Abstract: Ordered Statistic Decoding（OSD） algorithm and Chase algorithm are investigated in this paper，based on which，a new Chase-OSD parallel decoding algorithm for medium and short lengths Low Density Parity-Check（LDPC） codes is proposed.Chase-type decoding algorithm is based on processing certain LRPs of a received sequence，while OSD algorithm is based on processing certain MRIPs of a received sequence.If there are too many errors in MRIPs，the OSD algorithm will fail，while there are too much errors in LRPs，the Chase-type algorithm will fail.A parallel concatenation decoding algorithm is proposed based on that complementary characteristic.The simulation results show that the proposed algorithm is effective.The decoding performance is improved compared with BP-OSD and BP-Chase algorithm.

Key words: Chase algorithm, Ordered Statistic Decoding（OSD）, parallel decoding

摘要： 在研究分阶统计译码（OSD）算法和Chase算法的基础上，提出了一种新的针对中短LDPC码的OSD-Chase并行互补级联译码算法。OSD算法对接收序列的个可信度较高的符号（MRIPs）作为消息位进行比特翻转和重新编码，产生候选码字；而Chase算法则是对接收序列的可信度较低的符号（LRPs）进行比特翻转和代数译码。如果过多的错误出现在MRIPs中，则OSD算法不能成功，而如果过多的错误出现在LRPs部分，则Chase译码不会成功。为此充分利用OSD算法和Chase算法这种互补特性，设计了一种并联级联译码算法。仿真显示该文提出的算法是有效的，相比BP-Chase和BP-OSD算法，译码性能得到提高。

关键词: Chase算法, 分阶统计译码（OSD）, 并行互补译码