Iterative Detection And Decoding For Non-Binary Ldpc Coded Partial-Response Channels With Written-In Errors

In this study, the authors investigate the performance of iterative detection and decoding for non-binary low-density parity-check (LDPC) coded partial-response (PR) channels, where written-in errors are present to introduce bit-flipping to LDPC code bits prior to the transmission over PR channels. From a probabilistic perspective, the written-in errors are modelled as the output of a binary symmetrical channel (BSC) with crossover probability equal to the write error probability. Several iterative receivers are presented for the considered system. Specifically, the authors propose a symbol-level Bahl-Cocke-Jelinek-Raviv (BCJR) channel detector based on a sectionalised representation of the joint BSC and PR trellis to produce directly the soft information of non-binary LDPC code symbols, thus avoiding suboptimal symbol/bit log-likelihood ratio conversions as required in bit-level detection schemes. Simulation results show that the proposed symbol-level iterative receiver provides much better bit-error-rate performance over bit-level schemes. Moreover, the proposed receiver enables non-binary LDPC codes to achieve a notable coding gain over their binary counterparts for channels affected with written-in errors.