Optimality analysis of bit-interleaved LDPC coded modulation schemes

Bit-interleaved coded modulation (BICM) was first proposed by Zehavi to increase the time diversity of coded modulation over Rayleigh fading channels. In order to make up for the deficiency of BICM over Gaussian channel, BICM with iterative demapping and decoding (BICM-ID) was suggested by Li. Recent research on BICM-ID found that LDPC codes with BICM-ID could get better performance than traditional turbo codes. Since the information processed in BILCM-ID system contains both modulation information and decoding information, we show that the joint optimization for constellation mapping and degree distribution of LDPC codes is necessary. Moreover, we valued the effect of iteration on the bit error performance with different mapping schemes in this paper.