Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Optimizing and Testing WLANs Prelims-H7986.indd iPrelims-H7986.indd i 6/29/07 6:31:49 PM6/29/07 6:31:49 PM Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com This page intentionally left blank Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Optimizing and Testing WLANs Proven Techniques for Maximum Performance By Tom Alexander AMSTERDAM • BOSTON • HEIDELBERG • LONDON NEW YORK • OXFORD • PARIS • SAN DIEGO SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Newnes is an imprint of Elsevier Prelims-H7986.indd iiiPrelims-H7986.indd iii 6/29/07 6:31:51 PM6/29/07 6:31:51 PM Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Newnes is an imprint of Elsevier 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA Linacre House, Jordan Hill, Oxford OX2 8DP, UK Copyright © 2007, Elsevier Inc. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford, UK: phone: (ϩ44) 1865 843830, fax: (ϩ44) 1865 853333, E-mail: permissions@elsevier.com. You may also complete your request online via the Elsevier homepage (http://elsevier.com), by selecting “Support & Contact” then “Copyright and Permission” and then “Obtaining Permissions.” Recognizing the importance of preserving what has been written, Elsevier prints its books on acid-free paper whenever possible. Library of Congress Cataloging-in-Publication Data Alexander, Tom. Testing 802.11 WLANs : techniques for maximum performance / By Tom Alexander. p. cm. Includes bibliographical references and index. ISBN 978-0-7506-7986-2 (pbk. : alk. paper) 1. Wireless LANs–Security measures. 2. Local area networks (Computer networks)–Security measures. I. Title. TK5105.78.A44 2007 004.6Ј8–dc22 2007017031 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. ISBN: 978-0-7506-7986-2 For information on all Newnes publications visit our Web site at www.books.elsevier.com 07 08 09 10 10 9 8 7 6 5 4 3 2 1 Typeset by Charon Tec Ltd (A Macmillan Company), Chennai, India www.charontec.com Printed in the United States of America Prelims-H7986.indd ivPrelims-H7986.indd iv 6/29/07 6:31:53 PM6/29/07 6:31:53 PM Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Contents Preface ix Introduction xi Chapter 1: IEEE 802.11 WLAN Systems 1 1.1 IEEE 802.11 Wireless Local Area Networks 1 1.2 WLAN Standards Today 3 1.3 Inside WLAN Devices 13 1.4 The RF Layer 19 Chapter 2: Metrology, Test Instruments, and Processes 27 2.1 Metrology: the Science of Measurement 27 2.2 The Nomenclature of Measurement 28 2.3 Measurement Quality Factors 31 2.4 The WLAN Engineer’s Toolbox 33 2.5 Test Setups and Test Processes 37 2.6 Repeatability 48 Chapter 3: WLAN Test Environments 55 3.1 Wired vs. Wireless .55 3.2 Types of Environments 56 3.3 Outdoor and Indoor OTA 59 3.4 Chambered OTA Testing 64 3.5 Conducted Test Setups 69 3.6 Repeatability 72 Chapter 4: Physical Layer Measurements 75 4.1 Types of PHY Layer Measurements 75 4.2 Transmitter Tests 77 4.3 Receiver Tests 90 4.4 Electromagnetic Compatibility Testing 94 4.5 System Performance Tests 99 4.6 Getting the DUT to Respond 105 v Prelims-H7986.indd vPrelims-H7986.indd v 6/29/07 6:31:53 PM6/29/07 6:31:53 PM Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Chapter 5: Protocol Testing 109 5.1 An Introduction to Protocol Testing 109 5.2 Conformance and Functional Testing 111 5.3 Interoperability Testing 117 5.4 Performance Testing 121 5.5 Standardized Benchmark Testing 133 Chapter 6: Application-Level Measurements 137 6.1 System-level Measurements 137 6.2 Application Traffi c Mixes 146 6.3 VoIP Testing 150 6.4 Video and Multimedia 158 6.5 Relevance and Repeatability 162 Chapter 7: WLAN Manufacturing Test 165 7.1 The WLAN Manufacturing Flow 165 7.2 Manufacturing Test Setups 171 7.3 Radio Calibration 175 7.4 Programming 176 7.5 Functional and System Testing 177 7.6 Failure Patterns 179 Chapter 8: Installation Test 181 8.1 Enterprise WLANs 181 8.2 Hot-spots 188 8.3 The Site Survey 190 8.4 Propagation Analysis and Prediction 196 8.5 Maintenance and Monitoring 202 Chapter 9: Testing MIMO Systems 207 9.1 What is MIMO? 207 9.2 The IEEE 802.11n PHY 219 9.3 A New PLCP/MAC Layer 225 9.4 The MIMO Testing Challenge 231 9.5 Channel Emulation 233 9.6 Testing 802.11n MIMO Devices 237 Appendix A: A Standards Guide 241 A.1 FCC Part 15 241 A.2 IEEE 802.11 242 Contents vi Prelims-H7986.indd viPrelims-H7986.indd vi 6/29/07 6:31:54 PM6/29/07 6:31:54 PM Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com A.3 Wi-Fi® Alliance 243 A.4 CTIA 243 A.5 IETF BMWG 244 Appendix B: Selected Bibliography 245 Index 249 Contents vii Prelims-H7986.indd viiPrelims-H7986.indd vii 6/29/07 6:31:54 PM6/29/07 6:31:54 PM Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com This page intentionally left blank Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Preface My purpose in writing this book is to present a comprehensive review of measurement techniques used in the creation and optimization of IEEE 802.11 wireless LANs. Systematic optimization of a system or process involves extensive measurements, to identify issues and also to know when they have been fi xed. A thorough understanding of these measurements and the underlying metrics will aid engineers in improving and extending their wireless LAN equipment and installations. The extremely rapid development of IEEE 802.11 wireless LANs has resulted in a general lack of usable literature covering their test and measurement. As of this writing, wireless LANs are still in their infancy, and methods of measuring and optimizing their performance are not well understood. In fact, there is much confusion within the industry as to what should be measured, let alone how. Equipment vendors try to remedy this by publishing articles, whitepapers and application notes, but these are narrowly focused and usually promote the vendor’s point of view. It is not unusual to fi nd representatives of leading vendors disagreeing on basic metrics and approaches. This book tries to present a broad overview of the entire fi eld, to provide the reader with a context and foundation on which more detailed knowledge may be built. My goal is to supply introduction and training material for designers and test engineers. A reader armed with this knowledge should be able to sort out exactly what needs to be measured and how, and what sort of equipment is best suited for the quantity being measured. Such information also allows users, who may not be directly involved in equipment design, to understand the methods that their equipment suppliers should have used to measure the numbers claimed on datasheets. I would like to take this opportunity to thank many colleagues who indirectly contributed to the material covered in this book. In particular, many in-depth discussions of products and test approaches with the employees of VeriWave, Inc. added a great deal to my understanding of the wireless LAN test fi eld. I am especially grateful to Brian Denheyer of VeriWave for a critical review of Chapters 3 and 4, and for making many suggestions for improvement. To my long-review of Chapters 3 and 4, and for making many suggestions for improvement. To ix Prelims-H7986.indd ixPrelims-H7986.indd ix 6/29/07 6:31:54 PM6/29/07 6:31:54 PM Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com [...]... WLAN installation, and WLAN maintenance will find useful information presented For students, managers, and others, it offers an organized introduction to the many different disciplines of WLAN performance measurement, the equipment used, and some understanding of the techniques and complexities of each area Even design and development engineers, who usually do not run into performance testing on a daily... fascinating examples of engineering ingenuity and precision Modern microwave test equipment such as spectrum analyzers are often the “hot rods” of the RF world This book is devoted to the techniques and equipment used for the test and performance measurement of IEEE 802.11 Wireless LAN (WLAN) devices and systems It covers test equipment and methods for performance measurements at various network protocol... during device-level and board-level verification (i.e., before the complete system is integrated into a final product and manufactured), but may also be carried out as part of system-level performance measurements Chapter 5 deals with the diverse measurement methodologies and measuring equipment used to perform WLAN protocol testing Protocol tests usually cover conformance, performance, and interoperability... editors, Harry Helms and Rachel Roumeliotis, go my heartfelt thanks for their patience and constant encouragement, without which this book might never have been finished Last but certainly not the least, my gratitude to my wife and family, for unstinting supported throughout Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Tom Alexander x Simpo PDF Merge and Split Unregistered... architect and engineer of WLAN test equipment, as well as a writer of standards for measuring WLAN equipment performance Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Considerable attention has been paid in this book to the difficulties encountered with practical wireless measurement setups, and their solutions Making useful wireless measurements requires a good understanding... main 802.11 document in 2003 (forming Clause 18), but the 802.11T group is creating the 802.11.2 document, which will remain as a stand-alone performance test specification.1 1.2.1 PHY Standards In the US, the PHY layer of 802.11 occupies two principal microwave frequency bands: the ISM band at 2.400–2.483 GHz, and the Unlicensed National Information Infrastructure (U-NII) band at 5.150–5.825 GHz (There... EAPOL for 802.1X, which stands for EAP Over LANs The whole area of security is crucial to the setup and operation of modern enterprise WLAN devices; the reader is referred to the book Real 802.11 Security by Edney and Arbaugh for a good introductory explanation of the subject Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Finally, the centralization of AP management and configuration... engineering; Appendix B contains a bibliography of books and publications that should be consulted for further information xiv Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com CHAPTER 1 IEEE 802.11 WLAN Systems In order to successfully test something, it is essential to have a good understanding of how it works and what it does We will therefore begin with an introduction to the important... these bands for computer communications (i.e., radio LANs) to serve as a radio version of the popular Ethernet LAN technology As a result, in 1990 the IEEE standards development organization set up a group, referred to as the IEEE 802.11 committee, to standardize WLANs in the ISM bands However, it took 7 years (until 1997) before the first 802.11 standard was ratified and published That first standard... Operating System and Software PCMCIA or mini-PCI Client Card Figure 1.9: A Typical Client integrated form, a NIC may consist simply of a single CMOS chip supporting the RF and IF functions (up/down conversion, amplification, frequency synthesis and automatic gain control or AGC), the baseband functions (modulation and demodulation, and digitization), and the lower layers of the MAC functions (packet formatting, . http://www.simpopdf.com This page intentionally left blank Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Optimizing and Testing WLANs Proven Techniques for Maximum Performance By Tom. devoted to the techniques and equipment used for the test and performance measurement of IEEE 802.11 Wireless LAN (WLAN) devices and systems. It covers test equipment and methods for performance. http://www.simpopdf.com Chapter 5: Protocol Testing 109 5.1 An Introduction to Protocol Testing 109 5.2 Conformance and Functional Testing 111 5.3 Interoperability Testing 117 5.4 Performance Testing