中文摘要：

针对PEG（Progressive EdgeGrowth）算法构造的LDPC码在保证局部围长最大时仍有较多数目的小环，提出利用PC（Polynomial of Cycle）标记将PEG算法进行改进为PC-PEG算法，并应用于准循环码（QC-LDPC）中。该方法在满足局部围长尽可能大的前提下，减少了小环数目，提高了译码性能。引入QC-LDPC码的特性，其中校验矩阵是一种分块的循环移位码，该特定结构在工程上可以实现部分并行译码，节省存储空间。实验结果表明，该方法与PEG算法相比具有较少的小环数目，而准循环结构的特点在保证译码性能相当的前提下实现了工程上的部分并行译码。

英文摘要：

Since LDPC code based on progressive edge growth（PEG） algorithm construction still has many small cycles in the case of maximization of local girth, make use of polynomial cycle （PC）mark to improve PEG algorithm to be enhanced PC-PEG algorithm is proposed in this paper, and it is applied in Qc - LDPC. This approach can reduce the number of small circles and improve the performance under the maximization of local girth. By using of QC - LDPC, the parity check matrix is still block based cyclic shift code, this special structure can realize parallel decoding in the engineering and save the storage memory. The experimental results demonstrate that the proposed method has smaller number of girth compared with PEG algorithm, and the special structure of cyclic shift ensures parallel decoding with the same decoding performance.