中文摘要：

根据深空通信的特点及需求,JPL实验室提出了性能比常规奇偶校验码更优的原模图低密度奇偶校验码,即原模图LDPC（low-density parity-check）码.该文提出一种原模图LDPC码的联合优化算法,在不增加编译码复杂度的前提下能兼顾瀑布区性能,设计出地板区性能更好的码型.理论分析和仿真结果表明,用该算法设计出的新型重复积累码与新型重复-积累-重复码与传统码型（重复积累码和AR4JA码）相比,可在高信噪比区域获得显著的编码增益,降低了错误地板.

英文摘要：

According to the requirements and characteristic of space communication,protograph low-density parity-check（LDPC） codes have been proposed by Jet Propulsion Laboratory（JPL）,which have better performance than conventional LDPC codes.In this paper,we propose a joint optimization algorithm for protograph LDPC codes,aiming at lowering the error floor of protograph LDPC codes,while maintaining good performance at waterfall region without increasing encoding and decoding complexity.Theoretical analysis and simulation indicate that the repeat accumulate（RA） and accumulate repeat accumulate（ARA） codes designed by using the proposed algorithm have a remarkable coding-gain,and a lower error floor,as compared with the conventional RA and accumulated repeat by-4-jagged accumulate（AR4JA） codes at the high SNR region.