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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Following on from the successful first edition (March 2012), this book gives a clear explanation of what LTE does and how it works. The content is expressed at a systems level, offering readers the opportunity to grasp the key factors that make LTE the hot topic amongst vendors and operators across the globe. The book assumes no more than a basic knowledge of mobile telecommunication systems, and the reader is not expected to have any previous knowledge of the complex mathematical operations that underpin LTE.
This second edition introduces new material for the current state of the industry, such as the new features of LTE in Releases 11 and 12, notably coordinated multipoint transmission and proximity services; the main short- and long-term solutions for LTE voice calls, namely circuit switched fallback and the IP multimedia subsystem; and the evolution and current state of the LTE market. It also extends some of the material from the first edition, such as inter-operation with other technologies such as GSM, UMTS, wireless local area networks and cdma2000; additional features of LTE Advanced, notably heterogeneous networks and traffic offloading; data transport in the evolved packet core; coverage and capacity estimation for LTE; and a more rigorous treatment of modulation, demodulation and OFDMA. The author breaks down the system into logical blocks, by initially introducing the architecture of LTE, explaining the
techniques used for radio transmission and reception and the overall operation of the system, and concluding with more specialized topics such as LTE voice calls and the later releases of the specifications. This methodical approach enables readers to move on to tackle the specifications and the more advanced texts with confidence.
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Table of Contents
Cover
Title Page
Copyright
Dedication
Preface
Acknowledgements
List of Abbreviations
Chapter 1: Introduction
1.1 Architectural Review of UMTS and GSM
1.2 History of Mobile Telecommunication Systems
1.3 The Need for LTE
1.4 From UMTS to LTE
1.5 From LTE to LTE-Advanced
1.6 The 3GPP Specifications for LTE
References
Chapter 2: System Architecture Evolution
2.1 High-Level Architecture of LTE
2.2 User Equipment
2.3 Evolved UMTS Terrestrial Radio Access Network
2.4 Evolved Packet Core
2.5 Communication Protocols
2.6 Example Signalling Flows
2.7 Bearer Management
2.8 State Diagrams
2.9 Spectrum Allocation
References
Chapter 3: Digital Wireless Communications
3.1 Radio Transmission and Reception
3.2 Radio Transmission in a Mobile Cellular Network
3.3 Impairments to the Received Signal
3.4 Error Management
References
Chapter 4: Orthogonal Frequency Division Multiple Access
4.1 Principles of OFDMA
4.2 Benefits and Additional Features of OFDMA
4.3 Single Carrier Frequency Division Multiple Access
References
Chapter 5: Multiple Antenna Techniques
5.1 Diversity Processing
5.2 Spatial Multiplexing
5.3 Beamforming
References
Chapter 6: Architecture of the LTE Air Interface
6.1 Air Interface Protocol Stack
6.2 Logical, Transport and Physical Channels
6.3 The Resource Grid
6.4 Multiple Antenna Transmission
6.5 Resource Element Mapping
References
Chapter 7: Cell Acquisition
7.1 Acquisition Procedure
7.2 Synchronization Signals
7.3 Downlink Reference Signals
7.4 Physical Broadcast Channel
7.5 Physical Control Format Indicator Channel
7.6 System Information
7.7 Procedures after Acquisition
References
Chapter 8: Data Transmission and Reception
8.1 Data Transmission Procedures
8.2 Transmission of Scheduling Messages on the PDCCH
8.3 Data Transmission on the PDSCH and PUSCH
8.4 Transmission of Hybrid ARQ Indicators on the PHICH
8.5 Uplink Control Information
8.6 Transmission of Uplink Control Information on the PUCCH
8.7 Uplink Reference Signals
8.8 Power Control
8.9 Discontinuous Reception
References
Chapter 9: Random Access
9.1 Transmission of Random Access Preambles on the PRACH
9.2 Non-Contention-Based Procedure
9.3 Contention-Based Procedure
References
Chapter 10: Air Interface Layer 2
10.1 Medium Access Control Protocol
10.2 Radio Link Control Protocol
10.3 Packet Data Convergence Protocol
References
Chapter 11: Power-On and Power-Off Procedures
11.1 Power-On Sequence
11.2 Network and Cell Selection
11.3 RRC Connection Establishment
11.4 Attach Procedure
11.5 Detach Procedure
References
Chapter 12: Security Procedures
12.1 Network Access Security
12.2 Network Domain Security
References
Chapter 13: Quality of Service, Policy and Charging
13.1 Policy and Charging Control
13.2 Policy and Charging Control Architecture
13.3 Session Management Procedures
13.4 Data Transport in the Evolved Packet Core
13.5 Charging and Billing
References
Chapter 14: Mobility Management
14.1 Transitions between Mobility Management States
14.2 Cell Reselection in RRC_IDLE
14.3 Measurements in RRC_CONNECTED
14.4 Handover in RRC_CONNECTED
References
Chapter 15: Inter-operation with UMTS and GSM
15.1 System Architecture
15.2 Power-On Procedures
15.3 Mobility Management in RRC_IDLE
15.4 Mobility Management in RRC_CONNECTED
References
Chapter 16: Inter-operation with Non-3GPP Technologies
16.1 Generic System Architecture
16.2 Generic Signalling Procedures
16.3 Inter-Operation with cdma2000 HRPD
References
Chapter 17: Self-Optimizing Networks
17.1 Self-Configuration of an eNB
17.2 Inter-Cell Interference Coordination
17.3 Mobility Management
17.4 Radio Access Network Information Management
17.5 Drive Test Minimization
References
Chapter 18: Enhancements in Release 9
18.1 Multimedia Broadcast/Multicast Service
18.2 Location Services
18.3 Other Enhancements in Release 9
References
Chapter 19: LTE-Advanced and Release 10
19.1 Carrier Aggregation
19.2 Enhanced Downlink MIMO
19.3 Enhanced Uplink MIMO
19.4 Relays
19.5 Heterogeneous Networks
19.6 Traffic Offload Techniques
19.7 Overload Control for Machine-Type Communications
References
Chapter 20: Releases 11 and 12
20.1 Coordinated Multipoint Transmission and Reception
20.2 Enhanced Physical Downlink Control Channel
20.3 Interference Avoidance for in Device Coexistence
20.4 Machine-Type Communications
20.5 Mobile Data Applications
20.6 New Features in Release 12
20.7 Release 12 Studies
References
Chapter 21: Circuit Switched Fallback
21.1 Delivery of Voice and Text Messages over LTE
21.2 System Architecture
21.3 Attach Procedure
21.4 Mobility Management
21.5 Call Setup
21.6 SMS over SGs
21.7 Circuit Switched Fallback to cdma2000 1xRTT
21.8 Performance of Circuit Switched Fallback
References
Chapter 22: VoLTE and the IP Multimedia Subsystem
22.1 Introduction
22.2 Hardware Architecture of the IMS
22.3 Signalling Protocols
22.4 Service Provision in the IMS
22.5 VoLTE Registration Procedure
22.6 Call Setup and Release
22.7 Access Domain Selection
22.8 Single Radio Voice Call Continuity
22.9 IMS Centralized Services
22.10 IMS Emergency Calls
22.11 Delivery of SMS Messages over the IMS
References
Chapter 23: Performance of LTE and LTE-Advanced
23.1 Peak Data Rates of LTE and LTE-Advanced
23.2 Coverage of an LTE Cell
23.3 Capacity of an LTE Cell
23.4 Performance of Voice over IP
References
Bibliography
Index
End User License Agreement
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Guide
Table of Contents
List of Illustrations
Figure 1.1
Figure 1.2
Figure 1.3
Figure 1.4
Figure 1.5
Figure 1.6
Figure 1.7
Figure 1.8
Figure 1.9
Figure 1.10
Figure 2.1
Figure 2.2
Figure 2.3
Figure 2.4
Figure 2.5
Figure 2.6
Figure 2.7
Figure 2.8
Figure 2.9
Figure 2.10
Figure 2.11
Figure 2.12
Figure 2.13
Figure 2.14
Figure 2.15
Figure 2.16
Figure 2.17
Figure 2.18
Figure 2.19
Figure 2.20
Figure 2.21
Figure 2.22
Figure 2.23
Figure 2.24
Figure 2.25
Figure 2.26
Figure 3.1
Figure 3.2
Figure 3.3
Figure 3.4
Figure 3.5
Figure 3.6
Figure 3.7
Figure 3.8
Figure 3.9
Figure 3.10
Figure 3.11
Figure 3.12
Figure 3.13
Figure 3.14
Figure 3.15
Figure 3.16
Figure 4.1
Figure 4.2
Figure 4.3
Figure 4.4
Figure 4.5
Figure 4.6
Figure 4.7
Figure 4.8
Figure 4.9
Figure 4.10
Figure 4.11
Figure 4.12
Figure 4.13
Figure 5.1
Figure 5.2
Figure 5.3
Figure 5.4
Figure 5.5
Figure 5.6
Figure 5.7
Figure 5.8
Figure 5.9
Figure 5.10
Figure 5.11
Figure 5.12
Figure 6.1
Figure 6.2
Figure 6.3
Figure 6.4.
Figure 6.5.
Figure 6.6.
Figure 6.7
Figure 6.8
Figure 6.9
Figure 6.10
Figure 6.11
Figure 7.1
Figure 7.2
Figure 7.3
Figure 7.4
Figure 8.1
Figure 8.2
Figure 8.3
Figure 8.4
Figure 8.5
Figure 8.6
Figure 8.7
Figure 8.8
Figure 8.9
Figure 8.10
Figure 8.11
Figure 8.12
Figure 8.13
Figure 9.1
Figure 9.2
Figure 9.3
Figure 10.1
Figure 10.2
Figure 10.3
Figure 10.4
Figure 10.5
Figure 10.6
Figure 10.7
Figure 10.8
Figure 10.9
Figure 10.10
Figure 11.1
Figure 11.2
Figure 11.3
Figure 11.4
Figure 11.5
Figure 11.6
Figure 11.7
Figure 11.8
Figure 11.9
Figure 11.10
Figure 11.11
Figure 12.1
Figure 12.2
Figure 12.3
Figure 12.4
Figure 12.5
Figure 12.6
Figure 12.7
Figure 12.8
Figure 12.9
Figure 13.1
Figure 13.2
Figure 13.3
Figure 13.4
Figure 13.5
Figure 13.6
Figure 13.7
Figure 13.8
Figure 13.9
Figure 13.10
Figure 13.11
Figure 13.12
Figure 13.13
Figure 13.14
Figure 14.1
Figure 14.2
Figure 14.3
Figure 14.4
Figure 14.5
Figure 14.6
Figure 14.7
Figure 14.8
Figure 14.9
Figure 14.10
Figure 15.1
Figure 15.2
Figure 15.3
Figure 15.4
Figure 15.5
Figure 15.6
Figure 15.7
Figure 15.8
Figure 16.1
Figure 16.2
Figure 16.3
Figure 16.4
Figure 16.5
Figure 16.6
Figure 16.7
Figure 16.8
Figure 16.9
Figure 16.10
Figure 16.11
Figure 17.1
Figure 17.2
Figure 17.3
Figure 17.4
Figure 17.5
Figure 17.6
Figure 18.1
Figure 18.2
Figure 18.3
Figure 18.4
Figure 18.5
Figure 18.6
Figure 19.1
Figure 19.2
Figure 19.3
Figure 19.4
Figure 19.5
Figure 19.6
Figure 19.7
Figure 19.8
Figure 19.9
Figure 19.10
Figure 19.11
Figure 19.12
Figure 19.13
Figure 20.1
Figure 20.2
Figure 20.3
Figure 20.4
Figure 20.5
Figure 20.6
Figure 20.7
Figure 21.1
Figure 21.2
Figure 21.3
Figure 21.4
Figure 21.5
Figure 21.6
Figure 21.7
Figure 21.8
Figure 21.9
Figure 21.10
Figure 21.11
Figure 21.12
Figure 21.13
Figure 21.14
Figure 21.15
Figure 22.1
Figure 22.2
Figure 22.3
Figure 22.4
Figure 22.5
Figure 22.6
Figure 22.7
Figure 22.8
Figure 22.9
Figure 22.10
Figure 22.11
Figure 22.12
Figure 22.13
Figure 22.14
Figure 22.15
Figure 22.16
Figure 22.17
Figure 22.18
Figure 22.19
Figure 22.20
Figure 22.21
Figure 22.22
Figure 22.23
Figure 23.1
Figure 23.2
Figure 23.3
Figure 23.4
List of Tables
Table 1.1
Table 1.2
Table 1.3
Table 1.4
Table 1.5
Table 2.1
Table 2.2
Table 2.3
Table 2.4
Table 6.1
Table 6.2.
Table 6.3
Table 6.4.
Table 6.5.
Table 6.6.
Table 6.7.
Table 6.8
Table 6.9
Table 7.1
Table 7.2
Table 8.1
Table 8.2
Table 8.3
Table 8.4
Table 8.5
Table 8.6
Table 8.7
Table 9.1
Table 10.1
Table 13.1
Table 13.2
Table 13.3
Table 14.1
Table 15.1
Table 19.1
Table 19.2
Table 19.3
Table 22.1
Table 22.2
Table 22.3
Table 22.4
Table 23.1
Table 23.2
Table 23.3
Table 23.4
Table 23.5
Table 23.7
AN INTRODUCTION TO LTE
LTE, LTE-ADVANCED, SAE, VoLTE AND 4G MOBILE COMMUNICATIONS
Second Edition
Christopher Cox
Director, Chris Cox Communications Ltd, UK
This edition first published 2014
© 2014 John Wiley & Sons, Ltd
Registered office
John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom
For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com.
The right of the author to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher.
Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.
Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book.
Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. It is sold on the understanding that the publisher is not engaged in rendering professional services and neither the publisher nor the author shall be liable for damages arising herefrom. If professional advice or other expert assistance is required, the services of a competent professional should be sought.
Library of Congress Cataloging-in-Publication Data
Cox, Christopher (Christopher Ian), 1965-
An introduction to LTE LTE, LTE-advanced, SAE, VoLTE and 4G mobile communications / Christopher Cox.
pages cm
Includes index.
ISBN 978-1-118-81803-9 (cloth)
1. Long-Term Evolution (Telecommunications) 2. Mobile communication systems—Standards. I. Title.
TK5103.48325.C693 2014
621.3845′6—dc23
2014007432
A catalogue record for this book is available from the British Library.
ISBN:9781118818039
To my nieces, Louise and Zoe
Preface
This book is about the world's dominant 4G mobile telecommunication system, LTE.
In writing the book, my aim has been to give the reader a concise, system level introduction to the technology that LTE uses. The book covers the whole of the system, both the techniques used for radio communication between the base station and the mobile phone, and the techniques used to transfer data and signalling messages across the network. I have avoided going into excessive detail, which is more appropriate for specialized treatments of individual topics and for the LTE specifications themselves. Instead, I hope that the reader will come away from this book with a sound understanding of the system and of the way in which its different components interact. The reader will then be able to tackle the more advanced books and the specifications with confidence.
The target audience is twofold. Firstly, I hope that the book will be valuable for engineers who are working on LTE, notably those who are transferring from other technologies such as GSM, UMTS and cdma2000, those who are experts in one part of LTE but who want to understand the system as a whole and those who are new to mobile telecommunications altogether. Secondly, the book should give a valuable overview to those who are working in non technical roles, such as project managers, marketing executives and intellectual property consultants.
Structurally, the book has four parts. The first part lays out the foundations that the reader will need in the remainder of the book. Chapter 1 is an introduction, which relates LTE to earlier mobile telecommunication systems and lays out its requirements and key technical features. Chapter 2 covers the architecture of the system, notably the hardware components and communication protocols that it contains and its use of radio spectrum. Chapter 3 reviews the radio transmission techniques that LTE has inherited from earlier mobile telecommunication systems, while Chapters 4 and 5 describe the more recent techniques of orthogonal frequency division multiple access and multiple input multiple output antennas.
The second part of the book covers the air interface of LTE. Chapter 6 is a high level description of the air interface, while Chapter 7 relates the low level procedures that a mobile phone uses when it switches on, to discover the LTE base stations that are nearby. Chapter 8 covers the low level procedures that the base station and mobile phone use to transmit and receive information, while Chapter 9 covers a specific procedure, random access, by which the mobile phone can contact a base station without prior scheduling. Chapter 10 covers the higher level parts of the air interface, namely the medium access control, radio link control and packet data convergence protocols.
The third part covers the signalling procedures that govern how a mobile phone behaves. In Chapter 11, we describe the high level procedures that a mobile phone uses when it switches on, to register itself with the network and establish communications with the outside world. Chapter 12 covers the security procedures used by LTE, while Chapter 13 covers the procedures that manage the quality of service and charging characteristics of a data stream. Chapter 14 describes the mobility management procedures that the network uses to keep track of the mobile's location. Chapter 15 describes how LTE inter-operates with the earlier technologies of GSM and UMTS, while Chapter 16 discusses inter-operation with other technologies such as wireless local area networks and cdma2000. Chapter 17 covers the self-configuration and self-optimization capabilities of LTE.
The final part covers more specialized topics. Chapters 18, 19 and 20 describe the enhancements that have been made to LTE in later releases of the specifications, notably an enhanced version of the technology that is known as LTE-Advanced. Chapters 21 and 22 cover the two most important solutions for the delivery of voice calls to LTE devices, namely circuit switched fallback and the IP multimedia subsystem. Finally, Chapter 23 reviews the performance of LTE and discusses the techniques that are used to estimate the coverage and capacity of an LTE network.
LTE has a large number of acronyms, and it is hard to talk about the subject without using them. However, they can make the material appear unnecessarily impenetrable to a newcomer, so I have aimed to keep the use of acronyms to a reasonable minimum, often preferring the full name or a colloquial one. There is a full list of abbreviations in the introductory material and new terms are highlighted using italics throughout the text.
I have also endeavoured to keep the book's mathematical content to the minimum needed to understand the system. The LTE air interface makes extensive use of complex numbers, Fourier transforms and matrix algebra, but the reader will not require any prior knowledge of these in order to understand the book. We do make limited use of complex numbers in Chapters 3 and 4 to illustrate our discussion of modulation, and introduce Fourier transforms and matrices in subsections of Chapters 4 and 5 to cover the more advanced aspects of orthogonal frequency division multiple access and multiple antennas. Readers can, however, skip this material without detracting from their overall appreciation of the subject.
Acknowledgements
Many people have given me assistance, support and advice during the creation of this book. I am especially grateful to Liz Wingett, Susan Barclay, Sophia Travis, Sandra Grayson, Mark Hammond and the rest of the publishing team at John Wiley & Sons, Ltd for the expert knowledge and gentle encouragement that they have supplied throughout the production process.
I am indebted to Michael Salmon and Geoff Varrall for encouraging me to write the first edition of this book and to the publishing team at Wiley for requesting a second. The advice and feedback I have received while preparing the manuscript have been invaluable and have given me many opportunities to correct errors and improve the material. In this respect, I would particularly like to thank Jeff Cartwright, Joseph Hoy, Julian Nolan, Michael Salmon, Mohammad Anas, Obi Chiemeka, Pete Doherty, Les Granfield, Karl van Heeswijk, Kit Kilgour and Paul Mason. I am especially indebted to Nicola Rivers, for her support and encouragement throughout the preparation of the second edition. Naturally, the responsibility for any remaining errors or omissions in the text, and for any lack of clarity in the explanations, is entirely my own.
Much of my knowledge of the more detailed aspects of LTE, notably of circuit switched fallback and the IP multimedia subsystem, has been gathered while delivering courses on behalf of various training providers. I am indebted to the directors and staff of Imagicom, Informa Telecoms Academy, Wray Castle and Mpirical, for the support and learning opportunities that they have provided to me. I would also like to extend my thanks to the delegates who have attended my training courses on LTE. Their questions and corrections have extended my knowledge of the subject, while their feedback has regularly suggested ways to explain topics more effectively.
Several diagrams in this book have been reproduced from the technical specifications for LTE, with permission from the European Telecommunications Standards Institute (ETSI), © 2013, 2012, 2011, 2010, 2006. 3GPP™ TSs and TRs are the property of ARIB, ATIS, CCSA, ETSI, TTA and TTC who jointly own the copyright for them. They are subject to further modifications and are therefore provided to you ‘as is’ for information purposes only. Further use is strictly prohibited.
Analysys Mason Limited kindly supplied the market research data underlying the illustrations of network traffic and operator revenue in Figures 1.6 and 21.1. I would like to extend my appreciation to Hilary Bailey, Morgan Mullooly, Terry Norman and James Allen for providing this information. The measurements of network traffic in Figure 1.5 and the subscription data underlying Figures 1.9 and 1.10 are by Ericsson, and I am grateful to Elin Pettersson and Svante Bergqvist for making these available.
List of Abbreviations
16-QAM
16 quadrature amplitude modulation
1G
First generation
1xRTT
1x radio transmission technology
2G
Second generation
3G
Third generation
3GPP
Third Generation Partnership Project
3GPP2
Third Generation Partnership Project 2
4G
Fourth generation
64-QAM
64 quadrature amplitude modulation
AAA
Authentication, authorization and accounting
ABMF
Account balance management function
ABS
Almost blank subframe
ACK
Positive acknowledgement
ACM
Address complete message
ADC
Analogue to digital converter
AES
Advanced Encryption Standard
AF
Application function/Assured forwarding
AKA
Authentication and key agreement
AM
Acknowledged mode
AMBR
Aggregate maximum bit rate
AMR
Adaptive multi rate
AMR-WB
Wideband adaptive multi rate
ANDSF
Access network discovery and selection function
ANM
Answer message
API
Application programming interface
APN
Access point name
APN-AMBR
Per APN aggregate maximum bit rate
ARIB
Association of Radio Industries and Businesses
ARP
Allocation and retention priority
ARQ
Automatic repeat request
AS
Access stratum/Application server
ASME
Access security management entity
ATCF
Access transfer control function
ATGW
Access transfer gateway
ATIS
Alliance for Telecommunications Industry Solutions
AuC
Authentication centre
AVP
Attribute value pair/Audio visual profile
AWS
Advanced Wireless Services
B2BUA
Back to back user agent
BBERF
Bearer binding and event reporting function
BBF
Bearer binding function
BCCH
Broadcast control channel
BCH
Broadcast channel
BD
Billing domain
BE
Best effort
BGCF
Breakout gateway control function
BICC
Bearer independent call control
BM-SC
Broadcast/multicast service centre
BPSK
Binary phase shift keying
BSC
Base station controller
BSR
Buffer status report
BSSAP+
Base station subsystem application part plus
BSSGP
Base station system GPRS protocol
BTS
Base transceiver station
CA
Carrier aggregation
CAMEL
Customized applications for mobile network enhanced logic
CBC
Cell broadcast centre
CBS
Cell broadcast service
CC
Call control/Component carrier
CCCH
Common control channel
CCE
Control channel element
CCO
Cell change order
CCSA
China Communications Standards Association
CDF
Charging data function
CDMA
Code division multiple access
CDR
Charging data record
CFI
Control format indicator
CGF
Charging gateway function
CIF
Carrier indicator field
CLI
Calling line identification
CM
Connection management
CMAS
Commercial mobile alert system
C-MSISDN
Correlation mobile subscriber ISDN number
CoMP
Coordinated multi-point transmission and reception
COST
European Cooperation in Science and Technology
CP
Cyclic prefix
CQI
Channel quality indicator
CRC
Cyclic redundancy check
C-RNTI
Cell radio network temporary identifier
CS
Circuit switched
CS/CB
Coordinated scheduling and beamforming
CSCF
Call session control function
CSFB
Circuit switched fallback
CSG
Closed subscriber group
CSI
Channel state information
CS-MGW
Circuit switched media gateway
CTF
Charging trigger function
D2D
Device to device
DAC
Digital-to-analogue converter
dB
Decibel
dBi
Decibels relative to an isotropic antenna
dBm
Decibels relative to one milliwatt
DCCH
Dedicated control channel
DCI
Downlink control information
DeNB
Donor evolved Node B
DFT
Discrete Fourier transform
DFT-S-OFDMA
Discrete Fourier transform spread OFDMA
DHCP
Dynamic host configuration protocol
DiffServ
Differentiated services
DL
Downlink
DL-SCH
Downlink shared channel
DNS
Domain name server
DPS
Dynamic point selection
DRS
Demodulation reference signal
DRVCC
Dual radio voice call continuity
DRX
Discontinuous reception
DSCP
Differentiated services code point
DSL
Digital subscriber line
DSMIP
Dual-stack mobile IP
DTCH
Dedicated traffic channel
DTM
Dual transfer mode
DTMF
Dual tone multi-frequency
EAG
Explicit array gain
eAN
Evolved access network
EAP
Extensible authentication protocol
EATF
Emergency access transfer function
ECGI
E-UTRAN cell global identifier
ECI
E-UTRAN cell identity
ECM
EPS connection management
ECN
Explicit congestion notification
E-CSCF
Emergency call session control function
EDGE
Enhanced Data Rates for GSM Evolution
EEA
EPS encryption algorithm
EF
Expedited forwarding
eHRPD
Evolved high rate packet data
EIA
EPS integrity algorithm
EICIC
Enhanced inter cell interference coordination
EIR
Equipment identity register
EIRP
Equivalent isotropic radiated power
eMBMS
Evolved MBMS
EMM
EPS mobility management
eNB
Evolved Node B
EPC
Evolved packet core
ePCF
Evolved packet control function
EPDCCH
Enhanced physical downlink control channel
ePDG
Evolved packet data gateway
EPRE
Energy per resource element
EPS
Evolved packet system
E-RAB
Evolved radio access bearer
ERF
Event reporting function
ESM
EPS session management
E-SMLC
Evolved serving mobile location centre
ESP
Encapsulating security payload
ETSI
European Telecommunications Standards Institute
ETWS
Earthquake and tsunami warning system
E-UTRAN
Evolved UMTS terrestrial radio access network
EV-DO
Evolution data optimized
FCC
Federal Communications Commission
FDD
Frequency division duplex
FDMA
Frequency division multiple access
FD-MIMO
Full-dimension MIMO
FFT
Fast Fourier transform
FTP
File transfer protocol
GBR
Guaranteed bit rate
GCP
Gateway control protocol
GERAN
GSM EDGE radio access network
GGSN
Gateway GPRS support node
GMLC
Gateway mobile location centre
GMM
GPRS mobility management
GNSS
Global navigation satellite system
GP
Guard period
GPRS
General Packet Radio Service
GPS
Global Positioning System
GRE
Generic routing encapsulation
GRX
GPRS roaming exchange
GSM
Global System for Mobile Communications
GSMA
GSM Association
GTP
GPRS tunnelling protocol
GTP-C
GPRS tunnelling protocol control part
GTP-U
GPRS tunnelling protocol user part
GUMMEI
Globally unique MME identifier
GUTI
Globally unique temporary identity
HARQ
Hybrid ARQ
HeNB
Home evolved Node B
HI
Hybrid ARQ indicator
HLR
Home location register
H-PCRF
Home policy and charging rules function
HRPD
High rate packet data
HSDPA
High speed downlink packet access
HSGW
HRPD serving gateway
HSPA
High speed packet access
HSS
Home subscriber server
HSUPA
High-speed uplink packet access
HTTP
Hypertext transfer protocol
I
In phase
IAM
Initial address message
IARI
IMS application reference identifier
IBCF
Interconnection border control function
ICIC
Inter-cell interference coordination
ICS
IMS centralized services
I-CSCF
Interrogating call session control function
ICSI
IMS communication service identifier
IDC
In device coexistence
IEEE
Institute of Electrical and Electronics Engineers
IETF
Internet Engineering Task Force
iFC
Initial filter criteria
IFOM
IP flow mobility
II-NNI
Inter IMS network to network interface
IKE
Internet key exchange
IMEI
International mobile equipment identity
IM-MGW
IMS media gateway
IMPI
IP multimedia private identity
IMPU
IP multimedia public identity
IMS
IP multimedia subsystem
IMS-ALG
IMS application level gateway
IMSI
International mobile subscriber identity
IM-SSF
IP multimedia service switching function
IMT
International Mobile Telecommunications
IP
Internet protocol
IP-CAN
IP connectivity access network
IPSec
IP security
IP-SM-GW
IP short message gateway
IPv4
Internet protocol version 4
IPv6
Internet protocol version 6
IPX
IP packet exchange
IRL
Isotropic receive level
ISDN
Integrated services digital network
ISI
Inter symbol interference
ISIM
IP multimedia services identity module
ISR
Idle mode signalling reduction
ISRP
Intersystem routing policy
ISUP
ISDN user part
ITU
International Telecommunication Union
IWF
Interworking function
JP
Joint processing
JR
Joint reception
JT
Joint transmission
LA
Location area
LBS
Location-based services
LCS
Location services
LCS-AP
LCS application protocol
LDAP
Lightweight directory access protocol
LGW
Local gateway
LIPA
Local IP access
LIR
Location info request
LPP
LTE positioning protocol
LRF
Location retrieval function
LTE
Long term evolution
LTE-A
LTE-Advanced
M2M
Machine to machine
MAC
Medium access control
MAP
Mobile application part
MAPCON
Multi access PDN connectivity
MAR
Multimedia authentication request
MBMS
Multimedia broadcast/multicast service
MBMS-GW
MBMS gateway
MBR
Maximum bit rate
MBSFN
Multicast/broadcast over a single frequency network
MCC
Mobile country code
MCCH
Multicast control channel
MCE
Multicell/multicast coordination entity
MCH
Multicast channel
MDT
Minimization of drive tests
ME
Mobile equipment
MEGACO
Media gateway control
MeNB
Master evolved Node B
MGCF
Media gateway control function
MGL
Measurement gap length
MGRP
Measurement gap repetition period
MGW
Media gateway
MIB
Master information block
MIMO
Multiple input multiple output
MIP
Mobile IP
MM
Mobility management
MME
Mobility management entity
MMEC
MME code
MMEGI
MME group identity
MMEI
MME identifier
MMSE
Minimum mean square error
MMTel
Multimedia telephony service
MNC
Mobile network code
MO
Management object
MOS
Mean opinion score
MPLS
Multiprotocol label switching
MRB
Media resource broker
MRF
Multimedia resource function
MRFC
Multimedia resource function controller
MRFP
Multimedia resource function processor
M-RNTI
MBMS radio network temporary identifier
MSC
Mobile switching centre
MSISDN
Mobile subscriber ISDN number
MSK
Master session key
MSRP
Message session relay protocol
MT
Mobile termination
MTC
Machine-type communications
MTC-IWF
Machine-type communications interworking function
MTCH
Multicast traffic channel
M-TMSI
M temporary mobile subscriber identity
MTSI
Multimedia telephony service for IMS
MU-MIMO
Multiple user MIMO
NACC
Network-assisted cell change
NACK
Negative acknowledgement
NAI
Network access identifier
NAP-ID
Network access provider identity
NAS
Non-access stratum
NAT
Network address translation
NH
Next hop
NMO
Network mode of operation
OCF
Online charging function
OCS
Online charging system
OMA
Open Mobile Alliance
OFCS
Offline charging system
OFDM
Orthogonal frequency division multiplexing
OFDMA
Orthogonal frequency division multiple access
OSA
Open service access
OSI
Open systems interconnection
OTDOA
Observed time difference of arrival
OUI
Organizational unique identifier
PAPR
Peak-to-average power ratio
PBCH
Physical broadcast channel
PBR
Prioritized bit rate
PCC
Policy and charging control
PCCH
Paging control channel
PCEF
Policy and charging enforcement function
PCell
Primary cell
PCFICH
Physical control format indicator channel
PCH
Paging channel
PCRF
Policy and charging rules function
PCS
Personal Communications Service
P-CSCF
Proxy call session control function
PDCCH
Physical downlink control channel
PDCP
Packet data convergence protocol
PDN
Packet data network
PDP
Packet data protocol
PDSCH
Physical downlink shared channel
PDU
Protocol data unit
PESQ
Perceptual evaluation of speech quality
P-GW
Packet data network gateway
PHB
Per hop behaviour
PHICH
Physical hybrid ARQ indicator channel
PL
Path loss/Propagation loss
PLMN
Public land mobile network
PLMN-ID
Public land mobile network identity
PMCH
Physical multicast channel
PMD
Pseudonym mediation device
PMI
Precoding matrix indicator
PMIP
Proxy mobile IP
PoC
Push to talk over cellular
POLQA
Perceptual objective listening quality assessment
PPR
Privacy profile register
PRACH
Physical random access channel
PRACK
Provisional response acknowledgement
PRB
Physical resource block
P-RNTI
Paging radio network temporary identifier
ProSe
Proximity services
PS
Packet switched
PSAP
Public safety answering point
PSS
Primary synchronization signal
PSTN
Public switched telephone network
P-TMSI
Packet temporary mobile subscriber identity
PUCCH
Physical uplink control channel
PUSCH
Physical uplink shared channel
PWS
Public warning system
Q
Quadrature
QAM
Quadrature amplitude modulation
QCI
QoS class identifier
QoS
Quality of service
QPSK
Quadrature phase shift keying
RA
Routing area
RACH
Random access channel
RADIUS
Remote authentication dial in user service
RANAP
Radio access network application part
RA-RNTI
Random access radio network temporary identifier
RB
Resource block
RBG
Resource block group
RCS
Rich communication services
RE
Resource element
REG
Resource element group
RF
Radio frequency/Rating function
RFC
Request for comments
RI
Rank indication
RIM
Radio access network information management
RLC
Radio link control
RLF
Radio link failure
RN
Relay node
RNC
Radio network controller
RNTI
Radio network temporary identifier
ROHC
Robust header compression
R-PDCCH
Relay physical downlink control channel
RRC
Radio resource control
RRH
Remote radio head
RS
Reference signal
RSCP
Received signal code power
RSRP
Reference signal received power
RSRQ
Reference signal received quality
RSSI
Received signal strength indicator
RTCP
RTP control protocol
RTP
Real time transport protocol
S1-AP
S1 application protocol
SAE
System architecture evolution
SaMOG
S2a mobility based on GTP
SAR
Server assignment request
SC
Service centre
SCC-AS
Service centralization and continuity application server
SCell
Secondary cell
SC-FDMA
Single-carrier frequency division multiple access
SCS
Service capability server
S-CSCF
Serving call session control function
SCTP
Stream control transmission protocol
SDF
Service data flow
SDP
Session description protocol
SDU
Service data unit
SEG
Secure gateway
SeNB
Slave evolved Node B
SFN
System frame number
SGsAP
SGs application protocol
SGSN
Serving GPRS support node
S-GW
Serving gateway
SIB
System information block
SID
Silence information descriptor
SIM
Subscriber identity module
SINR
Signal-to-interference plus noise ratio
SIP
Session initiation protocol
SIPTO
Selective IP traffic offload
SI-RNTI
System information radio network temporary identifier
SLF
Subscription locator function
SM
Session management
SMS
Short message service
SMS-GMSC
SMS gateway MSC
SMS-IWMSC
SMS interworking MSC
SMTP
Simple mail transfer protocol
SNR
Subscribe notifications request
SOAP
Simple object access protocol
SON
Self-optimizing network/Self organizing network
SPR
Subscription profile repository
SPS
Semi persistent scheduling
SPT
Service point trigger
SR
Scheduling request
SRB
Signalling radio bearer
SRS
Sounding reference signal
SRVCC
Single radio voice call continuity
SS
Supplementary service
SS7
Signalling system 7
SSID
Service set identifier
SSS
Secondary synchronization signal
S-TMSI
S temporary mobile subscriber identity
STN-SR
Session transfer number single radio
SU-MIMO
Single-user MIMO
SVD
Singular value decomposition
TA
Timing advance/Tracking area
TAC
Tracking area code
TAI
Tracking area identity
TCP
Transmission control protocol
TDD
Time division duplex
TDMA
Time division multiple access
TD-SCDMA
Time division synchronous code division multiple access
TE
Terminal equipment
TEID
Tunnel endpoint identifier
TETRA
Terrestrial Trunked Radio
TFT
Traffic flow template
THIG
Topology hiding inter network gateway
TM
Transparent mode
TMSI
Temporary mobile subscriber identity
TPC
Transmit power control
TR
Technical report
TrGW
Transition gateway
TS
Technical specification
TTA
Telecommunications Technology Association
TTC
Telecommunication Technology Committee
TTI
Transmission time interval
UA
User agent
UAR
User authorization request
UCI
Uplink control information
UDP
User datagram protocol
UDR
User data repository/User data request
UE
User equipment
UE-AMBR
Per UE aggregate maximum bit rate
UICC
Universal integrated circuit card
UL
Uplink
UL-SCH
Uplink shared channel
UM
Unacknowledged mode
UMB
Ultra Mobile Broadband
UMTS
Universal Mobile Telecommunication System
URI
Uniform resource identifier
USIM
Universal subscriber identity module
USSD
Unstructured supplementary service data
UTDOA
Uplink time difference of arrival
UTRAN
UMTS terrestrial radio access network
VANC
VoLGA access network controller
VLR
Visitor location register
VoIP
Voice over IP
VoLGA
Voice over LTE via generic access
VoLTE
Voice over LTE
V-PCRF
Visited policy and charging rules function
VRB
Virtual resource block
vSRVCC
Single radio video call continuity
WCDMA
Wideband code division multiple access
WCS
Wireless Communications Service
WiMAX
Worldwide Interoperability for Microwave Access
WINNER
Wireless World Initiative New Radio
X2-AP
X2 application protocol
XCAP
XML configuration access protocol
XML
Extensible markup language
ZUC
Zu Chongzhi
Chapter 1Introduction
Our first chapter puts LTE into its historical context, and lays out its requirements and key technical features. We begin by reviewing the architectures of UMTS and GSM, and by introducing some of the terminology that the two systems use. We then summarize the history of mobile telecommunication systems, discuss the issues that have driven the development of LTE and show how UMTS has evolved first into LTE and then into an enhanced version known as LTE-Advanced. The chapter closes by reviewing the standardization process for LTE.
1.1 Architectural Review of UMTS and GSM
1.1.1 High-Level Architecture
LTE was designed by a collaboration of national and regional telecommunications standards bodies known as the Third Generation Partnership Project (3GPP) [1] and is known in full as 3GPP Long-Term Evolution. LTE evolved from an earlier 3GPP system known as the Universal Mobile Telecommunication System (UMTS), which in turn evolved from the Global System for Mobile Communications (GSM). To put LTE into context, we will begin by reviewing the architectures of UMTS and GSM, and by introducing some of the important terminology.
A mobile phone network is officially known as a public land mobile network (PLMN), and is run by a network operator such as Vodafone or Verizon. UMTS and GSM share a common network architecture, which is shown in Figure 1.1. There are three main components, namely the core network, the radio access network and the mobile phone.
Figure 1.1 High-level architecture of UMTS and GSM
The core network contains two domains. The circuit switched (CS) domain transports phone calls across the geographical region that the network operator is covering, in the same way as a traditional fixed-line telecommunication system. It communicates with the public switched telephone network (PSTN) so that users can make calls to land lines and with the circuit switched domains of other network operators. The packet switched (PS) domain transports data streams, such as web pages and emails, between the user and external packet data networks (PDNs) such as the internet.
The two domains transport their information in very different ways. The CS domain uses a technique known as circuit switching, in which it sets aside a dedicated two-way connection for each individual phone call so that it can transport the information with a constant data rate and minimal delay. This technique is effective, but is rather inefficient: the connection has enough capacity to handle the worst-case scenario in which both users are speaking at the same time, but is usually over-dimensioned. Furthermore, it is inappropriate for data transfers, in which the data rate can vary widely.
To deal with the problem, the PS domain uses a different technique, known as packet switching. In this technique, a data stream is divided into packets, each of which is labelled with the address of the required destination device. Within the network, routers read the address labels of the incoming data packets and forward them towards the corresponding destinations. The network's resources are shared amongst all the users, so the technique is more efficient than circuit switching. However, delays can result if too many devices try to transmit at the same time, a situation that is familiar from the operation of the internet.
The radio access network handles the core network's radio communications with the user. In Figure 1.1, there are actually two separate radio access networks, namely the GSM EDGE radio access network (GERAN) and the UMTS terrestrial radio access network (UTRAN). These use the different radio communication techniques of GSM and UMTS, but share a common core network between them.
The user's device is known officially as the user equipment (UE) and colloquially as the mobile. It communicates with the radio access network over the air interface, also known as the radio interface. The direction from network to mobile is known as the downlink (DL) or forward link and the direction from mobile to network is known as the uplink (UL) or reverse link.
A mobile can work outside the coverage area of its network operator by using the resources from two public land mobile networks: the visited network, where the mobile is located and the operator's home network. This situation is known as roaming.
1.1.2 Architecture of the Radio Access Network
Figure 1.2 shows the radio access network of UMTS. The most important component is the base station, which in UMTS is officially known as the Node B. Each base station has one or more sets of antennas, through which it communicates with the mobiles in one or more sectors. As shown in the diagram, a typical base station uses three sets of antennas to control three sectors, each of which spans an arc of 120°. In a medium-sized country like the United Kingdom, a typical mobile phone network might contain several thousand base stations altogether.
Figure 1.2 Architecture of the UMTS terrestrial radio access network
The word cell can be used in two different ways [2]. In Europe, a cell is usually the same thing as a sector, but in the United States, it usually means the group of sectors that a single base station controls. We will stick with the European convention throughout this book, so that the words cell and sector mean the same thing.
Each cell has a limited size, which is determined by the maximum range at which the receiver can successfully hear the transmitter. It also has a limited capacity, which is the maximum combined data rate of all the mobiles in the cell. These limits lead to the existence of several types of cell. Macrocells provide wide-area coverage in rural areas or suburbs and have a size of a few kilometres. Microcells have a size of a few hundred metres and provide a greater collective capacity that is suitable for densely populated urban areas. Picocells are used in large indoor environments such as offices or shopping centres and are a few tens of metres across. Finally, subscribers can buy home base stations to install in their own homes. These control femtocells, which are a few metres across.
Looking more closely at the air interface, each mobile and base station transmits on a certain radio frequency, which is known as the carrier frequency. Around that carrier frequency, it occupies a certain amount of frequency spectrum, known as the bandwidth. For example, a mobile might transmit with a carrier frequency of 1960 MHz and a bandwidth of 10 MHz, in which case its transmissions would occupy a frequency range from 1955 to 1965 MHz.
The air interface has to segregate the base stations' transmissions from those of the mobiles, to ensure that they do not interfere. UMTS can do this in two ways. When using frequency division duplex (FDD), the base stations transmit on one carrier frequency and the mobiles on another. When using time division duplex (TDD), the base stations and mobiles transmit on the same carrier frequency, but at different times. The air interface also has to segregate the different base stations and mobiles from each other. We will see the techniques that it uses in Chapters 3 and 4.
When a mobile moves from one part of the network to another, it has to stop communicating with one cell and start communicating with the next cell along. This process can be carried out using two different techniques, namely handover for mobiles that are actively communicating with the network and cell reselection for mobiles that are on standby. In UMTS, an active mobile can actually communicate with more than one cell at a time, in a state known as soft handover.
The base stations are grouped together by devices known as radio network controllers (RNCs). These have two main tasks. Firstly, they pass the user's voice information and data packets between the base stations and the core network. Secondly, they control a mobile's radio communications by means of signalling messages that are invisible to the user, for example by telling a mobile to hand over from one cell to another. A typical network might contain a few tens of radio network controllers, each of which controls a few hundred base stations.
The GSM radio access network has a similar design, although the base station is known as a base transceiver station (BTS) and the controller is known as a base station controller (BSC). If a mobile supports both GSM and UMTS, then the network can hand it over between the two radio access networks, in a process known as an inter-system handover. This can be invaluable if a mobile moves outside the coverage area of UMTS, and into a region that is covered by GSM alone.
In Figure 1.2, we have shown the user's traffic in solid lines and the network's signalling messages in dashed lines. We will stick with this convention throughout the book.
1.1.3 Architecture of the Core Network
Figure 1.3 shows the internal architecture of the core network. In the circuit switched domain, media gateways (MGWs) route phone calls from one part of the network to another, while mobile switching centre (MSC) servers handle the signalling messages that set up, manage and tear down the phone calls. They respectively handle the traffic and signalling functions of two earlier devices, known as the mobile switching centre and the visitor location register (VLR). A typical network might just contain a few of each device.
Figure 1.3 Architecture of the core networks of UMTS and GSM
In the packet switched domain, gateway GPRS support nodes (GGSNs) act as interfaces to servers and packet data networks in the outside world. Serving GPRS support nodes (SGSNs) route data between the base stations and the GGSNs, and handle the signalling messages that set up, manage and tear down the data streams. Once again, a typical network might just contain a few of each device.
The home subscriber server (HSS) is a central database that contains information about all the network operator's subscribers and is shared between the two network domains. It amalgamates the functions of two earlier components, which were known as the home location register (HLR) and the authentication centre (AuC).
1.1.4 Communication Protocols
In common with other communication systems, UMTS and GSM transfer information using hardware and software protocols. The best way to illustrate these is actually through the protocols used by the internet. These protocols are designed by the Internet Engineering Task Force (IETF) and are grouped into various numbered layers, each of which handles one aspect of the transmission and reception process. The usual grouping follows a seven layer model known as the Open Systems Interconnection (OSI) model.
As an example (see Figure 1.4), let us suppose that a web server is sending information to a user's browser. In the first step, an application layer protocol, in this case the hypertext transfer protocol (HTTP), receives information from the server's application software, and passes it to the next layer down by representing it in a way that the user's application layer will eventually be able to understand. Other application layer protocols include the simple mail transfer protocol (SMTP) and the file transfer protocol (FTP).
Figure 1.4 Examples of the communication protocols used by the internet, showing their mapping onto the layers of the OSI model
The transport layer manages the end-to-end data transmission. There are two main protocols. The transmission control protocol (TCP) re-transmits a packet from end to end if it does not arrive correctly, and is suitable for data such as web pages and emails that have to be received reliably. The user datagram protocol (UDP) sends the packet without any re-transmission and is suitable for data such as real time voice or video for which timely arrival is more important.
In the network layer, the internet protocol (IP) sends packets on the correct route from source to destination, using the IP address of the destination device. The process is handled by the intervening routers, which inspect the destination IP addresses by implementing just the lowest three layers of the protocol stack. The data link layer manages the transmission of packets from one device to the next, for example by re-transmitting a packet across a single interface if it does not arrive correctly. Finally, the physical layer deals with the actual transmission details; for example, by setting the voltage of the transmitted signal. The internet can use any suitable protocols for the data link and physical layers, such as Ethernet.
At each level of the transmitter's stack, a protocol receives a data packet from the protocol above in the form of a service data unit (SDU). It processes the packet, adds a header to describe the processing it has carried out, and outputs the result as a protocol data unit (PDU). This immediately becomes the incoming service data unit of the next protocol down. The process continues until the packet reaches the bottom of the protocol stack, at which point it is transmitted. The receiver reverses the process, using the headers to help it undo the effect of the transmitter's processing.
This technique is used throughout the radio access and core networks of UMTS and GSM. We will not consider their protocols in any detail at this stage; instead, we will go straight to the protocols used by LTE as part of Chapter 2.
1.2 History of Mobile Telecommunication Systems
1.2.1 From 1G to 3G
Mobile telecommunication systems were first introduced in the early 1980s. The first generation (1G) systems used analogue communication techniques, which were similar to those used by a traditional analogue radio. The individual cells were large and the systems did not use the available radio spectrum efficiently, so their capacity was by today's standards very small. The mobile devices were large and expensive and were marketed almost exclusively at business users.
Mobile telecommunications took off as a consumer product with the introduction of second generation (2G) systems in the early 1990s. These systems were the first to use digital technology, which permitted a more efficient use of the radio spectrum and the introduction of smaller, cheaper devices. They were originally designed just for voice, but were later enhanced to support instant messaging through the Short Message Service (SMS). The most popular 2G system was the Global System for Mobile Communications (GSM), which was originally designed as a pan-European technology, but which later became popular throughout the world. Also notable was IS-95, otherwise known as cdmaOne, which was designed by Qualcomm, and which became the dominant 2G system in the United States.
The success of 2G communication systems came at the same time as the early growth of the internet. It was natural for network operators to bring the two concepts together, by allowing users to download data onto mobile devices. To do this, so-called 2.5G systems built on the original ideas from 2G, by introducing the core network's packet switched domain and by modifying the air interface so that it could handle data as well as voice. The General Packet Radio Service (GPRS) incorporated these techniques into GSM, while IS-95 was developed into a system known as IS-95B.
At the same time, the data rates available over the internet were progressively increasing. To mirror this, designers first improved the performance of 2G systems using techniques such as Enhanced Data Rates for GSM Evolution (EDGE) and then introduced more powerful third generation (3G) systems in the years after 2000. 3G systems use different techniques for radio transmission and reception from their 2G predecessors, which increases the peak data rates that they can handle and which makes still more efficient use of the available radio spectrum.
Unfortunately, early 3G systems were excessively hyped and their performance did not at first live up to expectations. Because of this, 3G only took off properly after the introduction of 3.5G systems around 2005. In these systems, the air interface includes extra optimizations that are targeted at data applications, which increase the average rate at which a user can upload or download information, at the expense of introducing greater variability into the data rate and the arrival time.
1.2.2 Third Generation Systems
The world's dominant 3G system is the Universal Mobile Telecommunication System (UMTS). UMTS was developed from GSM by completely changing the technology used on the air interface, while keeping the core network almost unchanged. The system was later enhanced for data applications, by introducing the 3.5G technologies of high-speed downlink packet access (HSDPA) and high-speed uplink packet access (HSUPA), which are collectively known as high-speed packet access (HSPA).
The UMTS air interface has two slightly different implementations. Wideband code division multiple access (WCDMA) is the version that was originally specified, and the one that is currently used through most of the world. Time division synchronous code division multiple access (TD-SCDMA) is a derivative of WCDMA, which is also known as the low chip rate option of UMTS TDD mode. TD-SCDMA was developed in China, to minimize the country's dependence on Western technology and on royalty payments to Western companies. It is deployed by one of China's three 3G operators, China Mobile.
There are two main technical differences between these implementations. Firstly, WCDMA usually segregates the base stations' and mobiles' transmissions by means of frequency division duplex, while TD-SCDMA uses time division duplex. Secondly, WCDMA uses a wide bandwidth of 5 MHz, while TD-SCDMA uses a smaller value of 1.6 MHz.
cdma2000 was developed from IS-95 and is mainly used in North America. The original 3G technology was known as cdma2000 1x radio transmission technology (1xRTT). It was subsequently enhanced to a 3.5G system with two alternative names, cdma2000 high-rate packet data
