George Abe
`
`SECOND EDITION
`
`@
`Crsco PRESS
`www.ciscopress.com
`
`CSCO-1101
`Cisco v. TQ Delta, IPR2016-01009
`Page 1 of 4
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`

`

`Residential Broadband Second Edition
`
`George Abe
`
`Copyright
`
`2000 Cisco Press
`
`Cisco Press logo is
`
`trademark of Cisco Systems Inc
`
`Publisbed by
`Cisco Press
`
`201 West 103rd Street
`Indianapolis IN 46290 USA
`All rights reserved No pan of this book may be reproduced or transmitted in any form or by any means electronic or
`including photocopying recording or by any information storage and retrieval system without written
`mechanical
`permission from the publisher except for the inclusion of brief quotations
`in review
`
`Printed in the United States of America
`
`Library of Congress Cataloging-in-Publication Number 99-64088
`ISBN 1-57870-177-5
`
`Warning and Disclaimer
`
`This book is designed to provide information about residential broadband Every effort has been made to make this book
`as complete and as accurate as possible but no warranty or fitness is implied
`The information is provided on an as is basis The author Cisco Press and Cisco Systems Inc shall have neither
`to any loss or damages arising from the information
`liability nor responsibility to any person or entity with respect
`contained in this book or from the use of the discs or programs that may accompany
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`The opinions expressed in this book belong to the author and are not necessarily those of Cisco Systems Inc
`
`Trademark Acknowledgments
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`All terms mentioned
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`Cisco Press or Cisco Systems Inc cannot attest to the accuracy of this information Use of
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`the validity of any trademark or service mark
`not be regarded as affecting
`
`CSCO-1101
`Cisco v. TQ Delta, IPR2016-01009
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`Wave
`
`bits/symbol on
`bits/symbol on
`
`68
`
`Chapter
`
`Technical Foundations of Residential Broadband
`
`Amplitude Modulate Each
`
`Figure 2-6
`
`QAM Modulation
`
`Wav\
`
`using
`
`into
`
`Discrete Multitone
`QPSK QAM and CAP are examples of modulation techniques that permute
`single carrier or
`from each other These are called single-carrier
`single wave slightly offset
`two copies of
`techniques Frequency amplitude and phase of the carrier can be modulated to encode
`information These are well-understood techniques with
`lot of industrial and defense
`experience behind them
`But with the development of digital signal processing DSP multicarrier techniques are now
`techniques use an aggregate amount of bandwidth and divide it
`possible Multicarrier
`subbands thereby yielding multiple parallel narrower channels Each subband is encoded
`single-carrier technique such as QAM and bit streams from the subbands are bonded
`together at the receiver Important examples of multicarrier techniques include orthogonal
`frequency division multiplexing OFDM and discrete multitone DMT
`Consider Figure 2-7 which shows an example of multicarrier modulation using the current
`ANSI Ti .413 standard for ADSL Here MHz is segmented into 256 subbands of
`kHz each
`The transmitter modulates each subband using
`single-carrier modulation technique The
`the subband and bonds the 256 carriers together
`
`receiver accepts
`OFDM and DMT differ in that OFDM uses
`common modulation scheme for each subband
`is each subband transfers the same number of bits per second OFDM is used in European
`That
`over-the-air broadcast digital television In the case of over-the-air broadcast all subbands are
`common modulation technique makes
`presumed to have uniform noise characteristics so
`sense
`
`the OFDM model by allowing variable spectral efficiency among the subbands
`DMT enhances
`Some subbands can use more aggressive modulation schemes than other subbands DMT is
`used in wired media such as ADSL where the noise characteristics of each subband may differ
`Subbands which have high noise problems can be avoided
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`CSCO-1101
`Cisco v. TQ Delta, IPR2016-01009
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`Figure 2-7
`
`Multicarrier Modulation
`
`Modulation Techniques
`
`69
`
`0MHz
`
`Frequency
`
`1MHz
`
`digital bit compared
`latency penalty time delay to transmit
`Multicanier
`techniques have
`with single carriet In the DMT case for ADSL there are 256 subbands of
`kHz each So no
`kHz even if
`the line was perfectly clean
`faster than allowed by
`bit can travel
`One of the noisiest debates about modulation techniques is between proponents of DMT and
`proponents of CAP for use in ADSL DMT for ADSL uses 256 subbands whereas CAP uses
`single carrier with amplitude modulation very similar to QAM At the time of this writing CAP
`has an advantage over DMT in that
`thereby generating less heat and
`it consumes less power
`costs less because it is more mature more units in the field greater integration It
`is easy to see
`how DMT scales and why DMT has been selected by ANSI T1B1.4 and the Intemational
`Telecommunications Union ITU Furthermore
`number of U.S telephone companies have
`selected DMT Because of these factors and because of commercial
`to the
`issues with respect
`licensing of CAP it appears DMT is gaining the upper hand for ADSL
`
`Conderafions in Seecting Modulation Techniques
`Selection of modulation technique for each Access Network has been highly contentious partly
`because theres lot of money at stake Standards organizations for cable TV xDSL and HDTV
`have spent years arguing the requirements of modulation let alone the choice While
`national pride embedded base and personal
`cormnercial self-interest academic background
`role there are engineering and cost tradeoffs to consider as well
`
`ego play
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