Performance of Soft-Decision Block-Decoded Hybrid-ARQ Error Control

Abstract

Soft-decision correlation decoding with retransmission requests for block codes is proposed and the resulting performance is analyzed. The correlation decoding rule is modified to allow retransmission requests when the received word is rendered unreliable by the channel noise. The modification is realized by a reduction in the volume in Euclidean space of the decoding region corresponding to each codeword. The performance analysis reveals the typical throughput - reliability trade-off characteristic of error control systems which employ retransmissions. Performance comparisons with hard-decision decoding reveal performance improvements beyond those attainable with hard-decision decoding algorithms. The proposed soft-decision decoding rule permits the use of a simplified codeword searching algorithm which reduces the complexity of the correlation decoder to the point where practical implementation is feasible.