EXIT chart analysis of optimal signal constellation sets and symbol mappings for block-interleaved coded-modulation enabling ultra-high-speed optical transport

In this paper, we analyze the block-interleaved coded modulation with iterative decoding (BICM-ID) where the bit error rate is reduced by iteration of extrinsic information between a multilevel demapper and an LDPC decoder. Based on the mutual information concept of EXIT charts, a new mapping method based on optimal signal constellation (OSCD) is proposed that outperforms previously known ones. The simulation results have shown that optimized mappings for OSCD outperform natural mappings by 0.5 dB in 8-ary case and 0.6 dB in 16-ary case.