QAM调制下基于卷积码与累加编码调制级联的纠错码性能研究

Research on the Performance of Error Correction Codes Based on Convolutional Code and Accumulative Code Modulation Cascade under QAM Modulation

摘要:

基于卷积码与累加编码的PPM调制级联码（SCPPM）在泊松信道光PPM调制下具有极优异的性能。本文将这种累加编码结构引入到QAM调制中，分析其性能。并与常规基于卷积码、并行级联卷积码（Turbo）以及低密度奇偶校验码（LDPC）的比特交织编码调制迭代译码（BICM-ID）进行了比较，结果表明在高阶QAM调制下，卷积码+累加编码+QAM调制串行级联（SCAQAM）纠错方案具有极优异的误码性能。对于16QAM及64QAM调制，相对于另外几种纠错码结构的BICM-ID系统分别有约0.3dB和0.5dB的性能提升，并且只有卷积码与累加码结合才更具性能优势。对于这种纠错结构，进一步比较了自然、格雷、反格雷星座映射方式，将累加后的比特流以反格雷方式映射具有更优异的性能。

Abstract:

The PPM modulation cascaded code (SCPPM) based on convolutional codes and cumulative encoding has excellent performance in Poisson channel optical PPM modulation. This article introduces this cumulative encoding structure into QAM modulation and analyzes its performance. And compared with conventional bit interleaved encoding modulation iterative decoding (BICM-ID) based on convolutional codes, parallel concatenated convolutional codes (Turbo), and low density parity check codes (LDPC), the results show that under high-order QAM modulation, the convolutional code+cumulative encoding+QAM modulation serial concatenation (SCAQAM) error correction scheme has excellent error performance. For 16QAM and 64QAM modulation, the BICM-ID system has a performance improvement of about 0.3dB and 0.5dB respectively compared to other error correction code structures, and only the combination of convolutional code and accumulation code has a performance advantage. For this error correction structure, further comparisons were made between natural, Gray, and anti-Gray constellation mapping methods, and mapping the accumulated bitstreams in an anti-Gray manner showed better performance.