低复杂度串行级联LDGM码构造方案

On construction of low complexity serially-concatenated LDGM codes

针对LDGM码的稀疏矩阵构造复杂度较高的问题,提出了一种具有低复杂度的LDGM码随机稀疏矩阵构造算法,该算法既降低了编码的复杂度又保证了良好的性能.同时,针对LDGM码存在明显的错误平层的问题,引入了串行级联结构,并提出了一种改进的SCLDGM码译码算法,该算法将内译码器输出的错误信息看作是BEC信道的删除信息,利用该先验信息初始化外译码器的输入,从而进一步提高BER性能.通过对SCLDGM码编码系统模型的仿真,得到近优的内外编码速率组合和近优的内外码码重.仿真结果表明,本文提出的算法在保证低复杂度的前提下,可以获得良好的BER性能,并有效的降低了LDGM码错误平层.

According to the problem of sparse matrix with high complexity of LDGM codes,a low-complexity construction algorithm of LDGM codes is proposed,which can decrease the encoding complexity while keeping a good performance.Meanwhile,a serially-concatenated construction with a modified SCLDGM decoding algorithm is introduced to solve the problem of high error floor of LDGM codes.This algorithm considers the incorrect output of the inner decoder as the erasures from a BEC channel.The outer decoder uses the priori probability to initialize in the decoding process,which further reduces the residual errors.By simulations for the SCLDGM encoding and decoding system,the near-optimal combination of inner and outer coding rates and the near-optimal column weights of inner and outer codes are obtained.Simulation results show that,a good BER performance can be obtained and the error floor of LDGM codes can be decreased as well by using the proposed algorithms on the premise of keeping a low complexity.