Mobile WiMAX: A Systems Approach to Understanding IEEE 802.16m Radio Access Technology

Mobile WiMAX

To my wife Shahrnaz and my children Roya and Nima

Mobile WiMAX A Systems Approach to Understanding IEEE 802.16m Radio Access Technology

Sassan Ahmadi

AMSTERDAM  BOSTON  HEIDELBERG  LONDON  NEW YORK  OXFORD PARIS  SAN DIEGO  SAN FRANCISCO  SINGAPORE  SYDNEY  TOKYO

Academic Press is an imprint of Elsevier

Academic Press is an imprint of Elsevier The Boulevard, Langford Lane, Kidlington, Oxford, OX5 1GB, UK 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA First published 2011 Copyright Ó 2011 Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangement with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein).

Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. British Library Cataloguing in Publication Data Ahmadi, Sassan. Mobile WiMAX : a systems approach to understanding the IEEE 802.16m radio access network. 1. IEEE 802.16 (Standard) 2. Wireless communication systems. 3. Mobile communication systems. I. Title 621.3’84-dc22 Library of Congress Control Number: 2010935393 ISBN: 978-0-12-374964-2

For information on all Academic Press publications visit our website at www.elsevierdirect.com Printed and bound in the United States 10 11 12 11 10 9 8 7 6 5 4 3 2 1

Contents Preface .................................................................................................................................................. xi Introduction.......................................................................................................................................... xv Acknowledgements.......................................................................................................................... xxvii Abbreviations .................................................................................................................................... xxix

CHAPTER 1 Introduction to Mobile Broadband Wireless Access........................ 1 1.1 Mobile Broadband Wireless Access Technologies.................................................... 1 1.1.1 The 4th Generation of Mobile Broadband Wireless Access Technologies...................................................................................................... 4 1.1.2 Requirements of 4G Mobile Broadband Wireless Access Systems................. 6 1.1.3 Convergence of Mobile Broadband Wireless Access Technologies.................................................................................................... 13 1.2 Introduction to the IEEE 802.16 Standards ............................................................. 14 1.2.1 Evolution of the IEEE 802.16 Standards........................................................ 19 1.3 Introduction to WiMAX Forum Mobile System Profiles ........................................ 23 1.4 Introduction to 3GPP Standards............................................................................... 24

CHAPTER 2 WiMAX Network Architecture...................................................... 33 2.1 Design Principles of WiMAX Network Architecture.............................................. 33 2.2 Network Reference Model ....................................................................................... 37 2.2.1 Access Service Network (ASN)...................................................................... 38 2.2.2 Access Service Network Gateway (ASN-GW) .............................................. 39 2.2.3 Reference Points.............................................................................................. 40 2.2.4 Connectivity Service Network (CSN) ............................................................ 42 2.3 Authentication, Authorization, and Accounting (AAA).......................................... 42 2.4 Mobile IP .................................................................................................................. 44 2.5 Radio Resource Management (RRM)...................................................................... 46 2.6 Mobility Management .............................................................................................. 47 2.6.1 ASN-anchored Mobility .................................................................................. 47 2.6.2 CSN-anchored Mobility .................................................................................. 50 2.7 Paging and Idle State Operation .............................................................................. 51 2.8 Overview of 3GPP Evolved Packet Core Network Architecture ............................ 52

CHAPTER 3 IEEE 802.16m Reference Model and Protocol Structure................ 61 3.1 The IEEE 802.16m Reference Model...................................................................... 63 3.1.1 The MS and BS Interface ............................................................................... 66 3.1.2 Network Control and Management System.................................................... 67 3.1.3 Data-Plane ....................................................................................................... 69

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3.1.4 Control-Plane................................................................................................... 71 3.1.5 Management-Plane .......................................................................................... 73 3.1.6 Service Access Point ....................................................................................... 74 3.1.7 Media-Independent Handover Reference Model for IEEE 802.16................ 75 3.2 The IEEE 802.16m Protocol Structure .................................................................... 76 3.2.1 Data-Plane and Control-Plane Functions in Base Stations and Mobile Stations ........................................................................................ 79 3.2.2 Data-Plane and Control-Plane Functions in Relay Stations........................... 81 3.2.3 Protocol Structure for Support of Multi-Carrier Operation ........................... 87 3.2.4 Protocol Structure for Support of Multicast and Broadcast Services............................................................................................................ 88 3.3 3GPP LTE/LTE-Advanced Protocol Structure......................................................... 89

CHAPTER 4 IEEE 802.16m System Operation and State Diagrams.................... 97 4.1 IEEE 802.16m Mobile Station State Diagrams ....................................................... 98 4.1.1 Initialization State ......................................................................................... 101 4.1.2 Access State................................................................................................... 104 4.1.3 Connected State............................................................................................. 108 4.1.4 Idle State........................................................................................................ 111 4.2 Network Entry ........................................................................................................ 118 4.2.1 Normal Network Re-Entry............................................................................ 121 4.2.2 Fast Network Re-Entry ................................................................................. 122 4.3 State Transitions and Mobility ............................................................................... 122 4.4 State Transitions in Relay Stations ........................................................................ 124 4.4.1 Initialization State ......................................................................................... 126 4.4.2 Access State................................................................................................... 130 4.4.3 Operational State ........................................................................................... 130 4.5 Operational States of Femto Base Stations............................................................ 131 4.6 3GPP LTE User Equipment States and State Transitions ..................................... 138 4.6.1 Acquisition of System Information............................................................... 143 4.6.2 Connected Mode Mobility ............................................................................ 145

CHAPTER 5 The IEEE 802.16m Convergence Sub-Layer................................ 149 5.1 Header Compression............................................................................................... 150 5.1.1 Robust Header Compression......................................................................... 153 5.2 Service Flow Classification and Identification ...................................................... 155 5.2.1 Service Flow Attributes................................................................................. 156 5.2.2 Service Flow Types ....................................................................................... 156 5.2.3 Service Flow Classification........................................................................... 157 5.3 Packet Convergence Sub-layer............................................................................... 158 5.3.1 Packet CS Payload Header Suppression....................................................... 159 5.4 Generic Packet Convergence Sub-layer ................................................................. 161 5.5 The 3GPP LTE Packet Data Convergence Protocol.............................................. 162

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CHAPTER 6 The IEEE 802.16m Medium Access Control Common Part Sub-layer (Part I) ..................................................................... 169 6.1 Addressing ............................................................................................................ 171 6.2 MAC PDU Headers .............................................................................................. 173 6.2.1 Legacy Generic MAC Header..................................................................... 173 6.2.2 IEEE 802.16m MAC Headers..................................................................... 174 6.3 MAC Signaling Headers....................................................................................... 181 6.3.1 Legacy MAC Signaling Headers ................................................................ 181 6.3.2 IEEE 802.16m Signaling Headers .............................................................. 183 6.4 Mobility Management and Handover .................................................................. 184 6.4.1 Handover Mechanisms ................................................................................ 184 6.4.2 Handover Process ........................................................................................ 196 6.4.3 IEEE 802.16m Handover Scenarios ........................................................... 199 6.4.4 Handover to and From Legacy Systems..................................................... 206 6.5 Quality of Service................................................................................................. 209 6.5.1 Legacy QoS Classes .................................................................................... 209 6.6 IEEE 802.16m QoS Classes ................................................................................. 215 6.7 MAC Management/Control Messages ................................................................. 217 6.8 Connection and Session Management ................................................................. 243 6.9 Mobility and Power Management ........................................................................ 246 6.9.1 Sleep Mode Operation ................................................................................ 247 6.9.2 Idle Mode Operation ................................................................................... 249 6.10 Scheduling Services ............................................................................................. 252 6.10.1 Persistent Scheduling ................................................................................ 255 6.0.2 Group Resource Scheduling ....................................................................... 256 6.11 Bandwidth Request and Allocation ..................................................................... 258 6.12 Multi-radio Coexistence ....................................................................................... 261 6.13 3GPP LTE Radio Resource Control Functions ................................................... 264 6.13.1 Mobility Management and Handover....................................................... 268 6.13.2 Scheduling and Rate Control Functions ................................................... 271 6.13.3 Discontinuous Reception in RRC_CONNECTED State ......................... 274 6.13.4 Quality of Service ..................................................................................... 275 Appendix A: Proportional Fair Scheduling Algorithm ................................................. 277

CHAPTER 7 The IEEE 802.16m Medium Access Control Common Part Sub-layer (Part II) .................................................................... 281 7.1 Automatic Repeat Request ..................................................................................... 283 7.1.1 ARQ Principles ............................................................................................. 283 7.1.2 IEEE 802.16m ARQ Mechanism.................................................................. 284 7.1.3 ARQ State Machine ...................................................................................... 286 7.2 Hybrid Automatic Repeat Request Functions ....................................................... 289 7.2.1 HARQ Principles........................................................................................... 289

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7.2.2 IEEE 802.16m HARQ Mechanism............................................................... 292 7.2.3 HARQ Timing and Signaling Protocols ....................................................... 293 7.3 MAC PDU Formation ............................................................................................ 299 7.4 3GPP LTE Radio Link Control and Medium Access Control Sub-Layers .......... 304 7.4.1 3GPP LTE MAC Sub-Layer ......................................................................... 304 7.4.2 Logical and Transport Channels ................................................................... 305 7.4.3 3GPP LTE RLC Sub-Layer........................................................................... 310 7.4.4 ARQ and HARQ in LTE............................................................................... 314

CHAPTER 8 The IEEE 802.16m Security Sub-Layer....................................... 321 8.1 Security Architecture.............................................................................................. 321 8.2 Authentication......................................................................................................... 323 8.3 Key Management Protocol (PKMv3) .................................................................... 323 8.3.1 Key Derivation .............................................................................................. 323 8.3.2 Key Exchange................................................................................................ 324 8.3.3 Key Usage ..................................................................................................... 324 8.4 Security Association Management......................................................................... 325 8.5 Cryptographic Methods .......................................................................................... 326 8.6 Control-plane Signaling Protection ........................................................................ 326 8.7 User Privacy............................................................................................................ 328 8.8 3GPP LTE Security Aspects .................................................................................. 328

CHAPTER 9 The IEEE 802.16m Physical Layer (Part I) ................................. 335 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8

9.9

9.10 9.11 9.12

Overview of IEEE 802.16m Physical Layer Processing ....................................... 336 Characteristics of Wireless Channels..................................................................... 338 SC-FDMA and OFDMA Principles....................................................................... 342 Downlink and Uplink Multiple Access Schemes .................................................. 355 IEEE 802.16m Duplex Modes ............................................................................... 358 Frame Structure ...................................................................................................... 358 The Concept of Time Zones and Frequency Regions ........................................... 363 Subchannelization and Permutation....................................................................... 364 9.8.1 Downlink Subchannelization and Permutation ............................................ 366 9.8.2 Uplink Subchannelization and Permutation ................................................. 374 Pilot Structure and Channel Estimation................................................................. 382 9.9.1 Pilot Structure Design Criteria ..................................................................... 383 9.9.2 Downlink Pilot Structure .............................................................................. 386 9.9.3 Uplink Pilot Structure ................................................................................... 393 MIMO Midamble ................................................................................................... 394 Pilot-based Channel Estimation............................................................................. 395 Channel Coding and Modulation........................................................................... 398 9.12.1 Principles of Turbo Coding ........................................................................ 399 9.12.2 Coding and Modulation of Traffic Channels ............................................. 404 9.12.3 Coding and Modulation of the Control Channels...................................... 412

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9.12.4 HARQ-IR Physical Layer Procedures........................................................ 415 9.12.5 Constellation Rearrangement...................................................................... 416 9.12.6 Performance of Channel Coding and HARQ-IR ....................................... 416 9.13 Synchronization Channel ....................................................................................... 418 9.14 Superframe Headers (Broadcast Channel)............................................................. 426 9.15 3GPP LTE Physical Layer Protocols..................................................................... 448 9.15.1 Multiple Access Schemes ........................................................................... 448 9.15.2 Frame Structure........................................................................................... 449 9.15.3 Physical Resource Blocks........................................................................... 453 9.15.4 Modulation and Coding .............................................................................. 455 9.15.5 Physical Channel Processing ...................................................................... 458 9.15.6 Reference Signals........................................................................................ 463 9.15.7 Physical Control Channels.......................................................................... 467 9.15.8 Downlink and Uplink HARQ ..................................................................... 477 9.15.9 Physical Random Access Channel ............................................................. 477 9.15.10 Cell Search ................................................................................................ 479 9.15.11 PDSCH Transmission Modes ................................................................... 480

CHAPTER 10 The IEEE 802.16m Physical Layer (Part II)............................... 489 10.1 Control Channels ................................................................................................. 489 10.2 Downlink Control Channels ................................................................................ 490 10.2.1 Physical Structure of Advanced MAPs.................................................... 493 10.2.2 Advanced MAP Information Elements.................................................... 507 10.3 Uplink Control Channels ..................................................................................... 528 10.3.1 Fast-Feedback Channels........................................................................... 530 10.3.2 HARQ Feedback Channel ........................................................................ 534 10.3.3 Sounding Channel .................................................................................... 536 10.3.4 Ranging Channel ...................................................................................... 538 10.3.5 Bandwidth Request Channel .................................................................... 542 10.3.6 Power Control........................................................................................... 544 10.4 Multi-Antenna Transmission Schemes................................................................ 548 10.4.1 Capacity of MIMO Channels ................................................................... 550 10.4.2 Spatial Multiplexing and Diversity .......................................................... 557 10.4.3 MIMO Receivers ...................................................................................... 560 10.4.4 Precoding and Beamforming.................................................................... 564 10.4.5 Single-User and Multi-User MIMO......................................................... 569 10.4.6 Collaborative MIMO and Collaborative Spatial Multiplexing................ 575 10.5 IEEE 802.16m Downlink MIMO Schemes......................................................... 578 10.6 The IEEE 802.16m Uplink MIMO Schemes...................................................... 597 10.7 Multi-BS MIMO .................................................................................................. 601 10.8 Interference Mitigation ........................................................................................ 607 10.9 Multi-Antenna Techniques in 3GPP LTE ........................................................... 610 10.10 Multi-Antenna Techniques in 3GPP LTE-Advanced ......................................... 617

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CHAPTER 11 Multi-Carrier Operation........................................................... 625 11.1 11.2 11.3 11.4

Principles of Multi-Carrier Operation.................................................................. 626 Sub-carrier Alignment and Use of Guard Sub-Carriers ...................................... 629 Carrier Aggregation and Spectral Mask Considerations ..................................... 636 MAC Aspects of Multi-Carrier Operation........................................................... 638 11.4.1 Activation/Deactivation and Switching of Component Carriers.............. 642 11.4.2 Multi-Carrier Handover ............................................................................ 644 11.4.3 Multi-Carrier Power Management............................................................ 646 11.5 3GPP LTE-Advanced Multi-Carrier Operation ................................................... 649

CHAPTER 12 Performance of IEEE 802.16m and 3GPP LTE-Advanced............ 657 12.1 Definition of the Performance Metrics................................................................ 658 12.2 Calculation of Static and Dynamic Overhead..................................................... 662 12.3 Traffic Models...................................................................................................... 664 12.3.1 Statistical Model for Conversational Speech........................................... 664 12.3.2 Full Buffer Traffic Model......................................................................... 666 12.4 Link-to-system Mapping (PHY Abstraction) ...................................................... 667 12.5 IMT-Advanced Test Environments...................................................................... 669 12.6 Network Layout for System-Level Simulations ................................................. 670 12.7 IMT-Advanced Evaluation Methodology and Baseline Configurations............. 672 12.8 Link-level And System-level Channel Models ................................................... 672 12.9 IEEE 802.16m Link-level and System-level Performance ................................. 676 12.9.1 Cell Spectral Efficiency and Cell Edge User Spectral Efficiency........... 680 12.9.2 VoIP Capacity ........................................................................................... 681 12.9.3 Mobility .................................................................................................... 682 12.9.4 Peak Spectral Efficiency........................................................................... 683 12.9.5 User-Plane/Control-Plane Latency and Handover Interruption Time ..... 686 12.9.6 Frequency Bands and Operation Bandwidth ........................................... 689 12.9.7 IEEE 802.16m Link Budget..................................................................... 689 12.9.8 Additional Link-Level Simulation Results .............................................. 692 12.10 3GPP LTE-Advanced Link-level and System-level Performance ...................... 700 12.10.1 Cell Spectral Efficiency and Cell Edge Spectral Efficiency.................. 700 12.10.2 VoIP Capacity ......................................................................................... 703 12.10.3 Mobility................................................................................................... 703 12.10.4 Peak Spectral Efficiency ......................................................................... 704 12.10.5 User-Plane/Control-Plane Latency and Handover Interruption Time .....705 12.10.6 Estimation of the L1/L2 Overhead......................................................... 712 12.10.7 Frequency Bands and Operation Bandwidth.......................................... 714 12.10.8 3GPP LTE-Advanced Link Budget ........................................................ 714 12.10.9 Evaluation of 3GPP LTE-Advanced Against Release 10 Requirements ..................................................................................... 714 Index .................................................................................................................................................. 723

Preface Wireless communication comprises a wide range of technologies, services, and applications that have come into existence to meet the particular needs of users in different deployment scenarios. Wireless systems can be broadly characterized by content and services offered, reliability and performance, operational frequency bands, standards defining those systems, data rates supported, bi-directional and uni-directional delivery mechanisms, degree of mobility, regulatory requirements, complexity, and cost. The number of mobile subscribers has increased dramatically worldwide in the past decade. The growth in the number of mobile subscribers will be further intensified by the adoption of broadband mobile access technologies in developing countries such as India and China with large populations. It is envisioned that potentially the entire world population will have access to broadband mobile services, depending on economic conditions and favorable cost structures offered by regional network operators. There are already more mobile devices than fixed-line telephones or fixed computing platforms, such as desktop computers, that can access the Internet. The number of mobile devices is expected to continue to grow more rapidly than nomadic and stationary devices. Mobile terminals will be the most commonly used platforms for accessing and exchanging information. In particular, users will expect a dynamic, continuing stream of new applications, capabilities, and services that are ubiquitous and available across a range of devices using a single subscription and a single identity. Versatile communication systems offering customized and ubiquitous services based on diverse individual needs require flexibility in the technology in order to satisfy multiple demands simultaneously. Wireless multimedia traffic is increasing far more rapidly than voice, and will increasingly dominate traffic flows. The paradigm shift from predominantly circuit-switched air interface design to full IP-based delivery has provided the mobile users with the ability to more efficiently, more reliably, and more securely utilize packet-switched services such as e-mail, file transfers, messaging, browsing, gaming, voice-over Internet protocol, location-based, multicast, and broadcast services. These services can be either symmetrical or asymmetrical (in terms of the use of radio resources in the downlink or uplink) and real-time or non real-time, with different quality of service requirements. The new applications consume relatively larger bandwidths, resulting in higher data rate requirements. In defining the framework for the development of IMT-Advanced and systems beyond IMTAdvanced radio interface technologies, it is important to understand the usage models and technology trends that will affect the design and deployment of such systems. In particular, the framework should be based on increasing user expectations and the growing demand for mobile services, as well as the evolving nature of the services and applications that may become available in the future. The trend toward integration and convergence of wireless systems and services can be characterized by connectivity (provision of an information pipe including intelligence in the network and the terminal), content (information including push and pull services as well as peer-to-peer applications), and e-commerce (electronic transactions and financial services). This trend may be viewed as the integration and convergence of information technology, telecommunications, and content, which has resulted in new service delivery dynamics and a new paradigm in wireless telecommunications, where value-added services have provided significant benefits to both the end users and the service providers. Present mobile communication systems have evolved by incremental enhancements of system capabilities, and gradual addition of new functionalities and features to baseline IMT-2000 systems. The capabilities of IMT-2000 systems have continued to steadily evolve over the past decade as

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IMT-2000 technologies are upgraded and deployed (e.g., mobile WiMAX and the migration of UMTS systems to HSPA+). The IMT-Advanced and systems beyond IMT-Advanced are going to be realized by functional fusion of existing IMT-2000 system components, enhanced and new functions, nomadic wireless access systems, and other wireless systems with high commonality and seamless interworking. The systems beyond IMT-Advanced will encompass the capabilities of previous systems, as well as other communication schemes such as machine-to-machine, machine-to-person, and personto-machine. The framework for the development of IMT-Advanced and systems beyond IMT-Advanced can be viewed from multiple perspectives including users, manufacturers, application developers, network operators, and service and content providers. From the user’s perspective, there is a demand for a variety of services, content, and applications whose capabilities will increase over time. The users expect services to be ubiquitously available through a variety of delivery mechanisms and service providers using a variety of wireless devices. From the service provision perspective, the domains share some common characteristics. Wireless service provision is characterized by global mobile access (terminal and personal mobility), improved security and reliability, higher service quality, and access to personalized multimedia services, the Internet, and location-based services via one or multiple user terminals. Multi-radio operation requires seamless interaction of systems so that the user can receive/transmit a variety of content via different delivery mechanisms depending on the device capabilities, location and mobility, as well as the user profile. Different radio access systems can be connected via flexible core networks and appropriate interworking functions. In this way, a user can be connected through different radio access systems to the network and can utilize the services. The interworking among different radio access systems in terms of horizontal or vertical handover and seamless connectivity with service negotiation, mobility, security, and QoS management are the key requirements of radio-agnostic networks. The similarity of services and applications across different radio access systems is beneficial not only to users, but also to network operators and content providers, stimulating the current trend towards convergence. Furthermore, similar user experience across different radio interface systems leads to large-scale adoption of products and services, common applications, and content. Access to a service or an application may be performed using one system or using multiple systems simultaneously. The increasing prevalence of IP-based applications has been a key driver for this convergence, and has accelerated the convergence trend in the core network and radio air interface. The evolution of IMT-2000 baseline systems and the IMT-Advanced systems has employed several new concepts and functionalities, including adaptive modulation and coding and link adaptation, OFDM-based multiple access schemes, single-user/multi-user multi-antenna concepts and techniques, dynamic QoS control, mobility management and handover between heterogeneous radio interfaces (vertical and horizontal), robust packet transmission, error detection and correction, multi-user detection, and interference cancellation. Systems beyond IMT-Advanced may further utilize sophisticated schemes including software defined radio and reconfigurable RF and baseband processing, adaptive radio interface, mobile ad hoc networks, routing algorithms, and cooperative communication. In response to this demand, the IEEE 802.16 Working Group began the development of a new amendment to the IEEE 802.16 standard (i.e., IEEE 802.16m) in January 2007 as an advanced air interface to meet the requirements of ITU-R/IMT-Advanced for the fourth-generation of cellular systems. The 3rd Generation Partnership Project started a similar effort in 2008 to upgrade the UMTS standards and to further enhance its family of LTE technologies.

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Many articles, book chapters, and books have been published on the subject of mobile WiMAX and 3GPP LTE, varying from academic theses to network operator analyses and manufacturers’ application notes. By their very nature, these publications have viewed these subjects from one particular perspective, whether it is academic, operational, or promotional. A very different and unique approach has been taken in this book; a top-down system approach to understanding the system operation and design principles of the underlying functional components of 4th generation radio access networks. This book can be considered as the most up-to-date technical reference for the design of 4G cellular systems. In this book, the protocol layers and functional elements of both the IEEE 802.16m- and 3GPP LTE-Advanced-based radio access and core networks are described. While the main focus of the book (as will be understood from the title) is to provide readers with an in-depth understanding of the IEEE 802.16m radio access system design, and to demonstrate the operation of the end-to-end system; a detailed description of the 3GPP LTE Release 9 and 3GPP LTE-Advanced Release 10 systems is provided to allow readers to better understand the similarities and differences between the two systems by contrasting the protocols and functional elements. It can be concluded that, aside from the marketing propaganda and hype surrounding these technologies, the 3GPP LTE and mobile WiMAX systems are technically equivalent and a fair comparison of the two technologies and their evolutionary paths reveals a similar performance as far as user experience is concerned. In order to ensure the self-sufficiency of the material, the theoretical background and necessary definitions of all terms and topics has been provided either as footnotes or in separate sections to enable in-depth understanding of the subject under consideration without distracting the reader, and with no impact on the continuity of the subject matter. Additional technical references are cited in each chapter for further study. Each chapter in this book provides a top-down systematic description of the IEEE 802.16m entities and functional blocks, such as state transition models and corresponding procedures, protocol structures, etc., (including similarities and differences with the legacy mobile WiMAX systems to emphasize improvements) starting at the most general level and working toward the details or specifics of the protocols and procedures. The description of corresponding 3GPP LTE/LTEAdvanced protocols and procedures are further provided to enable readers to contrast the analogous terminal and base station behaviors, protocols, and functionalities. Such contrast is crucial in the design of inter-system interworking functions and to provide better understanding of the design strengths and weaknesses of each system.

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Introduction International Mobile Telecommunications-Advanced systems are broadband mobile wireless access systems that include new capabilities and versatility that goes beyond those of IMT-2000 systems. IMT-Advanced has provided a global framework for the development of the next generation of wireless radio access networks that enable low-delay, high-speed, bi-directional data access, unified messaging, and broadband wireless multimedia in the form of new service classes. Such systems provide access to a variety of mobile telecommunication services through entirely packet-based access/core networks. The IMT-Advanced systems support low to very high mobility applications and a wide range of data rates proportional to usage models and user density. The design and operational requirements concerning the 4th generation of radio interface technologies may vary from different perspectives with certain commonalities as follows: End User








Ubiquitous mobile Internet access; Easy access to applications and services with high quality at reasonable cost; Easily understandable user interface; Long battery life; Large choice of access terminals; Enhanced service capabilities; User-friendly billing policies.

Content Provider
Flexible billing;
Ability to adapt content to user requirements depending on terminal type, location, mobility, and user preferences;
Access to a sizable market based on the similarity of application programming interfaces. Service Provider





Fast, open service creation, validation, and provisioning; Quality of service and security management; Automatic service adaptation as a function of available data rate and type of terminal; Flexible billing.

Network Operator








Optimization of resources in terms of spectrum and equipment; Quality of service and security management; Ability to provide differentiated services; Flexible network configuration; Reduced cost of terminals and network equipment based on global economies of scale; Smooth transition from legacy systems to new systems; Maximizing commonalities among various radio access systems including sharing of mobile platforms, subscriber identity modules, network elements, radio sites;

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Single authentication process independent of the access network;
Flexible billing;
Access type selection optimizing service delivery. Manufacturer or Application Developer





Reduced cost of terminals and network equipment based on global economies of scale; Access to global markets; Open physical and logical interfaces between modular and integrated subsystems; Programmable/configurable platforms that enable fast and low-cost development.

The capabilities of IMT-2000 systems have continuously evolved over the past decade as IMT-2000 technologies have been upgraded and widely deployed. From the radio access perspective, the evolved IMT-2000 systems have built on the legacy systems, further enhanced the radio interface functionalities/protocols, and at the same time new systems have emerged to replace the existing IMT-2000 radio access systems in the long-term. This evolution has improved the reliability and throughput of the cellular systems and promoted the development of an expanding number of services and applications. The similarity of services and applications across different IMT technologies and frequency bands is not only beneficial to users, but also a similar user experience generally leads to a large-scale deployment of products and services. The technologies, applications, and services associated with systems beyond IMT-Advanced could well be radically different from the present systems, challenging our perceptions of what may be considered viable by today’s standards and going beyond what has just been achieved by the IMT-Advanced radio systems. The IEEE 802.16 Working Group began the development of a new amendment to the IEEE 802.16 baseline standard in January 2007 as an advanced air interface, in order to materialize the ITU-R vision for the IMT-Advanced systems as laid out in Recommendation ITU-R M.1645. The requirements for the IEEE 802.16m standard were selected to ensure competitiveness with the emerging 4th generation radio access technologies, while extending and significantly improving the functionality and efficiency of the legacy system. The areas of improvement and extension included control/signaling mechanisms, L1/L2 overhead reduction, coverage of control and traffic channels at the cell-edge, downlink/uplink link budget, air-link access latency, client power consumption including uplink peak-to-average power ratio reduction, transmission and detection of control channels, scan latency and network entry/ re-entry procedures, downlink and uplink symbol structure and subchannelization schemes, MAC management messages, MAC headers, support of the FDD duplex scheme, advanced single-user and multi-user MIMO techniques, relay, femto-cells, enhanced multicast and broadcast, enhanced location-based services, and self-configuration networks. The IMT-Advanced requirements defined and approved by ITU-R and published as Report ITU-R M.2134 were referred to as target requirements in the IEEE 802.16m system requirement document, and were evaluated based on the methodology and guidelines specified by Report ITU-R M.2135-1. The IEEE 802.16m baseline functional and performance requirements were evaluated according to the IEEE 802.16m evaluation methodology document. The IMT-Advanced requirements are a subset of the IEEE 802.16m system requirements, and thus are less stringent than baseline requirements. Since satisfaction of the baseline requirements would imply a minimum-featured (baseline) system, any minimum performance of the IEEE 802.16m implementation could potentially meet the IMT-Advanced requirements and could be certified as an IMT-Advanced technology. The candidate proposal submitted by the IEEE to the ITU-R

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(IEEE 802.16m) proved to meet and exceed the requirements of IMT-Advanced systems, and thus qualified as an IMT-Advanced technology. In the course of the development of the IEEE 802.16m, and unlike the process used in the previous amendments of the IEEE 802.16 standard, the IEEE 802.16m Task Group developed system requirements and evaluation methodology documents to help discipline and organize the process for the development of the new amendment. This would allow system design and selection criteria with widely agreed targets using unified simulation assumptions and methodology. The group further developed a system description document to unambiguously describe the RAN architecture and system operation of the IEEE 802.16m entities, which set a framework for the development of the IEEE 802.16m standard specification. To enable a smooth transition from Release 1.0 mobile WiMAX systems to the new generation of the mobile WiMAX radio access network, and to maximize reuse of legacy protocols, strict backward compatibility was required. The author’s original view and understanding of backward compatibility was similar to that already seen in other cellular systems such as the migration of 1  EV-DO Revision 0 to 1  EV-DO Revision A, to 1  EV-DO Revision B on the cdma2000 path and evolution of UMTS Release 99 to HSDPA to HSPA, and to HSPA+ on the WCDMA path. In these examples, the core legacy protocols were reused and new protocols were added as complementary solutions, such that the evolved systems maintained strict backward compatibility with the legacy systems, allowing gradual upgrades of the base stations, mobile stations, and network elements. Had it been materialized, the author’s vision would have resulted in a fully backward compatible system with improvement and extension of the legacy protocols and functionalities built on top of the existing protocols as opposed to from ground up. However, the enthusiasm for the IMT-Advanced systems and the ambitious baseline requirements set by the IEEE 802.16 group resulted in deviation from the original vision and the new amendment turned into describing a new system that was built more or less from scratch. A large number of legacy physical, lower and upper MAC protocols were replaced with new and non-backward compatible protocols and functions. The co-deployment of the legacy and the new systems on the same RF carrier is only possible via timedivision or frequency-division multiplexing of the legacy and new protocols in the downlink and uplink legacy/new zones. More specifically, the legacy and new zones are time division multiplexed in the downlink and are frequency division multiplexed in the uplink. Figure 1 illustrates an example where the legacy system is supported in an IEEE 802.16m system. The overhead channels corresponding to each system (i.e., synchronization, control, and broadcast channels) are duplicated due to incompatibility of the physical structures and transmission formats of these overhead channels. Although IEEE 802.16m specifies handover mechanisms to and from the legacy systems, the handover protocols, MAC messages, and triggers are different, requiring a separate protocol/software stack for dual-mode implementation of the two systems. Table 1 compares the physical layer and lower MAC features of the legacy mobile WiMAX and IEEE 802.16m. It can be seen that many important features and functions such as HARQ, subchannelization, control channels, and MIMO modes have changed in the IEEE 802.16m, making migration from legacy systems to the IEEE 802.16m systems not straightforward and also expensive. The complexity of later upgrades is similar to that of migration of UMTS/HSPA systems to 3GPP LTE systems given the non-backward compatible nature of 3GPP LTE enhancements relative to UMTS. The features and functions listed in this table will be described in Chapters 9 and 10. As a result of extensive changes and enhancements in the IEEE 802.16m standard relative to legacy mobile WiMAX, it will not be surprising to realize that the throughput and performance of the IEEE

xviii Introduction

Superframe Headers

New Downlink Zone

Legacy Uplink Zone

New Uplink Zone

New Uplink Zone

UL Subframe

DL Subframe

UL Subframe

DL Subframe

UL Subframe

DL Subframe

UL Subframe

Legacy Uplink Zone

New Uplink Zone

New Uplink Zone

DL Subframe

Legacy Uplink Control Channels

A-MAP Region

Legacy Downlink Zone

New Downlink Zone

Legacy Uplink Zone

Legacy Uplink Control Channels

A-MAP Region

Legacy Downlink Zone

Legacy Uplink Control Channels

Legacy Uplink Zone

New Downlink Zone

New Uplink Zone

A-MAP Region

Legacy Downlink Zone

New Downlink Zone

Legacy Uplink Zone

Legacy Uplink Control Channels

A-MAP Region

Legacy Downlink Zone

Superframe Headers

New Downlink Zone

Legacy Downlink Zone

Transmission Bandwidth

Legacy Uplink Control Channels

A-MAP Region

DL Subframe

UL Subframe

Legacy DL Subframe

Legacy Radio Frame 5 ms

DL DL DL UL UL UL DL DL DL DL DL UL UL UL DL DL DL DL DL UL UL UL DL DL DL DL DL UL UL UL DL DL DL DL DL UL UL UL DL DL New Frame 5 ms

New DL Subframe Superframe 20 ms

FIGURE 1 Example Sharing of Time-Frequency Resources over one Radio Frame between IEEE 802.16m and the Legacy Systems in TDD Mode

Table 1 Comparison of the Legacy Mobile WiMAX Features with IEEE 802.16m Feature

Legacy Mobile WiMAX based on Release 1.0 TDD 5 ms radio frames with flexible time-zones Not supported 5, 7, 8.75, and 10

Control Channel Subchannelization Traffic Channel Subchannelization

Partial Usage of Sub-Channels in the downlink and uplink (distributed permutations) Partial Usage of Sub-Channels in the downlink and uplink (distributed permutations)

Permutation Zone Multiplexing Pilot Design

Time Division Multiplexing of different zones

Turbo Codes

Convolutional Turbo Codes with minimum code rate of 1/3 and repetition coding

Fixed 48 data sub-carriers

Common (non-precoded) and dedicated (precoded) pilots depending on the permutation zone

TDD and FDD 5 ms radio frames with subframe-based fixed time-zones 20 ms duration (4 consecutive radio frames) 5, 7, 8.75, 10, and 20 (up to 100 MHz with carrier aggregation and other channel bandwidths through tone dropping) 18 sub-carriers by 6 OFDM symbols physical resource units and variable number of data sub-carriers depending on the MIMO mode Distributed logical resource units (tone-pair based distributed permutations) Distributed logical resource units (distributed permutations) Sub-band logical resource units (localized permutations) Mini-band logical resource units (physical resource unit-based diversity permutations) Frequency Division Multiplexing in the same subframe Non-adaptive precoded pilots for distributed logical resource units, dedicated pilots per physical resource unit for sub-band and mini-band logical resource units; interlaced pilots for interference mitigation Convolutional Turbo Codes with minimum code rate of 1/3 and rate matching

xix

(Continued )

Introduction

Duplexing Scheme Frame Structure Superframe Structure Operating Bandwidth (MHz) Resource Block Size

IEEE 802.16m

xx

Feature Convolutional Codes DL HARQ UL HARQ Downlink Open-loop Single-user MIMO Downlink Closed-loop Single-user MIMO

Legacy Mobile WiMAX based on Release 1.0 Tail-Biting Convolutional Codes with minimum code rate of ½ Asynchronous Chase Combining Asynchronous Chase Combining Space-Time Block Coding, Spatial Multiplexing; Cyclic Delay Diversity for more than two transmit antennas Sounding-based

Uplink Open-loop Single-user MIMO

Not Supported

Uplink Closed-loop Single-user MIMO Downlink Multi-user MIMO Uplink Multi-User MIMO

Not Supported

Uplink Power Control

Not Supported Single-transmit-antenna Collaborative MIMO

Basic open-loop power control, Messagebased closed-loop power control

Introduction

Table 1 Comparison of the Legacy Mobile WiMAX Features with IEEE 802.16m

Continued

IEEE 802.16m Tail-Biting Convolutional Codes with minimum code rate of 1/5 Asynchronous Incremental Redundancy (Chase Combining as a special case) Synchronous Incremental Redundancy Space Frequency Block Coding, Spatial Multiplexing, Nonadaptive precoding for more than two transmit antennas Transformed codebook-based scheme using sub-band logical resource unit, Long-term covariance matrix or codebook based using mini-band logical resource units Sounding-based using sub-band or mini-band logical resource units Space-Frequency Block Coding/Spatial Multiplexing, Nonadaptive precoding for more than two transmit antennas with distributed logical resource units Codebook-based precoding using sub-band or mini-band logical resource units Multi-User Zero-Forcing precoding based on transformed codebook or sounding Collaborative MIMO for up to four transmit antennas (codebookbased or vendor-specific precoding for more than one transmit antenna) Improved open-loop power control (SINR-based) and signalingbased closed-loop power control

Fractional Frequency Reuse

Basic Fractional Frequency Reuse

Advanced Fractional Frequency Reuse support with up to 4 frequency partitions (1 reuse-1 and 3 reuse-3), Low power transmission in other reuse-3 partitions

Downlink Control Channels

Medium Access Protocol

Individual (user-specific) MAP, separately-coded, once per subframe, Frequency Division Multiplexed with data

Broadcast Channel

Synchronization Channel

Uplink Control Channels

Midamble Channel Quality and Precoding Matrix Feedbacks Bandwidth Request

Sounding

Compressed Medium Access Protocol/ Sub- Medium Access Protocol, jointly-coded, once per frame, Time Division Multiplexed with data Frame Control Header/Downlink Channel Descriptor/ Uplink Channel Descriptor Full bandwidth, 114 codes, once per frame Not Supported 4-bit/6-bit CQI

Primary preamble in 5 MHz bandwidth once per superframe Secondary preamble in full bandwidth, 768 codes, 2 times per superframe Full bandwidth, once per frame, used for PMI/CQI feedback Primary and Secondary Fast Feedback Channel for CQI/PMI feedback 3 uplink 6  6 tiles, regular (5-step) and fast (3-step) contentionbased access

One OFDM symbol in the uplink subframe, CDM and FDM for mobile station and antenna multiplexing

Introduction

Reuse of initial ranging structure and sequence; 5-step access One OFDM symbol in the uplink subframe, CDM and FDM for mobile station multiplexing

Primary and Secondary Superframe Headers

xxi

xxii

Introduction

802.16m surpasses that of the legacy system, resulting in extended capabilities to support a variety of existing and future services and applications with high quality and capacity. Table 2 compares the throughput of the two systems under selected test scenarios that were specified in the IMT-Advanced evaluation methodology document. In Table 2, a TDD system with 10 MHz bandwidth and frequency reuse 1, as well as a DL:UL ratio of 29:18 was assumed for both systems. The legacy system employs a 4  2 single-user MIMO configuration and sounding-based beamforming in the downlink, along with a 1  4 collaborative MIMO in the uplink. The IEEE 802.16m uses a 4  2 multi-user MIMO in the downlink in addition to a 2  4 collaborative MIMO in the uplink with codebook-based beamforming for both links. There are up to four multi-user MIMO users in the downlink and up to two multi-user MIMO users in the uplink. A common confusion arises concerning the terminologies used for mobile and base stations compliant with different versions of the IEEE 802.16 standard and mobile WiMAX system profile. The IEEE 802.16-2009 standard specifies a large number of optional features and parameters that may define various mobile station and base station configurations. One of the possible implementation variants was selected and specified by the WiMAX Forum as Release 1.0 of the mobile WiMAX system profile. The latter configuration was chosen by the IEEE 802.16m as the reference for backward compatibility. Consequently, when referring to a mobile station and base station in different amendments of the IEEE 802.16 standard, as well as mobile WiMAX profiles, one must make sure that a consistent reference is made, and that backward compatibility and interoperability can be maintained. Unlike the IEEE 802.16m specification that refers to the new IEEE 802.16 entities as “advanced mobile station,” “advanced base station,” and “advanced relay station” to differentiate them from their counterparts in the IEEE 802.16-2009 and IEEE 802.16j-2009 standards specifications, we refer to these entities as mobile station, base station, and relay station, assuming that the reference system is compliant with Release 1.0 of the mobile WiMAX system profile and that the extended functions and protocols corresponding to IEEE 802.16m can be distinguished from their legacy counterparts by the reader. Similar to the IEEE, the 3GPP initiated a project on the long-term evolution of UMTS radio interface in late 2004 to maintain 3GPP’s competitive edge over other cellular technologies. The

Table 2 Comparison of the Throughput of the Legacy Mobile WiMAX and IEEE 802.16m Systems

Legacy Mobile WiMAX based on Release 1.0 IEEE 802.16m

Downlink Spectral Efficiency (bits/s/Hz/cell)

Uplink Spectral Efficiency (bits/s/Hz/cell)

IMT-Advanced Urban Microcell Test Environment (3 km/h)

IMT-Advanced Urban Macrocell Test Environment (30 km/h)

IMT-Advanced Urban Microcell Test Environment (3 km/h)

IMT-Advanced Urban Macrocell Test Environment (30 km/h)

2.02

1.44

1.85

1.70

3.22

2.45

2.46

2.25

Introduction

xxiii

evolved UMTS terrestrial radio access network substantially improved end-user throughputs, and sector capacity, and reduced user-plane and control-plane latencies, bringing a significantly improved user experience with full mobility. With the emergence of the Internet protocol as the protocol of choice for carrying all types of traffic, the 3GPP LTE provides support for IP-based traffic with end-toend quality of service. Voice traffic is supported mainly as voice over IP, enabling integration with other multimedia services. Unlike its predecessors, which were developed within the framework of UMTS architecture, 3GPP specified an evolved packet core architecture to support the E-UTRAN through a reduction in the number of network elements and simplification of functionality, but most importantly allowing for connections and handover to other fixed and wireless access technologies, providing network operators with the ability to deliver seamless mobility experience. Similar to the IEEE 802.16, 3GPP set aggressive performance requirements for LTE that relied on improved physical layer technologies, such as OFDM and single-user and/or multi-user MIMO techniques, and streamlined Layer 2/Layer 3 protocols and functionalities. The main objectives of 3GPP LTE were to minimize the system and user equipment complexities, to allow flexible spectrum deployment in the existing or new frequency bands, and to enable coexistence with other 3GPP radio access technologies. The 3GPP LTE has been used as the baseline and further enhanced under 3GPP Release 10 to meet the requirements of the IMT-Advanced. A candidate proposal based on the latter enhancements (3GPP LTE-Advanced) was submitted to the ITU-R and subsequently qualified as an IMT-Advanced technology. However, concurrent with the 3GPP LTE standard development, the operators were rolling out HSPA networks to upgrade their 2G and 2.5G, and early 3G infrastructure, thus they were not ready to embrace yet another paradigm shift in radio access and core network technologies. Therefore, 3GPP has continued to improve UMTS technologies by adding multi-antenna support at the base station, higher modulation order in the downlink, multi-carrier support, etc., to extend the lifespan of 3G systems. It is anticipated that the new releases of 3GPP standards (i.e., LTE/LTE-Advanced) will not be commercially available worldwide on a large scale until current operators’ investments are properly returned. A comparison of 3GPP LTE-Advanced and IEEE 802.16m basic and advanced features and functionalities reveals that the two systems are very similar and may perform similarly under the same operating conditions. Therefore, there is effectively no technical or performance distinction between the two technologies. It will be shown throughout this book that the two radio access technologies are practically equivalent as far as user experience is concerned. Table 3 summarizes the major differences between IEEE 802.16m and 3GPP LTE-Advanced physical layer protocols. The features and functions listed in this table will be described in Chapters 9 and 10. In the course of design and development of the IEEE 802.16m standard, the author decided to write a book and to take a different approach than was typically taken in other books and journal articles. The author’s idea was to take a top-down systems approach in describing the design and operation of the IEEE 802.16m, and to contrast the 3GPP LTE/LTE-Advanced and IEEE 802.16m/mobile WiMAX algorithms and protocols to allow readers to better understand both systems. The addition of the 3GPP LTE/LTE-Advanced protocols and system description further expanded the scope of the book to a systems approach to understanding the design and operation of 4th generation cellular systems. There has been no attempt anywhere in this book to compare, side-by-side, the performance and efficiency of the mobile WiMAX and 3GPP LTE systems and to conclude that one system outperforms the other, rather, it is left to the reader to arrive at such a conclusion. In addition to a top-down systems approach, another distinction of this book compared to other publications in the literature is the

xxiv

Introduction

Table 3 Major Differences between IEEE 802.16m and 3GPP LTE-Advanced Physical Layers Feature

3GPP LTE-Advanced

IEEE 802.16m

Multiple Access Scheme

Downlink: OFDMA Uplink: SC-FDMA Time Division Multiplex (Resource occupied by control channel in units of OFDM symbols)

Downlink: OFDMA Uplink: OFDMA Frequency Division Multiplex (Resource occupied by control channel in physical resource block units) Base codebook with long-term channel covariance matrix and Sounding Short and long TTI scheduling and Persistent scheduling

Control Channel Multiplexing with Data

Channel State Information (CSI) Feedback

Long-term CSI and Short-term CSI (e.g., sounding)

Scheduling Period

Per Transmission Time Interval (TTI) scheduling and Persistent scheduling 12 sub-carriers  14 OFDM/SCFDMA Symbols ¼ 168 Resource elements 600 sub-carriers  15 kHz (subcarrier spacing) ¼ 9 MHz (Spectrum Occupancy ¼ 90%) 70 OFDM/SC-FDMA symbols (FDD) 56 OFDM/SC-FDMA symbols (TDD) 42000 Resource Elements (subcarriers) 27 Levels

Physical Resource Block Size

Usable Bandwidth at 10 MHz

Usable OFDM/SC-FDMA Symbols per 5 ms

Usable Resource Elements per 5 ms Modulation and Coding Scheme Levels Downlink Antenna Configuration for IMT-Advanced Scenarios Uplink Antenna Configuration for IMT-Advanced Scenarios Multi-antenna Schemes for IMT-Advanced Scenarios

Number of Users Paired in Downlink Multi-user MIMO L1/L2 Overhead

18 sub-carriers  6 OFDM symbols ¼ 108 Resource elements 864 sub-carriers  10.9375 kHz (sub-carrier spacing) ¼ 9.45 MHz (Spectrum Occupancy ¼ 94.5%) 51 OFDM symbols (FDD) 50 OFDM symbols (TDD)

44064 Resource Elements (subcarriers) 32 Levels

4  2/8  2

42

1  4/1  8/2  4

24

Single-user MIMO, Multi-user MIMO/Beamforming, Coordinated Multipoint Transmission Up to 2 users paired in selfevaluation Statically Modeled Number of OFDM symbols L ¼ 1 (18%) Number of OFDM symbols L ¼ 2 (24%) Number of OFDM symbols L ¼ 3 (31%)

Multi-user MIMO/Beamforming

Up to 4 users paired in selfevaluation Dynamically Modeled Example: IMT-Advanced Urban Macrocell Scenario TDD ¼ 11% (Control channel) + 11% (Pilot) z 22% FDD ¼ 14% (Control channel) + 11 % (Pilot) z 25%

Introduction

xxv

inclusion of the theoretical background or a description of uncommon terminologies and concepts in each chapter, so that readers can understand the subject matter without getting distracted with additional reading in the citations and references. In each chapter the design criteria and justification for modifications and extensions relative to the legacy systems have been described. The present book begins with an introduction to the history of broadband mobile wireless access and an overview of the IEEE and 3GPP standards and standardization processes in Chapter 1. The approach taken in this book required the author to review the network architecture and to examine each and every significant network element in mobile WiMAX and 3GPP LTE networks. Since the WiMAX Forum has yet to update the WiMAX Network Architecture specification to support the IEEE 802.16m standard, the latest revision of the WiMAX Network Architecture document which is publicly available from the WiMAX Forum has been used. It is expected that the early deployment of IEEE 802.16m would rely on the legacy network architecture until network upgrades become available. Once the access network and core network aspects of the system are described, we turn our attention to the reference model and protocol structure of IEEE 802.16m and 3GPP LTE/LTE-Advanced, and discuss the operation and behavior of each entity (base station, mobile station, and relay station), as well as functional components and their interactions in the protocol stack. The remaining chapters of this book are organized to be consistent with the protocol layers, starting from the network layer and moving down to the physical layer. The overall operation of the mobile station, relay station, and base station and their corresponding state machines are described in Chapter 4. Perhaps this chapter is the most important part of the book, as far as understanding the general operation of the system is concerned. Chapter 5 describes the interface with the packet data network. Chapters 6 and 7 describe the medium access control layer protocols. Due to the size of content, the medium access control and physical layer chapters (Chapters 6, 7, 9 and 10) have been divided into two parts. The security aspects of the systems under consideration are described in Chapter 8. The additional functional components, algorithms, and protocols which have been introduced by the 3GPP LTE-Advanced are emphasized so that they are not confused with the legacy components. The multi-carrier operation of the IEEE 802.16m and 3GPP LTE-Advanced are described in Chapter 11. The performance evaluation of the IEEE 802.16m and 3GPP LTE-Advanced against the IMT-Advanced requirements has been described in Chapter 12, where all the performance metrics are defined and link-level and system-level simulation methodologies and parameters are elaborated. The existing mobile broadband radio access systems will continue to evolve and new systems will emerge. The vision, service and system requirements for systems beyond IMT-Advanced will be defined as soon as the IMT-Advanced standardization process winds down. While it is not exactly clear what technologies will be incorporated into the design of such systems and whether the existing radio access technologies will converge into a single universal radio interface, it is envisioned that the future radio interfaces will rely on distributed antenna systems, low-power emission, distributed computing, seamless connectivity, software defined radio, cognitive radio systems, multi-resolution wireless multimedia, and cooperative communication concepts, as well as reconfigurable RF and baseband circuitry in order to provide a higher quality of user experience, higher capacities, and a wider range of services with minimal cost and complexity.

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Acknowledgements The author would like to acknowledge and sincerely thank his colleagues at Intel Corporation, ZTE Corporation, Samsung Electronics, Motorola, LG Electronics, the IEEE 802.16, and the 3GPP RAN groups for their contributions, consultation, and assistance in proofreading and improving the quality and content of the chapters of this book. The author would like to sincerely thank Academic Press (Elsevier) publishing and editorial staff for providing the author with the opportunity to publish this book and for their assistance, cooperation, patience, and understanding throughout the past two years. Finally, the author would like to thank his wife (Shahrnaz) and his children (Roya and Nima) for their unwavering encouragement, support, patience, and understanding throughout this long and challenging project.

xxvii

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CHAPTER

Introduction to Mobile Broadband Wireless Access

1

INTRODUCTION The last two decades have witnessed a rapid growth in the number of subscribers and incredible advancement in technology of cellular communication from simple, all-circuit-switched, analog first generation systems with limited voice service capabilities, limited mobility, and small capacity to the third generation systems with significantly increased capacity, advanced all-digital packet-switched all-IP implementations that offer a variety of multimedia services. With the increasing demand for high-quality wireless multimedia services, the radio access technologies continue to advance with faster pace toward the next generation of systems. The general characteristics envisioned for the fourth generation of the cellular systems include all-IP core networks, support for a wide range of user mobility, significantly improved user throughput and system capacity, reliability and robustness, seamless connectivity, reduced access latencies, etc. In this chapter we discuss the current status of broadband wireless access technologies and the efforts that are made by prominent standardization organizations to materialize the vision and to fulfill the objectives for the next generation of broadband radio access systems. Presently, the most important activities in this area are conducted by the Institute of Electrical and Electronics Engineers and 3rd Generation Partnership Project. These two organizations have historically contributed to the development and advancement of fixed and mobile broadband systems such as the IEEE 802.16, IEEE 802.11, IEEE 802.3, and the UMTS family of standards. Both organizations have already taken significant steps toward the next generation of fixed and mobile broadband wireless access technologies also known as IMT-Advanced systems. There is a great amount of commonality and similarity between the latest generations of wireless access system standards that started with similar system requirements and has further continued with similar functional blocks, protocols, and baseband processing, resulting in the notion of ultimate convergence in the 4th or later generations of broadband wireless access technologies. An attempt will be made to provide the background information and justification for this viewpoint throughout this chapter, while adhering to a systematic and structured approach.

1.1 MOBILE BROADBAND WIRELESS ACCESS TECHNOLOGIES Wireless broadband technologies provide ubiquitous broadband access to mobile users, enabling consumers with a broad range of mobility and a variety of wireless multimedia services and applications. Broadband wireless access technologies provide broadband data access through wireless media to consumer and business markets. The most common example of broadband wireless access is Mobile WiMAX. DOI: 10.1016/B978-0-12-374964-2.10001-3 Copyright Ó 2011 Elsevier Inc. All rights reserved.

1

2

CHAPTER 1 Introduction to Mobile Broadband Wireless Access

wireless local area network. There have been continued efforts to deliver ubiquitous broadband wireless access by developing and deploying advanced radio access technologies such as 3GPP UMTS and LTE, as well as mobile WiMAX systems. The broadband wireless access is also an attractive option to network operators in geographically remote areas with no or limited wired network. The advantages in terms of savings in speed of deployment and installation costs are further motivation for broadband wireless access technologies. There are various types of broadband wireless access technologies that are classified based on the coverage area and user mobility as follows: 1. Personal Area Network (PAN) is a wireless data network used for communication among data devices/peripherals around a user. The wireless PAN coverage area is typically limited to a few meters with no mobility. Examples of PAN technologies include Bluetooth or IEEE 802.15.1 [1] and Ultra Wideband (UWB) technology [2]. 2. Local Area Network (LAN) is a wireless or wireline data network used for communication among data/voice devices covering small areas such as home or office environments with no or limited mobility. Examples include Ethernet (fixed wired LAN) [3] and Wi-Fi or IEEE 802.11 [4] (wireless LAN for fixed and nomadic users). 3. Metropolitan Area Network (MAN) is a data network that connects a number of LANs or a group of stationary/mobile users distributed in a relatively large geographical area. Wireless infrastructure or optical fiber connections are typically used to link the dispersed LANs. Examples include the IEEE 802.16-2004 (fixed WiMAX) [5] and Ethernet-based MAN [3]. 4. Wide Area Network (WAN) is a data network that connects geographically dispersed users via a set of inter-connected switching nodes, hosts, LANs, etc., and covers a wide geographical area. Examples of WAN include the Internet [3] and cellular networks such as 3GPP UMTS [6], 3GPP LTE [7], and mobile WiMAX or IEEE 802.16-2009 [8]. The user demand for broadband wireless services and applications are continually growing. In particular, users expect a dynamic, continuing stream of new applications, capabilities, and services that are ubiquitous and available across a range of devices using a single subscription and a single or unique identity. Offering customized and ubiquitous services based on diverse individual needs through versatile communication systems will require certain considerations in the technology design and deployment. A number of important factors are accelerating the adoption of wireless data services. These include increased user demand for wireless multimedia services, advances in smart-phone technologies, and global coverage of broadband wired and wireless access. In the meantime, application and content providers are either optimizing their offerings or developing new applications to address the needs and expectations of fixed and mobile users. Wireless multimedia applications are growing far more rapidly than voice, and are increasingly dominating network traffic. There has been a gradual change from predominantly circuitswitched to packet-based and all-IP networks since the beginning of this millennium [9]. This change will provide the user with the ability to more efficiently utilize multimedia services including e-mail, file transfers, IP TV, VoIP, interactive gaming, messaging, and distribution services. These services are either symmetrical or asymmetrical and real-time or non real-time. They require wider frequency bandwidths, lower transmission and processing latencies, and higher data throughputs.

1.1 Mobile broadband wireless access technologies

3

It is envisioned that within the next decade a large number of the world population would have access to advanced mobile communication devices. The statistics suggest that the number of broadband wireless service subscribers can exceed two billion in the next few years [9]. There are already more portable handsets than either fixed line telephones or wired line equipment such as desktops that can access the Internet, and the number of mobile devices is expected to continue to grow more rapidly than fixed line devices. Mobile terminals will be the most commonly used devices for accessing and exchanging information as well as e-commerce [10]. This trend is viewed as the integration and convergence of information technology, telecommunications, and content. This trend has resulted in new service delivery dynamics and a paradigm shift in telecommunications that will benefit both end users and service providers [10]. The following general requirements are applied to telecommunication services and applications, noting that the requirements may be different from one service offering to another:
Seamless and continuous connectivity, as well as seamless handover across heterogeneous networks to support a wide range of user mobility from stationary to high speed. This includes mobility management and inter-system interoperability when users are in multi-mode service [11].
Low power consumption in multi-mode devices through complexity and size reduction.
Application scalability and quality of service to maintain services despite changes of radio channel condition by adapting the data rate and/or the error tolerance of the application.
Security and data integrity for multimedia and e-commerce applications. In the latter, authentication of user information integrity and protection of user information are required to support high security services and prevent security breaches.
Prioritization for applications with urgency such as emergency/disaster. Such applications require higher priority than other applications and support of prioritization of access to network resources.
Location determination capability and accuracy to enable certain location-dependent applications. An important aspect of this capability is the ability to protect the privacy information of the user.
Broadcast and multicast and efficient support for point-to-multipoint transmission is required because broadcast and multicast services are expected to be an important part of an operator’s service offering in the future.
Presence to allow a set of users to be informed about the availability, willingness, and means of communication of the other users in a group.
Usability and interactiveness of applications to allow easy and convenient use of services. The usability may include voice recognition and user-friendliness of human-to-machine interfaces. Good user experience plays a crucial role in the acceptance and proliferation of services. In defining the framework for development of IMT-Advanced, and systems beyond IMT-Advanced, it is important to understand the user demands and technology trends that will affect the development of such systems. In particular, the framework should be based on increasing user expectations and the growing demand for mobile services, as well as the evolving nature of the services and applications that may become available. Figure 1-1 shows four service classes (conversational, interactive, streaming, and background services) and their characteristics in terms of reliability, bit rate, and latency [12]. We will further discuss these requirements and characteristics in the next sections. In this figure, BER denotes bit error rate which is a measure of reliability of communication link, and is the ratio of the number of incorrectlyreceived information bits to the total number of information bits sent within a certain time interval.

4

CHAPTER 1 Introduction to Mobile Broadband Wireless Access

Data Rate (Mbps)

50 Background Services BER < 10–6

10 Streaming Services 10–9 < BER < 10–6

5

Interactive Services 10–9 < BER < 10–6

1

0.5 Conversational Services 10–6 < BER < 10–3

10

100

1000

Delay (ms)

FIGURE 1-1 Service classes and their characteristics

Prominent standards developing organizations such as the 3rd Generation Partnership Project (3GPP),i the 3rd Generation Partnership Project 2 (3GPP2),ii and the Institute of Electrical and Electronics Engineers Standards Association (IEEE-SA)iii have actively contributed to the design, development, and proliferation of broadband wireless systems in the past decade. A number of broadband wireless access standards for fixed, nomadic, and mobile systems have been developed by these standardization groups and deployed by a large number of operators across the globe [9,13,14].

1.1.1 The 4th Generation of Mobile Broadband Wireless Access Technologies International Mobile Telecommunications-Advanced (IMT-Advanced) or alternatively 4th Generation (4G) cellular systems are mobile systems that extend and improve upon the capabilities of the IMT-2000 family of standards. Such systems are expected to provide users with access to a variety of advanced IP-based services and applications, supported by mobile and fixed broadband networks, which are predominantly packet-based. The IMT-Advanced systems can support a wide range of data rates, with different quality of service requirements, proportional to user mobility conditions in multi-user environments. The key features of IMT-Advanced systems can be summarized as follows [11,15]:
Enhanced cell and peak spectral efficiencies, and cell-edge user throughput to support advanced services and applications;
Lower airlink access and signaling latencies to support delay sensitive applications; i

http://www.3gpp.org http://www.3gpp2.org iii http://standards.ieee.org ii

1.1 Mobile broadband wireless access technologies

High Mobility (120–500 km/h)

5

New Mobile Access

IMT-Advanced Systems

Enhanced IMT 2000 Systems

y, nc ate es L c ing rvi as Se cre ing e D as s, re ate , Inc R y t ta ili a D ob New Nomadic/Local ing g M as vin Wireless Access e r o r Inc Imp

IMT 2000 Systems

Low Mobility/ Nomadic (0–30 km/h) 1

10

100

1000

Layer 2 Data Rate (Throughput at MAC Layer) Mbps

FIGURE 1-2 Illustration of the capabilities and evolution of IMT-2000 systems [10]










Support of higher user mobility while maintaining session connectivity; Efficient utilization of spectrum; Inter-technology interoperability, allowing worldwide roaming capability; Enhanced air–interface–agnostic applications and services; Lower system complexity and implementation cost; Convergence of fixed and mobile networks; Capability of interworking with other radio access systems.

These features enable IMT-Advanced systems to accommodate emerging applications and services. The capabilities of IMT systems have been continuously enhanced proportional to user demand and technology advancements in the past decade. However, the framework and overall objectives of the systems beyond IMT-2000 are considered to be a paradigm shift in the design and development of radio air interfaces [10]. Present mobile communication systems have evolved by incremental addition of more capabilities and enhancement of features to the baseline systems. Examples include evolution of the UMTS family of standards in 3GPP. The systems beyond IMT-2000 have been realized by combining the existing components of IMT-2000 systems, with enhanced and newly developed functions, nomadic wireless access systems, and other wireless systems with high commonality and seamless interworking. The capabilities and evolution of IMT-2000 systems is illustrated in Figure 1-2. As it appears from the figure, the services and performance of the systems noticeably increase as the systems evolve from one generation to another.

6

CHAPTER 1 Introduction to Mobile Broadband Wireless Access

The International Telecommunication Union (ITU)iv framework for the future development of IMT-2000 and systems beyond IMT-2000 encompasses both the radio access, i.e., IMT-Advanced systems initiative, and the core network, i.e., Next Generation Networks (NGN)v project. However, it is recognized that, in the future, the evolution of technologies and redistribution of traditional functions between radio access networks and core networks in practical systems may blur this distinction. Table 1-1 shows the service requirements for IMT-Advanced systems [11]. There are four user experience classes where each is further divided into a number of service classes based on the intrinsic characteristics of corresponding services, such as required throughput and latency to ensure the QoS requirements for each class are met. The service class requirements can be translated into system requirements, which are directly mapped to data transport over a wireless network. As a result, a limited number of QoS attributes, such as data throughput, packet delay and/or delay variations (often referred to as jitter), bit/packet error rate are defined. Examples of applications corresponding to each service class are provided in Table 1-1. In this table, the interactive gaming services mainly involve data transferred between multiple users that are connected to a server, or directly between the equipment of multiple users. Real-time communication with low delay and low jitter is required for interactive gaming. Multimedia refers to media that uses multiple forms of information content and information processing (e.g., text, audio, graphics, animation, video, and interactivity) to inform or entertain users. Wireless multimedia is an essential element of various application services described in this section which must be supported by IMT-Advanced systems. Furthermore, location-based services, which depend on the present location of a user, enable users to find other people, vehicles, resources, services, or machines. Video conferencing is a full-duplex, real-time audiovisual communication between or among end users. Remote collaboration is sharing of files and documents in real-time among users that are members of a project. It mainly involves data transferred between multiple users that are connected to a server or directly between the user terminals. This includes facilities for a virtual office that is a personal online office, where the data and files can be shared in real-time. Mobile commerce service is the buying and selling of goods and services through wireless terminals. It mainly involves data transferred between user equipment and financial servers connected with secured databases. This service also enables the real-time sharing and management of information on products, inventory, availability, etc. This service requires a high level of reliability. Mobile broadcasting is a point-to-multipoint transmission of multimedia content over one or multiple radio access networks. This further includes interactive content or IP-TV, which requires the ability to interact with an audio/video program by exchanging multimedia information. The IP television is a system where a digital television service is delivered using a broadband IP network infrastructure.

1.1.2 Requirements of 4G Mobile Broadband Wireless Access Systems The service and application requirements have been translated to design requirements for the next generation of mobile broadband wireless access systems. The design requirements encompass a wide range of system attributes, such as data and signaling transmission latency over the airlink, system data iv

http://www.itu.int/ITU-R/ A Next Generation Network (NGN) is a packet-switched access network capable of providing telecommunication services through use of multiple broadband, QoS-enabled transport technologies where service-related functions are independent of underlying transport-related technologies. It offers unrestricted access by users to different service providers. It supports generalized mobility which will allow consistent and ubiquitous provision of services to users [16].

v

Table 1-1 IMT-Advanced Service Classification Requirements [11] User Experience Class Conversational

The basic conversational service class comprises basic services that are dominated by voice communication characteristics. The rich conversational service class consists of services that mainly provide synchronous communication enhanced by additional media such as video, collaborative document viewing, etc. Conversational low delay class comprises real-time services that have very strict delay and delay jitter requirements.

The differentiating factor of these service classes is the live or non-live nature of the content transmitted. In case of live content, buffering possibilities are very limited, which makes the service very delay-sensitive. In the case of non-live (i.e., prerecorded) content, play-out buffers at the receiver side provide a high robustness against delay and jitter.

Service Class Basic conversational service Rich conversational service

Conversational low delay Streaming live

Throughput Delay Throughput Delay

Throughput Delay Throughput Delay

Streaming non-live

Throughput Delay