الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
In digital communication systems, the channel is subject to various types of noise, distortion and interference, therefore the output differs from the input because of errors. The error control techniques error are applied to guarantee the correct reception of the messages at the receiver. Block code is an important class of codes used in forward error control techniques, the redundant bits are used for error detection and error correction. As the number of redundant bits increase, the capability of the block code to detect and correct errors increase , but the code rate efficiency decreases. In type II hybrid ARQ scheme, parity bits are for error detection only , and sent on the first transmission. If errors are detected in the first transmitted packet, parity bits for error correction are sent, which together with the first packet (which form a rate half error correction codeword). This process requires what is called ?codeword partitioning ? . In codeword partitioning, the coded word (message plus parity bits) is partitioned so that the message bits plus part of the parity bits are transmitted in the first transmission. If the receiver detects an error according to the parity bits in the first transmission, the second part of the partitioned codeword is transmitted for error correction. Codeword partitioning is considered in the study reported here .To show its advantage, codeword partitioning in conjunction with Goback N hybrid ARQ is applied to asynchronous transfer mode ( ATM ) transmission. The performance of the proposed hybrid ARQ scheme is measured by comparing the performance results of the scheme with and without codeword partitioning. Results show that the hybrid ARQ scheme with the codeword partitioning provides higher code rate efficiency at the expense of minor decrease in throughput.