Design of BICM-ID Systems with Suboptimal Log-MAP Decoding Algorithm

This paper addresses the performance degradation of near-capacity bit-interleaved coded modulation with iterative demapping and decoding (BICM-ID) when both demapping and decoding employ max-log-MAP algorithm. Two approaches are proposed to overcome the performance degradation: scaling of the transferred log-likelihood-ratios (LLRs) between demapping and decoding to mitigate the bias of LLRs values, and decoding-oriented labeling search to avoid the extrinsic information transfer (EXIT) curve mismatch with max-log-MAP algorithm. In addition, balanced labeling search is developed to achieve the EXIT curve-matching over both AWGN and Rayleigh channel. Simulation results have shown that the designed BICM-ID system with max-log-MAP algorithm could be superior to the referenced LDPC-based BICM system in DVB-T2 with log-MAP demapping and SPA decoding, over both AWGN and Rayleigh channel.