中文摘要：

提出一种对随机构造LDPC码校验矩阵算法的改进，该方法基于LDPC校验矩阵与双向图的对应关系。与改进前的算法相比，改进后的算法可确保随机构造的校验矩阵中不会出现长度为4的短环，增大了信息节点之间的独立性，保证了构造的码子的性能。

英文摘要：

An improved algorithm to structure random LDPC based on the correspondence between LDPC check matrix and Tanner graph is presented in this paper. Compared with the initial algorithm, the improved algorithm can assure that it doesn＇t exist short cycles （length 4） in length in the check matrix, so the code is much better.