中文摘要：

针对传统Gray映射在中高信噪比区域内对迭代译码的比特交织编码调制（BICMID）光通信系统改善信道容量性能有限的问题,基于互信息准则和比特的不等保护度提出了一种新颖的16QAM星座映射方案。仿真分析表明：在中高信噪比下,所提出的新映射方案比传统Gray映射方案的信道容量最大改善值可达1.18bit/channel。结合低密度奇偶校验（LDPC）码并借助外部信息传递（EXIT）图,该方案在光通信系统中具有很好的性能优势与应用前景。

英文摘要：

A novel constellation mapping scheme of 16 quadrature amplitude modulation（QAM）based on the criterion of the mutual information and the unequal degree protection of the bit position is proposed so as to improve the limited channel capacity performance of the traditional Gray mapping for the bit-interleaved-coded-modulation with iterative decoding（BICMID）optical communication systems at the medium-to-high signal noise ratio（SNR）region.The simulation analysis shows that the channel capacity of the novel proposed mapping scheme is 1.18bit/channel higher than that of the traditional Gray mapping scheme at the medium-to-high SNR region.Furthermore,combined with the low-density parity-check（LDPC）code,the novel proposed mapping scheme with the assistance of the extrinsic information transfer（EXIT）charts owns good performance advantage and application promise in optical communication systems.