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Error-control schemes for broadcast channels
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|Title:||Error-control schemes for broadcast channels|
|Authors:||Chandran, S. Ram|
|Abstract:||Today's information age has created a virtual explosion in the need for connectivity, resource sharing and transfer of information on a global scale. This has resulted in the mushrooming of data networks. The satisfactory functioning of these networks is becoming increasingly dependent on the fast and reliable transfer of information over broadcast (one-to-many) and multiple-access (many-to-one) channels. Historically, almost all the efforts towards error-control in data transmission have been for the point-to-point channel. In this dissertation, we have investigated some error-control schemes for the reliable transfer of data over broadcast channels. The goal of this study is to meet a given reliability criterion for the transmission of data while making efficient use of the channel. Excepting some degenerate cases, most of the interesting broadcast scenarios also include a multiple-access channel in tandem. In other words, many of these broadcast channels have a built-in feedback channel. We have proposed several error-control schemes for the broadcast channels that make use of this feedback channel. The broadcast environments have been classified into two categories: Homogeneous and Non-homogeneous. Homogeneous broadcast channel (HB) is the case where a single source sends messages to all the destinations in the channel. The transmitter tries to deliver the same messages error-free to all the receivers. In the Non-Homogeneous broadcast (NHB) channel, successive messages from the transmitter may be addressed to different subsets of receivers in the broadcast environment and these subsets may not be disjoint. Several retransmission-error-control schemes have been proposed for these two channels. We introduce criteria for characterizing channel utilization and algorithms for achieving superior channel throughput. The coding problem for the HB channel is synonymous to that of the point-to-point channel. We have proposed a selective repeat ARQ protocol for the HB channel that uses a dynamic programming optimization technique to choose the optimum number of copies of a message to be transmitted by considering the number of receivers that are yet to acknowledge the message. We have also proposed two hybrid ARQ schemes that use powerful codes combined with parity retransmission. These two schemes are suitable for noisier channels. All these schemes significantly improve upon all the existing schemes in literature both in terms of achievable throughput and reliability. For the NHB channel, we have examined several retransmission schemes that exploit the broadcast nature of the channel. The proposed schemes are non-timeshared in general. Time-shared schemes can however be realized as special cases of these schemes. We have considered two cases of the NHB channel: Finite Broadcast Population and Infinite Broadcast Population. The finite population case allows us to exploit the broadcast nature of the channel more effectively. Various trade- offs that arise in the choice of these schemes have been investigated. The non-timeshared schemes significantly outperform the time-shared schemes almost always. To the best of our knowledge, this work constitutes the first systematic study of NHB channels. The NHB channels closely model the computer communications networks so prevalent today. The schemes proposed here achieve much higher throughput than the ones being used today. Moreover, these schemes can be used with UEP codes to achieve different levels of protection for the messages intended for different destination groups.|
|Description:||Thesis (Ph. D.)--University of Hawaii at Manoa, 1991.|
Includes bibliographical references (leaves 124-127)
xii, 127 leaves, bound ill. 29 cm
|Rights:||All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.|
|Appears in Collections:||Ph.D. - Electrical Engineering|
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