Performance optimisation for bit-interleaved coded modulation with iterative demapping with max-log- maximum a posterior detection

Max-log-maximum a posterior (MAP) detection is preferred in practical systems rather than log-MAP because of its lower complexity, but also suffers from a considerable performance loss. In this study, the authors focus on the performance optimisation for (doped) bit-interleaved coded modulation with iterative demapping schemes where max-log-MAP detection is employed. First, they study the effects of max-log-MAP detection to the extrinsic information transfer curves of the (doped) demapper and decoder, and reselect the constellation labelling. Second, they find that the small difference between max-log-MAP and log-MAP detection in each iteration would be accumulated during the whole iterative procedure referred to as error accumulation, which causes a large performance loss, and consequently they propose some methods to control the error accumulation. Owing to the labelling reselection and error-accumulation control, the proposed scheme exhibits several tenths to 1 dB gains, compared with the conventional schemes, while maintaining low complexity.