中文摘要：

原模图低密度奇偶校验码相较于传统LDPC码,具有结构简单、迭代译码门限低、易于扩展及线性编译码复杂度等优点。针对强多途、长时延、窄带宽的浅海水声信道,该文研究了PG-LDPC码的设计及性能特征,提出一种码型设计方案,并采用基于原模图度分布的外部信息转移图算法,对所设计PG-LDPC码的纠错性能进行分析及预测。仿真与实验结果表明,与（3,6）随机规则LDPC码相比,所提的PG-LDPC码在低、高信噪比区域均有良好的纠错性能。

英文摘要：

Proto Graph-based Low Density Parity Check（PG-LDPC） codes have many advantages over the conventional LDPC codes, such as simple structure, low iterative decoding threshold, easy extension and linear encoding/decoding complexity. After investigating the characteristics of PG-LDPC codes over the Shallow Water Acoustic（SWA） channels, which have the features of strong multipath interference, long delay spreading and limited bandwidth, a new design scheme to search for good codes is proposed. Furthermore, protographdegree-distribution-based EXtrinsic Information Transfer（EXIT） chart algorithm is used to predict and analyze the error performances of protograph-based LDPC codes. The simulation and experiment results show that the proposed code outperforms the（3, 6） randomly regular LDPC code in both low and high SNR region, over the SWA channels.