RADIO ACCESS NETWORKS FOR UMTS - download.e … · RADIO ACCESS NETWORKS FOR UMTS PRINCIPLES AND PRACTICE Chris Johnson Nokia Siemens Networks, UK

RADIO ACCESSNETWORKS FOR UMTSPRINCIPLES AND PRACTICE

Chris Johnson

Nokia Siemens Networks, UK

RADIO ACCESSNETWORKS FOR UMTS

RADIO ACCESSNETWORKS FOR UMTSPRINCIPLES AND PRACTICE

Chris Johnson

Nokia Siemens Networks, UK

Copyright # 2008 John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester,West Sussex PO19 8SQ, England

Telephone (þ44) 1243 779777

Email (for orders and customer service enquiries): [email protected] our Home Page on www.wiley.com

All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system or transmittedin any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, exceptunder the terms of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by theCopyright Licensing Agency Ltd, 90 Tottenham Court Road, London W1T 4LP, UK, without the permission inwriting of the Publisher. Requests to the Publisher should be addressed to the Permissions Department, John Wiley& Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England, or emailed [email protected], or faxed to (þ44) 1243 770620.

Designations used by companies to distinguish their products are often claimed as trademarks. All brand names andproduct names used in this book are trade names, service marks, trademarks or registered trademarks of theirrespective owners. The Publisher is not associated with any product or vendor mentioned in this book. Alltrademarks referred to in the text of this publication are the property of their respective owners.

This publication is designed to provide accurate and authoritative information in regard to the subject mattercovered. It is sold on the understanding that the Publisher is not engaged in rendering professional services. Ifprofessional advice or other expert assistance is required, the services of a competent professional should be sought.

Other Wiley Editorial Offices

John Wiley & Sons Inc., 111 River Street, Hoboken, NJ 07030, USA

Jossey-Bass, 989 Market Street, San Francisco, CA 94103-1741, USA

Wiley-VCH Verlag GmbH, Boschstr. 12, D-69469 Weinheim, Germany

John Wiley & Sons Australia Ltd, 42 McDougall Street, Milton, Queensland 4064, Australia

John Wiley & Sons (Asia) Pte Ltd, 2 Clementi Loop #02-01, Jin Xing Distripark, Singapore 129809

John Wiley & Sons Canada Ltd, 6045 Freemont Blvd, Mississauga, ONT, L5R 4J3, Canada

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not beavailable in electronic books.

Library of Congress Cataloging-in-Publication Data

Johnson, Chris (Chris W.)Radio access networks for UMTS : principles and practice / Chris Johnson.

p. cm.Includes index.ISBN 978-0-470-72405-7 (cloth)

1. Mobile communication systems. I. Title.TK6570.M6J63 2008621.384–dc22 2007040535

British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library

ISBN 978-0-470-72405-7 (HB)

Typeset in 9/11pt Times by Thomson Digital, New Delhi.Printed and bound in Great Britain by Antony Rowe Ltd, Chippenham, England.This book is printed on acid-free paper responsibly manufactured from sustainable forestry in which at least twotrees are planted for each one used for paper production.

www.wiley.com

Contents

Preface ix

Acknowledgements xi

Abbreviations xiii

1 Introduction 1

1.1 Network Architecture 1

1.2 Radio Access Technology 4

1.3 Standardisation 10

2 Flow of Data 13

2.1 Radio Interface Protocol Stacks 13

2.1.1 Radio Interface Control Plane 14

2.1.2 Radio Interface User Plane 19

2.2 RRC Layer 27

2.2.1 RRC States 28

2.2.2 RRC Procedures 54

2.2.3 RRC Messages 56

2.2.4 UE RRC Timers, Counters and Constants 61

2.2.5 Other Functions 67

2.3 RLC Layer 74

2.3.1 Transparent Mode 75

2.3.2 Unacknowledged Mode 77

2.3.3 Acknowledged Mode 81

2.4 MAC Layer 101

2.4.1 Architecture of the MAC Layer 102

2.4.2 Format of MAC PDU 109


2.5 Frame Protocol Layer 112

2.5.1 Dedicated Channels - Data Frames 113

2.5.2 Dedicated Channels - Control Frames 118

2.5.3 Common Channels - Data Frames 121

2.5.4 Common Channels - Control Frames 126

2.6 Physical Layer 127

2.6.1 Physical Layer Processing 128

2.6.2 Spreading, Scrambling and Modulation 144


3 Channel Types 155

3.1 Logical Channels 155

3.2 Transport Channels 158

3.3 Physical Channels 166

3.3.1 Common Pilot Channel (CPICH) 168

3.3.2 Synchronisation Channel (SCH) 172

3.3.3 Primary Common Control Physical Channel (P-CCPCH) 174

3.3.4 Secondary Common Control Physical Channel (S-CCPCH) 176

3.3.5 Paging Indicator Channel (PICH) 182

3.3.6 MBMS Indicator Channel (MICH) 186

3.3.7 Acquisition Indicator Channel (AICH) 188

3.3.8 Physical Random Access Channel (PRACH) 191

3.3.9 Dedicated Physical Channel (DPCH) 204

3.3.10 Fractional Dedicated Physical Channel (F-DPCH) 228

4 Non-Access Stratum 231

4.1 Concepts 231

4.2 Mobility Management 233

4.3 Connection Management 239

4.4 PLMN Selection 244

5 Iub Transport Network 249

5.1 Protocol Stacks 249

5.1.1 Radio Network Control Plane 251

5.1.2 Transport Network Control Plane 253

5.1.3 Transport Network User Plane 257

5.2 Architecture 260

5.3 Overheads 264

5.4 Service Categories 268

6 HSDPA 273

6.1 Concept 273

6.2 HSDPA Bit Rates 278

6.3 PDCP Layer 283

6.4 RLC Layer 284

6.5 MAC-d Entity 287


6.6.1 HS-DSCH Data Frame 289

6.6.2 HS-DSCH Control Frames 292

6.7 Iub Transport 294

6.7.1 ATM Transport Connections 294

6.7.2 Transport Overheads 296

6.8 MAC-hs Entity 300

6.8.1 Flow Control 301

6.8.2 Scheduler 304

6.8.3 Adaptive Modulation and Coding 307

6.8.4 Hybrid Automatic Repeat Request (HARQ) 313

6.8.5 Generation of MAC-hs PDU 320

vi Contents


6.9.1 High Speed Shared Control Channel (HS-SCCH) 323

6.9.2 High Speed Physical Downlink Shared Channel (HS-PDSCH) 329

6.9.3 High Speed Dedicated Physical Control Channel (HS-DPCCH) 332

6.10 Mobility 337

7 HSUPA 343

7.1 Concept 343

7.2 HSUPA Bit Rates 349

7.3 PDCP Layer 355

7.4 RLC Layer 355

7.5 MAC-d Entity 357

7.6 MAC-es/e Entity (UE) 358

7.6.1 E-TFC Selection 359

7.6.2 Hybrid Automatic Repeat Request (HARQ) 368

7.6.3 Generation of MAC-es PDU 371

7.6.4 Generation of MAC-e PDU 372


7.7.1 E-DCH Dedicated Physical Control Channel (E-DPCCH) 376

7.7.2 E-DCH Dedicated Physical Data Channel (E-DPDCH) 378

7.7.3 E-DCH Hybrid ARQ Indicator Channel (E-HICH) 387

7.7.4 E-DCH Relative Grant Channel (E-RGCH) 390

7.7.5 E-DCH Absolute Grant Channel (E-AGCH) 392

7.8 MAC-e Entity (Node B) 394

7.8.1 Packet Scheduler 395

7.8.2 De-multiplexing 399


7.9.1 E-DCH Data Frame 400

7.9.2 Tunnel Congestion Indication Control Frame 401

7.10 MAC-es Entity (RNC) 402

7.11 Mobility 402

8 Signalling Procedures 405

8.1 RRC Connection Establishment 405

8.2 Speech Call Connection Establishment 429

8.2.1 Mobile Originated 430

8.2.2 Mobile Terminated 454

8.3 Video Call Connection Establishment 459

8.3.1 Mobile Originated and Mobile Terminated 460

8.4 Short Message Service (SMS) 469


8.4.2 Mobile Terminated 474

8.5 PS Data Connection Establishment 477


8.6 Soft Handover 501

8.6.1 Inter-Node B 501

8.6.2 Intra-Node B 512

8.7 Inter-System Handover 514

8.7.1 Speech 515

Contents vii

9 Planning 533

9.1 Link Budgets 533

9.1.1 DPCH 535

9.1.2 HSDPA 545

9.1.3 HSUPA 547

9.2 Radio Network Planning 548

9.2.1 Path Loss based Approach 550

9.2.2 3G Simulation based Approach 553

9.3 Scrambling Code Planning 556

9.3.1 Downlink 557

9.3.2 Uplink 560

9.4 Neighbour Planning 561

9.4.1 Intra-Frequency 563

9.4.2 Inter-Frequency 564

9.4.3 Inter-System 566

9.4.4 Maximum Neighbour List Lengths 567

9.5 Antenna Subsystems 572

9.5.1 Antenna Characteristics 573

9.5.2 Dedicated Subsystems 576

9.5.3 Shared Subsystems 578

9.6 Co-siting 578

9.6.1 Spurious Emissions 581

9.6.2 Receiver Blocking 583

9.6.3 Intermodulation 585

9.6.4 Achieving Sufficient Isolation 586

9.7 Microcells 587

9.7.1 RF Carrier Allocation 588

9.7.2 Sectorisation 588

9.7.3 Minimum Coupling Loss 589

9.7.4 Propagation Modelling 590

9.7.5 Planning Assumptions 591

9.8 Indoor Solutions 592

9.8.1 RF Carrier Allocation 593

9.8.2 Sectorisation 593

9.8.3 Active and Passive Solutions 593

9.8.4 Minimum Coupling Loss 594

9.8.5 Leakage Requirements 595

9.8.6 Antenna Placement 596

References 597

Index 599

viii Contents

Preface

This book provides a comprehensive description of the Radio Access Networks for UMTS. It is

intended to address the requirements of both the beginner and the more experienced mobile

telecommunications engineer. An important characteristic is the inclusion of sections from example

log files. More than 180 examples have been included to support the majority of explanations and to

reinforce the reader’s understanding of the key principles. Another important characteristic is the

inclusion of summary bullet points at the start of each section. The reader can use these bullet points

either to gain a high-level understanding prior to reading the main content or for subsequent revision.

The main content is based upon the release 6 version of the 3GPP specifications. Changes since the

release 99 version are described while some of the new features appearing within the release 7 version

are introduced.

Starting from the high-level network architecture, the first sections describe the flow of data between

the network and end user. The functionality and purpose of each protocol stack layer is explained while

the corresponding structure and content of packets are studied. A section is dedicated to describing and

contrasting the sets of logical, transport and physical channels. The increasing importance of the

bandwidth offered by the transport network connecting the population of Node B to the RNC justifies

the inclusion of a dedicated section describing the Iub interface and the associated transport solutions.

Dedicated sections are also included for both HSDPA and HSUPA. The bit rates and functionality

associated with these technologies are described in detail. A relatively large section is used to describe

some of the most important signalling procedures. These include RRC connection establishment,

speech call connection establishment, video call connection establishment, PS data connection

establishment, SMS data transfer, soft handover and inter-system handover. The accompanying

description provides a step-by-step analysis of both the signalling flow and message content. Other

sections focus upon the more practical subjects of link budgets and radio network planning. Topics

include scrambling code planning, neighbour list planning, antenna subsystem design, co-siting,

microcells and indoor solutions.

The content of this book represents the understanding of the author. It does not necessarily represent

the view nor opinion of the author’s employer. Descriptions are intended to be generic and do not

represent the implementation of any individual vendor.

Acknowledgements

The author would like to acknowledge his employer, Nokia Siemens Networks UK Limited for

providing the many opportunities to gain valuable project experience. The author would also like to

thank his managers from within Nokia Siemens Networks UK Limited for supporting participation

within projects which have promoted continuous learning and development. These include Andy King,

Peter Love, Aleksi Toikkanen, Stuart Davis, Mike Lawrence and Chris Foster. The author would also

like to thank Florian Reymond for providing the opportunities to work on global projects within Nokia

Siemens Networks.

The author would like to acknowledge colleagues from within Nokia Siemens Networks who have

supported and encouraged the development of material for this book. These include Poeti Boedhi-

hartono, Simon Browne, Gareth Davies, Martin Elsey, Benoist Guillard, Terence Hoh, Harri Holma,

Steve Hunt, Sean Irons, Phil Pickering, Kenni Rasmussen, Mike Roche, Lorena Serna Gonzalez, Ian

Sharp, Achim Wacker, Volker Wille and Nampol Wimolpitayarat. In addition, the author would like to

thank the managers and colleagues from outside Nokia Siemens Networks who have also supported the

development of this book. These include Mohamed AbdelAziz, Paul Clarkson, Tony Conlan, Patryk

Debicki, Nathan Dyson, Gianluca Formica, Dave Fraley, Ian Miller, Balan Muthiah, Pinaki

Roychowdhury, Adrian Sharples and Ling Soon Leh.

The author would also like to offer special thanks to his parents who provided a perfect working

environment during the weeks spent in Scotland. He would also like to thank them for their continuous

support and encouragement.

The author would like to thank the team at John Wiley & Sons Limited who have made this

publication possible. This team has included Mark Hammond, Sarah Hinton, Katharine Unwin and

Brett Wells.

Comments regarding the content of this book can be sent to [email protected]. These will be

considered when generating material for future editions.

Abbreviations

16QAM 16 Quadrature Amplitude Modulation

3GPP 3rd Generation Partnership Project

4PAM 4 Pulse Amplitude Modulation

64QAM 64 Quadrature Amplitude Modulation

AAL2 ATM Adaptation Layer 2

AAL5 ATM Adaptation Layer 2

ABR Available Bit Rate

AC Access Class

ACIR Adjacent Channel Interference Ratio

ACLR Adjacent Channel Leakage Ratio

ACS Adjacent Channel Selectivity

AI Access Indicator

AICH Access Indicator Channel

ALCAP Access Link Control Application Part

AM Acknowledged Mode

AMC Adaptive Modulation and Coding

AMR Adaptive Multi Rate

APN Access Point Name

ARFCN Absolute Radio Frequency Channel Number

AS Access Stratum

ASC Access Service Class

ASN Abstract Syntax Notation

ATM Asynchronous Transfer Mode

BCC Base station Colour Code

BCCH Broadcast Control Channel

BCD Binary Coded Decimal

BCH Broadcast Channel

BER Bit Error Rate

BFN Node B Frame Number

BLER Block Error Rate

BMC Broadcast/Multicast Control

BSIC Base Station Identity Code

CAC Connection Admission Control

CBC Cell Broadcast Centre

CBR Constant Bit Rate

CBS Cell Broadcast Services

CC Call Control

CCCH Common Control Channel

CCTrCh Coded Composite Transport Channels

CDMA Code Division Multiple Access

CDVT Cell Delay Variation Tolerance

CFN Connection Frame Number

CGI Cell Global Identity

CI Cell Identity

CID Channel Identifier

CIO Cell Individual Offset

CLP Cell Loss Priority

CLR Cell Loss Ratio

CM Compressed Mode

COI Code Offset Indicator

CPCH Common Packet Channel

CPCS Common Part Convergence Sublayer

CPI Common Part Indicator

CPICH Common Pilot Channel

CPS Common Part Sublayer

CQI Channel Quality Indicator

CRC Cyclic Redundancy Check

C-RNTI Cell Radio Network Temporary Identity

CS Circuit Switched

CTCH Common Traffic Channel

CTD Cell Transfer Delay

CTFC Calculated Transport Format Combination

DAS Distributed Antenna System

DCCH Dedicated Control Channel

DCH Dedicated Channel

DDI Data Description Indicator

DPCCH Dedicated Physical Control Channel

DPCH Dedicated Physical Channel

DPDCH Dedicated Physical Data Channel

DRT Delay Reference Time

DRX Discontinous Receive

DSAID Destination Signaling Association Identifier

DSCH Downlink Shared Channel

DTCH Dedicated Traffic Channel

DTX Discontinuous Transmit

E-AGCH E-DCH Absolute Grant Channel

Eb/No Energy per bit/Noise spectral density

ECF Establish Confirm

E-DCH Enhanced Dedicated Channel

E-DPCCH E-DCH Dedicated Physical Control Channel

E-DPDCH E-DCH Dedicated Physical Data Channel

EGPRS Enhanced General Packet Radio Service

E-HICH E-DCH Hybrid ARQ Indicator Channel

xiv Abbreviations

EIRP Effective Isotropic Radiated Power

E-RGCH E-DCH Relative Grant Channel

ERQ Establish Request

E-TFC E-DCH Transport Format Combination

E-TFCI E-DCH Transport Format Combination Indicator

FACH Forward Access Channel

FBI Feedback Information

FDD Frequency Division Duplex

F-DPCH Fractional Dedicated Physical Channel

FSN Frame Sequence Number

FTP File Transfer Protocol

GFR Guaranteed Frame Rate

GGSN Gateway GPRS Support Node

GMM GPRS Mobility Management

GMSK Gaussian Minimum Shift Keying

GPRS General Packet Radio Service

GRAKE Generalised RAKE

GSMS GPRS Short Message Service

GTP-U User plane GPRS Tunnelling Protocol

HARQ Hybrid Automatic Repeat Request

HCS Hierarchical Cell Structure

HEC Header Error Correction

HFN Hyper Frame Number

HLBS Highest Priority Logical Channel Buffer Status

HLID Highest Priority Logical Channel Identity

HLR Home Location Register

HLS Higher Layer Scheduling

HPLMN Home Public Land Mobile Network

H-RNTI HS-DSCH Radio Network Temporary Identity

HSCSD High Speed Circuit Switched Data

HSDPA High Speed Downlink Packet Access

HS-DPCCH High Speed Dedicated Physical Control Channel

HS-DSCH High Speed Downlink Shared Channel

HS-PDSCH High Speed Downlink Shared Channel

HS-SCCH High Speed Shared Control Channel

HSUPA High Speed Uplink Packet Access

ICP IMA Control Protocol

IE Information Element

IETF Internet Engineering Task Force

IMA Inverse Multiplexing for ATM

IMEI International Mobile Equipment Identity

IMSI International Mobile Subscriber Identity

IPDL Idle Period Downlink

IPv4 Internet Protocol version 4

IPv6 Internet Protocol version 6

ITP Initial Transmit Power

Abbreviations xv

ITU International Telecommunications Union

LAC Location Area Code

LAI Location Area Identity

LLC Logical Link Control

LSN Last Sequence Number

MAC Medium Access Control

MAP Mobile Application Part

MBMS Multimedia Broadcast Multicast Services

MBS Maximum Burst Size

MCC Mobile Country Code

MCCH MBMS Control Channel

MCL Minimum Coupling Loss

MCR Minimum Cell Rate

MDC Macro Diversity Combination

MDCR Minimum Desired Cell Rate

MFS Maximum Frame Size

MHA Mast Head Amplifier

MIB Master Information Block

MICH MBMS Indicator Channel

MIMO Multiple Input Multiple Output

MLP MAC Logical channel Priority

MM Mobility Management

MNC Mobile Network Code

MSCH MBMS Scheduling Channel

MSS Maximum Segment Size

MTCH MBMS Traffic Channel

MTU Maximum Transmission Unit

MUD Multi User Detection

NAS Non-access Stratum

NBAP Node B Application Part

NCC Network Colour Code

NI Notification Indicator

NMO Network Mode of Operation

NNI Network to Network Interface

NRT Non Real Time

NSAP Network Service Access Point

NSAPI Network layer Service Access Point Identifier

OSAID Originating Signalling Association Identifier

OTDOA Observed Time Difference of Arrival

PAP Password Authentication Protocol

PCA Power Control Algorithm

PCCH Paging Control Channel

P-CCPCH Primary Common Control Physical Channel

PCH Paging Channel

PCR Peak Cell Rate

xvi Abbreviations

PDCP Packet Data Convergence Protocol

PDH Plesiochronous Digital Hierarchy

PDU Packet Data Unit

PER Packed Encoding Rules

PI Paging Indication

PICH Paging Indication Channel

PLMN Public Land Mobile Network

PRACH Physical Random Access Channel

PS Packet Switched

P-SCH Primary Synchronisation Channel

PSTN Public Switched Telephone Network

P-TMSI Packet Temporary Mobile Subscriber Identity

PWE3 Psuedo Wire Emulation Edge to Edge

QoS Quality of Service

QPSK Quadrature Phase Shift Keying

RAB Radio Access Bearer

RAC Routing Area Code

RACH Random Access Channel

RAI Routing Area Identity

RAN Radio Access Network

RANAP Radio Access Network Application Part

RAT Radio Access Technology

RB Radio Bearer

RDI Restricted Digital Information

RFN RNC Frame Number

RIP Radio Interface Protocol

RL Radio Link

RLC Radio Link Control

RM Rate Matching

RNC Radio Network Controller

RNS Radio Network Sub-system

ROHC Robust Header Compression

RPP Recovery Period Power control

RRC Radio Resource Control

RRM Radio Resource Management

RSCP Received Signal Code Power

RSN Re-transmission Sequence Number

RSSI Received Signal Strength Indicator

RT Real Time

RV Redundancy Version

SA Service Area

SAC Service Area Code

SAI Service Area Identity

SAR Segmentation and Reassembly

SAW Stop and Wait

S-CCPCH Secondary Common Control Channel

SCH Synchronisation Channel

Abbreviations xvii

SCR Sustainable Cell Rate

SDH Synchronous Digital Hierarchy

SDU Service Data Unit

SEAL Simple and Efficient ATM Adaptation Layer

SF Spreading Factor

SFN System Frame Number

SGSN Serving GPRS Support Node

SI Scheduling Information

SIB System Information Block

SID Size Index Identifier

SIR Signal to Interference Ratio

SM Session Management

SM-AL Short Message Application Layer

SM-RL Short Message Relay Layer

SMS Short Message Service

SM-TL Short Message Transfer Layer

SONET Synchronous Optical Networking

SRB Signalling Radio Bearer

SRNS Serving Radio Network Sub-system

S-RNTI SRNC Radio Network Temporary Identity

SS Supplementary Services

SSADT Service Specific Assured Data Transfer

SSCF Service Specific Coordination Function

S-SCH Secondary Synchronisation Channel

SSCOP Service Specific Connection Orientated Protocol

SSCS Service Specific Convergence Sublayer

SSDT Site Selection Diversity Transmit

SSSAR Service Specific Segmentation and Reassembly

SSTED Service Specific Transmission Error Detection

STTD Space Time Transmit Diversity

SUFI Super Field

TB Transport Block

TBS Transport Block Set

TCP Transmission Control Protocol

TCTF Target Channel Type Field

TDD Time Division Duplex

TDMA Time Division Multiple Access

TEBS Total E-DCH Buffer Status

TF Transport Format

TFC Transport Format Combination

TFCI Transport Format Combination Indicator

TFCS Transport Format Combination Set

TFI Transport Format Indicator

TFO Tandem Free Operation

TFS Transport Format Set

TGD Transmission Gap Distance

TGL Transmission Gap Length

TGPL Transmission Gap Pattern Length

TGPRC Transmission Gap Pattern Repetition Count

xviii Abbreviations

TGPS Transmission Gap Pattern Sequence

TGPSI Transmission Gap Pattern Sequence Identifier

TGSN Transmission Gap Starting Slot Number

THP Traffic Handling Priority

TM Transparent Mode

TMSI Temporary Mobile Subscriber Identity

toAWE Time of Arrival Window End point

toAWS Time of Arrival Window Start point

TPC Transmit Power Control

TPDU Transfer Protocol Data Unit

TR Technical Report

TrFO Transcoder Free Operation

TS Technical Specification

TSN Transmission Sequence Number

TSTD Time Switched Transmit Diversity

TTI Transmission Time Interval

TTL Time To Live

UARFCN UTRA Absolute Radio Frequency Channel Number

UBR Unspecified Bit Rate

UDI Unrestricted Digital Information

UE User Equipment

UEA UMTS Encryption Algorithm

UIA UMTS Integrity protection Algorithm

UM Unacknowledged Mode

UMTS Universal Mobile Telecommunications System

UNI User to Network Interface

UPH UE Power Headroom

URA UTRAN Registration Area

U-RNTI UTRAN Radio Network Temporary Identity

USIM Universal Subscriber Identity Module

UTRAN UMTS Terrestrial Radio Access Network

UUI User to User Indication

VBR Variable Bit Rate

VCC Virtual Channel Connection

VPC Virtual Path Connection

VCI Virtual Channel Identifier

VoIP Voice over IP

VPI Virtual Path Identifier

VPLMN Visited Public Land Mobile Network

WCDMA Wideband Code Division Multiple Access

Abbreviations xix

1

Introduction

1.1 Network Architecture

� The RAN includes RNC, Node B and UE. RNC are connected to Node B using the Iub interface.

Neighbouring RNC are connected using the Iur interface. UE are connected to Node B using the

Uu interface. The RAN is connected to the CN using the Iu interface.

� Each Node B has a controlling RNC and each UE connection has a serving RNC. The serving

RNC provides the Iu connection to the CN. Drift RNC can be used by UE connections in addition

to the serving RNC.

The network architecture defines the network elements and the way in which those network elements

are interconnected. Figure 1.1 illustrates a section of the network architecture for UMTS. This book

focuses upon the Radio Access Network (RAN) rather than the core network. The RAN represents the

section of the network which is closest to the end-user and which includes the air-interface.

The RAN includes the Radio Network Controller (RNC), the Node B and the User Equipment (UE).

The MSC and SGSN are part of the core network. An example UMTS network could include thirty

RNC, ten thousand Node B and five million UE. The UE communicate with the Node B using the air-

interface which is known as the Uu interface. The Node B communicates with the RNC using a

transmission link known as the Iub interface. The RNC communicates with the core network using a

transmission link known as the Iu interface. There is an Iu interface for the Circuit Switched (CS) core

network and an Iu interface for the Packet Switched (PS) core network. The capacity of the Iu interface

is significantly greater than the capacity of the Iub interface because the Iu has to be capable of

supporting a large quantity of Node B whereas the Iub supports only a single Node B. Neighbouring

RNC can be connected using the Iur interface. The Iur interface is particularly important for UE which

are moving from the coverage area of one RNC to the coverage area of another RNC.

Each Node B has a controlling RNC and each UE connection has a serving RNC. The controlling

RNC for a Node B is the RNC which terminates the Iub interface. The serving RNC for a UE

connection is the RNC which provides the Iu interface to the core network. Figure 1.2 illustrates an

example for a packet switched connection and four Node B.

RNC 1 is the controlling RNC for Node B 1 and 2 whereas RNC 2 is the controlling RNC for Node

B 3 and 4. The controlling RNC is responsible for managing its Node B. RNC 1 is the serving RNC for

the packet switched connection because it provides the connection to the PS core network. The serving

Radio Access Networks for UMTS Chris Johnson

# 2008 John Wiley & Sons, Ltd

RNC is responsible for managing its UE connections. As this example illustrates, an RNC can be

categorised as both controlling and serving.

In the case of UE mobility, an RNC can also be categorised as a drift RNC. If a UE starts its

connection within the coverage area of RNC 1 then that RNC becomes the serving RNC and will

provide the connection to the core network. If the UE subsequently moves into the coverage area of the

second RNC then the UE can be simultaneously connected to Node B controlled by both RNC 1 and

RNC 2. This represents a special case of soft handover, i.e. inter-RNC soft handover. This scenario is

illustrated in Figure 1.3. In general, soft handover allows UE to simultaneously connect to multiple

Node B. This is in contrast to hard handover in which case the connection to the first Node B is broken

before the connection to the second Node B is established. Soft handover helps to provide seamless

mobility to active connections as UE move throughout the network and also helps to improve the RF

conditions at cell edge where signal strengths are generally low and cell dominance is poor. In the case

of inter-RNC soft handover, the UE is simultaneously connected to multiple RNC. The example

illustrated in Figure 1.3 is based upon two RNC but it is possible for UE to be connected to more than

two RNC if the RNC coverage boundaries are designed to allow it. In this example, RNC 1 is the

serving RNC because it provides the Iu connection to the core network. RNC 2 is a drift RNC because

it is participating in the connection, but it is not providing the connection to the core network. A single

connection can have only one serving RNC, but can have more than one drift RNC.

Communication between the UE and the serving RNC makes use of the Iur interface when a drift

RNC is involved. The Iur interface is an optional transmission link and is not always present. For

Figure 1.1 UMTS network architecture

2 Radio Access Networks for UMTS

example, if a network is based upon RNC from two different network vendors then it is possible

that those RNC are not completely compatible and the Iur interface is not deployed. If the Iur interface

is not present then inter-RNC soft handover is not possible because there is no way to transfer

information from the drift RNC to the serving RNC. In this case, the UE has to complete a hard

handover when moving into the coverage area of the second RNC. The inter-RNC hard handover

procedure allows the second RNC to become the serving RNC while the first RNC no longer

participates in the connection.

Assuming that the Iur interface is present and that a UE continues to move into the coverage area of

the drift RNC then it becomes inefficient to leave the original RNC as the serving RNC. There will be a

time when the UE is not connected to any Node B which are controlled by the serving RNC and all

information is transferred across the Iur interface. In this scenario it makes sense to change the drift

RNC into the serving RNC and to remove the original RNC from the connection. This procedure of

changing a drift RNC into the serving RNC is known as serving RNC relocation, or Serving Radio

Network Subsystem (SRNS) relocation. A Radio Network Subsystem (RNS) is defined as an RNC and

the collection of Node B connected to that RNC.

The radio network plan defines the location and configuration of the Node B. The density of Node B

should be sufficiently great to achieve the target RF coverage performance. If the density of Node B is

not sufficiently great then there may be locations where the UE does not have sufficient transmit power

to be received by a Node B, i.e. coverage is uplink limited. Alternatively, there may be locations where

a Node B does not have sufficient transmit power to be received by a UE, i.e. coverage is downlink

limited. The connection from the UE to the Node B is known as the uplink or reverse link whereas the

connection from the Node B to the UE is known as the downlink or forward link.

Figure 1.2 Categorising controlling and serving RNC

Introduction 3

1.2 Radio Access Technology

� The air-interface is based upon full duplex FDD with a nominal channel bandwidth of 5 MHz.

Channel separations can be <5 MHz because the occupied bandwidth is <5 MHz.

� Operators are typically assigned between 2 and 4 UMTS channels.

� A frequency reuse of 1 is applied allowing both soft and hard handovers.

� Multiple access is based upon Wideband CDMA with a chip rate of 3.84 Mcps.

� The release 7 version of the 3GPP specifications defines 9 operating bands.

� The most common Node B configuration for initial network deployment is three sectors with

1 RF carrier, i.e. a 1þ1þ1 Node B configuration.

� HSDPA and HSUPA offer significantly increased throughput performance.

The UMTS air-interface makes use of separate RF carriers for the uplink and downlink. This

approach is known as Frequency Division Duplexing (FDD) and is in contrast to technologies which

use the same RF carrier for both the uplink and downlink. Using the same RF carrier for both the uplink

and downlink requires time sharing, i.e. the RF carrier is assigned to the uplink for a period of time and

then the RF carrier is assigned to the downlink for a period of time. This approach is known as Time

Division Duplexing (TDD). A set of operating bands have been standardised for use by the UMTS air-

interface. These operating bands are presented in Table 1.1.

Figure 1.3 Categorising serving and drift RNC


The availability of each operating band depends upon existing spectrum allocations and the strategy

of the national regulator. The majority of countries deploying UMTS make use of operating band I as

the core set of frequencies. The remaining operating bands can either be used as extension bands or can

be used by countries where operating band I is not available. For example, operating band II is used in

North America because operating band I is not available. Operating band II cannot be used as an

extension for operating band I because the two sets of frequencies overlap with one another. Operating

band VIII is commonly viewed as an extension band which benefits from improved coverage

performance as a result of using lower frequencies. Operating band VIII is the same as the extended

GSM 900 band and so its use for UMTS may require re-farming of any existing GSM 900 allocations.

Each operating band is divided into 5 MHz channels. Operating bands I and II have 12 uplink

channels and 12 downlink channels. Operating band I has a frequency difference of 190 MHz between

the uplink and downlink channels whereas operating band II has a frequency difference of 80 MHz.

The difference between the uplink and downlink frequencies is known as the duplex spacing. Large

duplex spacings cause more significant differences between the uplink and downlink path loss. The

uplink is assigned the lower set of frequencies because the path loss is lower and link budgets are

traditionally uplink limited. Small duplex spacings make it more difficult to implement transmit and

receive filtering within the UE. Transmit and receive filtering is less of an issue within the Node B

because larger and more expensive filters can be used. The uplink and downlink channels belonging to

operating band I are illustrated in Figure 1.4.

National regulators award the 5 MHz channels to operators. Those operators then become

responsible for deploying and operating UMTS networks. It is common to award between two and

four channels to each operator. For example, a country which has four operators could have three

channels assigned to each operator. It is possible that not all twelve channels are available and only a

subset of the channels are allocated. Once an operator has been assigned a subset of the 5 MHz

channels then the operator has some flexibility in terms of configuring the precise centre frequencies of

its RF carriers. A UMTS RF carrier occupies less than 5 MHz and so the frequency separation between

adjacent RF carriers can also be less than 5 MHz. An example deployment strategy is illustrated in

Figure 1.4. In this example, three 5 MHz UMTS channels have been awarded to operator 2 while the

adjacent channels have been awarded to operators 1 and 3. Adjacent channel interference mechanisms,

e.g. non-ideal transmit filtering and non-ideal receive filtering are less significant when RF carriers are

co-sited, or at least coordinated. Operator 2 is likely to co-site adjacent RF carriers which are assigned

to the macrocell network (multiple RF carriers assigned to the same Node B) and is likely to coordinate

adjacent RF carriers which are assigned to the microcell layer or to any indoor solutions. The Node B

belonging to operators 1 and 3 may be neither co-sited nor coordinated with the Node B belonging to

operator 2. Operator 2 can help to reduce the potential for any adjacent channel interference by

reducing the frequency separation between its own RF carriers. This allows an increased frequency

Table 1.1 UMTS operating bands for the FDD air-interface

Operating Uplink Downlink Duplex spacing Equivalent

Band (MHz) (MHz) (MHz) 2G band

I 1920–1980 2110–2170 190

II 1850–1910 1930–1990 80 PCS 1900

III 1710–1785 1805–1880 95 DCS 1800

IV 1710–1755 2110–2155 400

V 824–849 869–894 45 GSM 850

VI 830–840 875–885 45

VII 2500–2570 2620–2690 120

VIII 880–915 925–960 45 E-GSM

IX 1749.9–1784.9 1844.9–1879.9 95

Introduction 5

separation from the adjacent operators. The RF carriers within operating band I have been standardised

using a 200 kHz channel raster. This means that the centre frequency of each RF carrier can be adjusted

with a resolution of 200 kHz.

The Node B configuration defines characteristics such as the number of sectors and the number of

RF carriers. The most common configuration for initial network deployment is three sectors with one

RF carrier. This is known as a 1þ1þ1 Node B configuration. It requires at least three antennas to be

connected to the Node B cabinet, i.e. at least one antenna serving each sector. If uplink receive diversity

or downlink transmit diversity is used then either six single element antennas or three dual element

antennas are required. If six single element antennas are used then there should be spatial isolation

between the two antennas belonging to each sector. This tends to be less practical than using three dual

element antennas. It is common to use cross polar antennas which accommodate two antenna elements

within each antenna housing. In this case, isolation is achieved in the polarisation domain rather than

the spatial domain. Figure 1.5 illustrates an example 1þ1þ1 Node B configuration using cross polar

antennas.

When diversity is used then a separate RF feeder is required for each diversity branch. A 1þ1þ1

Node B with uplink receive diversity requires six RF feeders to connect the antennas to the Node B

cabinet. Likewise, if Mast Head Amplifiers (MHA) are used then six of them would be required. The

1þ1þ1 Node B configuration has three logical cells, i.e. a logical cell is associated with each sector of

the Node B. When the capacity of a single RF carrier becomes exhausted then it is common to upgrade

to a second RF carrier. The Node B configuration is then known as a 2þ2þ2. This configuration has

three sectors, but now has two RF carriers and six logical cells. Alternatively, a six sector single RF

carrier configuration could be deployed which would be known as a 1þ1þ1þ1þ1þ1. This config-

uration also has six logical cells but has six sectors and 1 RF carrier.

When a UMTS operator deploys a single RF carrier then that carrier must be shared between all

users of the network and the frequency re-use is 1, i.e. all cells make use of the same RF carrier. GSM

networks make use of frequency re-use patterns to assign different RF carriers to neighbouring cells.

For example, a frequency re-use of 12 means that the radio network is planned in clusters of 12 cells

and each cell within a cluster can use 1/12th of the available RF carriers. This type of approach helps to

reduce co-channel interference, but leads to a requirement for hard handovers and a relatively large

Figure 1.4 UMTS FDD operating band I


number of RF carriers. GSM channels have a bandwidth of 200 kHz and so it is possible to place

25 GSM channels within the bandwidth of a single UMTS channel. The use of a wide bandwidth and a

frequency re-use of 1 for UMTS provides benefits in terms of receiver sensitivity and spectrum

efficiency. The air-interface of a single UMTS cell can support approximately 50 speech users when

assuming the maximum Adaptive Multi-Rate (AMR) bit rate of 12.2 kbps. A single GSM RF carrier

can support a maximum of 8 speech users when assuming Full Rate (FR) connections. This means that

5 MHz of GSM spectrum can support a maximum of 200 speech users (ignoring the impact of the

broadcast channel which in practise would reduce the maximum number of GSM speech users).

Assuming a frequency reuse of 10 reduces this figure to 20 speech users per 5 MHz in contrast to the 50

speech users supported by UMTS. The spectrum efficiency of GSM can approach that of UMTS when

using small frequency re-use patterns which require more careful planning to avoid co-channel

interference. Frequency hopping can also be used to improve the performance and spectrum efficiency

of GSM. The number of speech users supported by both UMTS and GSM can be increased by

decreasing the bit rates assigned to each connection. The UMTS AMR codec supports bit rates ranging

from 4.75 to 12.2 kbps. The GSM Half Rate (HR) feature may be used to reduce the GSM speech

bit rate.

GSM RF carriers are shared between multiple connections using Time Division Multiple Access

(TDMA). A GSM radio frame is divided into eight time slots and these time slots can be assigned to

different connections. An RF carrier belonging to a cell is never simultaneously assigned to more than

one connection. A GSM speech connection is assigned different time slots within the radio frame for

the uplink and downlink, i.e. the GSM MS does not have to simultaneously transmit and receive. This

approach is known as half-duplex and tends to make the MS design easier and less expensive. GSM

Figure 1.5 Example 1þ1þ1 Node B configuration

Introduction 7

base stations have to simultaneously transmit and receive because they serve multiple connections and

the uplink time slot of one connection can coincide with the downlink time slot of another connection.

This is known as full-duplex operation.

UMTS RF carriers are shared between multiple connections using Code Division Multiple Access

(CDMA). CDMA allows multiple connections to simultaneously use the same RF carrier. Instead of

being assigned time slots, connections are assigned codes. These codes are used to mask the transmitted

signal and allow the receiver to distinguish between signals belonging to different connections. The RNC

assigns codes to both the uplink and downlink during the establishment of a connection. The version of

CDMA used for UMTS is known as Wideband CDMA (WCDMA) because the bandwidth is relatively

large compared with earlier CDMA systems. WCDMA connections are able to use all time slots in both

the uplink and downlink directions. This means that WCDMA is full-duplex rather than half-duplex

because UE must be capable of simultaneously transmitting and receiving.

The WCDMA air-interface makes use of two types of code in both the uplink and downlink.

Channelisation codes are used to increase the bandwidth of the connection subsequent to physical layer

processing at the transmitter. These codes are sometimes referred to as spreading codes. For example, a

connection could have a bit rate of 240 kbps after physical layer processing. Each individual bit would

then be multiplied by a 64 chip channelisation code. This would increase the bit rate of 240 kbps by a

factor of 64 to a chip rate of 3.84Mcps. The chip rate of 3.84Mbps is standardised for WCDMA and all

connections have the same chip rate after spreading. If the bit rate after layer 1 processing had been

480 kbps then each individual bit would have been multiplied by a 32 chip channelisation code. This

would have increased the bit rate of 480 kbps by a factor of 32 to a chip rate of 3.84Mcps. The chip rate

of 3.84Mcps defines the approximate bandwidth of the WCDMA signal in the frequency domain, i.e. the

approximate bandwidth after baseband filtering is 3.84MHz. Once the transmitted signal has been spread

by a channelisation code then it is multiplied by a scrambling code. Scrambling codes have a chip rate of

3.84Mcps and do not change the chip rate of the already spread signal. In the downlink direction,

channelisation codes are used to distinguish between different connections and scrambling codes are used

to distinguish between different cells, i.e. each connection within a cell is assigned a different

channelisation code and each cell within the same geographic area is assigned a different scrambling

code. In the uplink direction, channelisation codes are used to distinguish between the different physical

channels transmitted by a single UE and scrambling codes are used to distinguish between different UE.

Table 1.2 summarises some of the most important characteristics of the GSM and UMTS air-

interfaces.

Table 1.2 Comparison of GSM and UMTS air-interfaces

GSM WCDMA

Duplexing FDD FDD

Multiple access TDMA CDMA

MS transmit and receive Half-duplex Full-duplex

Handover Hard Hard and soft

Frequency re-use 4–18 1

Channel bandwidth 200 kHz 5 MHz

RF carrier bandwidth 200 kHz 3.84 MHz

Typical maximum bit rates GSM 9.6 kbps DPCH 403.2 kbps

HSCSD 43.2 kbps HSDPA 7.2Mbps

GPRS 62.4 kbps HSUPA 1.44Mbps

EGPRS 179.2 kbps

Power control rate 2 Hz or lower 1500 Hz

Typical maximum uplink transmit power 33 dBm 24 dBm

Typical minimum uplink transmit power 5 dBm �50 dBm


Documents

RADIO ACCESS NETWORKS FOR UMTS - download.e … · RADIO ACCESS NETWORKS FOR UMTS PRINCIPLES AND PRACTICE Chris Johnson Nokia Siemens Networks, UK