UMTS. Javier Sanchez Mamadou Thioune

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1 UMTS Javier Sanchez Mamadou Thioune

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3 UMTS

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5 UMTS Javier Sanchez Mamadou Thioune

6 Part of this book adapted from the 2 nd edition of UMTS published in France by Hermès Science/Lavoisier in 2004 First Published in Great Britain and the United States in 2007 by ISTE Ltd Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address: ISTE Ltd ISTE USA 6 Fitzroy Square 4308 Patrice Road London W1T 5DX Newport Beach, CA UK USA ISTE Ltd, 2007 LAVOISER, 2004 The rights of Javier Sanchez and Mamadou Thioune to be identified as the authors of this work have been asserted by them in accordance with the Copyright, Designs and Patents Act Library of Congress Cataloging-in-Publication Data Sanchez, Javier. UMTS/Javier Sanchez, Mamadou Thioune. p. cm. ISBN-13: ISBN-10: Universal Mobile Telecommunications System. I. Thioune, Mamadou. II. Title. III. Title: Universal mobile telecommunications system. TK S '6--dc British Library Cataloguing-in-Publication Data A CIP record for this book is available from the British Library ISBN 10: ISBN 13: Printed and bound in Great Britain by Antony Rowe Ltd, Chippenham, Wiltshire.

7 Table of Contents Preface... xiii Chapter 1. Evolution of Cellular Mobile Systems Multiple-access techniques used in mobile telephony Frequency division duplex (FDD) and time division duplex (TDD) Frequency division multiple access (FDMA) Time division multiple access (TDMA) Code division multiple access (CDMA) Space division multiple access (SDMA) Orthogonal frequency division multiplexing (OFDM) Evolution from 1G to 2.5G From 1G to 2G Enhancements to 2G radio technologies: 2.5G G systems in IMT-2000 framework IMT-2000 radio interfaces Core network approaches in 3G systems Standardization process in 3G systems Worldwide spectrum allocation for IMT-2000 systems WARC WARC Chapter 2. Network Evolution from GSM to UMTS Introduction UMTS definition and history Overall description of a UMTS network architecture Network architecture evolution from GSM to UMTS GSM network architecture of Phases 1 and GSM network architecture of Phase

8 vi UMTS Architecture of UMTS networks: evolutionary revolution of GSM Bearer services offered by UMTS networks UMTS protocol architecture based on stratum concept Access stratum Non-access stratum Chapter 3. Services in UMTS Introduction UMTS mobile terminals UE functional description UE maximum output power Dual-mode GSM/UMTS terminals UE radio access capability Services offered by UMTS networks Standard UMTS telecommunication services UMTS bearer services Teleservices Supplementary services Operator specific services: service capabilities The virtual home environment Traffic classes of UMTS bearer services Conversational services Streaming services Interactive services Background services Service continuity across GSM and UMTS networks Chapter 4. UMTS Core Network Introduction UMTS core network architecture Main features of UMTS core network based on Release Circuit-switched and packet-switched domains Network elements and protocols of the CS and PS domains Network elements of the CS domain Protocol architecture in the CS domain Network elements of the PS domain Protocol architecture in the PS domain Integrated UMTS core network Network elements not included in UMTS reference architecture Interoperability between UMTS and GSM core networks... 82

9 Table of Contents vii Chapter 5. Spread Spectrum and WCDMA Introduction Spread spectrum principles Processing gain Advantages of spread spectrum Direct sequence CDMA Multiple access based on spread spectrum Maximum capacity of CDMA Effect of background noise and interference Antenna sectorization Voice activity detection Spreading code sequences Orthogonal code sequences Pseudo-noise code sequences: Gold codes Spreading sequences used in UTRA Principles of wideband code division multiple access Effects of the propagation channel Techniques used in WCDMA for propagation impairment mitigation Chapter 6. UTRAN Access Network Introduction UTRAN architecture The radio network sub-system (RNS) Handling of the mobility in the UTRAN Summary of functions provided by the UTRAN General model of protocols used in UTRAN interfaces Horizontal layers Vertical planes Control plane of the transport network Use of ATM in the UTRAN network transport layer ATM cell format ATM and virtual connections ATM reference model Protocols in the Iu interface Protocol architecture in Iu-CS and Iu-PS interfaces RANAP Protocols in internal UTRAN interfaces Iur interface (RNC-RNC) Iub interface (RNC-Node B) Data exchange in the UTRAN: example of call establishment Summary of the UTRAN protocol stack

10 viii UMTS Chapter 7. UTRA Radio Protocols Introduction Channel typology and description Logical channels Transport channels Physical channels Physical layer Physical layer functions Mapping of transport channels onto physical channels MAC Main functions of MAC Mapping of logical channels onto transport channels MAC PDU RLC Main functions of RLC RLC PDU RLC transmission and reception model PDCP BMC RRC Handling of the RRC connection Handling of RRC service states System information broadcast Handling of the paging Cell selection and reselection UTRAN mobility handling Radio bearer management Measurement control Ciphering and integrity Outer loop power control Protocol layers termination in the UTRAN Chapter 8. Call and Mobility Management Introduction PLMN selection Automatic PLMN selection mode Manual PLMN selection mode PLMN reselection Forbidden PLMNs Principle of mobility management in UMTS Location areas Service states in the core network and the UTRAN

11 Table of Contents ix 8.4. Network access control Allocation of temporary identities UE identification procedure Ciphering and integrity protection activation Authentication Network registration IMSI attach procedure GPRS attach procedure UE location updating procedures Location updating procedure Routing area updating procedure SRNS relocation Detach procedures Call establishment Circuit call Packet call Intersystem change and handover between GSM and UMTS networks Intersystem handover from UMTS to GSM during a CS connection Intersystem handover from GSM to UMTS during a CS connection Intersystem change from UMTS to GPRS during a PS session Intersystem change from GPRS to UMTS during a PS session Chapter 9. UTRA/FDD Transmission Chain Introduction Operations applied to transport channels Multiplexing and channel coding in the uplink Multiplexing and channel coding in the downlink Operations applied to physical channels Characteristics of physical channels in UTRA/FDD Channelization codes Scrambling codes UTRA/WCDMA transmitter Spreading and modulation of dedicated physical channels Uplink dedicated channels Downlink dedicated channel Time difference between uplink and downlink DPCHs Spreading and modulation of common physical channels The Physical Random Access Channel (PRACH) The Physical Common Packet Channel (PCPCH) The Physical Downlink Shared Channel (PDSCH)

12 x UMTS The Synchronization Channel (SCH) The Common Pilot Channel (CPICH) The Primary Common Control Physical Channel (P-CCPCH) The Secondary Common Control Physical Channel (S-CCPCH) The Paging Indicator Channel (PICH) The Acquisition Indicator Channel (AICH) Other downlink physical channels associated with the PCPCH Chapter 10. UTRA/FDD Physical Layer Procedures Introduction The UE receptor Synchronization procedure First step: slot synchronization Second step: frame synchronization and code-group identification Third step: primary scrambling code identification Fourth step: system frame synchronization Random access transmission with the RACH Random access transmission with the CPCH Paging decoding procedure Power control procedures Open loop power control Inner loop and outer loop power control Transmit diversity procedures Time Switched Transmit Diversity (TSTD) Space Time block coding Transmit Diversity (STTD) Closed loop transmit diversity Chapter 11. Measurements and Procedures of the UE in RRC Modes Introduction Measurements performed by the physical layer Measurement model for physical layer Types of UE measurements Cell selection process PLMN search and selection Phases in the cell selection process S cell selection criterion Cell reselection process Types of cell reselection Measurement rules for cell reselection R ranking criterion Phases in the cell reselection process Handover procedures

13 Table of Contents xi Phases in a handover procedure Intrafrequency handover Interfrequency handover Intersystem UMTS-GSM handover Measurements in idle and connected RRC modes Measurements in RRC idle, CELL_PCH and URA_PCH states Measurements in CELL_FACH state Measurements in the CELL_DCH state: the compressed mode Chapter 12. UTRA/TDD Mode Introduction Technical aspects of UTRA/TDD Advantages of UTRA/TDD Drawbacks of UTRA/TDD Transport and physical channels in UTRA/TDD Physical channel structure Dedicated Physical Data Channels Common physical channels Service multiplexing and channel coding Examples of UTRA/TDD user bit rates Physical layer procedures in UTRA/TDD Power control Downlink transmit diversity Timing advance Dynamic channel allocation Handover UTRA/TDD receiver Chapter 13. UMTS Network Evolution Introduction UMTS core network based on Release UMTS core network based on Release Multimedia Broadcast/Multicast Service (MBMS) Network aspects MBMS operation modes MBMS future evolution UMTS-WLAN interworking UMTS-WLAN interworking scenarios Network and UE aspects UMTS evolution beyond Release HSDPA/HSUPA enhancements System Architecture Evolution Long Term Evolution (LTE)

14 xii UMTS Chapter 14. Principles of HSDPA HSDPA physical layer HS-DSCH transport channel Mapping of HS-DSCH onto HS-PDSCH physical channels Physical channels associated with the HS-DSCH Timing relationship between the HS-PDSCH and associated channels Adaptive modulation and coding Hybrid Automatic Repeat Request (H-ARQ) H-ARQ process example Fast scheduling New architecture requirements for supporting HSDPA Impact on Node B: high-speed MAC entity Impact on the UE: HSDPA terminal capabilities Future enhancements for HSDPA Enhanced UTRA/FDD uplink Multiple Input Multiple Output antenna processing Appendix 1. AMR Codec in UMTS A1.1. AMR frame structure and operating modes A1.2. Dynamic AMR mode adaptation A1.3. Resource allocation for an AMR speech connection A1.4. AMR wideband Appendix 2. Questions and Answers Bibliography Glossary Index

15 Preface During the first decade of this millennium, more than 100 billion will be invested in third generation (3G) Universal Mobile Telecommunications System (UMTS) in Europe. This fact represents an amazing challenge from both a technical and commercial perspective. In the evolution path of GSM/GPRS standards, the UMTS proposes enhanced and new services including high-speed Internet access, video-telephony, and multimedia applications such as streaming. Based on the latest updates of 3GPP specifications, this book investigates the differences of a GSM/GPRS network compared with a UMTS network as well as the technical aspects that ensure their interoperability. Students, professors and engineers will find in this book a clear and concise picture of key ideas behind the complexity of UMTS networks. This can also be used as a starter before exploring in more depth the labyrinth of 3GPP specifications which remain, however, the main technical reference. Written by experts in their respective fields, this book gives detailed description of the elements in the UMTS network architecture: the User Equipment (UE), the UMTS Radio Access Network (UTRAN) and the core network. Completely new protocols based on the needs of the new Wideband Code Division Multiple Access (WCDMA) air interface are given particular attention by considering both Frequency- and Time-Division Duplex modes. Later on, the book further introduces the key features of existing topics in Releases 5, 6 and 7 such as High Speed Downlink/Uplink Packet Access (HSDPA/HSUPA), IP Multimedia Subsystem (IMS), Long Term Evolution (LTE), WLAN interconnection and Multicast/ Broadcast Multimedia Services (MBMS). We would like to offer our heartfelt thanks to all our work colleagues for their helpful comments.

16 xiv UMTS Some of the figures and tables reproduced in this book are the result of technical specifications defined by the 3GPP partnership ( 3G_Specs.htm). The specifications are by nature not fixed and are susceptible to modifications during their transposition in regional standardization organizations which make up the membership of the 3GPP partnership. Because of this, and as a result of the translation and/or adaptation of these points by the authors, these organizations cannot be considered responsible for the figures and tables reproduced in this book.

17 Chapter 1 Evolution of Cellular Mobile Systems The purpose of this chapter is to describe the milestones in the evolution of cellular mobile systems. Particular attention is paid to the third generation (3G) systems to which the UMTS belong. The performance of mobile cellular systems is often discussed with respect to the radio access technology they support, thus neglecting other important aspects. However, a cellular mobile communication system is much more than a simple radio access method, as illustrated in Figure 1.1. The mobile terminal is the vector enabling a user to access the mobile services he subscribed to throughout the radio channel. The core network is in charge of handling mobile-terminated and mobileoriginated calls within the mobile network and enables communication with external networks, both fixed and mobile. Billing and roaming functions are also located in the core network. The transfer of users data from the terminal to the core network is the role of the radio access network. Implementing appropriate functions gives to the core network and to the terminal the impression of communicating in a wired link. One or several radio access technologies are implemented in both the radio access network and the mobile terminal to enable wireless radio communication. Radio access technology Mobile communications network Radio access Core network network Fixed & mobile networks (PSTN, ISDN, Internet ) Figure 1.1. Basic components of a mobile communications network

18 2 UMTS 1.1. Multiple-access techniques used in mobile telephony Surveying the different multiple-access techniques is equivalent to describing the key milestones in the evolution of modern mobile communication systems. In the past, not all users of the radio spectrum recognized the need for the efficient use of the spectrum. The spectrum auctions for UMTS licenses have emphasized the fact that the radio spectrum is a valuable resource. Thus, the major challenge of multiple-access techniques is to provide efficient allocation of such a spectrum to the largest number of subscribers, while offering higher data rates, increased service quality and coverage Frequency division duplex (FDD) and time division duplex (TDD) Conventional mobile communication systems use duplexing techniques to separate uplink and downlink transmissions between the terminal and the base station. Frequency division duplex (FDD) and time division duplex (TDD) are among the transmission modes which are the most commonly employed. The main difference between the two modes, as shown in Figure 1.2, is that FDD uses two separate carrier bands for continuous duplex transmission, whereas in TDD duplex transmission is carried in alternate time slots in the same frequency channel. In order to minimize mutual interference in FDD systems, a guard frequency is required between the uplink and downlink allocated frequencies (usually 5% of the carrier frequency). On the other hand, a guard period in TDD systems is required in order to reduce mutual interference between the links. Its length is decided from the longest round-trip delay in a cellular system (in the order of s). Base station f 1 (a) FDD mode DL Mobile terminal frequency f 2 Guard frequency UL frequency Base station f 1 time (b) TDD mode UL: Uplink DL: Downlink UL DL DL DL DL UL Guard period Mobile terminal time Figure 1.2. Duplexing modes used in modern mobile communications systems

19 Evolution of Cellular Mobile Systems Frequency division multiple access (FDMA) FDMA is the access technology used for first generation analog mobile systems such as the American standard AMPS (Advanced Mobile Phone Service). Within an FDMA system, each subscriber is assigned a specific frequency channel as illustrated in Figure 1.3a. No one else in the same cell or in a neighboring cell can use the frequency channel while it is allocated to a user when an FDMA terminal establishes a call, it reserves the frequency channel for the entire duration of the call. This fact makes FDMA systems the least efficient cellular systems since each physical channel can only be used by one user at a time. Far from having disappeared, the FDMA principle is part most of modern digital mobile communication systems where it is used as a complement to other radio multiplexing schemes Time division multiple access (TDMA) GSM, TDMA/136 and PCS are second generation mobile standards based on TDMA. The key idea behind TDMA relies on the fact that a user is assigned a particular time slot in a frequency carrier and can only send or receive information in those particular times (see Figure 1.3b). When all available time slots in a given frequency are used, the next user must be assigned a time slot on another frequency. Information flow is not continuous for any user, but rather is sent and received in bursts. The important factor to be considered while designing is that these time slices are so small that the human ear does not perceive the time being divided. In GSM up to 8 users may in theory share the same 200 khz frequency band almost simultaneously, whereas in IS-136 different users can be allocated to 3 time slots within a 30 khz frequency channel. The capacity of TDMA is about 3 to 6 times as much as that of FDMA [RAP 96] Code division multiple access (CDMA) In a CDMA system, unique digital codes, rather than separate radio frequencies, are used to differentiate users (see Figure 1.3c). The codes are shared by the terminal and the base station. All users access the entire spectrum allocation all of the time, that is, every user uses the entire block of allocated spectrum space to carry his/her message. CDMA technology is used in 2G IS-95 (cdmaone) mobile communication systems and is also part of UMTS and cdma2000 3G standards.

20 4 UMTS time base station user 1 utilisateur user 2 2 user 3 f 1 f 2 f 3 frequency frequency spectral density f f f f 1 f call 1 call 2 call 3 call 1 call 2 call 3 frequency frequency f 2 f 3 f 2 f 3 f f 1 1 time time a) FDMA base station user 1 utilisateur user 2 2 user 3 frequency t 1 t 2 t 3 time time spectral density call 4 call 4 call 1 call 2 call 3 f 1 f 2 f 1 f 2 frequency frequency call 7 call 7 call 8 call 9 call 5 call 6 call 1 call 2 call 3 call 8 call 9 call 5 call 6 f 3 t 1 f 3 t 1 f f 1 1 f f 2 t 2 t 3 2 t 2 t 3 time time b) FDMA/TDMA frequency base station user 1 utilisateur user 2 2 user 3 user 4 c 1 c 2 c 3 c 4 code code spectral density call 4 call 4 c 4 c 4 call 3 call 3 c 3 c 3 call 2 call 2 c 2 c 2 call 1 call 1 c 1 c 1 call 8 c 4 call 7 c 3 call 6 c 2 call 5 c 1 frequency frequency f 1 f2 f3 f 1 f2 f3 call 8 c 4 call 7 c 3 call 6 c 2 call 5 c 1 call 12 call 12 c 4 c 4 call 11 call 11 c 3 c 3 call 10 call 10 c 2 c 2 call 9 call 9 c 1 c 1 time time c) FDMA/CDMA Figure 1.3. FDMA, TDMA and CDMA multiplex access principle

21 Evolution of Cellular Mobile Systems 5 A very popular example used to stress the differences between FDMA, TDMA and CDMA is as follows. Imagine a large room (frequency spectrum) intended to accommodate many pairs of people. Due to dividing walls, individual offices can be created within the room. They are then allocated to each pair of people so that their conversation can be isolated from noise generated by the other parties. Each office is like a single frequency/channel (principle of FDMA). No one else could use the office until the conversation was complete, whether or not the different pairs were actually talking. A better usage of each office can be achieved by accommodating multiple pairs of people within the same room. For this to work, each party shall respect a rule that is to keep silent while one pair is talking (principle of TDMA). The important factor to be considered is that these silence periods shall be small enough that the human ear cannot perceive the time slicing. In the analogy with CDMA technology, all the offices are eliminated to create open-spaces instead, so that conversation can be carried out at any time. The rule is now for all pairs to hold their conversations in a different language the brains of contiguous pairs of people being able to naturally filter interference from the other pairs. The languages are analog to the codes assigned by the CDMA system. In theory, it should be possible to accommodate in the large room as much pairs as permitted by the cubic-volume of each person and provided that the number of available languages is enough. Unfortunately, even if the parties speak in different languages, a sudden raise of the voice volume of one couple may disturb the conversations of all the neighboring pairs. This problem may be overcome by implementing an automatic mechanism to control the voice volume of each party. In a CDMA system, this is actually a power control scheme whose performance is of paramount importance for the system to operate properly. However, despite such mechanism, adding the contribution of all the voices, no matter how low their level is, may produce an overall background noise in the room that makes it too difficult to hold a clear conversation. In such a case, some couples may be required to get out from the room or just to remain silent Space division multiple access (SDMA) SDMA technique is based on deriving and exploiting information on the spatial position of mobile terminals. The radiation pattern of the base station is adapted in both uplink and downlink directions to each different user in order to obtain, as illustrated in Figure 1.4, the highest gain in the direction of the mobile user. At the same time, radiation which is zero shall be positioned in the directions of interfering mobile terminals, the ultimate goal being the overall enhancement of capacity and coverage within the mobile system [RHE 96]. SDMA approach can be integrated

22 6 UMTS with different multiple access techniques (FDMA, TDMA, CDMA) and therefore it can be optionally used in all modern mobile communications systems. user 2 interferer user N user 1 f 1 f 1 f 1 base station Figure 1.4. Space division multiple access (SDMA) principle Orthogonal frequency division multiplexing (OFDM) OFDM is a special case of multi-carrier modulation. The main idea is to split a data stream into N parallel streams of reduced data rate and transmit each of them on a separate sub-carrier. High spectral efficiency is achieved in OFDM since a large number of sub-carriers where overlapping spectra is used. OFDM can be combined with FDMA, TDMA and CDMA methods in order to obtain the access schemes referred to as MC-FDMA, MC-TDMA and MC-CDMA, respectively (see Figure 1.5). OFDM has been adopted in the terrestrial digital video broadcasting (DVB-T) standard and in the digital audio broadcasting (DAB) standard followed by the wireless local area network standards IEEE a/g, IEEE , BRAN, HIPERLAN/2 and HIPERMAN. Although not used in current 2G/3G mobile radio systems, the successful deployment of the OFDM technique has encouraged several studies intended to design new broadband air interfaces for 4G mobile systems (see Chapter 13).

23 Evolution of Cellular Mobile Systems 7 OFDM symbols Sub-carrier user 1 user 2 user 2 user 1 a) MC-FDMA time OFDM symbols Sub-carrier user 1 user 2 user 2 user 1 Sub-carrier b) MC-TDMA time OFDM symbols user 1 and user 2 c) MC-CDMA time Figure 1.5. Examples of multiple access for two users based on the OFDM principle

24 8 UMTS 1.2. Evolution from 1G to 2.5G Rather than a revolution, third-generation (3G) systems are an evolution from second-generation (2G) digital systems From 1G to 2G 1G phones were analog, used for voice calls only, and their signals were transmitted by the method of frequency modulation (FM). AMPS was the first 1G system to start operating in the USA (in July 1978). It was based on the FDMA technique and FDD. In Europe, the situation was every man for himself and almost each country developed a standard in its own: Radiocom 2000 in France, NMT 900 in Nordic countries, TACS in England, NETZ in Germany, etc. International roaming was at that time more of a utopia. 2G mobile telephone networks were the logical next stage in the development of cellular mobile systems after 1G, and they introduced for the first time a mobile phone system that used purely digital technology. At the end of the last century, 2G mobile phones become a mass consumer product due to the amazing progress in semiconductors reducing the size and cost of electronic components. Also, aggressive deregulation of telecommunications policies enabled the development of several operators within a same country, thus leading to attractive subscription offers. Being digital, 2G systems introduced new services besides traditional voice transmission, such as short messaging service (SMS) and fax. They also enabled the access to digital fixed networks like Internet and ISDN. One of the successful 2G digital systems is GSM, a European mobile phone standard based on the TDMA technique. Around 70% of mobile phone subscribers in the world have adopted GSM nowadays. In the USA, a different form of TDMA is used in the system known as TDMA/136 (formerly IS-136 or D-AMPS) and there is another US system called IS-95 (cdmaone), based on the CDMA approach. Finally, the Personal Digital Communications (PDC) standard is the Japanese contribution to 2G, which also relies on the TDMA principle. Table 1.1 shows key radio characteristics of 2G mobile cellular systems Enhancements to 2G radio technologies: 2.5G By the late 1990s the market was ready for new mobile communication technologies to evolve from 2G and created pressure for enhanced data delivery and telephony services, global roaming, Internet access, , and even video. Unfortunately, standards for 3G systems were in the process of being developed. A

25 Evolution of Cellular Mobile Systems 9 more immediate solution to meet these demands was needed, thus leading to the socalled 2.5G. Standard TDMA/136 (D-AMPS) IS-95 (cdmaone) GSM PDC Origin USA USA Europe Japan Commercial launch Main operation band (Mhz) (UL) (DL) 1,850-1,910 (UL) 1,930-1,990 (DL) (UL) (DL) 1,850-1,910 (UL) 1,930-1,990 (DL) (UL) (DL) (UL) (DL) 1,710-1,785 (UL) 1,805-1,880 (DL) 1,850-1,910 (UL) 1,930-1,990 (DL) (UL) (DL) 1,429-1,453 (UL) 1,477-1,501 (DL) Access method FDMA/TDMA FDMA/CDMA FDMA/TDMA FDMA/TDMA Duplexing FDD FDD FDD FDD Channel bandwidth 30 khz 1,250 khz 200 khz 25 khz Modulation /4 DQPSK QPSK/O-QPSK GMSK /4 DQPSK Table 1.1. Comparison of radio specifications for 2G cellular mobile systems As shown in Figure 1.6, three technologies have most often been proposed to upgrade GSM in the context of 2.5G: High-Speed Circuit Switched Data (HSCSD), General Packet Radio Service (GPRS) and Enhanced Data Rates for Global Evolution (EDGE). HSCSD enables transfer rates of up to 57.6 Kbps by allocating more than one time slot per user. GPRS enables the efficient use of the air interface by accommodating flexible user rates for packet oriented transfer using time slot

26 10 UMTS assignment on demand (rather than via permanent occupation as in GSM and HSCSD). The result is an improved data rate of up to (theoretical) Kbps ( Kbps), versus the 9.6 Kbps rate of standard GSM networks. EDGE offers advanced modulation (8-QPSK in addition to GMSK) to achieve higher data rates (in the theoretical order of 384 Kbps). By applying EDGE to GPRS and EDGE to HSCSD, the hybrid techniques EGPRS and ECSD are obtained, respectively. While the role of ECSD in today s cellular market is marginal, EGPRS has been adopted by several GSM operators to make cost-effective the investments on GPRS and as a complement to UMTS network coverage. IS-95B brings about improvements for handover algorithms in multi-carrier environments to the first version of the cdmaone standard (IS-95A). Although IS-95B is based on CDMA, its logic for improvement is very similar to that of GPRS: rather than time slots given to the user as in GPRS, in IS-95B channels can still be aggregated to allow higher data rates of up to 115 Kbps bundling up to eight 14.4 or 9.6 Kbps data channels. IS-136 < 14.4 kbps GSM < 14.4 kbps IS kbps GSM/HSCSD 57 kbps GSM/GPRS kbps IS-136HS indoor 2 Mbps IS-136HS outdoor 384 kbps (GPRS/EDGE) EGPRS UMTS PDC/PDC-P < 30 kbps cdma2000 1XEV-DO (HDR) 2.4 Mbps UTRA/FDD 2 Mbps UTRA/TDD 2 Mbps cdma2000 1XEV-DV 3.1 Mbps HSDPA 10 Mbps HSUPA 5.5 Mbps cdmaone A cdma2000 phase 1 cdma2000 phase 2 cdmaone B < 14.4 kbps (cdma2000 1X-MC) (cdma2000 3X-MC) 115 kbps 307 kbps 2 Mbps 2G 2.5G 3G 3.5G Figure 1.6. Migration of 2G standards towards 3G. Some data rates are purely theoretical and they may be different depending on the hypothesis considered for their calculation

27 Evolution of Cellular Mobile Systems 11 TDMA/136 is also being enhanced to provide better voice capabilities, capacity, coverage, quality and data rates. In its evolution to 3G, an intermediate phase is envisaged where the bitrate of 30 khz radio carrier will be increased by means of high-level modulation and by the use of 6 time slots rather than 3 within a 40 ms frame. This enhanced version of TDMA/136 is designated by By applying GPRS technology, packet transmission data rates of up to 64 Kbps can be obtained. In 2001, Japan was the first country to introduce a 3G system commercially known as FOMA (Freedom Of Mobile Multimedia Access). It was based on an early version of UMTS standard specifications. Unlike the GSM systems, which developed various ways to deal with demand for improved services, Japan had no 2.5G enhancement stage to bridge the gap between 2G and 3G, and so the move into the new standard was seen as a fast solution to their capacity problems in PDC networks. Nevertheless, the standard implemented a packet mode variant to PDC (P- PDC), which gives packet data rates of up to 28.8 Kbps. After the USA that leaded the 1G of mobile cellular systems; after Europe that played the first role in 2G, Asia, and more precisely, Japan, China and Korea, are willing to be the key players in the newborn 3G G systems in IMT-2000 framework It is wrong to believe that UMTS is the only 3G system around the world, although this was the original purpose of the ITU (International Telecommunications Union). This unique 3G system should be called FPLMTS (Future Public Land Mobile Telecommunications System). The name being unpronounceable, it was changed to IMT-2000 (IMT stands for international mobile telecommunications 1 ). A problem arose when, in 1998, no less that ten terrestrial radio access technologies were submitted to the ITU by its members the regional standardization organisms. In the end, the term IMT-2000 generated not a single 3G standard but a family of standards, most of them associated to their numerous 2G predecessors. Note that IMT-2000 consists of both terrestrial component and satellite component radio interfaces. Only the analysis of its terrestrial radio interfaces is in the scope of this book. 1 The number 2000 was supposed to represent: the year 2000, when the ITU expected the system would become available; the data rates offering services around 2000 Kbps and the spectrum in the 2000 MHz region that the ITU hoped to make it available worldwide.

28 12 UMTS The key features of 3G systems in the IMT-2000 framework are: high data rates. Minimum 144 Kbps in high mobility environments (more than 120 km/h); 384 Kbps, in common mobility environments (less than 120 km/h) and 2 Mbps, achievable in stationary and low mobility environments (less than 10 km/h); support for circuit-switched services (e.g. PSTN- and ISDN-based networks) as well as packet-switched services (e.g. IP-based networks); capability for multimedia applications, involving services with different quality of services (bitrate, bit error rate, delay, etc.); high voice quality; similar to that provided by wired-networks; small terminal for worldwide use and with worldwide roaming capability; compatibility of services within IMT-2000 and with the fixed networks; interoperability with their 2G/2.5G predecessors. Restraining the definition of a 3G system to radio data rates and mobility environments made the term 3G become rather vague. This can be understood by keeping in mind that at that time (around 1992) usage of Internet was limited to academic and technical circles. The definition was originally quite specifically defined, as any standard that provided mobile users with the performance of ISDN or better. It is one of the goals of this book to show all the technical innovations behind a 3G network such as UMTS in addition to the amazing feats performed by its radio access technology (UTRA) IMT-2000 radio interfaces The radio interfaces for the terrestrial component of IMT-2000 are shown in Table 1.2, whereas Table 1.3 lists their major technical parameters. Parameters of DECT technology were deliberately omitted since this is not a major player in the 3G networks arena today, but this may change in the future. NOTE. besides the names given by IMT-2000, there is no global consensus on how to designate the 3G radio access technologies out of the ITU framework. For instance, UTRA/FDD and UTRA/TDD radio interfaces are often called WCDMA (Wideband-CDMA).

29 Evolution of Cellular Mobile Systems 13 3G radio access technology UTRA/FDD Universal terrestrial radio access frequency division duplex IMT-2000 designation IMT-2000 CDMA Direct Spread UTRA/TDD UTRA time division duplex TD-SCDMA (low chip rate UTRA/TDD) Time division synchronous CDMA Cdma2000 UWC-136 Universal wireless communications DECT Digital enhanced cordless telecommunications IMT-2000 CDMA TDD IMT-2000 CDMA Multi-carrier IMT-2000 CDMA Single-carrier IMT-2000 FDMA/TDMA Table 1.2. Radio access technologies defined in the IMT-2000 framework. The terms Cdma2000, UWC-136 and DECT designate also a complete 3G mobile network. The term multi-carrier given to cdma2000 does not mean that the OFDM technique is implemented IMT-2000 radio access technologies used by UMTS networks A UMTS network may use either UTRA/FDD, UTRA/TDD, TD-SCDMA or DECT radio access technologies. IMT-2000 CDMA Direct Spread: UTRA/FDD This radio interface is called universal terrestrial radio access (UTRA) FDD or wideband CDMA (WCDMA). UTRA/FDD employs CDMA as radio access technology. Based on direct sequence CDMA approach, the chip rate is 3.84 Mcps and operates in paired frequency bands with a 5 MHz bandwidth carrier in UL and the same in DL (see Figure 1.7a). It should be stressed that current UMTS systems deployed in Europe and in Japan are based exclusively on UTRA/FDD technology.

30 14 UMTS IMT-2000 CDMA TDD: UTRA/TDD This radio interface is called UTRA/TDD and comprises two variants, called 1.28 Mcps TDD (TD-SCDMA) and 3.84 Mcps TDD. Chinese standardization authorities originally proposed TD-SCDMA as an alternative to European UTRA/TDD. A harmonization process was then carried out and TD-SCDMA is now part of UTRA/TDD specifications and it is referred to as the UTRA/TDD low-chip rate option [TS , R4]. a) UTRA/FDD 5 MHz ( 2) b) Cdma2000 GB 1X 1X 1X GB 1.25 MHz 1.25 MHz 1.25 MHz 5 MHz ( 2) c) UTRA/TDD (3.84 Mcps variant) 5 MHz d) TS-SCDMA (1.28 Mcps variant) 1.6 MHz 1.6 MHz 1.6 MHz 5 MHz Figure 1.7. Spectrum usage for IMT-2000 technologies based on CDMA (GB: guard band)