有限长低密度奇偶校验码的去环分析

Analysis of loop removal from finite-length LDPC codes

针对低密度奇偶校验码(LDPC)中环的存在影响LDPC码性能的问题,研究了基于校验阵的有限长LDPC码的去环和优化,指出搜索随机矩阵的方法比较直观,但计算量是码长和列重乘积的指数函数。给出了搜索并替换的去环方法,该方法能够显著减小短环对译码性能的影响。计算机仿真结果表明,去除长度为4和6的环能够在误比特率为10-5时获得0.5dB的编码增益。讨论了去环图的优化和判定准则,计算机仿真结果表明,优选的去环编码方案的性能要好于未经优选的方案。

In order to eliminate the negative effect of loops on the performance of low-density parity-check codes （LDPC）, the paper studies loop removal and optimization of finite-length LDPC codes based on parity-check matrices, and points out that the overall search is simple but has a computation complexity with the exponential degree of the product of code length and column weight. A method of search and substitution is given, and its computer simulation results indicate that the performance of codes gain can be improved 0.5dB with 10^-5BER when girth is more than 6. The optimization rules of loop-removal graph are analysed and the simulation results indicate that the selected coding is better.