3G CDMA2000 Wireless System Engineering

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3 3G CDMA2000 Wireless System Engineering

4 For a listing of recent titles in the Artech House Mobile Communications Library, turn to the back of this book.

5 3G CDMA2000 Wireless System Engineering Samuel C. Yang Artech House, Inc. Boston London

6 Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the U.S. Library of Congress. British Library Cataloguing in Publication Data Yang, Samuel C. 3G CDMA2000 wireless system engineering. (Artech House mobile communications library) 1. Wireless communication systems. 2. Code division multiple access I. Title 621.3'845 ISBN x Cover design by Yekaterina Ratner 2004 ARTECH HOUSE, INC. 685 Canton Street Norwood, MA All rights reserved. Printed and bound in the United States of America. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the publisher. All terms mentioned in this book that are known to be trademarks or service marks have been appropriately capitalized. Artech House cannot attest to the accuracy of this information. Use of a term in this book should not be regarded as affecting the validity of any trademark or service mark. International Standard Book Number: x

7 To my wife Jenny and my son Daniel

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9 Contents Preface Acknowledgments xiii xvii CHAPTER 1 Introduction to 3G CDMA Third Generation Systems Protocol Architecture Other Elements of Protocol Architecture Spreading Rate 1 and Spreading Rate Differences Between IS-2000 and IS Signaling Transmission Concluding Remarks 8 References 9 CHAPTER 2 Physical Layer: Forward Link Introduction Radio Configurations Signaling Channels Forward Dedicated Control Channel (F-DCCH) Quick Paging Chanel (F-QPCH) Forward Common Control Channel (F-CCCH) Broadcast Control Channel (F-BCCH) Common Assignment Channel (F-CACH) Common Power Control Channel (F-CPCCH) Pilot Channels User Channels Forward Fundamental Channel (F-FCH) Forward Supplemental Channel (F-SCH) Channel Structure Modulation Capacity Gain: Forward Link 34 References 35 Selected Bibliography 35 vii

10 viii Contents CHAPTER 3 Physical Layer: Reverse Link Introduction Radio Configurations Signaling Channels Reverse Dedicated Control Channel (R-DCCH) Reverse Common Control Channel (R-CCCH) Enhanced Access Channel (R-EACH) Reverse Pilot Channel (R-PICH) User Channels Reverse Fundamental Channel (R-FCH) Reverse Supplemental Channel (R-SCH) Channel Structure Modulation Capacity Gain: Reverse Link 52 References 53 Selected Bibliography 53 CHAPTER 4 Medium Access Control Introduction Primitives Multiplex Sublayers Radio Link Protocol (RLP) Overview of Layer 2 Protocols llustration of the RLP Concluding Remarks Signaling Radio Burst Protocol (SRBP) System Access Basic Access Mode Reservation Access Mode Power Controlled Access Mode Designated Access Mode 68 References 68 CHAPTER 5 Signaling Link Access Control Introduction LAC Sublayers Authentication and Addressing Sublayers ARQ Sublayer Utility Sublayer Segmentation and Reassembly Sublayer Sublayer Processing Common Signaling: Forward Link Common Signaling: Reverse Link Dedicated Signaling: Forward Link 77

11 Contents ix Dedicated Signaling: Reverse Link Interaction of Layer and Sublayers Transmit Side Receive Side 82 References 83 CHAPTER 6 Signaling: Upper Layers Overview State Transitions: Call Processing Initialization State Mobile Station Idle State System Access State Mobile Station Control on the Traffic Channel State Mode Transitions: Packet Data Transmission Active Mode Control Hold Mode Dormant Mode Transitions Channel Setup Example 1: Base Station-Originated Voice Call Example 2: Mobile Station-Originated Voice Call Example 3: Mobile Station-Originated Packet Data Call Example 4: Supplemental Channel Request During a Packet Data Call Concluding Remarks 104 References 104 CHAPTER 7 Power Control Introduction Power Control of the Forward Link Inner Loop and Outer Loop Power Control of Multiple Forward Traffic Channels Power Control of the Reverse Link: Open Loop Power Control of Multiple Reverse Channels Summary Power Control of the Reverse Link: Closed Loop Inner Loop and Outer Loop Power Control of Multiple Reverse Channels 119 References 121 CHAPTER 8 Handoff Introduction Soft Handoff Active Set 124

12 x Contents Candidate Set Neighbor Set Remaining Set Set Transitions Example: Soft Handoff Idle Handoff Active Set Neighbor Set Private Neighbor Set Remaining Set Idle Handoff Process Access Entry Handoff Access Handoff Active Set Neighbor Set Remaining Set Access Handoff Process Access Probe Handoff Concluding Remarks 139 References 140 CHAPTER 9 System Performance Introduction Channel Supervision Forward Link: Traffic Channel Forward Link: Common Channel Reverse Link Code Management Generation of Walsh Codes Assignment of Walsh Codes: Forward Link Quasi-Orthogonal Functions Assignment of Walsh Codes: Reverse Link Turbo Codes Transmit Diversity Orthogonal Transmit Diversity Space Time Spreading Concluding Remarks 156 References 156 Selected Bibliography 157 CHAPTER 10 System Design: Coverage Introduction Forward Pilot Channel Forward Fundamental Channel Forward Supplemental Channel 163

13 Contents xi 10.5 Upper Bounds of Interference: Forward Link Reverse Fundamental Channel Reverse Supplemental Channel Upper Bounds of Interference: Reverse Link E b /N 0 and Receiver Sensitivity Concluding Remarks 169 Reference 170 CHAPTER 11 System Design: Capacity Introduction Mathematical Definitions Received Signal Power Loading Factor Reverse Link Capacity Capacity Improvements in IS Capacity Improvements in a System Forward Link Capacity Capacity Improvements in IS Capacity Improvements in a System 183 References 185 CHAPTER 12 Network Architecture Introduction G Network Network Elements Protocols G Network Network Elements Protocols Simple IP Mobile IP Concluding Remarks 196 References 197 CHAPTER 13 1xEV-DO Network Introduction xEV-DO Network Protocol Architecture Application Layer Stream Layer Session Layer Connection Layer 206

14 xii Contents Security Layer Concluding Remarks 210 References 211 CHAPTER 14 1xEV-DO Radio Interface: Forward Link Introduction MAC Layer Forward Traffic Channel MAC Protocol Control Channel MAC Protocol Physical Layer Pilot Channel Forward Traffic Channel/Control Channel MAC Channel Time Division Multiplexing Modulation Concluding Remarks 226 References 226 Selected Bibliography 226 CHAPTER 15 1xEV-DO Radio Interface: Reverse Link Introduction MAC Layer Reverse Traffic Channel MAC Protocol Access Channel MAC Protocol Physical Layer Reverse Traffic Channel Access Channel Modulation Reverse Power Control Open-Loop Power Control Closed-Loop Power Control 240 References 240 Selected Bibliography 240 About the Author 241 Index 243

15 Preface Over the past few years, many fundamental changes have taken place in wireless communications that will influence the future of this dynamic field. One phenomenon driving these changes has been the integration of wireless communication devices in people s lives. While the 1990s were the years when wireless voice telephony became popular, the 2000s should be the time when wireless data applications are truly un-tethered from homes and offices. As more people adopt wireless communication devices and applications effected by these devices, the demand on wireless networks will continue to grow. Although code division multiple access (CDMA) has become an integral part of the ensemble of third generation (3G) standards, many wireless network operators have found the implementation of IS-2000 affords a good balance between cost and performance of providing 3G services, especially if an operator evolves its network from IS-95 to IS As such, IS-2000 has become a popular choice of 3G for operators around the world, notably in Asia and the Americas. This book has been written to address the technical concepts of IS The focus is on basic issues, and every effort has been made to present the material in an expository and interesting fashion. One strategy is to utilize examples not to offer proofs (as they cannot) but to help the reader grasp the fundamental issues at hand. In this regard, mathematical details and models have an important role but serve as means to an end. While CDMA is by nature theory-intensive, every attempt is made to strike a balance between theory and practice. In addition, to minimize the duplication of foundational material of spread spectrum communications and IS-95, this book does not describe those introductory concepts (e.g., synchronization of PN codes) in detail and assumes that the reader is familiar with basic material such as those found in CDMA RF System Engineering (Samuel Yang, Artech House, 1998). Furthermore, this book assumes that the reader is familiar with the layered frameworks of the Internet Model and OSI Model. In 3G, the system requires the full participation of not only the physical layer but also medium access control, link access control, and upper layers to provide not only circuit voice call but also packet data call functions. Hence in 3G, one needs to focus on the entire system rather than just on a particular layer. To that end, the book starts with a layer-by-layer treatment of IS In Chapters 1 to 6, it follows the protocol layer framework and describes IS-2000 from Layers 1 to 3. Chapter 1 introduces basic concepts and requirements of 3G and highlights key differences between IS-2000 and IS-95. Chapters 2 and 3 describe physical layers of forward and reverse links, respectively. The channel structure and functions of different channels are described in these two chapters. Chapter 4 covers medium access xiii

16 xiv Preface control and focuses on radio link protocol, signaling radio burst protocol, and system access. Then, Chapter 5 goes into link access control; this chapter first reviews the functions of the sublayers of link access control, then it illustrates sublayer processing on both forward and reverse links. Chapter 6 goes over Layer 3 or upper layer signaling of IS-2000; the emphasis here is on call processing, state transition, and mode transitions. After building the foundation of the structure of an IS-2000 system, the book proceeds to the systems aspects of IS-2000 in Chapters 7 to 12. Since IS-2000 contains power control and handoff functions that are superior to those in IS-95-A, Chapters 7 and 8 describe in detail power control and handoff functionalities, respectively. Chapter 9 then proceeds to cover system performance and describes those features adopted by IS-2000 to increase performance such as code management, turbo codes, and transmit diversity. Since a CDMA system essentially trades off coverage versus capacity, these design aspects are presented in Chapters 10 and 11. In particular, Chapter 10 covers coverage, and Chapter 11 covers capacity. These two chapters contain systematic developments of key concepts, and necessary mathematical developments are included where necessary to clarify the material. Chapter 12 is on network architecture and serves as a capstone on all the chapters presented thus far. It describes the IS-2000 architecture from a network perspective and shows how a 3G network differs and evolves from a 2G network. This chapter introduces how IS-2000 works and interacts with other elements in the network. Advanced concepts such mobile IP are also introduced here. The last three chapters concern a special topic that is of particular interest 1xEV-DO (1x Evolution for Data Optimized), which has gained popularity in recent years and is designed to work with an IS-2000 system. The topics related 1xEV-DO are included to make the book a more complete reference. Specifically, Chapter 13 focuses on the top five layers of 1xEV-DO (i.e., application, stream, session, connection, and security), and Chapters 14 and 15 cover medium access control and physical layers of forward and reverse links, respectively. Without a loss generality, this book emphasizes Spreading Rate 1 at 1.25 MHz. The discussions on Spreading Rate 1 can be readily extended to direct-spread or multiple-carrier options of wider bandwidths. In addition, throughout the book we cite specific examples of radio configurations instead of exhaustively describe the details of every radio configuration. These selective descriptions serve to illustrate more fully the reason for a particular implementation. Overall, the emphasis of the book is on the conceptual understanding of the salient points, focusing on the how and why instead of the what. It is hoped that the mastery of the material presented will serve as a strong foundation from which readers can further explore the technology. This book is intended as a reference for radio frequency (RF) and system engineers, technical managers, and short-course students who desire to quickly get up to speed on the essential technical issues of IS The material covered in the book is broad enough to serve students of various backgrounds and interests and to allow teachers much flexibility in designing their course material. As such, this book should be a good complement to advanced undergraduate or first-year graduate level courses in wireless communications as well.

17 Preface xv Finally, the material presented in this book is given for informational purpose and instructional value and is not guaranteed for any particular purpose. The publisher or the author does not offer any warranties or representations and does not accept any liabilities with respect to the material presented in this book. Furthermore, as technical information changes quickly, the purchaser of the book or user of the information contained in this book should seek updated information from other sources. The publisher or the author assumes no obligation to update or modify the information, nor does the publisher or the author undertake any obligation to notify the purchaser of the book or user of the information contained in the book of any update. The purchase of the book or the use of the information contained in the book signifies the purchaser s or user s agreement to the above.

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19 Acknowledgments As always, the completion of a book would not be possible without the support of many people. I would like to thank Barry Pasternack who has given me encouragement during this project as well as guidance in other areas, Mabel Kung who has spent many hours giving me support and words of wisdom, Paul Minh who has given me advice during the writing of this book, and Joseph Sherif who is always willing to make himself available for conversations. I appreciate Samir Chatterjee who often meets with me to discuss various technical topics, and Lorne Olfman who has continued to give me guidance out of his busy schedule. I also thank the reviewer whose suggestions have made this a better book. I am also grateful to the editors at Artech: Mark Walsh who has given me much valuable feedback in the initial formulation of this project, and Barbara Lovenvirth who has done a great job managing the project and keeping me on track. I also thank Jill Stoodley and the staff at Artech for their help in the production of the book. No acknowledgment will be complete without mentioning my wife, Jenny, who has supported all my endeavors with a gentle spirit and has always encouraged me. I can always count on her for being there, and I am very much thankful for her. Last and not the least, I would like to mention my son, Daniel, who has been a source of my joy; his laughter and cheerful spirit have always given me strength during challenging parts of this project, and this book is also dedicated to him. xvii

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21 CHAPTER 1 Introduction to 3G CDMA 1.1 Third Generation Systems While there are several wireless standards and systems that qualify as third generation (3G) systems, this book specifically deals with the IS-2000 implementation of 3G. In the mid-1990s, the International Telecommunication Union (ITU) initiated an effort to develop a framework of standards and systems that will provide wireless and ubiquitous telecommunications services to users anywhere at anytime. Subsequently, International Mobile Telecommunications-2000 (IMT-2000), a subgroup of the ITU, published a set of performance requirements of 3G. It is useful to review the performance requirements of a 3G wireless system, which are as follows (for both packet-switched and circuit-switched data): A minimum data rate of 144 Kbps in the vehicular environment; A minimum data rate of 384 Kbps in the pedestrian environment; A minimum data rate of 2 Mbps in the fixed indoor and picocell environment. In addition, in all environments the system must support same data rates for both forward and reverse links (symmetric data rates), as well as support different data rates for both forward and reverse links (asymmetric data rates) [1]. Some standards and systems such as Universal Mobile Telephone System (UMTS) are implemented in the new 3G spectrum (e.g., in Europe). While other standards and systems such as IS-2000 can introduce 3G services in spectrums already used by second generation (2G) systems (e.g., in North America). The latter case takes into account those investments already deployed in the field where useful and necessary [2]. The correction in the valuation of high-technology assets in early 2000 underscores the importance of making calculated infrastructure investment while taking into account the market demand for these services. This consideration is one reason why IS-2000 has gained popularity in the initial deployment of 3G [3]. In addition, as will be seen in later chapters of this book, IS-2000 is backward compatible with existing 2G IS-95 systems. This backward compatibility gives IS-2000 two important advantages. First, IS-2000 is able to support the reuse of existing IS-95 infrastructure equipment and hence requires only incremental investment to provide 3G services. Second, because IS-2000 represents a natural technical evolution from its predecessor, there is a lower implementation risk when transitioning to 3G. 1

22 2 Introduction to 3G CDMA 1.2 Protocol Architecture One architectural difference between the IS-2000 standard and the IS-95 standard is that IS-2000 calls out explicitly the functions of four different protocol layers. These layers are the physical layer, medium access control, signaling link access control, and upper layer. Physical layer (Layer 1) [4]: The physical layer is responsible for transmitting and receiving bits over the physical medium. Since the physical medium in this case is over the air, the layer would have to convert bits into waveforms (i.e., modulation) to enable their transmission through air. In addition to modulation, the physical layer also carries out coding functions to perform error control functions at the bit and frame levels. Medium access control (MAC) sublayer (Layer 2) [5]: The MAC sublayer controls higher layers access to the physical medium that is shared among different users. In this regard, MAC carries out analogous functions as a MAC entity that controls a local area network (LAN). Whereas a LAN MAC controls different computers access to the shared bus, the IS-2000 MAC sublayer manages the access of different (low-speed voice and high-speed data) users to the shared air interface. Signaling link access control (LAC) sublayer (Layer 2) [6]: The LAC sublayer is responsible for the reliability of signaling (or overhead) messages that are exchanged. Recall that the over-the-air medium is extremely error-prone, and information messages are at times received (and accepted) with errors. On the other hand, since signaling messages provide important control functions, these messages have to be reliably transmitted and received. The LAC sublayer performs a set of functions that ensure the reliable delivery of signaling messages. Upper layer (Layer 3) [7]: The upper layer carries out the overall control of the IS-2000 system. It exercises this control by serving as the point that processes all and originates new signaling messages. The information (both data and voice) messages are also passed through Layer 3. Recall that the IS-95 standard does not explicitly and separately describe the functions of each layer. However in IS-95 those functions that are carried out by the layers do exist. For example, in IS-95 mobile access is logically a function of the MAC sublayer, but its descriptions are lumped together with the other functions within a single standard. At this point the reader may ask why the layered architecture was not employed in IS-95 but now used in IS The layered architecture is now used in IS-2000 because it brings the system into conformance with the 3G architecture delineated in IMT The IMT-2000 framework calls for different networks to cooperate to provide services to end users, and the level and extent of these cooperation are more clearly organized if viewed from the perspective of the layered architecture. Welldefined layer functions provide modularity to the system. As long as a layer still performs its functions and provides the expected services, the specific implementation

23 1.3 Other Elements of Protocol Architecture 3 of its functions can be modified or replaced without requiring changes to the layers above and below it [8]. Figure 1.1 shows the structure of the protocol architecture used by IS Without a loss of generality, this figure is shown from the perspective of the mobile station; a similar figure can also be drawn from the perspective of the base station by reversing the direction of some arrows and changing the placement of some entities. Figure 1.1 is a rather important figure and we will refer to it from time to time throughout the book. For now, note the three different layers (Layers 1, 2, and 3), the two sublayers in Layer 2 (MAC and LAC), the entities in the layers [e.g., Signaling Radio Burst Protocol (SRBP)], and the communication paths among the layers and entities. Also note that the layer structure shown in Figure 1.1 resembles that of the Open Systems Interconnection (OSI) Reference Model [9]. 1.3 Other Elements of Protocol Architecture In addition to the individual layers themselves, other important elements of the protocol architecture are described as follows: Physical channels: The physical channels are the communication paths between the physical layer and the common/dedicated channel multiplex sublayers. The physical channels are designated by uppercase letters. In the designation, the first Layer 3 Upper layers LAC sublayer Signaling L3PDU L3PDU Signaling LAC LAC PDU Data burst Data burst Data services RLP SDU RLP SDU Voice services r-dtch voice f-dtch voice Layer 2 MAC sublayer SRBP r-csch f-csch f-csch r-dsch f-dsch RLP r-dtch f-dtch Common channel multiplex sublayer Dedicated channel multiplex sublayer Layer 1 Physical layer R-ACH R-EACH R-CCCH F-SYNCH F-CPCCH F-CACH F-PCH F-CCCH F-BCCH R-FCH R-SCH R-DCCH F-FCH F-SCH F-DCCH Reverse link: coding and modulation Forward link: demodulation and decoding RL FL Figure 1.1 Structure of the protocol architecture used by IS (Note that this structure is shown from the perspective of the mobile station. After: [5].)

24 4 Introduction to 3G CDMA letter and the dash stand for either forward link (F-) or reverse link (R-), and the last two letters CH always stand for channel. For example, R-ACH stands for reverse access channel, and F-FCH stands for forward fundamental channel. A list of physical channel names and their designations is shown in Table 1.1; note that legacy IS-95 physical channels are denoted with asterisks. Logical channels: The logical channels are the communication paths between the common/dedicated channel multiplex sublayers and higher layer entities. One can think of logical channels as carrying the logical units of signaling or user information. Contrast those with physical channels which can be thought of as the actual physical vehicles that transport the signaling or user information over the air. The logical channels are designated by lower-case letters. The first letter and the dash stand for either forward link (f-) or reverse link (r-), and the last two letters ch always stand for channel. For example, r-csch stands for reverse common signaling channel, and f-dtch stands for forward dedicated traffic channel. A list of logical channel names and their designations are shown in Table 1.2. Data unit: The data units are logical units of signaling and user information that are exchanged between SRBP entity/radio Link Protocol (RLP) entity and higher layer entities. There are two types of data units: payload data units (PDU) and service data units (SDU). PDU is used to designate those data units that are accepted by a Table 1.1 Physical Channel Designations in IS-2000 Forward Link Channel Designation Channel Name Reverse Link Channel Designation Channel Name F-SCH Forward supplemental channel R-SCH Reverse supplemental channel F-SCCH Forward supplemental code channel R-SCCH Reverse supplemental code channel F-FCH* Forward fundamental channel R-FCH* Reverse fundamental channel F-DCCH Forward dedicated control channel R-DCCH Reverse dedicated control channel F-PCH* Paging channel F-QPCH Quick paging channel R-ACH* Access channel R-EACH Enhanced access channel F-CCCH Forward common control channel R-CCCH Reverse common control channel F-BCCH Broadcast control channel F-CPCCH Common power control channel F-CACH Common assignment channel F-SYNCH* Sync channel F-PICH* Forward pilot channel R-PICH Reverse pilot channel F-TDPICH Transmit diversity pilot channel F-APICH Auxiliary pilot channel F-ATDPICH Auxiliary transmit diversity pilot channel

25 1.4 Spreading Rate 1 and Spreading Rate 3 5 Table 1.2 Logical Channel Designations in IS-2000 Forward Link Channel Designation Channel Name Reverse Link Channel Designation Channel Name f-csch Forward common signaling channel r-csch Reverse common signaling channel f-dsch Forward dedicated signaling channel r-dsch Reverse dedicated signaling channel f-dtch Forward dedicated traffic channel r-dtch Reverse dedicated traffic channel provider of service from a requester of service, and SDU those data units that are given to a provider of service by a requester of service 1. The use of PDUs and SDUs is discussed in more detail later in Chapter 4 (medium access control), Chapter 5 (link access control), and Chapter 6 (upper layer signaling). In the MAC sublayer, there are four different entities: SRBP, RLP, common channel multiplex sublayer, and dedicated channel multiplex sublayer. Common channel multiplex sublayer performs the mapping between the logical common channels (channels that are shared among multiple users) and the physical common channels. Dedicated channel multiplex sublayer performs the mapping between the logical dedicated channels (channels that are dedicated to specific users) and the physical dedicated channels. Note that while dedicated channels can be used for both signaling and user data, common channels are only used for signaling. SRBP and RLP are protocol entities in the MAC sublayer. They are described in more detail in Chapter 4. It suffices to say now that SRBP handles common-channel signaling (as opposed to dedicated-channel signaling) and RLP handles user information that is packetized in nature. 1.4 Spreading Rate 1 and Spreading Rate 3 Without a loss of generality, this book will focus on Spreading Rate 1 (also known as 1x ) of IS Spreading Rate 1 by definition uses one times the chip rate of IS-95 (i.e., Mcps). See Figure 1.2. In addition, the IS-2000 standard also supports Spreading Rate 3 (also known as 3x ). Spreading Rate 3 is used when higher data rates are desired. Spreading Rate 3 has two implementation options: direct spread (DS) or multicarrier (MC). On the forward link, Spreading Rate 3 uses the MC option by utilizing three separate RF carriers, each spread using a chip rate of Mcps. In this case, the user data is multiplexed onto three separate RF carriers that are received by the mobile. On the reverse link, Spreading Rate 3 uses the DS option. The DS option allows the mobile to directly spread its data over a wider bandwidth using a chip rate of Mcps. See Figure 1.3. To harmonize with other 3G systems such as 1. In the OSI Reference Model, a higher layer entity typically requests services from a lower-layer entity.

26 6 Introduction to 3G CDMA 1.25 MHz Forward link Base station Reverse link 1.25 MHz Mobile station Figure 1.2 Spreading Rate 1. A chip rate of Mcps occupies an RF bandwidth of 1.25 MHz MHz Forward link Base station Reverse link 3.75 MHz Mobile station Figure 1.3 Spreading Rate 3. UMTS, a Spreading Rate 3 signal can have 625 khz of guard band on each side resulting in a total RF bandwidth of 5 MHz. These options for the forward and reverse links are included in the standard in order to reduce the complexity of the mobile s receiver. As readers may have already noticed, the above-stated configurations mean that the mobile s receiver only has to receive and demodulate 1x carriers and does not have to receive and demodulate any 3x carrier. Incidentally, a mobile can also receive at Spreading Rate 3 and transmit at Spreading Rate 1. See Figure 1.4. This particular arrangement takes advantage of the fact that data rates required for downstreaming are typically higher than those required for upstreaming. Wider bandwidth options such as 6x, 9x, and 12x are under consideration for even higher data rate applications. As far as 3G systems are concerned, Spreading Rate 3 satisfies all the performance requirements as set forth by IMT-2000.

27 1.5 Differences Between IS-2000 and IS MHz Forward link Base station Reverse link 1.25 MHz Mobile station Figure 1.4 Spreading Rate 3 on forward link and Spreading Rate 1 on reverse link. As a final note: The original intention of the IS-2000 family of standards is to evolve progressively to higher data rates using wider bandwidths (i.e., 3x 12x). However, the current trend seems to be one of deploying high data rate solutions that use 1.25 MHz of bandwidth (e.g., 1xEV-DO). There are several advantages of using solutions like 1xEV-DO, one of which is that wireless operators can carve out selected 1.25 MHz carriers dedicated to and optimized for high rate data. 1xEV-DO is covered later in Chapters Differences Between IS-2000 and IS-95 IS-2000 represents a natural technical extension from its IS-95 predecessor, and this extension can be seen in the fact that IS-2000 users and IS-95 users can coexist in the same carrier. Although IS-2000 is backward compatible with IS-95, there are many differences between IS-2000 and IS-95. We will point out now, by way of introduction, those differences that represent a substantial departure from IS-95. Since the requirement of 3G and IS-2000 is transmitting and receiving at a higher data rate, two types of improvements are needed to enable data rates at or above 144 Kbps: improvements in signaling and improvements in transmission Signaling In order to implement high-rate packet-switched data, IS-2000 needs to dynamically acquire and release air link resources, and efficient signaling is required to perform quick acquisitions and releases of these resources. These new signaling mechanisms include: On the forward link, there are new overhead/signaling physical channels. They are quick paging channel (F-QPCH), forward common control channel (F-CCCH), broadcast control channel (F-BCCH), common power control channel (F-CPCCH), and common assignment channel (F-CACH).

28 8 Introduction to 3G CDMA On the reverse link, there are new overhead/signaling physical channels. They are reverse dedicated control channel (R-DCCH), enhanced access channel (R-EACH), and reverse common control channel (R-CCCH). On the reverse link, there are shorter signaling messages. IS-2000 can transmit shorter 5-ms frames on the enhanced access channel (R-EACH). This is done to reduce the probability of access collision. On the forward link, IS-2000 can also transmit shorter signaling messages. It can use shorter 5-ms frames (i.e., 1/8 rate) on the forward fundamental channel for this purpose. In addition, an IS-2000 mobile can now be in one of several modes (e.g., dormant mode) to accommodate bursty packet data transmissions and to conserve air link resources. These modes are described in more detail in Chapter 6 on upper layer signaling. The new overhead/signaling physical channels on the forward link are discussed in Chapter 2, and the new overhead/signaling physical channels on the reverse link are discussed in Chapter Transmission A higher air link capacity is obviously needed to implement high-rate data, and various changes are made to improve air link capacity to beyond that of IS-95. These changes are also made to effect a more efficient use of air link resources. Some major changes are listed below: Forward supplemental channel (F-SCH) and reverse supplemental channel (R-SCH) are added to transport high-rate user data. Reverse link now has a reverse pilot channel (R-PICH) to support coherent modulation on the reverse link. Forward link now has fast closed-loop power control (compared with the slower power control in IS-95). Power control groups are transmitted on the reverse pilot channel to enable fast closed-loop power control of the forward link. In addition to power controlling the traffic channels, IS-2000 can also power control the signaling channel (i.e., forward dedicated control channel [F-DCCH]). Supplemental channels are discussed in more detail in Chapter 2 and Chapter 3. IS-2000 power controls are discussed in more detail in Chapter 7. Other transmission improvements include the implementation of a more efficient quadrature phase-shift keying (QPSK) in the modulation stage and the use of more efficient turbo codes for high date rate transmissions Concluding Remarks The differences between IS-2000 and IS-95 are not limited to those introduced above. Throughout the book, we will regularly point out, where appropriate, more

29 1.5 Differences Between IS-2000 and IS-95 9 differences to which system engineers and planners should pay attention. Noting these differences is important because being aware of them not only facilitates the understanding of 3G IS-2000, but also leverages the experience already gained in operating 2G IS-95 systems. References [1] ITU-R Recommendation M.1225, Guidelines for Evaluation of Radio Transmission Technologies for IMT-2000, International Telecommunication Union, [2] Prasad, R., W. Mohr, and W. Konhauser (eds.), Third Generation Mobile Communication Systems, Norwood, MA: Artech House, 2000, p. 2. [3] The Economist, Mobile Telecoms: Time for plan B, Economist, September 28 October 4, 2002, pp [4] TIA/EIA/IS A, Physical Layer Standard for cdma2000 Spread Spectrum Systems, Telecommunications Industry Association, March [5] TIA/EIA/IS A, Medium Access Control (MAC) Standard for cdma2000 Spread Spectrum Systems, Telecommunications Industry Association, March [6] TIA/EIA/IS A, Signaling Link Access Control (LAC) Standard for cdma2000 Spread Spectrum Systems, Telecommunications Industry Association, March [7] TIA/EIA/IS A, Upper Layer (Layer 3) Signaling Standard for cdma2000 Spread Spectrum Systems, Telecommunications Industry Association, March [8] Forouzan, B. A., Data Communications and Networking, New York: McGraw-Hill, [9] ITU-T Recommendation X.210, Information Technology Open Systems Interconnection Basic Reference Model: Conventions for the Definition of OSI Services, International Telecommunication Union, 1993.

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31 CHAPTER 2 Physical Layer: Forward Link 2.1 Introduction The physical layer is responsible for transmitting and receiving bits (organized in frames) over the physical medium. The physical layer carries out coding functions to enable error correction and detection at the bit and frame levels. Besides coding, the layer would have to convert bits into waveforms (i.e., modulation) and vice versa to enable their transmission over the air. In addition to coding and modulation, the physical layer also carries out the channelization function by which different users of the system can be distinguished from one another. In a shared direct sequence spread spectrum system (such as IS-2000 and IS-95), channelization is done via the use of orthogonal and nearorthogonal codes. This chapter deals with the physical channels that exist on the forward link in the IS-2000 system, and their descriptions are organized into two broad categories: signaling channels and user channels. Signaling channels, described in Section 2.3, are those channels that carry signaling and control information. Signaling channels can be further classified into two types: dedicated and common channels. The F-DCCH is a dedicated signaling channel because this channel, once assigned, is only used by one user. The remaining signaling channels, such as the F-CCCH and F-QPCH are examples of common signaling channels because they are shared among multiple users. User channels, described in Section 2.4, are those channels that carry user information. The user information may be voice, low-rate data (e.g., short message service or SMS), or high-rate data (e.g., video streaming). There are three physical channels primarily used to carry user information: (1) F-FCH which is equivalent to forward traffic channel in IS-95, (2) F-SCCH which is equivalent to forward supplemental code channel in IS-95 (more specifically, IS-95-B [1]), and (3) F-SCH which is a new channel in IS Figure 2.1 shows the categorization of these forward link channels, both signaling and user. Table 2.1 is a list of physical channels used by the physical layer. Both forward link and reverse link channels and their descriptions are shown for completeness. Also, for each forward link physical channel, its counterparts on the reverse link are shown in the same row for correspondence. Asterisked channel designations show those channels that also exist in IS-95 systems. Note that (forward and reverse) fundamental channels are equivalent to the IS-95 traffic channels. In addition, boldfaced channel names show those channels that are collectively known as the 11

32 12 Physical Layer: Forward Link Signaling channels Common channels Paging channel (F-PCH*) Quick paging channel (F-QPCH) Forward common control channel (F-CCCH) Broadcast control channel (F-BCCH) Common assignment channel (F-CACH) Common power control channel (F-CPCCH) Sync channel (F-SYNCH*) Forward pilot channel (F-PICH*) Transmit diversity pilot channel (F-TDPICH) Auxiliary pilot channel (F-APICH) Auxiliary transmit diversity pilot channel (F-ATDPICH) Dedicated channels Forward dedicated control channel (F-DCCH) User channels Forward fundamental channel (F-FCH*) Forward supplemental channel (F-SCH) Forward supplemental code channel (F-SCCH*) Figure 2.1 Categories of forward link physical channels. Legacy IS-95 physical channels are denoted with asterisks. Table 2.1 Forward Link Physical Channels and Their Reverse Link Counterparts Channel Channel Name Description Channel Channel Name Description F-SCH F-SCCH* F-FCH* F-DCCH Forward supplemental channel Forward supplemental code channel Forward fundamental channel Forward dedicated control channel For transmitting user data while a call is R-SCH active; uses convolutional or turbo coding For transmitting user data while a call is active; uses convolutional coding For transmitting user and signaling data while a call is active; uses convolutional coding For transmitting signaling and user data while a call is active R-SCCH* R-FCH* R-DCCH Reverse supplemental channel Reverse supplemental code channel Reverse fundamental channel Reverse dedicated control channel For transmitting user data while a call is active; uses convolutional or turbo coding For transmitting user data while a call is active; uses convolutional coding For transmitting user and signaling data while a call is active; uses convolutional coding For transmitting signaling and user data while a call is active F-PCH* Paging channel For transmitting MSspecific and system overhead data

33 2.1 Introduction 13 Table 2.1 (continued) Channel Channel Name Description Channel Channel Name Description F-QPCH F-CCCH F-BCCH F-CPCCH F-CACH F-SYNCH* F-PICH* F-TDPICH Quick paging channel Forward common control channel Broadcast control channel Common power control channel Common assignment channel Sync channel Forward pilot channel Transmit diversity pilot channel For telling MS (operating in slotted mode while in the idle state) whether or not it should receive F-CCCH or F-PCH starting in the next F-CCCH or F-PCH slot For transmitting signaling data when F-FCH, F-SCCH, F-SCH, or F-DCCH is not active R-ACH* R-EACH R-CCCH For transmitting signaling data when F-FCH, F-SCCH, F-SCH, or F-DCCH is not active For transmitting common power control subchannels (one bit per subchannel) to power-control multiple R-CCCHs and R-EACHs For transmitting signaling data to allocate R-CCCH resources For providing MS time and frame synchronization For assisting MS to acquire initial time R-PICH synchronization For implementing transmit diversity on the forward link Access channel Enhanced access channel Reverse common control channel Reverse pilot channel For initial communications with BS, i.e., initiating access and responding to pages For initial communications with BS, i.e., initiating access or responding to MS-specific messages For transmitting signaling and user data when R-FCH, R-SCCH, R-SCH, or R-DCCH is not active For assisting BS to detect MS transmission

34 14 Physical Layer: Forward Link Table 2.1 (continued) Channel Channel Name Description Channel Channel Name Description F-APICH F-ATDPICH Auxiliary pilot channel Auxiliary transmit diversity pilot channel For supporting the use of spot beam For implementing transmit diversity in the spot beam IS-2000 traffic channels (not to be confused with IS-95 traffic channels) since these channels can all carry user traffic data in IS-2000 systems. 2.2 Radio Configurations In IS-2000, each traffic channel (i.e., forward fundamental channel, forward supplemental code channel, forward supplemental channel, and forward dedicated control channel) can assume different configurations to implement different data rates. For any one configuration, the associated coding rate, modulation characteristics, and spreading rate would have to be matched to achieve a specified final transmitted data rate. Table 2.2 shows these different radio configurations [2]. For these radio configurations, the data rates shown in the table are maximum data rates. For a given radio configuration, data rates lower than the maximum are possible. Note that Radio Configuration 1 and Radio Configuration 2 are backward compatible with IS-95 in that they are equivalent to Rate Set 1 and Rate Set 2 of IS-95. For each radio configuration, the table shows the maximum achievable data rate (instead of all possible data rates). For example, for Radio Configuration 1 the system is capable of transmitting at 1.2 Kbps, 2.4 Kbps, 4.8 Kbps, and 9.6 Kbps; only the maximum data rate of 9.6 Kbps is shown. In addition, for each radio Table 2.2 Radio Configurations on the Forward Link Radio Configuration Coding Rate R Modulation Spreading Rate Maximum Data Rate 1 1/2 BPSK Kbps 2 1/2 BPSK Kbps 3 1/4 QPSK Kbps 4 1/2 QPSK Kbps 5 1/4 QPSK Kbps 6 1/6 QPSK Kbps 7 1/3 QPSK Kbps 8 1/4 (20 ms) QPSK Kbps 1/3 (5 ms) 9 1/2 (20 ms) QPSK Mbps 1/3 (5 ms)

35 2.3 Signaling Channels 15 configuration the coding rate R is normally the same regardless of the size of the frame (20 ms or 5 ms). But for Radio Configurations 8 and 9 (i.e., Spreading Rate 3), the coding rate is dependent on the size of the frame transmitted. 2.3 Signaling Channels One of the key requirements of 3G is high-data rate. In order to meet this requirement one needs to make the physical layer more efficient. Recall that in 2G IS-95, while a call is active signaling information is typically carried by the traffic channel (i.e., fundamental channel). In doing so, signaling bits rob traffic channel s ability to carry user data bits. 3G IS-2000 deals with this issue by implementing separate signaling channels that carry signaling information. Although signaling data can still be carried by the fundamental channel, IS-2000 has the option of sending signaling data on separate signaling channels. This frees up fundamental channel s and supplemental channel s capability to transport more user data Forward Dedicated Control Channel (F-DCCH) The F-DCCH is a unique signaling channel in two respects: Unlike other signaling channels, the F-DCCH is a dedicated signaling channel. Once assigned, the F-DCCH is only allocated to one designated user. All other signaling channels (to be described later) are common to and shared with other users. Just as the forward fundamental channels can carry signaling data (through dim-and-burst and blank-and-burst), the F-DCCH can carry user data. The kind of user data that the F-DCCH carries is typically low-rate (such as SMS). Such data service requests are sporadic in nature and short in duration. For such transmission requests, instead of expending resources to set up a fullfledge fundamental channel or supplemental channel, the system can choose to temporarily suspend transmitting signal data and start sending user data over the F-DCCH. In addition, both 20-ms and 5-ms frame formats are supported by the F-DCCH. For example, one 20-ms frame format for the F-DCCH is 192 bits in length consisting of 172 information bits, 12 cyclic redundancy check (CRC) bits, and 8 encoder tail bits. This gives an F-DCCH data rate of (192 bits/20 ms) 9.6 Kbps. See Figure 2.2. Note that in this case, this F-DCCH frame has the same capacity as an IS-95 Rate Set 1 paging channel frame. On the other hand, a 5-ms frame structure for the F-DCCH is 48 bits in length consisting of 24 information bits, 16 CRC bits, and 8 encoder tail bits. This gives an F-DCCH data rate of (48 bits/5 ms) also 9.6 Kbps. Also see Figure 2.2. Note that a 5-ms frame obviously does not have as much datacarrying capacity as a 20-ms frame. The reason why 5-ms frames are necessary is that at times a signaling message is short and cannot fill up the entire (traditional) 20-ms frame, and it would be

36 16 Physical Layer: Forward Link 20-ms frame (9.6 Kbps) 172 information bits 12 CRC bits 8 encoder tail bits 5-ms frame (9.6 Kbps) Figure 2.2 Examples of 20-ms and 5-ms F-DCCH frames. 24 information bits 16 CRC bits 8 encoder tail bits inefficient to transmit a short minimessage using a 20-ms frame. Using a 5-ms frame to transport a short signaling message is a more efficient use of the air link resources. An important type of signaling data that the F-DCCH carries is power control bits used to power-control the reverse link. Recall that in IS-95 the power control bits are multiplexed onto the forward traffic channel at 800 bps in power control groups. In a similar fashion, the power control bits can be multiplexed onto the F-DCCH as well. The structure and organization of the power control groups on the F-DCCH is referred to as forward power control subchannel. In effect, a forward power control subchannel exists on the F-DCCH to transport the power control bits. The mobile uses these power control bits to perform closed-loop power control of the reverse dedicated control channel, reverse fundamental channel, and reverse supplemental channel Quick Paging Channel (F-QPCH) The F-QPCH is a new physical channel used in IS-2000 to improve the efficiency of sending page messages. The IS-95 F-PCH, while effective, does have some drawbacks: In the nonslotted mode the mobile has to monitor continuously the entire paging channel slot, which in IS-95 lasts 80 ms. As a result, the mobile expends a lot of battery power to perform this continuous monitoring. In the slotted mode the mobile monitors only those time slots that are assigned to it. While this does save some battery power, it is still inefficient. From the base station s perspective, it is inefficient because when the base station has a