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本文研究了准循环LDPC码的一致校验矩阵与其对应Tanner图环结构之间的关系,将局部平均围长优化算法引入优化构造算法中,提出了一种基于PEG算法的准循环扩展LDPC码构造的改进算法。在改进算法中,首先利用PEG算法产生基矩阵,然后基于平均围长最大准则选择循环移位置换矩阵对基矩阵进行准循环扩展,通过围长分布的优化,从而改善了迭代译码的性能。仿真结果表明,在码长相同、码率和度分布近似情况下,与文献[7]中基于PEG算法的准循环扩展构造的码字比较,改进算法构造的码字能够获得更加优异的性能。
In this paper, the relationship between the parity check matrix of quasi-cyclic LDPC codes and its corresponding Tanner graph ring structure is studied. The algorithm of local average girth length is introduced into the optimal construction algorithm, and a quasi-cyclic extended LDPC code structure based on PEG algorithm Improved algorithm. In the improved algorithm, we first generate the basis matrix by using the PEG algorithm, and then select the cyclic shift permutation matrix based on the average maximum length criterion to quasi-cyclically extend the basis matrix. By optimizing the girth and length distribution, the performance of iterative decoding is improved. The simulation results show that compared with the quasi-cyclic extended codeword based on the PEG algorithm in [7], the codeword constructed by the improved algorithm achieves more excellent performance with the same code length and the similar code rate and degree distribution.