic Channels (DTCH) are allocated to carry AMR voice frames. Each DTCH is mapped to a Dedicated Transport Channel (DCH).

These four DCHs are mapped by the Physical Layer to a Coded Composite Transport Channel (CCTrCh) and then to a Dedicated Physical Data Channel (DPDCH).



3-22




Section 3-22


WCDMA Protocol Layers and Channels –What Did We Learn?

What are the UMTS Release 99 AS/NAS protocols?

What are the main AS protocol functions?

What are the UMTS Rel99 channels and how are they mapped in the different protocol layers?

Notes



3-23




Section 3-23


Exercises

1. What is the major horizontal dividing line in the protocol stack?

2. What are the names of the Access Stratum layers?

3. What NAS layer is responsible for mobility between location areas?Between routing areas?

4. What Access Stratum protocol layer never touches user data?

5. What Assess Stratum protocol deals with header compression?

6. What type of channel is the output of RLC? Of MAC? Of PHY?

7. Fill in the blanks:

Logical channels are defined by _____ type of information is transferred, e.g., signalling or user data. Transport channels are defined by ______ data is transferred over the air interface, e.g., multiplexing of Logical Channels.

Exercises



3-24




Section 3-24



1. What is the major horizontal dividing line in the protocol stack?Answer: AS/NAS

2. What are the names of the Access Stratum layers?Answer:

• Radio Resource Control (RRC)

• Packet Data Convergence Protocol (PDCP)

• Broadcast/Multicast Control (BMC)

• Radio Link Control (RLC)

• Medium Access Control (MAC)

• Layer 1 or Physical Layer (L1 or PHY)

3. What NAS layer is responsible for mobility between location areas?Between routing areas?Answer: MM and GMM




3-25




Section 3-25



4. What Access Stratum protocol layer never touches user data?Answer: RRC

5. What Assess Stratum protocol deals with header compression? Answer: PDCP

6. What type of channel is the output of RLC? LogicalOf MAC? Transport Of PHY? Physical

7. Fill in the blanks:

Logical channels are defined by WHAT type of information is transferred, e.g., signalling or user data. Transport channels are defined by HOW data is transferred over the air interface, e.g., multiplexing of Logical Channels.




3-26



Comments/Notes



4-1

Section 4: Key WCDMA Radio Concepts and Procedures80-W1447-1 Rev A



Section 4-1


Section 4:Key WCDMA Radio Concepts and Procedures

4SECTION Key WCDMA

Radio Conceptsand Procedures

Notes



4-2




Section 4-2



Describe the main radio differences between FDMA, TDMA, and CDMA.

Explain the concepts of spreading and scrambling in WCDMA.

Describe the key Power Control concepts in WCDMA.

Describe the main Mobility procedures in WCDMA.


UMTS/WCDMA is a Code Division Multiple Access (CDMA) based technology. We begin by comparing CDMA with two other popular multiple access technologies: Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA). Then we demonstrate conceptually how CDMA works by explaining orthogonal codes and how they are used in orthogonal spreading and despreading. Finally, we show how channelization (OVSF) codes and scrambling (Gold) codes are used in WCDMA.



4-3




Section 4-3


WCDMA Basic Radio Concepts

• FDMA, TDMA, and CDMA

• Spreading and scrambling in WCDMA

Notes



4-4




Section 4-4


Multiple Access Methods

TIME

TIME

TIMEFREQUENCY

FREQUENCY

FREQUENCYPOWER

POWER

POWER

FDMA

TDMA

CDMA

MMT98010114Ad.emf

AMPS, NMT

WCDMA, CDMA2000

GSM

Multiple Access Methods

To accommodate multiple users, users are separated by assigning them to different channels. Depending on the technology, users can be channelized by frequency, time, or codes.

Frequency Division Multiple Access (FDMA) is a multiple access method in which users are assigned specific frequency bands. The user has the sole right of using the frequency band for the entire call duration. First generation analog cellular systems such as Nordic Mobile Telephone (NMT) and Advanced Mobile Phone System (AMPS) use FDMA.

Time Division Multiple Access (TDMA) assigns a frequency band to a set of users. Each user can transmit in predetermined time slots. Channelization of users in the same band is achieved through separation in time. GSM uses TDMA as its multiple access technology.

Code Division Multiple Access (CDMA) is a method in which multiple users occupy the same time and frequency allocations and are channelized by unique assigned codes. Both WCDMA and CDMA2000 employ CDMA.

Ideally, isolation between channels (frequency, time, or code) would be perfect and a user on one channel would not cause interference for other users on other channels. In the real-world, the isolation between channels is not perfect. For example, filtering for FDMA and TDMA is not perfect and some interference between channels exists. For CDMA-based technologies like WCDMA, the nearly perfect isolation between channels offered by orthogonal codes is degraded by channel dispersion caused by multipath.



4-5




Section 4-5


Interference Between Cells

Area C

If Cell 1 and Cell 2 were both on the same frequency in FDMA and TDMA systems, the overlap area (Area C) would have a frequency conflict.

FDMA and TDMA need Frequency Planning and Reuse to avoid the conflict.

When two cells are both on the same frequency, there is INTERFERENCE where the coverage overlaps. Interference is BAD!

Interference Between Cells

In FDMA and TDMA systems, there is a conflict when adjacent cells use the same channel (frequency). The frequency conflict does not allow users to communicate because the interference between the two users degrades the call quality. A good analogy is the interference between radio stations using the same radio channel in two different cities. Can you think of any FM or AM radio stations that interfere with one other as you drive between two cities like San Diego and Los Angeles?

With the deployment of Frequency Division Multiple Access (FDMA) or Time Division Multiple Access (TDMA) networks, channel (frequency) reuse is required. The frequency plan for reusing frequencies requires that no adjacent cells use the same frequency, thereby avoiding the conflict.

Note that all cellular systems are interference limited due to the nature of the cells overlapping their coverage to provide handover capability. Controlling interference is one of the primary objectives in a network plan.



4-6




Section 4-6


BC

C

CC

GG

G

AA

EE

EE

FF

FF

D

DD

C

D

B

CDMA permits the use of the same frequency in all the cells in the network (N=1). This increases capacity.

FDMA/TDMA cannot reuse the same frequency in nearby cells without causing frequency conflicts due to interference. Reuse patterns of 3 and 7 are common.

A A AA A A A

A A AA A A A

A A AA A A A

A A AA A A A

B

BB

TDMA and GSM Systems CDMA/WCDMA Systems

N = 7 N = 1

WCDMA Frequency Reuse is N=1

Frequency Reuse

A

Universal Frequency Reuse

A key advantage of WCDMA is that it allows universal frequency reuse, which is the ability to reuse the same radio channel frequency throughout the network.

In FDMA and TDMA networks, a frequency used in one cell cannot be reused in nearby cells because that would create interference. Cells using the same frequency must be sufficiently separated geographically. Reuse patterns of 3 and even 7 are common – meaning, in the case of a reuse factor of 7, only 1/7th of the available frequencies or radio channels can be used in any one sector. This is a major reason for the low spectral efficiency of FDMA and TDMA systems compared to CDMA systems.



4-7




Section 4-7


“Maganda”

“Bonjour”

“Hello”“Guten Tag”

“Buenos Dias”

The “CDMA Cocktail Party”

Common Frequency Channel

The “CDMA Cocktail Party”

The CDMA concept is analogous to the situation encountered at a party. At the “CDMA Cocktail Party,” all subscribers are talking in the same room simultaneously. Imagine that every conversation in the room is being carried on in a different language that you do not understand. They would all sound like noise from your perspective.

However, if you “knew the code,” the appropriate language, you could filter out the unwanted conversations and listen only to the conversation of interest to you. This is analogous to the technique used in a CDMA system, which filters noise and interference in a similar way.

Even with knowledge of the appropriate language, though, the conversation of interest may not be completely audible. To hear that conversation better, the listener could signal the speaker to speak more loudly and signal other people to speak more softly. A CDMA system accomplishes this using a power control process.



4-8




Section 4-8


WCDMA Code Types

• User separation

• ~ 17 million Scrambling Codes available

Separate Data and Control channels from same UE

Uplink

• Cell separation

• Uses 512 Primary Scrambling Codes (PSC)

• 7680 Secondary Scrambling Codes (SSC) also available

Scrambling codes (Gold Codes)

Separate users within a cell

Channelization(spreading) Codes (OVSF Codes)

Code Type Downlink

WCDMA Code Types

WCDMA uses two types of codes: Spreading (sometimes referred to as Channelization codes) and Scramblingcodes. These codes are used to separate channels, users, or cells.

This slide summarizes how Spreading and Scrambling codes are employed in WCDMA. The functions of these codes changes depending whether the Uplink or Downlink is being used. On the WCDMA Downlink, isolation between users involves the combination of user-specific channelization (spreading) codes and cell-specific scrambling codes.

Spreading codes are orthogonal codes called Orthogonal Variable Spreading Factor (OVSF) codes. All OVSF codes at a given spreading factor (SF) are orthogonal to each other. Spreading codes provide channelization in both the Uplink and Downlink directions.

OVSF codes can have different spreading factors, which allows different symbol rates. With a fixed chip rate of 3.84 Mcps, the spreading factor determines the symbol rate. As the symbol rate increases, the symbol period decreases, resulting in a small number of chips per symbol. Thus, as the symbol rate increases, there is a corresponding decrease in SF.

Scrambling occurs after spreading, so the waveform has already been spread to a chip rate of 3.84 Mcps. Thus, scrambling results in no further spreading of the waveform. The primary purpose of scrambling is to enable identification of a particular cell on the Downlink and identify users on the Uplink.

Scrambling codes used for scrambling are pseudorandom noise (PN) codes called Gold codes. Scrambling using Gold codes makes the waveform look noise-like, which increases the spectral efficiency of WCDMA.



4-9




Section 4-9


Example of Spreading with Three Users

A= 1 -1Spreading Code for

A = -1 1 1 -1

B= -1 -1Spreading Code for

B = -1 1 -1 1

MMT98010784Ac_RevB.eps

- 3

Spread Waveform Representation ofUser A's signal

+ 1

- 1

C= 1 1Spreading Code for

C = -1 -1 -1 -1

Spread Waveform Representation ofUser B's signal

+ 1

- 1

Spread Waveform Representation ofUser C's signal

+ 1

- 1

of the Three Spread SignalsAnalog Signal Formed by the Summation

+ 1

- 1

Example of Spreading with Three Users

In this example, three users, A, B, and C, are assigned three orthogonal codes for spreading purposes:

• User A signal = 1 -1, Spreading Code = {-1 1 1 -1}

• User B signal = -1 -1, Spreading Code = {-1 1 -1 1}

• User C signal = 1 1, Spreading Code = {-1 -1 -1 -1}

The analog signal shown at the bottom of the example is the composite signal when all of the spread symbols are summed together.



4-10




Section 4-10


De-spreading Example

t

t

t

+1

-1

Spreading Code for User A: " -1 1 1 -1"

+1

-3

Received Composite Signal

Average = 5-1=1V4

Average = 1-5 = -1V4

"1" "-1"MMT98010164Bg_RevB.epsMMT98010164Bg_RevB.eps

+1

-1

+3Product

-3

De-spreading Example

At User A’s receiver, the composite analog signal is multiplied by the orthogonal code corresponding to User A, and the result is then averaged over the symbol time. This process is called correlation. Note that the average voltage value over one symbol time is equal to 1 or -1; therefore, the original bit transmitted by A was 1 or -1. You may try to decode the symbols for Users B and C in the same way. This process occurs in WCDMA UEs to recover their Downlink signals.



4-11




Section 4-11


OVSF Tree

SF = 1 SF = 2 SF = 4

C ch,1,0 = (1)

C ch,2,0 = (1,1)

C ch,2,1 = (1 ,-1)

C ch,4,0 = (1 ,1,1,1)

C ch,4,1 = (1,1 ,-1 ,-1)

C ch,4,2 = (1,-1 ,1 ,-1)

C ch,4,3 = (1,-1 ,-1 ,1)

Using a branch…

HigherData Rates

LowerData Rates

OVSF Tree

Spreading Factors (SF) and data rates go together. A lower SF results in a higher data rate, because there are fewer chips per symbol. An SF of 4 indicates 4 chips per symbol, while an SF of 64 indicates 64 chips per symbol—a difference of 16 times the symbol rate.

If a low spreading factor branch is used, you cannot use a higher spreading factor branch that connects to it. This is due to the orthogonality property of OVSF. For example, C2,0 is not orthogonal to either C4,0 or C4,1 over a 2-chip period.

Spreading Example 1: Voice at 12.2 kbps has symbols at 60 ksps.

64-bit OVSF code runs 64 times faster than symbol, or 64 x 60 ksps = 3.84 Mcps

Spreading Example 2: Data at 384 kbps has symbols at 960 ksps.

4-bit OVSF code runs four times faster than the symbol rate, or 4 x 960 ksps = 3.84 Mcps



4-12




Section 4-12


Scrambling Codes

Downlink Primary Scrambling Codes

0

0

038399

38399

0

0

38399

38399

38399

38399

0

38399

Comparative_009b_Rev2.eps

0

Uplink Scrambling Codes

0

0

038399

38399

0

0

38399

38399

38399

38399

0

38399

Comparative_009b2_Rev2.eps

0

Scrambling Codes

Downlink

On the Downlink, each cell is assigned a unique (1 of 512) Primary Scrambling Code (PSC). Each scrambling code has low cross-correlation with any other scrambling code, regardless of the timing offset between the two scrambling codes. This allows the cells to be deployed asynchronously and allows the use of secondary scrambling codes.

An additional 7680 Secondary Scrambling Codes (SCC) are available when no more channelization codes are available that are currently being scrambled with the PSC.

Uplink

On the Uplink, each UE is assigned one of ~16.8 million unique scrambling codes. This channelizes the users. The UE is signaled which Uplink scrambling code to use when a dedicated physical channel is assigned.



4-13




Section 4-13


Secondary Scrambling Codes (SSC)

Each PSC has a set of 16 SSCs.

SSCs:

– Are used when transmitting channels that do not need to be received by everyone in the cell.

– Should be used selectively because they are not orthogonal to PSCs.

– Work best in applications that do not require pure orthogonality (e.g., spot beams, sectored cells).

Secondary Scrambling codes (SSCs)

A major drawback of using SSC is that they are not orthogonal to channels that use the PSC. This reduced orthogonality effectively increases intra-cell interference and ultimately reduces the capacity of the cell. SSCs work best when there is spatial isolation between the areas using an SSC and the areas using a PSC. This can be achieved by using adaptive antenna arrays to create spot beams. The spatial isolation inherent in these spot beams makes scrambling code orthogonality less critical.



4-14




Section 4-14


WCDMA Power Control

• WCDMA Power Control

Notes



4-15




Section 4-15


The Near-Far Problem

Strong S

ignal

Weak Signal

Power Control Basics – Near-Far Problem

A robust WCDMA system requires good power control. Power control minimizes the transmit power of both the UE and the network. Because WCDMA systems are interference limited, reducing the power from all users increases the capacity. Inefficiencies in power control reduces system capacity.

The most basic problem in power control is the near-far problem. Close-in transmitters are heard more easily than transmitters farther away. Transmitters (e.g., UEs) can use power control so their signals are received at the same power (or nearly so).

Efficient power control, to minimize systems capacity loss, requires fast feedback. Fast power control is also known as inner loop power control, and runs at 1500 Hz. Thus, the transmitter gets commands 1500 times a second from the receiver to either increase or decrease its power.

For voice calls, good quality of service may be approximately 1% Block Error Rate (BLER). To maintain a 1% BLER, a specific signal-to-interference (SIR) target may be required. A user in a bad fading environment (moving fast in a cluttered environment) needs a higher SIR target than a user in a better fading environment (slow moving, not much clutter). Since both users require a 1% BLER, power control must determine the appropriate SIR target. The process of finding the right SIR target is called outer loop power control. Differences in SIR targets cause differences in receive power.



4-16




Section 4-16


Closed Loop Power Control

Closed LoopControl

arrowcircle.eps

Closed Loop Power Control

A closed loop process controls transmission power on both the Downlink and Uplink. Closed loop control is basically a three-step process:

A transmission is made.

A measurement is made at the receiver.

Feedback is provided to the transmitter indicating whether the power should be increased or decreased.

The closed loop process can eventually correct the mobile’s transmit power regardless of the initial transmit level. Significant gain can be achieved, however, if the mobile’s initial transmit level is close to the appropriate power.

Selection of a metric is affected by the speed that is required of the closed loop process. Block Error Rate is a good metric, for example, but measuring Block Error Rate can be a slow process.

If faster response is needed, a different indicator, such as Signal-to-Interference Radio (SIR), may be more appropriate. For quick response to power control commands, multiple commands are sent every radio frame.



4-17




Section 4-17


R99 Closed Loop Power Control

Inner Loop• Cell/UE actively minimizes UE/Cell power.

• Maintains the desired Signal-to-Interference Ratio (SIR).

• DL/UL Power Control rate at 1500 Hz.

• Is implemented at the Node B and in the UE.

Outer loop feeds the inner loop

CRC calculatedevery TTI, 20ms (50Hz)

X= CRC error

Outer Loop50hz

Slow

SIR Target

Inner Loop1500hzFast

SIR Estimate SIR Target<>?

if < send

if > send

Outer loop• UE/UTRAN monitoring Quality of Service (QoS),

e.g., BLER.

• Update rate is much slower than the inner loop

• Adjusts the SIR Target to maintain QoS.

• Implemented at the RNC and UE.

• Procedure is unspecified.

R99 Closed Loop Power Control

Outer Loop (Slow PC)

A SIR target algorithm based on BLER may be adjusted slowly. Since BLER is based on CRCs, and AMR voice CRCs are received on 20 ms TTI boundaries, the fastest this outer loop power control method can be adjusted is 50 times a second.

Inner Loop (Fast PC)

The SIR estimate must be calculated every slot (15 times per 10 ms radio frame), since the DPCCH’s Pilot is present every slot. The inner loop is given the SIR target, and compares the SIR estimate to the SIR target. If the SIR estimate is greater than the SIR target, inner loop signals the transmitter to power down. If the SIR estimate is less than the SIR target, inner loop signals the transmitter to power up. This happens quickly, 1500 times a second, to rapidly compensate for quickly changing fading conditions.

Interaction

The inner loop uses a slowly changing SIR target. The outer loop must deliver the SIR target to the inner loop.



4-18




Section 4-18


R99 Uplink Power Control

Outer loop power control is based on BLER measurements that are based on UE data.

R99 Uplink Power Control (Open and Closed Loop)

Closed loop is critical in a CDMA system. Closed loop power control minimizes the required transmit power of the UE. Inner loop is fast, up to 1500 Hz. Outer loop adjusts the required power based on BLER; it operates more slowly because these metrics are frame based.

TPC = Transmit Power Control



4-19




Section 4-19


R99 Downlink Power Control

DL Power Control (Inner and Outer Loops)

R99 DL Power Control (Inner and Outer Loops)

The UE runs its own Downlink Closed Loop Power Control. The outer-loop algorithm is unspecified. In one algorithm, the UE measures its received Downlink BLER over a number of frames and increases or decreases the SIR target. Based on the SIR target, the UE tells UTRAN to increase or decrease the transmit power of its dedicated channel.

Node B power adjustment for its dedicated channel may be around 20 dB.

DL power control (inner loop) is run at either 1500 Hz or 500 Hz.



4-20




Section 4-20


Open Loop Power Control

• UE estimates its minimum required transmit power.

• Power is based on received power measurement and transmit power information sent on the BCH.

• Used on Random Access Channel (RACH).

• Used at the start of a dedicated Physical Channel.

OLPCOLPC UE TXPower

CPICH RSCP

Signaled Parameters

Open Loop Power Control

Open Loop Power Control (OLPC) is used only when the UE is first accessing the system, at which time the UE estimates its minimum required power needed for the network to receive its signal. There is no feedback for the UE to increase or decrease its power. UTRAN effectively transmits the FACH on the SCCPCH using OLPC.

When the UE estimate begins a PRACH procedure, it computes its initial preamble power based on three signaled parameters, transmitted on the BCCH, and a CPICH RSCP measurement:

Preamble_Initial_Power = Primary CPICH TX power + UL interference + Constant Value – CPICH_RSCP

When the UE begins transmission on the DPCH, it computes its initial DPCCH power based on one signaled parameter, transmitted on the DCCH, and a CPICH RSCP measurement:

DPCCH_Initial_Power = DPCCH power offset – CPICH_RSCP

The initial power of the Downlink dedicated Physical Channel depends on the UTRAN implementation.



4-21




Section 4-21


WCDMA Mobility Procedures

• WCDMA Cell Reselection

• WCDMA Handover

Notes



4-22




Section 4-22


Cell Reselection versus Handover

Cell Reselection• No dedicated channels.

• UE changes the cell it is camped on.– Typically, the UE should always camp on the best

surrounding cell

Handover• Dedicated channels.

• UE provides measurements.

• UTRAN commands the handover.

Cell Reselection vs. Handover

Cell reselection is the process of selecting a new cell when the UE is not operating on a dedicated Traffic Channel. The UE selects a new cell autonomously without requiring intervention from UTRAN. However, UTRAN provides parameters in the system information messages that influence the UE’s cell reselection decision.

Handover

Handover is the process of adding or removing cells with which the UE is communicating on a dedicated Traffic Channel. The UE assists in the process by taking measurements of the signal strength of neighbor cells and reporting this to UTRAN, but ultimately UTRAN decides when to perform a handover.



4-23




Section 4-23


Types of Cell Reselection and Handover

Intra-frequency• Within the same UMTS frequency.• Measurements can be taken at any time.• Handover can be soft or softer.

Inter-frequency• Between different UMTS frequencies.

• Measurements must be taken when it is possible to tune the radioaway from the serving cell without losing data.

• Handover can only be hard.

Inter-RAT• Between Radio Access Technologies (e.g., GSM or TD-SCDMA).

• Measurements must be taken when it is possible to tune the radioaway from the serving cell without losing data.

• Handover can only be hard.

Types of Cell Reselection and Handover

Intra-frequency cell reselection or handover occurs between cells on the same radio frequency. The UE can measure the signal strength of other cells without interrupting connectivity with the current cell.

Inter-frequency cell reselection or handover occurs between cells on different radio frequencies. To measure the signal strength of an inter-frequency neighbor cell, the UE must tune away from the serving cell’s frequency and tune to the neighbor cell’s frequency.

Inter-RAT cell reselection or handover occurs between cells on different Radio Access Technologies. For example, handover to GSM or UMTS TDD is considered an inter-RAT handover. This requires significant reconfiguration of hardware and software in the UE.

For Inter-frequency and Inter-RAT handover, UTRAN typically configures some pre-defined time gaps when the UE can measure the other frequency or RAT (Compressed Mode operation).



4-24




Section 4-24


Soft Handover

handoff.emf

Node B #1 Node B #2

SoftHandover

Handovers

What happens to a call as a UE travels farther from one Node B and closer to another? How is the call maintained while the mobile is transferred to a different Node B?

In a cellular system, the call undergoes a handover or handoff between the Node Bs. A handover can be soft, hard, or softer.

Let’s look first at a soft handover. Assume we have a single mobile in a network that includes two Nobe Bs, each with omni-directional antennas (that is, a single cell per Node B).

As the mobile moves away from Node B #1, the link between the mobile and Node B #1 becomes weaker. Before the link becomes marginal or breaks, another link is established between the mobile and the second Node B. This is known as a soft handover. If one link experiences a deep fade (e.g., due to shadowing of the radio signal or interference in congested areas), the call will stay up as long as the other link is maintained. This makes soft handovers more reliable than hard handovers, where only a single link is maintained at any given time.

Using two (or more) redundant links actually reduces the transmit power of the UE while maintaining the call. This results in less drain on the battery and longer battery life.

During soft handover:

UE combines symbols received from each Node B.

RNC selects the best radio frame from each Node B.



4-25




Section 4-25


Softer Handovers

Softer Handovers

Softer handovers are “make-before-break” handovers between two cells within the same Node B on the same Absolute Radio Frequency Channel Number (ARFCN). The graphic above shows a softer handover between the beta (β) and gamma (γ) cells.

During softer handover:

UE combines symbols received from each cell.

Node B combines symbols received from each cell.

In UMTS, multi-way soft/softer handovers are possible. Soft handovers can occur between 2, 3, 4, and sometimes even 5 cells. Not only that, some of these handovers can be soft handovers (between cells located at different Node Bs) while others can be softer (between cells from the same Node B).

Wireless networks are designed to support enough soft/softer handovers to produce a low dropped call rate. However, networks must avoid unnecessary handovers, which can waste network resources and reduce network capacity.



4-26




Section 4-26


Inter-RAT Hard Handover

UMTS/WCDMA Node B

F1 F2GSM Base Station

handoff.emf

Inter – Radio Access Technology (Inter-RAT) Handover allows users to handover between WCDMA networks and GSM networks.

This is a hard handover since WCDMA and GSM are different radio networks.

F1 F2

Inter-RAT Handovers

WCDMA and GSM support handovers between the two radio access networks. These handovers are often referred to as Inter Radio Access Technology or Inter-RAT handover. These handovers can be used for load balancing or simply coverage changes. For initial UMTS deployments, it is not expected that the WCDMA coverage will be as widespread as GSM, and therefore handover to and from the UMTS network will be needed. Most likely the UMTS coverage will be initially available in the major metropolitan areas, while outlying areas maintain the current GSM coverage.

Since the GSM and WCDMA radio access networks use different radio channels on different radio frequencies, inter-RAT handover will be a hard handover. This requires the mobile to tune away from its current serving radio channel and measure the quality of the other system’s radio channel. To accomplish this, the WCDMA phone is designed to operate in a compressed mode where time is taken away from the current system to determine the need and ability to handover to the other system. The typical inter-RAT handover occurs from WCDMA to GSM.



4-27




Section 4-27


UMTS/WCDMA Key Concepts –What Did We Learn?

What are the key differences between FDMA, TDMA, and CDMA?

What is the difference between spreading and scrambling?

How does power control solve the near-far problem?

What are the differences between inner loop and outer loop power control?

What is the difference between cell-reselection and handover?

Notes



4-28




Section 4-28


Exercises

1. Which codes (spreading or scrambling) are used to separate users on UL and DL in WCDMA?

2. As the Spreading Factor increases, does the data rate increase or decrease?

3. For each PSC, there is a set of ____ SSCs.

4. Which is more orthogonal, PSCs or SSCs?

Exercises



4-29




Section 4-29


Exercises (continued)

5. What is the rate of the Closed Loop Power Control (Inner/Outer)?

6. When is the Open Loop Power Control used?

7. True or False: Cell reselection requires dedicated channels.

8. Is handover between UMTS and GSM possible?

9. What is the difference between soft, softer and hard handover?

Exercises



4-30




Section 4-30



1. Which codes (spreading or scrambling) are used to separate users on UL and DL in WCDMA?Answer: OVSF codes separate users on the DL. Scrambling codes separate users on the UL.

2. As the Spreading Factor increases, the data rate decreases.

3. For each PSC, there is a set of 16 SSCs.

4. Which is more orthogonal, PSCs or SSCs?Answer: PSCs are orthogonal. SSCs are not perfectly orthogonal.

Exercises - Answers



4-31




Section 4-31



5. What is the rate of the Close Loop Power Control (Inner/Outer)? Answer: 1500 Hz (Inner), < 50 Hz (Outer).

6. When is the Open Loop Power Control used by the UE?Answer: First access on RACH and start of DPDCH.

7. True or False: Cell reselection requires dedicated channels. Answer: False.

8. Is handover between UMTS and GSM possible? Answer: Yes, it is called Inter-RAT HO.

9. What is the difference between soft, softer and hard handover?Answer: Soft HO is inter-Node B; Softer HO is intra-Node B. Hard handover can be inter-frequency, inter-RAT or inter-RNC without Iur interface.

Exercises - Answers



4-32



Comments/Notes


5-1

80-W1447-1 Rev A


UMTS/WCDMA Technical OverviewSection 5: Basic UE Call Flow Procedures and Operations


Section 5-1


Section 5:Basic UE Call Flow Procedures and Operations

5SECTION Basic UE Call Flow

Procedures and Operations

Notes


5-2

80-W1447-1 Rev A




Section 5-2



Describe the life of a phone: main procedures and call flows from UE power-on to UE power-off.

Describe the main UMTS security aspects.

Describe the concepts of NAS connections, NAS/AS Bearers and states.

Describe the main Quality of Service aspects.

Notes


5-3

80-W1447-1 Rev A




Section 5-3


Life of a Phone

• Initial acquisition at power on

• PLMN and cell selection process

• NAS registration procedure

• UMTS security features

• Call setup procedure

• Call release procedure

• UE procedures at power off

Notes


5-4

80-W1447-1 Rev A




Section 5-4


What Happens When the Phone is Turned On?

First, the phone must find an RF channel that has UMTS service.

The phone is programmed to search specified frequencies in a pre-determined order. The goal is to acquire the highest prioritized UARFCN.

Determine the list of frequencies

Search each frequency until a service signal is found

Perform initial system acquisition

Read system information and perform Idle Mode operations

What Happens when the Phone is turned on?

When a UE is first powered up, it begins to search for a suitable system by deciding which band and Absolute Radio Frequency Channel Number (ARFCN) to search. The specific algorithm used is proprietary and is not specified in the standard. In most cases, the UE attempts to find a suitable cell on the list of frequencies that the UE has camped on in the past, or from information provided from the operator. This Public Land Mobile Network (PLMN) information (which can include frequencies in multiple bands) is stored on the USIM.

For a multi-mode phone, for instance a WCDMA/GSM dual mode phone, the phone can be configured to look for GSM when WCDMA service is not available, or it can be configured to look for GSM first.

Initial system acquisition in WCDMA is performed as a three-step search process:

1. Slot Synchronization – Use P-SCH to find slot timing.

2. Frame Synchronization and Code Group Identification – Find the start of the 10 ms frame and reduce the number of PSCs to search in Step 3 from 512 to 8.

3. Scrambling Code Identification – Find the correct PSC (out of 8 possible).


5-5

80-W1447-1 Rev A




Section 5-5


Initial PLMN and Cell Selection

• The UE shall select a PLMN and a suitable cell to camp on.

• PLMN selection can be:

– Manual: User will select among the available PLMNs indicated by the UE

– Automatic: UE will use the following priority order:

1. Last registered PLMN (or one Equivalent PLMN)

2. Home PLMN (if not the same as in 1)

3. Preferred PLMNs (in priority order, as stored in the SIM/USIM)

4. Other PLMNs (first the ones with received high quality signal or, if not available, other PLMNs)

The selected PLMN shall not be one of the “Forbidden PLMNs”stored in the SIM/USIM.

• A suitable cell (typically the best in quality) of the selected PLMN is chosen for camping, then the UE needs to register to the CS and/or PS domain.

Initial PLMN and Cell Selection

Equivalent PLMN is a PLMN that is stored in the EPLMN list in the UE, which may have been received at Location Registration on the last registered PLMN (optional for the network).

The preferred PLMN list can differ depending on if a SIM or USIM is inserted in the phone. The SIM can contain only a Preferred PLMN list, which typically can be edited by the user. The USIM can contain two Preferred Lists: the operator-controlled list and the user-controlled list.

USIM also provides more flexibility than SIM when choosing a Radio Access Technology (applicable for dual-mode UEs). All the PLMN entries (Last registered PLMN, Home PLMN, and Preferred PLMNs) can have a RAT preference indicated in the USIM, which the UE may optionally use if the same PLMN is available on multiple RATs.

The Other PLMNs (referenced in step 4 in the slide) are explained in the specification, which states the following criteria for “high quality signal”: primary CPICH RSCP value shall be greater than or equal to -95 dBm. The UE may choose one of those PLMNS at random. If no PLMN fulfills this criteria, other PLMNs can be selected, in order of decreasing signal quality.

The only standard constraint related to having a SIM in a dual-mode UE is that UE is required to search its Home PLMN starting with GSM as initial RAT.


5-6

80-W1447-1 Rev A




Section 5-6


NAS Registration Procedure –RRC Connection Establishment and NAS Attach

SECURITY MODE COMMAND

SECURITY MODE COMPLETE

RRC CONNECTION COMPLETE

RRC CONNECTION SETUP

RRC CONNECTION REQUEST

UE RNC CS CN

INITIAL DIRECT TRANSFER [MM: Location Updating (IMSI Attach)]

DOWNLINK DIRECT TRANSFER [MM: Authentication Request]

UPLINK DIRECT TRANSFER [MM: Authentication Response]

DOWNLINK DIRECT TRANSFER [MM: Location Updating Accept]

UPLINK DIRECT TRANSFER [MM: Location Updating Complete]

RRC CONNECTION RELEASE COMPLETE

RRC CONNECTION RELEASE Iu RELEASE

SECURITY MODE COMMAND

SECURITY MODE COMPLETE

RRC CONNECTION COMPLETE

RRC CONNECTION SETUP

RRC CONNECTION REQUEST

UE RNC PS CN

INITIAL DIRECT TRANSFER [GMM: Attach Request]

DOWNLINK DIRECT TRANSFER [GMM: Authentication and Ciphering Request]

UPLINK DIRECT TRANSFER [GMM: Authentication and Ciphering Response]

DOWNLINK DIRECT TRANSFER [GMM: Attach Accept]

UPLINK DIRECT TRANSFER [GMM: Atta ch Complete]

RRC CONNECTION RELEASE COMPLETE

RRC CONNECTION RELEASE Iu RELEASE

CS domain PS domain

At location registration, the network typically performs Authentication, and may perform Identification as well (e.g., asking for the IMEI).

NAS Registration Procedure – RRC Connection Establishment and NAS Attach

In the RRC Connection Request, the UE will set the establishment cause = “Registration ”.

The Initial Direct Transfer, carrying the NAS Attach message, will indicate toward which domain (CS or PS) it is directed.


5-7

80-W1447-1 Rev A




Section 5-7


UMTS Security Overview –Security Procedures and Messages

UMTS Authentication (AKA)

Integrity Protection and/or Ciphering activated

Security Procedures and Messages

Security procedures are performed whenever an RRC Connection is established (including PS and CS call setup, IMSI attach, PS attach, and location/routing area updating).

After the UE’s Initial Direct Transfer message, the Core Network decides whether to perform the AKA procedure. For a PS call, the messages exchanged between UE and CN are different, but the functionality is the same.

Whether AKA is performed on each call is determined by network security policy. There are mechanisms for reusing the ciphering and integrity keys from one call to the next, so the AKA step may be omitted some of the time.

The Security Mode Command is mandatory because it enables integrity protection, which is a mandatory procedure. The NAS layers will not transmit any more messages after the Initial Direct Transfer message until RRC indicates that integrity protection was started. The Security Mode Command message may optionally enable ciphering.


5-8

80-W1447-1 Rev A




Section 5-8


UMTS Security Overview – Features

• Authentication and Key Agreement (AKA)– Similar to GSM AKA, with additional network authentication at the UE

– Prevents USIM fraud and false network attacks

– Generates keys for ciphering and integrity protection

– Mandatory procedure, although not required on every call

• Integrity protection– UMTS-only, not defined in GSM

– Protects signaling information from being corrupted

– Mandatory procedure

• Ciphering– Similar to GSM, but using a 128-bit key (instead of 64-bits as

in GSM)

– Protects user data from being overheard

– Optional procedure

UMTS Security Features

Authentication and Key Agreement (AKA)

The primary goal of authentication is to prevent fraud that occurs when a third party obtains a copy of a subscriber’s network identification information and uses it to fraudulently access the system. This is called “cloning.” In UMTS, subscriber information is stored in the USIM, so this type of fraud is called USIM cloning.

Performing network authentication at the UE also prevents false network attacks; this is a UMTS-only procedure, not defined in GSM.

In UMTS, authentication is a bi-directional challenge and response procedure in which the serving network corroborates the identity of the user, and the user corroborates that he is connected to a serving network that is authorized by the user’s home service provider to give him services.

Integrity Protection

In today’s wireless systems, a great deal of sensitive information is exchanged over radio channels, such as bank account numbers, PIN numbers, position location information, etc. Integrity protection is a message authentication function that prevents a signaling message from being intercepted and altered by an unauthorized device.

Ciphering

Ciphering is used to protect all user data and signaling from being overheard by an unauthorized entity.


5-9

80-W1447-1 Rev A




Section 5-9


Call Establishment –Mobile Originated/Terminated Calls

Mobile Originated Mobile Terminated

UTRANAccess using PRACH Procedure

Paging Procedureusing PICH

MO/MT Calls Establishment – PRACH and Paging

Physical Random Access Channel (PRACH) Procedure

When the phone is not connected to UTRAN (i.e., in Idle Mode), the phone needs to access the network on the PRACH. The Access procedure is designed to minimize interference to the network and reduce the time required to get a response to its request for access.

The UE begins by sending a preamble on the PRACH and waiting for a response on the AICH. If there is no response after power ramping through preambles, the process is repeated.

The RACH procedure uses open loop power control, which is much less accurate than closed loop power control. To reduce possible interference caused by inaccurate power control, transmission times are typically short: 1 ms preambles and 10 ms or 20 ms messages.

Page Procedure

Paging occurs when UTRAN wants to communicate with the UE. Because the UE sleeps to conserve battery life using discontinuous reception (DRX), UTRAN sets the appropriate Paging Indicator (PI) on the PICH when it has a Paging Message to be delivered to the UE. When the UE wakes up, it sees its PI on and listens to the transport Paging Channel (PCH) on the Secondary Common Control Physical Channel (SCCPCH). There is a fixed timing delay that allows time for the UE to begin successfully reading the PCH Transport Channel.


5-10

80-W1447-1 Rev A




Section 5-10


Mobile Originated Voice Call Flow

RRC connection: establishing dedicated

control link

RACH process: accessing the system

Negotiation with CN

RB Setup: establishing dedicated payload link

Authentication and Security Procedures

UL Direct Transfer [CC: Setup]

DL Direct Transfer [CC: Call Proceeding]

CoreRNCUE

RRC Connection Request

RRC Connection Setup

RRC Connection Setup Complete

Radio Bearer Setup

Radio Bearer Setup Complete

Request to establish RAB

RACH Procedures

DL Direct Transfer [CC: Alerting ]

User decides tooriginate a call

Mobile Originated Voice Call Flow

In this simplified call flow, messages are grouped according to complete sub-processes. The call flow ends after the DL Direct Transfer [Alerting] message because this message indicates call Access failure and a dropped call.

This simplified four-step process is used in the analysis that follows. Each step is governed by different parameters:

1. RACH process – Mostly involves RACH and AICH physical channels, but would also, in the case of Mobile Terminated (MT) calls, involve the Paging Channel, which is transmitted over the SCCPCH.

2. RRC connection – Involves the establishment of the Dedicated Channel; thus it can be characterized by the performance of the RACH (in the Uplink) and FACH (in the Downlink) channels in the initial stages until the DCH is set.

3. CN (Core Network) negotiation – During the CN negotiation, the low data rate DCH is used to negotiate all the authentication and security procedures as well as additional processes in the Core Network to establish the end-to-end link.

4. RB setup – After the CN negotiation, the DCH can be reconfigured to accommodate the data rate required for the requested service.


5-11

80-W1447-1 Rev A




Section 5-11


Packet Switched Data Call Flow

PS Data Call Setup

1. Call setup always begins with RRC connection establishment. After three connection messages are exchanged, the UE and RNC are communicating on either DCH or FACH/RACH.

2. GPRS Mobility Management (GMM) indicates the desire for service, but first the UE is authenticated. Note that the authentication step is optional.

3. After authentication, ciphering and integrity protection are enabled with the Security Mode Command. The security procedure serves as an implicit GMM Service Accept.

4. The Session Manager (SM) requests that the PDP context be activated.

5. The Radio Bearers that will carry the user data are established.

6. After the PDP Context is activated, higher layers of the data protocol stack may perform any negotiation or setup required to allow data to begin flowing.

PDP Context Preserved and Radio Bearer Reestablishment

If there is a period of inactivity, the data Radio Bearers may be torn down and the RRC connection may be released. The PDP context remains in a “preserved state” and may be reestablished by reestablishing an RRC connection and the user data Radio Bearers.


5-12

80-W1447-1 Rev A




Section 5-12


Mobile Terminated Voice Call Setup

Mobile Terminated Voice Call Setup

The messages exchanged for a mobile terminated voice call are similar to those for a mobile originated call:

1. Paging and Notification/RRC Connection Setup.

2. Routing of NAS layer messages for Mobility Management.

3. Ciphering and Integrity Protection.

4. Routing of NAS layer messages for Call Control.

5. Radio Bearer Management.

6. Routing of NAS layer messages for Call Control.


5-13

80-W1447-1 Rev A




Section 5-13


Call Release

Call Release

When a voice call ends, NAS layer call clearing procedures are performed first, then the RRC connection is released. The UE transitions to Idle state. The message sequence is:

1. Call Control call clearing messages are exchanged. In this example, the CS Core Network initiates the procedure, but it could also be initiated by the UE.

2. When requested by CS Core Network, RNC releases the RRC connection. Note that this procedure is always initiated by UTRAN, never by the UE, regardless of which side initiates the NAS layer call clearing procedure.


5-14

80-W1447-1 Rev A




Section 5-14


UE Procedures at Power Off

When a UE is turned off, it shall:

• Detach from the CS domain (if it was CS registered) and/or from the PS domain (if it was PS registered)

• Establish a RRC connection and send:

– A MM IMSI detach message to the MSC, and/or

– A GMM Detach Request to the SGSN

The SGSN will delete all PDP contexts, if still active, from SGSN and GGSN

– The MSC and/or the SGSN will notify the HLR about the detached user, so the last User Location is reset and the user can be marked as “Unreachable” in the HLR

• Store (either in the UE or in the SIM/USIM) helpful information for next power on, such as:– the Last Registered PLMN

– the last Used Frequency and/or RAT

UE Procedures at Power Off

A CS or PS Detach also can be initiated for reasons other than UE power off, such as when the SIM/USIM is removed from the UE.

UE indicates in the MM/GMM Detach messages which type of Detach is to be performed.


5-15

80-W1447-1 Rev A




Section 5-15


NAS/AS Interaction and QoS

• NAS logical connections

• The relationship between AS and NAS states

• Main QoS concepts

Notes


5-16

80-W1447-1 Rev A




Section 5-16


NAS CS and PS Logical Connections

One NAS Radio Access Bearer (RAB) is made up of a Radio Bearer (RB) and a IuBearer.

Control Plane User Plane

One NAS signaling connection is made up of a RRC connection and a Iusignaling connection.

NAS CS and PS logical connections

NAS Signaling Connection

A signaling connection between the UE and the CN refers to a logical connection on the Control Plane consisting of:

an RRC connection between the UE and UTRAN, and

an Iu signaling connection (“one RANAP instance”) between UTRAN and the CN node.

Signaling related to the CS service domain and the PS service domain uses one common RRC connection and two Iu signaling connections (one for the CS service domain and one for the PS service domain).

This means that the release of a CS signaling connection does not necessarily imply the release of the RRC connection which may be in use for the PS signaling procedure.

NAS Radio Access Bearer

A Radio Access Bearer between the UE and the CN refers to a logical connection on the User Plane consisting of:

a Radio Bearer between the UE and UTRAN, and

an Iu data bearer between UTRAN and the CN node.


5-17

80-W1447-1 Rev A




Section 5-17


UTRA RRC States

WCDMA RRC States

• Idle Mode

• Connected Mode

– Cell DCH

– Cell FACH

– Cell PCH

– URA PCH

UTRAN Connected Mode

Establish RRC Connection

URA_PCH CELL_PCH

CELL_FACH

Release RRCConnection

Release RRCConnection

Idle Mode Cam ped on UTR AN Cell

Establish RRC Connection

CELL_DCH

Idle Mode

In Idle Mode, the UE is receiving messages from the network on a Paging Channel, but does not transmit anything back to the network. In this mode, the UE may be camped on a UTRAN cell, a GSM cell, or it may be operating in GPRS Packet Idle Mode. The UE may be attached (registered for service) to the CS and/or PS core networks.

UTRAN Connected Mode – The UE has established an RRC connection for exchange of signaling messages with UTRAN.

CELL_DCH State – Used for circuit-switched calls or high data rate packet calls.

CELL_FACH State – UE and UTRAN can send information at any time. There are no dedicated resources. Used for sending bursts of information.

CELL_PCH State – UE is asleep, but UTAN knows the cell location. Used when there is no activity during a packet data call.

URA_PCH State – Similar to CELL_PCH, but used to limit the UE’s cell update procedure. Used when there is no activity during a packet data call, but the UE has high mobility.


5-18

80-W1447-1 Rev A




Section 5-18


Relationship Between NAS and AS States

For PS services, a PS call (PDP context) can be active with no RRC connection (RRC Idle) and no RAB established (the PS call is said to be “preserved”)

UTRA and NAS states

When a PDP context is preserved, the PS signaling connection (Iu signaling connection + RRC connection) on the Control Plane and the Radio Access Bearer (Iu Bearer + Radio Bearer) on the user plane can be released. Thus, GMM and RRC can be in Idle state while a PDP context is in active state.

Instead, on the CS domain, there is a direct correspondence between Idle and Connected states at NAS and AS layers.


5-19

80-W1447-1 Rev A




Section 5-19


Quality of Service

What is it?• Quality of a requested service as perceived by the customer.

• Applies mainly to the PS domain and applications.

Why is it important?• Determines customer satisfaction.

– Does actual experience match expectations?

How is it controlled?• 3GPP specifications define QoS between UE, UTRAN, and Core

Network at different bearer service levels (UMTS bearer, Radio Bearer, CN Bearer).

Quality of Service (QoS)

Quality of Service is defined as the quality of a requested service as perceived by the customer. It is assessed by the overall end-to-end experience, including the performance of several network elements of the originating and terminating networks. In order to offer the customer a specific QoS, the serving network must consider the network performance components of its network and the performance of the terminal, and add sufficient margin for the terminating networks in case network performance requirements cannot be negotiated.

Within the 3GPP specifications, QoS is defined between the UE and the Core Network (CN). For any given call, the offered QoS may be influenced by the following:

UE capabilities – The UE capabilities may impose a limit on the QoS. For example, the maximum data rate over the air may be limited.

Application Request – The end-user application may request a QoS that is then used in service negotiation during call setup.

Subscriber QoS Profile – The user’s subscription may have a default or upper limit QoSassociated with it.

Network Default QoS Profile – The network may assign a default QoS for a particular service.

Network Capacity – The network may impose a limit on the QoS as a function of overall network capacity.


5-20

80-W1447-1 Rev A




Section 5-20


PS Quality of Service Architecture

• UMTS Bearer Service QoS for the PS domain.

• The Local Bearer and the External Bearer Services are not standardized within 3GPP.

• The External Bearer Service can use operator-specific policies, e.g., Service Level Agreements (SLA) on the inter-operator network e.g., GPRS Exchange (GRX).

• GGSN is required to support DIffserv, whilst other QoS mechanisms e.g. Intserv, RSVP, MPLS are all optional

TE MT RAN SGSN GGSN TE

PLMN

End-to-End Service

UMTS Bearer Service

Radio Access Bearer(RAB) Service

Core Network Bearer Service

Local Bearer Service

External Bearer Service

Radio Bearer Service

Iu Bearer Service

3GPP standard QoS architecture

Different Bearer Services

Quality of Service Architecture

Ref: 23.107 and 23.207

Acronyms

GRX: GPRS Exchange

DiffServ: Differentiated Services

IntServ: Integrated Services

RSVP: Reservation Protocol

MPLS: Multi Protocol Label Switching


5-21

80-W1447-1 Rev A




Section 5-21


QoS – UMTS Traffic Classes: Delay and Error Tolerance

Errortolerant

Errorintolerant

Conversational InteractiveStreaming Background

Conversationalvoice and video Voice messagingStreaming audio

and videoFax over IP

High Delay Tolerance Low Delay Tolerance

E-mail, FTP Still image,Paging

E-commerce,WWW browsing

Telnet,interactive games

Real Time Non Real Time

Delay Tolerance

Traffic classes determine delay tolerances. Note that transfer delay is only the delay between the UE and the Core Network and does not consider other delay introduced by external elements like the PSTN.

The Streaming class is typically used for a unidirectional stream having few idle periods. An initial delay to start the stream is tolerated, and some delay variation is tolerated, up to the limit of the receiver, to buffer and time align the packets.

The Interactive class is typically used for interactions between human and machine during which a response is requested. Some longer delays are acceptable.

The Background class is typically used for machine to machine transfers, such as FTP, background email downloading, and SMS. A long delay is tolerated, up to the limit at which the information is received too late for any practical purpose. For example, voice mail notification that arrives hours after the message was recorded may be unacceptable, but a delay of a few minutes is tolerated. The standard does not specify the maximum transfer delay for Interactive and Background classes

Error Tolerance

Within a given traffic class, different applications may be more or less error tolerant. The human ear and eye can tolerate some errors, while data applications require essentially error-free delivery.


5-22

80-W1447-1 Rev A




Section 5-22


QoS – UMTS Traffic Classes: UMTS Bearer Service Attributes

UMTS bearer service attributes describe the service provided by the network to the user of the UMTS bearer service.

A set of QoS attributes (QoS profile) specifies this service.

Quality of Service (QoS) Attributes:• Traffic Class• Maximum Bit Rate• Guaranteed Bit Rate• Delivery Order• Maximum SDU Size• SDU Error Ratio• Residual Bit Error Ratio• Delivery of Erroneous SDUs• Transfer Delay• Traffic Handling Priority• Allocation/Retention Priority

For standard ranges/values for these attributes, see TS 23.107.

QoS Attributes

Traffic class (conversational, streaming, interactive, background): Type of application.

Maximum bit rate (kbps): Maximum number of bits delivered within a period of time, divided by the duration of the period. The Maximum bit rate is the upper limit a user or application can accept or provide.

Guaranteed bit rate (kbps): Guaranteed number of bits delivered within a period of time (provided there is data to deliver), divided by the duration of the period. Applies only to Conversational and Streaming classes.

Delivery order (y/n): Indicates if the UMTS bearer shall provide in-sequence SDU delivery.

Maximum SDU size (octets): Maximum allowed SDU size (used for admission control and policing).

SDU error ratio: Indicates the fraction of SDUs lost or detected as erroneous.

Residual bit error ratio: Indicates the undetected bit error ratio in the delivered SDUs.

Delivery of erroneous SDUs (y/n/-): Indicates whether SDUs detected as erroneous shall be delivered or discarded.

Transfer delay (ms): Indicates maximum delay for 95th percentile of the distribution of delay for all delivered SDUs during the lifetime of a bearer service, where delay for an SDU is defined as the time from a request to transfer an SDU to its delivery at the other SAP. It applies only to Conversational and Streaming classes.

Traffic handling priority: Specifies the relative importance for handling of all SDUs belonging to a UMTS bearer compared to the SDUs of other UMTS bearers. It applies only to the Interactive Class.

Allocation/Retention Priority: Specifies the relative importance compared to other PS bearers for allocation and retention of the UMTS bearer. The Allocation/Retention Priority attribute is a subscription attribute which is not negotiated from the mobile terminal. All other attributes are negotiated between the UE and Core Network.


5-23

80-W1447-1 Rev A




Section 5-23


QoS Negotiation in CS and PS Domain

QoS Negotiation in CS and PS Domain

MSC and SGSN will map the requested QoS attributes at UMTS bearer level to QoS attributes at RAB level according to: subscriber data stored in the HLR, and/or the configuration of the local nodes, and/or current congestion/load conditions.

The following RAB attributes usually have different attribute values compared to UMTS Bearer attributes:

Residual BER (reduced with the bit errors introduced in the CN)

SDU error ratio (reduced with the errors introduced in the CN)

Transfer delay (reduced with the delay introduced in the CN)

Some QoS attributes/settings only exist on the Radio Access Bearer level:

SDU format information

Source statistics descriptor


5-24

80-W1447-1 Rev A




Section 5-24


Basic UE Call Flow Procedures and Operations – What Did We Learn?

What are the main procedures and call flows, from UE power-on to UE power-off?

What are the main UMTS security aspects?

What are the main concepts of NAS connections, NAS/AS Bearers and states?

What are the main Quality of Service aspects?

Notes


5-25

80-W1447-1 Rev A




Section 5-25


Exercises

1. Which PLMNs will the UE select at power on, in priority order?

2. What are the 4 major steps of a Mobile Originated voice call?

3. What is the primary purpose of authentication?

4. What is the primary purpose of integrity protection?

5. What is the primary purpose of ciphering?

6. Can the UE release the RRC connection?

7. Which events can trigger the UE to send a Detach message to the network?

8. What UE call states are used only during a packet call?

9. Name four types of traffic classes and give an example application for each.

10. What is a NAS signaling connection made up of? And a RAB?

Exercises


5-26

80-W1447-1 Rev A




Section 5-26



1. Which PLMNs will the UE select at power on, in priority order? Answer: Last registered PLMN (or Equivalent), HPLMN, Preferred PLMN, Other PLMNs.

2. What are the 4 major steps of a Mobile Originated voice call? Answer: RACH Process, RRC Connection, Core Network Negotiation, and Radio Bearer Setup.

3. What is the primary purpose of authentication?Answer: To prevent SIM fraud and False network attack.

4. What is the primary purpose of integrity protection? Answer: To prevent signaling corruption.

5. What is the primary purpose of ciphering? Answer: To prevent eavesdropping.



5-27

80-W1447-1 Rev A




Section 5-27



6. Can the UE release the RRC connection?Answer: No, it is always released by the RNC.

7. Which events can trigger the UE to send a Detach message to the network?Answer: UE power off or SIM/USIM removal.

8. What UE call states are used only during a packet call?Answer: Cell_PCH, URA_PCH, Cell_FACH.

9. Name four types of traffic classes and give an example application for each.Answer: Conversational – Voice; Streaming – Mobile TV;

Interactive – Web browsing; Background – Email download.

10. What is a NAS signaling connection made up of? And a RAB?Answer: CS/PS signaling connection = RRC connection + Iu

signaling connection.CS/PS RAB = Radio Bearer + Iu bearer



5-28

80-W1447-1 Rev A



Comments/Notes



6-1

Section 6: High Speed Downlink Packet Access (HSDPA)80-W1447-1 Rev A


Section 6-1


UMTS /WCDMA Technical OverviewSection 6:

High Speed Downlink Packet Access (HSDPA)

6SECTION

High Speed DownlinkPacket Access (HSDPA)

Notes



6-2



Section 6-2


UMTS /WCDMA Technical OverviewSection Learning Objectives

Describe the limitations associated with Release 99 packet data.

Describe WCDMA Release 5 and High Speed Downlink Packet Access (HSDPA).

State the motivations for deploying HSDPA.

Describe the HSDPA channels and their functions.

Describe how Link Adaptation works.

Notes



6-3



Section 6-3


UMTS /WCDMA Technical OverviewHigh Speed Downlink Packet Access (HSDPA)

• Data Rate– Demand for high data rate

multimedia services

– Demand for higher peak data rates

• Throughput– Cost per megabyte

• Capacity– Improved Link Adaptation

dependent on radio conditions

What are the drivers and motivations for migrating to HSDPA?

Data Services and High Speed Downlink Packet Access (HSDPA)

Data Services are expected to grow significantly within the next few years. Current 2.5G and 3G operators are already reporting that a significant proportion of usage now involves data. There will therefore be an increasing demand for high-data-rate, content-rich multimedia services.

Current Release 99 WCDMA systems offer a maximum practical data rate of 384 kbps. However, in Release 5 of the specifications, the 3rd Generation Partnership Project (3GPP) has included a new high-speed, low-delay feature referred to as High Speed Downlink Packet Access (HSPDA).

HSDPA provides significant enhancements to the Downlink compared to WCDMA Release 99 in terms of peak data rate, cell throughput, and round trip delay. This is achieved through the implementation of a fast channel control and allocation mechanism that employs such features as Adaptive Modulation and Coding and fast Hybrid-Automatic Repeat Request (H-ARQ). Shorter Physical Layer frames are also employed.



6-4



Section 6-4


UMTS /WCDMA Technical OverviewUMTS Network Architecture

with HSDPA and HSUPA

UMTS Network Architecture with HSDPA and HSUPA

Adding HSDPA and HSUPA (High Speed Uplink Packet Access, which we will discuss in the next section) to an existing UMTS network requires no new network entities. However, hardware and/or software changes may be required for each entity. The changes are concentrated in the UE, Node B, and RNC. Interface changes are concentrated on the Uu interface between the UE and the Node B, and on the Iub interface between the Node B and the RNC.

UE and Node B – Require hardware and software changes to support the new HSDPA and HSUPA channels and functionality.

RNC – Requires software changes to support new functionality and the new signaling messages used to configure and manage HSDPA &and HSUPA channels.

Uu Interface – Requires new signaling messages exchanged over existing signaling channels and new transport and physical channels to support high-speed operation.

Iub Interface – Requires an updated frame protocol for sending high-speed user data from the RNC to the Node B.

No functional changes to the Iu interface for the PS domain are required, although there may bebandwidth issues to support higher data rates to multiple users.



6-5



Section 6-5


UMTS /WCDMA Technical OverviewPacket Data in Release 99

How do we do packet data in Release 99 (FDD)?

• DCH (Dedicated Channel)

– Spreading codes assigned per user

– Closed loop power control

– Macro diversity

• FACH (Common Channel)

– Common spreading code

– Header defines user

– No closed loop power control

• DSCH (Downlink Shared Channel) – not implemented for FDD. Removed from R5 and onwards.

Packet Data in Release 99

Release 99 includes three different channels for Downlink packet data transmission: the Dedicated Channel (DCH), the Downlink-Shared Channel (DSCH), and the Forward Access Channel (FACH).

DCH – the primary data channel, which can be used for any traffic class. In the Downlink, the DCH is allocated a certain orthogonal variable spreading factor (OVSF: 4-512) according to the connection peak data rate, while the block error rate (BLER) is controlled by inner and outer loop power control. The DCH code and power allocation are therefore inefficient for bursty and low duty cycle data applications since channel re-allocation can be very slow (in the range of 500 ms).

DSCH – provides the possibility to time-multiplex different users, improving the channel re-allocation time. Although the DSCH has been implemented in commercial TDD networks (as of the time this is being written), there have been no such implementations in Release 99 FDD systems.

FACH – a common channel offering low latency. However, it is not efficient since it does not support fast closed loop power control. It is therefore limited to carrying only small amounts of data traffic.



6-6



Section 6-6


UMTS /WCDMA Technical OverviewHSDPA Basic Concepts

How will HSDPA address the limitations of Release 99?• Slow outer loop power control Adaptive modulation and

coding– Fast feedback of channel condition

– QPSK and 16-QAM

– Coding from R=1/3 to R=1

• Limited data rate shorter TTI, 16-QAM and Multi-code operation– TTI as short as 2 ms

– 16-QAM can be used when channel quality is good

– Multiple codes allocated per user

• Slow rate and type switching Node B scheduling– Physical Layer HARQ

HSDPA Basic Concepts

In HSDPA, a common channel with fixed power is employed for data transfer. Users are separated in both the time and code domains. A fixed spreading factor is employed but multi-code operation is possible for increased data rates. Adaptive Modulation and Coding (AMC) replaces the role of power control so that the modulation and coding rate are changed depending on the channel condition. This is accomplished by locating the scheduling algorithm for channel allocation at the Node B instead of the RNC in Release 99.



6-7



Section 6-7


UMTS /WCDMA Technical OverviewHigh Speed Downlink Shared Channel

(HS-DSCH)

Common Transport Channel for DL data transfer is the High Speed Downlink Shared Channel (HS-DSCH).

High Speed Downlink Shared Channel (HS-DSCH)

A new transport channel named High-Speed Downlink Shared Channel (HS-DSCH) has been introduced as the primary radio bearer. Similar to the DSCH, the HS-DSCH resources can be shared among all users in a particular sector.

The primary channel multiplexing occurs in the time domain, where each Transmission Time Interval (TTI) consists of three slots (or 2 ms). The TTI is also referred to as a “sub frame.” The TTI has been significantly reduced from the 10, 20, 40 or 80 ms TTI sizes supported in R99 in order to better achieve short round trip delay between the UE and the Node B, and improve the link adaptation rate and efficiency of the AMC.

Within each 2 ms TTI, a constant Spreading Factor (SF) of 16 is used for code multiplexing, with a maximum of 15 parallel codes allocated to the HS-DSCH. These codes may all be assigned to one user during the TTI, or may be split across several users. The number of parallel codes allocated to each user depends on cell loading, QoS requirements, and the UE code capabilities (five, 10 or 15 codes).



6-8



Section 6-8


UMTS /WCDMA Technical OverviewHS-PDSCH (continued)

Common Transport Channel for DL data transfer is the High Speed Downlink Shared Channel (HS-DSCH).

High Speed Downlink Shared Channel (HS-DSCH) (continued)

To support the HS-DSCH operation, two control channels have been added: the High-Speed Shared Control Channel (HS-SCCH) and the High-Speed Dedicated Physical Control Channel (HS-DPCCH).

HS-SCCH – a fixed rate (60 kbps, SF=128) channel used for carrying Downlink signaling between the Node B and the UE before the beginning of each scheduled TTI. This includes the UE identity (via a UE-specific CRC), HARQ-related information and the parameters of the HS-DSCH transport format selected by the link adaptation mechanism.Multiple HS-SCCHs can be configured in each cell to support parallel HS-DSCH transmissions. A UE can be allocated a set of up to four HS-SCCHs, which it needs to monitor continuously. In any given TTI, a maximum of one of these HS-SCCHs may be addressed to a particular UE.

HS-DPCCH (SF=256) – carries ACK/NAK signaling indicating whether the corresponding Downlink transmission was successfully decoded, as well as a Channel Quality Indicator (CQI) to be used for the purpose of link adaptation. The CQI is based on the Common Pilot Channel (CPICH) and is used to estimate the transport block size, modulation type, and number of channelization codes that can be supported at a given reliability level in case of a Downlink transmission.



6-9



Section 6-9


UMTS /WCDMA Technical OverviewNode B Transmit Power Allocation

Node B Transmit Power Allocation

The Node B transmit power allocation algorithm is not specified by the standard, but two possible schemes are likely:

Static – A fixed amount of power is allocated to the HS-PDSCHs and HS-SCCHs. Remaining power is distributed among common channels and power controlled dedicated channels. The overall transmit power fluctuates as a function of the power controlled channels.

Dynamic – HS-PDSCH and HS-SCCH power is allocated dynamically as a function of the remaining available power, which fluctuates due to the power controlled dedicated channels. The overall transmit power of the cell remains constant.

The above diagram does not consider the Node B’s power margin, whereby the Node B’s power fluctuates. The Node B power does not really remain constant, due to the peak-to-average ratio of transmit power.



6-10



Section 6-10


UMTS /WCDMA Technical OverviewMulti-Code Operation

• Fixed Spreading Factor SF=16– (Typical Spreading Factor for 128 kbps in Release 99)

• 1-15 codes can be reserved for HS-PDSCH.• Can be TDM or CDM between users.

Up to 15 Codes reserved for HS-PDSCH transmission

2 ms (3 slots)

Multi-Code Operation

Unlike R99, which assigns each user a single fixed OVSF code for the DCH with a SF ranging from 4 to 512, HSDPA employs multi-code operation that permits assigning 15 OVSF codes among the users of the cell. Code assignments can be assigned dynamically every 2 ms (3 slots) in multiples of 128 kbps (SF = 16). If we think of the HS-PDSCH as a shared “fat data pipe” we can view multi-code operation as means to share the bandwidth of the channel among many users based on their radio conditions and required QoS.



6-11



Section 6-11


UMTS /WCDMA Technical OverviewHARQ Protocol

Hybrid ARQ (HARQ)

• Combines ARQ with adaptive coding (FEC).

• Transmitter sends new set of parity bits if the previous transmission failed (NAK’d).

• Receiver buffers the failed decodes for soft combining with future retransmissions.

• Soft combining is done before each FEC decoding attempt.

Hybrid Automatic Repeat Request (HARQ)

HARQ is a technique combining Forward Error Correction (FEC) and ARQ methods that save information from previous failed decode attempts to be used in the future decoding. With HARQ, the UE does not discard the energy from failed transmissions; the UE stores and later combines it with the retransmission(s) to increase the probability of successful decoding. This is a form of soft combining. HSDPA supports both Chase Combining (CC) and Incremental Redundancy (IR):

CC is the basic combining scheme. It consists of the Node B simply retransmitting the exact same set of coded symbols of the original packet.

With IR, different redundancy information can be sent during retransmissions, thus incrementally increasing the coding gain. This can result in fewer retransmissions than for CC.



6-12



Section 6-12


UMTS /WCDMA Technical OverviewRetransmissions

Retransmissions

If the UE is unable to decode an HSDPA data block, it sends a NAK 5 ms after the end of the received block. The Node B may choose to retransmit the data as early as the next HS-SCCH assignment following the NAK. The earliest a retransmitted block may be sent is 10 ms after the beginning subframe boundary of the previous transmission.

The retransmitted block may be identical to the previous transmission, or it may be a different redundancy version. This means that a different combination of systematic and parity bits are sent. In either case, the UE retains the symbols from the first transmission and uses either Chase Combining or Incremental Redundancy to increase the probability that the data will be decoded correctly on the 2nd attempt.

Retransmissions decrease the data rate, as the retransmitted data occupies an interval that would otherwise be used to transmit new data.



6-13



Section 6-13


UMTS /WCDMA Technical OverviewAdaptive Modulation and Coding (AMC)

• Coding from R=1/3 to R=1 (bit/symbol)

• HSPDA supports 16QAM modulation

– 4 bits per symbol versus 2 bits per symbol with QPSK

Adaptive Modulation and Coding (AMC)

HSDPA uses Adaptive Modulation and Coding (AMC) a technique where modulation and coding are dynamically changed to adapt to changes in the radio link.

Modulation: HSDPA can use one of two types of modulation, Quadrature Phase Shift Keying (QPSK) or 16-Quadrature Amplitude Modulation (QAM).

QPSK, which provides 2 bits per modulation symbol, is less spectrally efficient and thus produces a lower data rate (in bps) per Hertz of radio spectrum. Despite this drawback, QPSK is better suited for weaker (i.e., lower SINR) radio links and more immune to bit errors than higher order modulations like 16-QAM.

16-QAM is twice as spectrally efficient as QPSK, with 4 bits per modulation symbol. However, examining the constellation in figure above, we can see there is less separation between the symbols which makes 16-QAM more susceptible to symbol errors under low SINR conditions. For this reason, 16-QAM is used only with higher SINR radio links.

Coding: HSDPA uses coding rates that range from R = 1/3 (that is 3 coding symbols per bit) to R = 1 (1 coding symbol per bit). R = 1/3 provides more coding gain and thus more immunity against bit errors when used with low SINR radio links. This robust coding comes at a cost of decreased data rates because more symbols are required for every data bit. With high SINR radio links, the coding rate can be lowered, providing higher data rates.



6-14



Section 6-14


UMTS /WCDMA Technical OverviewAMC versus Power Control

• Release 99– Uses fast power control

with fixed data rate (DCH)

• HSDPA– Adapts the modulation

and coding to the link quality

Rate #1 Rate #2 Rate #3 Rate #2 Rate #1 Rate #2Rate #2

Switchinglevels

Channel quality (C/I)Fast Link adaptation:

time

Rate #1: e.g., QPSK, R=1/2

Rate #2: e.g., QPSK, R=3/4

Rate #3: e.g., 16QAM, R=3/4

AMC versus Power Control

As we learned in a previous section, R99 employs a fixed data rate using fast power control to compensate for differences in path loss and the effects of fading in the radio channel.

HSDPA Downlink does not use fast power control to compensate for these effects. Instead, it employs AMC. In HSDPA, AMC is implemented having high quality radio links use more spectrally efficient 16-QAM modulation along with lower code rates, resulting in higher data rates. Similarly, weaker radio links use more robust modulation (QPSK) and higher coding rates, resulting in lower data rates. In this way both modulation and coding adapt to the changing radio conditions.

With HSDPA, modulation and coding can change based on the TTI used, which in HSDPA can be as frequently as every 2 ms. Channel quality information (CQI) provides fast feedback to the Node B about the quality of the radio link.



6-15



Section 6-15


UMTS /WCDMA Technical OverviewHSDPA Scheduling and Retransmissions

• Scheduling– Done at the Node B

– No interaction with the RNC

– Based on Channel Quality Feedback from the UE

• Retransmissions– H-ARQ (link level retransmissions)

– Done at the Node B

– Based on UE feedback (ACK/NAK)

– Soft combining at the UE

HSDPA Scheduling and Retransmissions

In Release 99, many packet data scheduling functions reside in the RNC. This adds delays to scheduling of packet transmission, RLC ARQs, and resource allocation, which adds to packet latency. HSDPA moves these functions to the Node B; this reduces latency by eliminating the delays associated with communicating with the RNC for these functions.

Hybrid Automatic Repeat Request (H-ARQ) is a Scheme combining ARQ and Forward Error Correction (FEC). In H-ARQ, the FEC Decoder combines energy from new packets and retransmitted packets for decoding. Unsuccessful transmissions thus act to improve the probability of receiving the retransmitted packet successfully.

In R99 there is no H-ARQ, so all retransmissions come from the RNC. At the Physical Layer, you could not tell the difference between a new packet and a retransmission.



6-16



Section 6-16


UMTS /WCDMA Technical OverviewFunctional Overview of Fast Scheduling

Scheduled UE for C/I-max scheduler

time

time

time

C/I

C/I

C/I

Transmission time interval 3 slots = 2 ms

CQI reporting

priority queue 1

priority queue 2

priority queue N

...

User 3 buffer

priority queue 1

priority queue 2

priority queue N

...

User 2 buffer

priority queue 1

priority queue 2

priority queue N

...

User 1 buffer

Scheduler

Functional Overview of Fast Scheduling

HSDPA employs fast scheduling, which uses CQI reporting coming from UEs to schedule transmission of data on the Downlink. The fast feedback provided by CQI permits the scheduler (which is not standardized) to serve Downlink data to UEs when their channel quality (carrier to interference ratio) is “at their best” (i.e., above their own average). As a result, individual UEsare on average, served at higher data rates. This results in higher peak rates on the DL for individual UEs and higher average cell data rates.

As the number of users on a cell increases, there are many more opportunities for the scheduler to schedule data to UEs who are “at their best.” As a result, the average data rate from the cell increases as the number of UEs active on the cell increases. This effect is sometimes called “multi-user diversity gain.”

Schedulers usually balance efficiency (i.e., the desire to pick UEs with good DL rates) versus fairness (i.e., the need to serve every active UE, at least occasionally, regardless of its DL data rate).



6-17



Section 6-17


UMTS /WCDMA Technical OverviewHSDPA Functional Overview

Node B

Node B

RNC RNC

HS-SCCH set

Iur

Iub

Iu

R99 DPCHs

HS-PDSCHs

“HS-DSCH serving cell”

HS-DPCCH

HSDPA Functional Overview

This slide shows a functional overview of HSDPA operation. The UE is served from one Serving HS-DSCH cell only. From this cell, we have these Physical Layer channels operating:

HS-PDSCH (DL) – carries high speed user data shared by several UEs.

HS-SCCH (DL) – carries control information for HSDPA use.

HS-DPCCH (UL) – the HS-DPCCH caries UL feedback information including the HARQ feedback to indicate if the packet on the DL was received correctly. The HS-DPCCH runs in parallel with the R99 DPCHs that carry the DCH. This leaves the DCH operation unchanged and enables DCH operation in soft handoff.

R99 DPCHs (UL and DL) – these channels can operate in soft handover and carry DCHs, which carry user and control data and can operate when the UE is out of HSDPA coverage.



6-18



Section 6-18


UMTS /WCDMA Technical OverviewHSDPA Channels

DTCH

DTCH

HS-DSCH

HS-PDSCH

HS-SCCH HS-DPCCH

New in HSDPA

UM / AM

HSDPA Channels

Only dedicated logical channels may be mapped to HS-DSCH. The Dedicated Signaling Channel (DCCH) may be mapped to HS-DSCH, though the more important mapping is to DTCH, which carries user data. When DTCH is mapped to HS-DSCH, only Unacknowledged Mode (UM) and Acknowledged Mode (AM) channels may be used.

A UE operating in HSDPA mode also has at least one Release 99 dedicated channel (DCH/ DPDCH) allocated, to ensure that RRC and NAS signaling can always be sent, even if the UE cannot receive the high speed channels. This also enables operation in networks in which not all the Node Bs have been converted to HSDPA.

The HS-DPCCH is a Physical Layer control channel. It carries no upper layer information, and therefore has no logical or transport channel mapping. Likewise, the HS-SCCH is the Physical Layer Control Channel used for carrying Downlink signaling between the Node B and the UE with no logical or transport channel mapping.



6-19



Section 6-19


UMTS /WCDMA Technical OverviewMAC-hs for HSDPA

MAC-hs for HSDPA

HSDPA introduces a new protocol element into the Access Stratum called MAC-hs. MAC-hs is responsible for the high speed HSDPA channels and is the only entity of MAC that resides in the Node B. When a UE operates in HSDPA mode, MAC-hs maps user data and signaling from DCCH and DTCH onto the shared HS-DSCH transport channels. In HSDPA, MAC-hs is used in the Node B to handle Layer 2 functions related to the HS-DSCH including:

Handling of ACK/NAK messages for the HARQ protocolReordering of out-of-sequence subframesMultiplexing of multiple MAC-d flows onto one MAC-hs streamDownlink packet scheduling

The UTRAN MAC protocol consists of two entities in addition to MAC-hs:

MAC-c/sh – Responsible for common and shared logical (PCCH, BCCH, CCCH, and CTCH) and transport (PCH, BCH, RACH, FACH) channels. MAC-c/sh resides in the RNC, and there is one MAC-c/sh entity per RNC. When a UE operates in CELL_FACH state, MAC-c/sh maps user data and signaling from its DCCH and DTCH onto the common FACH and RACH transport channels.

MAC-d – Responsible for mapping data from dedicated logical channels (DCCH and DTCH) onto dedicated transport channels (DCH). MAC-d resides in the RNC, and there is one MAC-d entity for each UE to which dedicated logical channels have been assigned.



6-20



Section 6-20


UMTS /WCDMA Technical OverviewChange of Serving Node B – Repointing

Serving Node B Change

HSDPA channels do not operate in soft handover. For a given UE, the Node B from which it receives the HSDPA channels is called the Serving Node B.

The UE may be in soft handover on the associated Dedicated Physical Channel (DPCH).

If the radio conditions change such that there is a better cell on another Node B for HSDPA operations, the Serving HSDPA Node B Change procedure is performed. This procedure occurs independently from the Active Set Update procedure.



6-21



Section 6-21


UMTS /WCDMA Technical OverviewOverall Comparison Summary

Mode DCH FACH HSDPA

Channel Type Dedicated Common Common

Power ControlClosed Inner Loop at 1500 Hz - Slow

Outer LoopOpen Loop Fixed Power

Soft Handover Supported Not supported Not supported

Suitability for Bursty Data

Poor Good Good

Data Rate Medium Low High

Summary of PS Data on DCH, FACH, and HSDPA

DCH and FACH are typically used in Release 99 for packet switched data. The advantages and disadvantages of each approach are apparent.

Whereas DCH is suited for high data traffic volumes (with a maximum rate of 384 kbps), setup time is slow, making it unsuitable and inefficient for bursty data such as a web browsing application.

By contrast, FACH has a low setup time but is a common channel without power control or other mechanisms to account for channel conditions. This makes it highly suitable for bursty traffic but unsuitable for larger traffic volumes.

HSDPA mode, on the other hand, is well suited for bursty packet data and provides much higher data rates than operation DCH or FACH operation.



6-22



Section 6-22


UMTS /WCDMA Technical OverviewHSDPA Performance Summary

• Maximum Theoretical Data Rate:– 14.4 Mbps

Virtually impossible to obtain in the field.

• Practical Peak Data Rate:– 10.0 Mbps

Full capability UEGood RF conditions (High Cell Geometry)Single UE

Dedicated HSDPA carrier

• Significant Performance Gains over Release 99– Peak Data Rate

– Cell Throughput

HSDPA Performance Summary

Although HSDPA has a theoretical peak rate of 14.4 Mbps, this is virtually impossible to obtain on real-world networks. As a practical limit, 10 Mbps is obtainable using a dedicated HSDPA carrier under ideal conditions such as having a good radio link, being the only UE using the cell, and the use of a full-capability UE. Typically peak data rates are usually less. Despite this, HSDPA still provides significant improvements of peak data rate and cell throughput when compared to R99.



6-23



Section 6-23


UMTS /WCDMA Technical OverviewHSDPA Fundamentals –

What Did We Learn?

What are the limitations associated with Release 99 packet data?

What are WCDMA Release 5 and High Speed Downlink Packet Access (HSDPA)?

What are the motivations for deploying HSDPA?

What are the HSDPA channels and what are their functions?

What are the limitations associated with Release 99 packet data?

How does Link Adaptation work?

Notes



6-24



Section 6-24


UMTS /WCDMA Technical OverviewExercises

1. What are 3 drivers and motivations for migrating from Release 99 to HSDPA?

2. What is the name of the MAC sublayer added for HSDPA?

3. What are the functions of this new MAC sublayer?

4. What are the names/functions of the new HSDPA channels?

Exercises



6-25



Section 6-25


UMTS /WCDMA Technical OverviewExercises – Answers

1. What are 3 drivers and motivations for migrating from Release 99 to HSDPA? Answer: Data rate, throughput, and capacity

2. What is the name of the MAC sublayer added for HSDPA?Answer: MAC-hs (Media Access Control high speed)

3. What are the functions of this new MAC sublayer? Answer: Handling of ACK/NAK messages for the HARQ protocol, reordering of out-of-sequence subframes, multiplexing of multiple MAC-d flows onto one MAC-hs stream, and Downlink packet scheduling

4. What are the names/functions of the new HSDPA channels? Answer: HS-DSCH (DL) is a shared transport channel that carries user data; HS-PDSCH (DL) is a physical channel that carries high speed user data shared by several UEs. The HS-SCCH (DL) is a physical channel that carries control information for HSDPA use; the HS-DPCCH (UL) is a physical channel that carries UL feedback information including the HARQ feedback to indicate if the packet on the DL was received correctly.

Exercises - Answers



6-26



Comments/Notes


UMTS/WCDMA Technology Overview

7-1

Section 7: High Speed Uplink Packet Access80-W1447-1 Rev A


Section 7-1


UMTS /WCDMA Technical OverviewSection 7:

High Speed Uplink Packet Access (HSUPA)

7SECTION


Notes



7-2



Section 7-2


UMTS /WCDMA Technical OverviewSection Learning Objectives

State the main motivations behind the introduction of HSUPA in the 3GPP standard.

Explain the basic HSUPA concepts.

Explain how to achieve the maximum Uplink data rate.

Identify the main differences between the HSUPA Uplink and the Release 99 Uplink.

Notes



7-3



Section 7-3


UMTS /WCDMA Technical OverviewHigh Speed Uplink Packet Access (HSUPA)

• Data Rate– Demand for higher peak

data rates in Uplink (UL)

• Delay– Lower latency

• Capacity– Better Uplink capacity

• Coverage– Better Uplink coverage with

higher data rate

What are the drivers and motivations for migrating to HSUPA?


Demand for higher peak Uplink data rates, lower latency, increased Uplink capacity, and better coverage are all drivers for migrating to HSUPA.



7-4



Section 7-4


UMTS /WCDMA Technical OverviewApplications Requiring an Improved

Uplink (UL)

• Voice over IP (VoIP)

- Low latency, Quality of Service (QoS) control, fine resource granularity, and improved Uplink capacity

• Video Telephony (in Packet Switched domain)- Low latency, Quality of Service (QoS) control, high data rates,

and improved Uplink coverage and capacity

• Gaming

- Low latency, fast resource allocation

• Video Share / Picture Share- High Uplink data rates and improved Uplink coverage and

capacity

• File Uploading (large files)- High Uplink data rates and improved Uplink coverage and

capacity

Delay Sensitive

Delay Tolerant

Applications Requiring an Improved Uplink

Delay tolerant applications typically require reliable delivery of packets, while delay sensitive applications may accept dropped packets if delay requirements would be exceeded otherwise. In addition, jitter sensitive applications may require guaranteed bandwidth.



7-5



Section 7-5


UMTS /WCDMA Technical OverviewRelease 99 Uplink Limitations

• Large Scheduling Delays

– Slow scheduling from RNC

• Large Latency

– Transmission Time Interval (TTI) durations of 10/20/40/80 ms

– RNC-based retransmissions in case of errors

• Limited Uplink Data Rate

– Deployed peak data rate is 384 kbps

• Limited Uplink Cell Capacity

– Typically in the range of 400 to 800 kbps

Release 99 Uplink Limitations

Release 99 has many Uplink performance limitations. For example, the maximum peak data rate for any given user is typically only 384 kbps. Cell Uplink capacity is also limited, typically only 400 kbps to 800 kbps in deployed systems.

In addition to Uplink capacity and peak rate limitations, R99 also suffers from large latencies compared to HSUPA. For example, Uplink data rates in R99 are scheduled from the RNC. This process is slow and makes it impractical to change data rates quickly to adapt the transmission rate to changing channel conditions (which would increase throughput).

Another drawback is that the shortest Transmission Time Interval (TTI) used in R99 is 10 ms. This results in larger latency than if smaller TTIs where employed. In addition, R99 uses RNC-based retransmissions, which are slow and increase Uplink latency.

We will see later in this section how HSUPA overcomes the limitations of R99 to provide improvements in Uplink peak rates, capacity, and latency.



7-6



Section 7-6


UMTS /WCDMA Technical OverviewEnhancements Provided by HSUPA

• Higher Peak Data Rate in Uplink– Enable new services and improve user perception

• Improved Uplink Coverage with Higher Data Rates

• Improved Uplink Cell Capacity

• Reduced Latency

• Fast Scheduling and Resource Control– Increase resource utilization and efficiency

• Quality of Service (QoS) support– Improve QoS control and resource utilization

Enhancements Provided by HSUPA

HSUPA overcomes the limitations of the R99 Uplink; it provides higher peak data rates and improved Uplink coverage with higher data rates. In addition, HSUPA improves the Uplink cell capacity while reducing latency.

HSUPA introduces Node B-based fast scheduling and resource control for the Uplink. The advantage of this is that the user’s data transmission rate can be scheduled as frequently as every2 ms (the TTI) based on channel conditions and cell loading. This increases resource utilization and efficiency. HSUPA also provides improved Quality of Service (QoS) support.

HSUPA can operate with or without HSDPA in the Downlink. However, it is likely that most networks will use the two approaches together.

The improved Uplink mechanisms provide better coverage. For rural deployments, this results in larger cell sizes.



7-7



Section 7-7



Improved Cell Capacity

Higher Peak Data Rates

Reduced Latency

Improved QoS Support

Faster Resource Control

How are HSUPA Enhancements Achieved?

R99 UL DCH HSUPA

Minimum TTI of 10 ms

Smaller TTI of 2 ms

Slow UL rate switching

(RNC based)

Fast UL data ratecontrol in the Node B

Improved physical layer performance

through H-ARQ

Multiplexing at Physical Layer

Multiplexing of logical channels at MAC layer

Slow mechanism to request resources

Fast mechanism to request UL resources

Dedicated resource allocation for latency sensitive applications

Dedicated resource allocation that could

not be used efficiently

New Transport Channel

New Physical Channels

How are HSUPA Enhancements Achieved?

HSUPA provides a number of enhancements to R99 for higher data rates and higher spectral efficiency which lower the cost per byte of information. The combination of smaller TTI, fast scheduling, and Hybrid ARQ work together to reduce latency. Lower latency is a requirement for many new applications such as VoIP and PS-based video telephony.



7-8



Section 7-8


UMTS /WCDMA Technical OverviewTheoretical HSUPA Maximum Data Rate

How do we get 5.76 Mbps?• Lower Coding Gain

– Effective code rate = 1

– Requires very good channel conditions to decode

• Lower Spreading factor– UE can use SF2

• Multi-code transmission– UE can use up to 4 codes, 2 with SF4 plus 2 with SF2

– Requires some power back-off by the UE

• Shorter TTI– Requires higher processing capabilities at terminal and Node B

Theoretical HSUPA Maximum Data Rate

The following assumptions are needed to achieve the theoretical maximum data rate of 5.76 Mbps:

Lower Coding Gain – Using an effective code rate of 1 increases the data rate, but the channel conditions must be very good for the UE to correctly decode every data block on the first transmission.

Lower Spreading Factor – The Node B must send back-to-back assignments to a single UE, and the UE must be able to correctly decode every block without requiring retransmission.

Multi-code transmission – All 15 HS-PDSCH channels must be assigned to a single UE during one 2 ms TTI. This uses up a significant portion of the OVSF tree, leaving very few codes for non-HSDPA users and overhead channels.

Shorter TTI – Needed because the maximum transport block size is 20000 bits with 10 ms TTI. Requires higher processing capabilities at the UE and Node B.

Realistically, the practical maximum data rate will be less than 5.76 Mbps, due to less than ideal channel conditions, the need for retransmission, and the need to share the UE power with other channels.



7-9



Section 7-9


UMTS /WCDMA Technical OverviewNew UL Transport Channel –

Enhanced Uplink Dedicated Channel (E-DCH)

E-DCH is the new dedicated transport channel for HSUPA.

• E-DCH can be mapped to one or more E-DPDCH.

• Control information for E-DCH is sent on E-DPCCH.

E-DCH characteristics:

• Single Transport Block (TB) per TTI.

• TTI can be 10 ms or 2 ms.– Support for 10 ms TTI is mandatory in the UE.

• Transport block size varies from 18 bits to 20000 bits.

– Highest data rate is 5.76 Mbps.

New UL Transport Channel – Enhanced Uplink Dedicated Channel (E-DCH)

The structure of the HSUPA E-DCH channel resembles that of the R99 DCH with changes to support HARQ and fast scheduling. Each UE has its own dedicated E-DCH data path to the Node B and is independent from the E-DCH and DCHs of other UEs. The E-DCH can be mapped to a maximum of 4 Enhanced-DCH Dedicated Physical Data Channels (E-DPDCHs).

Abbreviations:

E-DCH = Enhanced Uplink Dedicated Channel

E-DPDCH = Enhanced DCH Dedicated Physical Data Channel

E-DPCCH = Enhanced DCH Dedicated Physical Control Channel

TTI = Transmit Time Interval



7-10



Section 7-10


UMTS /WCDMA Technical OverviewNew Uplink Physical Channels

UL Physical Channels

• E-DPDCH – Enhanced Dedicated Physical Data Channel– Carries the E-DCH Transport Channel (up to 4

physical channels can be allocated per E-DCH)

– Also carries UE requests for grant (Scheduling Info)

• E-DPCCH – Enhanced Dedicated Physical Control Channel– E-DCH Transmission Format Indicator

– HARQ retransmission sequence number

– Also includes 1 bit to support scheduling, to indicate unsatisfactory granted rate (the “Happy Bit”)

RNC

3dTower.emf

Node B

UL Channels

E-D

PD

CH

-U

E R

equ

est

E-D

PD

CH

-D

ata

Tra

nsp

ort

E-D

PC

CH

–H

app

y B

it

New Uplink Physical Channels

The new physical channel E-DPDCH carries the new transport channel E-DCH. There may be zero, one, or up to four E-DPDCHs on each radio link.

The UE also uses the E-DPDCH to request a grant using the SI field (Scheduling Information); this SI can be sent later (typically infrequently).

The E-DPCCH is a physical channel used to carry control information associated with the E-DCH. There is at most one E-DPCCH on each radio link. The E-DPCCH also carries one bit that the UE uses, if set to “unhappy”, to inform the Node B that the granted data rate is not satisfactory. This is sometimes referred to as the “Happy Bit”. The standard includes specific conditions under which the UE may set the bit to ‘Unhappy’ (the happy bit is carried on the E-DPCCH every TTI).



7-11



Section 7-11


UMTS /WCDMA Technical OverviewNew Downlink Physical Channels

DL Physical Channels

• E-HICH – HARQ Indicator Channel– ACK/NAK indicator for HARQ

• E-RGCH – Relative Grant Channel– Relative Scheduling Grant Indication

• E-AGCH – Absolute Grant Channel– Absolute Scheduling Grant Indication

RNC

3dTower.emf

Node B

DL Channels

E-H

ICH

–A

CK

/NA

K

E-R

GC

H–

Rel

ativ

e G

rant

E-A

GC

H–

Abs

olut

e G

rant

New DL Physical Channels

The E-HICH is a new dedicated channel on the Downlink that is used to provide feedback for the HARQ process.

The Node B informs the UE about the Traffic-to-Pilot ratio it can use to transmit on E-DCH. Two channels are used for this purpose: the E-AGCH and the E-RGCH.

The E-AGCH is a common channel, which transmits absolute grant values to UEs. The E-AGCH is used to indicate the maximum usable power (which determines the transmission rate). Specifically, the E-AGCH provides a grant that indicates the Traffic-to-Pilot power ratio the UE is allowed to use. The UE uses this channel to determine the maximum data rate it can transmit.

The E-RGCH is a dedicated channel. This channel is used to adjust the UE’s Uplink transmission rate. The E-RGCH orders the UE to either increase, decrease, or keep unchanged the Traffic-to-Pilot power ratio grant. It carries one of three commands: “Up,” “Down,” or “Hold” for that purpose.



7-12



Section 7-12


UMTS /WCDMA Technical OverviewNew Channels in HSUPA Operation

1. The UE sends a request for resources. The request includes status of its data buffers and is sent on E-DPDCH.

2. Based on the request from the UE, the Node B allocates a resource grant to the UE. The grant is sent on the E-AGCH channel.

3. This grant can be modified by the Node B every TTI using the E-RGCH channel.

4. The UE transmits data PDU on E-DPDCH. Control information needed to decode this PDU is sent on E-DPCCH.

5. The Node B decodes the received packet and informs the UE if it could decode the PDU successfully on the E-HICH channel.

3dTower.emf

New Channels in HSUPA Operation

The E-DCH (Enhanced Dedicated Channel) carries the Uplink high speed data. The E-DCH can be mapped to one of four Uplink E-DPDCHs (Dedicated Physical Data Channels for E-DCH). The Physical Layer control information, TFCI, etc., are carried on one E-DPCCH (Dedicated Physical Control Channel for E-DCH).

The Downlink physical channels E-HICH (HARQ Indicator Channel for E-DCH) and E-RGCH (Relative Grant Channel for E-DCH) are dedicated channels; they share a single channelization code assigned by the higher layer to the UE. The UE increases or decreases its E-DCH data rate based on the relative grant indicator on E-RGCH. The Downlink channel E-AGCH (Absolute Grant Channel for E-DCH) is a common channel shared by all the users in the cell. Addressing on E-AGCH is realized by masking CRC bits with E-RNTI (RNTI for E-DCH).



7-13



Section 7-13


UMTS /WCDMA Technical OverviewHSUPA Channels Mapping

Rel. 99

Rel.5

Rel.6

HSUPA Channels Mapping

Only the dedicated logical channel can be mapped to E-DCH. When DTCH is mapped to E-DCH, only Unacknowledged Mode (UM) and Acknowledged Mode (AM) channels may be used.

A UE operating HSUPA can also have additional Release 99 DCH and/or HSDPA channels, though restrictions of the possible combinations are specified in the standard. Since power control and soft handover are supported for E-DCH, the channel can be considered an extension of the Release 99 DCH.

Another addition to the standard is the ability to map the DCCH logical channel to the HS-DSCH Downlink transport channel and to the E-DCH Uplink transport channel. In this case, the Fractional Dedicated Physical Channel (F-DPCH) will be used for power control bits.

The E-DPCCH as well as E-HICH, E-AGCH, and E-RGCH are Physical Layer (control) channels. They carry no upper layer information, and have no logical or transport channel mapping.



7-14



Section 7-14


UMTS /WCDMA Technical OverviewHSUPA Features – HARQ Operation

E-DPCCH

E-DCH

E-HICH

• HARQ is based on Stop-and-Wait (SAW) protocol

– Provides retransmission capability

• HARQ feedback is transmitted on E-HICH

HSUPA Features – HARQ Operation

HARQ is based on the Stop-and-Wait (SAW) Protocol. A stop and wait protocol transmits a Protocol Data Unit (PDU) of information and then waits for a response. The receiver receives each PDU and sends an Acknowledgement (ACK) PDU if a data PDU is received correctly, and a Negative Acknowledgement (NACK) PDU if the data was not received.

The HSUPA HARQ has synchronous retransmissions, which eliminates the need for process IDs on E-DPCCH.

The example above refers to 10 ms TTI. Two transmissions are needed for successful transmission of the transport block because of the two NAKs sent on the E-HICH. Once the second transmission is successful, the UE transmits a new transport block on E-DCH.



7-15



Section 7-15


UMTS /WCDMA Technical OverviewHSUPA Features – Hybrid ARQ

N-channel Stop-and-Wait (SAW) protocol

3dTower.emf

Node B

3dTower.emf

Node BDATA

DA

TA

NA

K

ACK

E-DCH cells part of the Active Set

• Synchronous retransmissions

• Separate HARQ feedback is provided per radio link

HSUPA Features – Hybrid ARQ

The Hybrid ARQ for HSUPA consists of an N-Channels Stop-and-Wait (SAW) protocol.

The retransmission is synchronous, with separate feedback provided for each radio link.

After requesting and receiving a grant for data transmissions:

1. The UE transmits the data of the corresponding HARQ process to all Node Bs for which a radio link exists.

2. Each Node B connected to the UE sends an ACK/NAK back to the UE.

3. Receipt of an acknowledgment (ACK) for the transmission is sufficient for successful completion.

Rel6 HSUPA employs HARQ (as well as HSDPA), but does not support higher modulation schemes (e.g., 16 QAM) or Adaptive Modulation (features added in Rel7). HSUPA does use Adaptive Coding, which adjusts the amount of error correction depending on loading and channel conditions. Unlike HARQ in HSDPA, HARQ in HSUPA is fully synchronous. Another difference is that HSUPA supports UL soft handover. This means that HARQ can involve ACK/NACKs from more than one Node B.



7-16



Section 7-16


UMTS /WCDMA Technical OverviewHSUPA Features – Resource Control

Rate Control

• Scheduled Transmissions– Serving Node B signals granted rate using the Absolute and Relative

grants, which are transmitted on the E-AGCH and E-RGCH channels, respectively.

Suitable for high rate, delay tolerant services

• Non-Scheduled Transmissions– Serving RNC configures autonomous rate for Non-Scheduled

Transmissions.

Used to support real-time services like signaling radio bearer or VoIP

HSUPA Features – Resource Control

HSUPA has two different types of resource allocation:

Scheduled transmissions – The RNC indicates to the Node B the amount of resources that can be used for the E-DCH channel. The Node B scheduler then determines how and to which UE the resources shall be assigned. This is done by means of Absolute and Relative grants, and with fast resource control.

Non-scheduled transmissions – The RNC configures a certain amount of resources for a specific UE directly. The UE can use those resources at any time, without waiting for scheduler decisions. This is useful for delay sensitive applications, to meet tight delay requirements.

The two resource assignments are independent of each other and are treated separately. The UE cannot use scheduled resources to transmit non-scheduled data and vice versa.



7-17



Section 7-17


UMTS /WCDMA Technical OverviewHSUPA Features – Load Control

Load Control

• The E-RGCH channel can also be used for Load Control by signaling certain UEs to decrease their data rate.

– Used to control undesired excessive Rise-over-Thermal (RoT) noise at the Node B receiver, thus preventing overloading.

3dTower.emf

Node BDOWN

DO

WN

DOW

N

DO

WN

DOWN

☺

send DOWN

time

RoTNoise Limit

3dTower.emf

ServingNode B

HSUPA Features – Load Control

The shared resource on the Uplink is Rise Over Thermal (RoT). The higher the UE’s data rate, the higher its transmit power, and hence the higher its contribution to the RoT.

Load Control functionality is intended for non-serving Node Bs (i.e., Node Bs that do not include the serving cell), to avoid an excessive noise rise from HSUPA-transmitting UEs that are not under their control. Non-serving cells can use RGCH commands for load control, by applying either DOWN or HOLD commands. The serving cell can also use the absolute grant channel for load control (cells of the serving Node B should be aligned with the serving cell).

Each command is associated with a specific HARQ process, based on transmission timing:

The DOWN command indicates one index down relative to the last used grant index on the same HARQ process.

The HOLD command indicates that there is no new command.

When several UEs receive a ‘Down’ command on the RGCH, each UE can report Happy or Unhappy depending on items such as Power headroom available, data present in buffer, and current grant.



7-18



Section 7-18


UMTS /WCDMA Technical OverviewHSUPA versus Release 99 –

Data Transmission

RNC

3dTower.emf

Node B

Rel. 99 Uplink

1

Pac

ket

2

RLC ACK/NAK

Release 99 Data Transmission

1. UE sends data packets.

2. RNC replies with RLC ACK/NAK.

3. The UE retransmits erroneous packets.

3

HSUPA Data Transmission

1. UE sends data packets.

2. Node B replies with L1 ACK/NAK.

3. The UE retransmits erroneous packets.

4. Node B combines packets and deliver them to RNC.

RNC

3dTower.emf

Node B

HSUPA

3Pac

ket

1

L1 ACK/NAK

2

H-ARQ

Packets combining

4Packets delivery

HSUPA versus R99 – Data Transmission

In R99, physical layer packet losses are recovered through RLC retransmissions.

In HSUPA, physical layer packet losses can be more efficiently recovered by the MAC layer. If MAC layer recovery is not successful, RLC tries to recover losses through retransmissions. The use of MAC layer recovery “cleans up” many errors and consequently greatly reduces the number of RLC retransmission required. This reduces latency.



7-19



Section 7-19


UMTS /WCDMA Technical OverviewHSUPA versus Release 99 –

Rate Adaptation

RNC

3dTower.emf

Node B

HSUPA

Rate Adaptation – HSUPA

1. UE requests data transmission.

2. Node B grants scheduled data transmission with (new) rate.

3. Data transmission with granted data rate begins.

UE

Req

ues

t

1

Rate Control

2

Dat

a T

ran

smis

sio

n

3

Fast

Scheduling

Rate Switching – Release 99

1. UE reports traffic volume measurements.

2. RNC updates the data rate.

3. Data transmission with new data rate begins.

RNC

3dTower.emf

Node B

Rel 99 Uplink

1

Tra

ffic

vo

lum

e m

easu

rem

ents

3

Dat

a T

ran

smis

sio

n

2

Rate Control

HSUPA versus Release 99 – Rate Adaptation

Rate Adaptation in HSUPA, which employs fast scheduling, differs from Rate Switching used in R99. Rate Adaptation is Node B-based and employs fast scheduling. This allows the Node B to allocate radio resource more efficiently than R99 RNC-based Rate Switching.



7-20



Section 7-20


UMTS /WCDMA Technical OverviewHSUPA vs. HSDPA

HARQ with Fast Retransmission at Layer 1

Fast Node-B Scheduler

“Many-to-One”

Rise-over-Thermal (RoT)

Fast Node B Scheduler

“One-to-Many”

Shared Node-B Power and Code

Fast Power Control

Soft Handover

Rate/Modulation Adaptation

Single Serving Cell

Dedicated Channel with Enhanced Capabilities

New high-speed Shared Channel

HSUPAHSDPA

HSUPA vs. HSDPA

This slide compares several aspects of HSDPA and HSUPA.

The HSDPA concept is based on a high speed shared channels with fast L1 HARQ retransmission and rate and modulation adaptation to adjust to channel conditions. The fast scheduler is located in the Node B and assigns the available resources (power and codes) to several users. The cell power can be directed to a single user (or to a small group of users) for a short period of time, during which other users do not get any data. This enables one Node B transmitter to be shared among many UE receivers (one-to-many).

For HSUPA, the channel remains a dedicated channel but with enhanced capabilities like fast scheduling and L1 HARQ retransmissions; power control and soft handover are still used to adapt to the radio channel conditions. Due to the fact that each UE has an independent transmitter with its own power and code availability, the HSUPA scheduler accommodates many users to be received by the same Node B (many-to-one), where the Rise-over-Thermal Noise level indicates the Uplink loading of the system.



7-21



Section 7-21


UMTS /WCDMA Technical OverviewHSDPA Fundamentals –

What Did We Learn?

What are the main motivations behind the introduction of HSUPA in the 3GPP standard?

What are some basic HSUPA concepts?

What is the maximum data rate achievable with HSUPA?

What are the new HSUPA channels?

What are the main differences between the HSUPA Uplink and the Release 99 Uplink?

Notes



7-22



Section 7-22


UMTS /WCDMA Technical OverviewExercises

1. What are the main motivations for the introduction of HSUPA? Which applications may be improved?

2. How are HSUPA enhancements achieved?

3. What is the new HSUPA Uplink Transport channel?

4. H-ARQ is based on what protocol?

5. What is the shared resource on the Uplink?

6. What is the major difference between Rate Switching in R99 and Rate Adaptation in HSUPA?

Exercise



7-23



Section 7-23


UMTS /WCDMA Technical OverviewExercises – Answers

1. What are the main motivations for the introduction of HSUPA? Which applications may be improved? Answer: Higher peak data rates, improved Uplink coverage and capacity for packet services, reduced latency, and finer granularity in UL resources.

2. How are HSUPA enhancements Achieved?Answer: Smaller TTI, Fast UL data rate control in the Node B, Improved Physical Layer performance through H-ARQ, Dedicated resource allocation, Fast mechanism to request UL resources, and multiplexing of logical channels at MAC Layer.

3. What is the new HSUPA Uplink Transport channel? Answer: Enhanced-Dedicated Channel (E-DCH).

4. H-ARQ is based on what protocol? Answer: Stop-and-Wait (SAW) Protocol

5. What is the shared resource on the Uplink? Answer: Rise over Thermal

6. What is the major difference between Rate Switching in R99 and Rate Adaptation in HSUPA? Answer: R99 Rate Switching involves the RNC allocates radio resources while in HSUPA the radio recourses are allocated by the Node B.

Exercises - Answers



7-24



Comments/Notes


lte qualcom

Engineering

qualcomm cdma university

technical data

registered trademarks

rev aviettel telecom

transfer export laws

international training

rev atable of contents

individual training