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Simpo PDF Merge and Split Unregistered Version - ht Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf Voice over 802.11 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf For a listing of recent titles in the Artech House Telecommunications Library, turn to the back of this book. Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf Voice over 802.11 Frank Ohrtman Artech House Boston • London www.artechhouse.com Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf Library of Congress Cataloging-in-Publication Data Ohrtman, Frank. Voice over 802.11/Frank Ohrtman. p. cm. Includes bibliographical references and index. ISBN 1-58053-677-8 (alk. paper) 1. IEEE 802.11 (Standard) 2. Internet telephony. I. Title. TK5105.5668.O34 2004 641.382’12—dc22 2004041074 British Library Cataloguing in Publication Data Ohrtman, Frank Voice over 802.11.—(Artech House telecommunications library) 1. Internet telephony 2. Wireless communication systems 3. Broadband communications systems 4. IEEE 802.11 (Standard) I. Title 621.3’845 ISBN 1-58053-677-8 Cover design by Gary Ragaglia © 2004 ARTECH HOUSE, INC. 685 Canton Street Norwood, MA 02062 All rights reserved. Printed and bound in the United States of America. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the publisher. All terms mentioned in this book that are known to be trademarks or service marks have been appropriately capitalized. Artech House cannot attest to the accuracy of this information. Use of a term in this book should not be regarded as affecting the validity of any trademark or service mark. International Standard Book Number: 1-58053-677-8 10 9 8 7 6 5 4 3 2 1 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf To Michelle Otte Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf Contents 1 2 Overview of Vo802.11 1 Access 1 Switching 2 Transport 2 Vo802.11: Bypassing the Local Loop Reference 3 4 802.11: Alternative Access 5 How Does WiFi Work? How Data Is Transmitted Via Wireless Technology The Significance of Spread Spectrum Radio 5 6 8 802.11 Variants FHSS (802.11a) DSSS Orthogonal Frequency-Division Multiplexing Carrier Multiplexing 8 9 11 11 13 MAC Concepts and Architecture MAC Layer Services Power Management and Time Synchronization 13 13 14 MAC Layer Architecture 14 vii viii Voice over 802.11 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf 3 MIB DCF 17 18 PCF 18 IEEE 802.11 Architecture IEEE 802.11 Components Mobility 19 21 22 Conclusion References 23 24 Voice over Internet Protocol 25 What Is VoIP? 25 Origins How Does VoIP Work? Protocols Related to VoIP 25 26 27 Signaling Protocols H.323 SIP 28 28 29 What Is SIP? SIP Architecture Interworking with Other Multimedia Networks H.323 Zone 30 30 36 37 Gateway Control Protocols Media Gateway Control Protocol SS7-Related Protocols 38 39 40 Routing Protocols RIP OSPF SPF Algorithm BGP Resource Reservation Protocol 41 41 41 42 42 44 Transport Protocols RTP 45 45 RTCP 46 Contents ix Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf 4 5 Internet Protocol Version 6 46 Conclusion References 47 47 Switching TDM and VoIP Networks 49 TDM Switching Multiplexing 49 49 Voice Digitization Signaling 50 55 Transport 58 Softswitch and Distributed Architecture: A “Stupid” Network 59 Access PC-to-PC and PC-to-Phone Applications IP Phones (IP Handsets) Phone-to-Phone VoIP 61 61 61 Switching in IP Networks Applications for Softswitch 66 69 Conclusion References 74 75 Objections to Vo802.11 77 Objections Related to 802.11 QoS Security Range 77 77 78 78 Objections Related to Voice over IP Reliability Scalability QoS Signaling Features and Applications 79 79 79 79 79 80 Conclusion References 80 81