中文摘要：

低密度奇偶校验（LDPC）码的译码硬件实现方案大多采用计算复杂度较低的修正最小和（NMS）算法,然而对于低码率LDPC码,由于校验节点度数低,NMS算法的修正误差较大,导致其译码性能和标准的置信传播（BP）算法相比有较大差异。该文针对基于原图构造的一类低码率LDPC码,提出了在NMS迭代译码中结合震荡抵消（OSC）处理和多系数（MF）修正技术的方案。结合低码率原型图LDPC码行重分布差异较大的特点,MF修正算法可以有效地减少计算误差,从而改善译码性能。另外低码率原型图LDPC码的收敛较慢,而OSC处理则可以较好地抑制正反馈信息,进一步提高NMS算法的性能增益。仿真结果表明,对于此类低码率LDPC码,MF-OSC-NMS算法可以达到接近BP算法的性能。OSC处理和MF修正技术硬件实现简单,与NMS算法相比几乎没有增加计算复杂度,因此MF-OSC-NMS算法是译码算法复杂度和性能之间一个较好的折中处理方案。

英文摘要：

The Normalized Min-Sum（NMS） algorithm can be implemented with low complexity and is widely used in the LDPC decoders,but there is a significant performance gap between the Belief Propagation（BP） algorithm and NMS algorithm for low-rate LDPC codes due to the inaccurate approximations of the check-nodes with low weight.In this paper,an improved NMS algorithm combined with the Oscillation（OSC） correction of bit-node updating and Multiple Factors（MF） modification of check-node updating is proposed.Although the row weights of the low-rate protograph LDPC codes may vary considerably,the error of the approximation in check-node updating can be effectively reduced by MF modification.Moreover,the OSC correction can reduce the positive feedback and achieve furthermore improvement on the decoding performance of low-rate protograph LDPC codes,where the decoding convergence is slow.Simulation results show that the OSC-MF-NMS algorithm can obtain a noticeable performance gain in decoding of low-rate protograph LDPC codes.The complexity of the OSC and MF process is quite low,so the proposed algorithm is a good trade-off between the decoding complexity and error performance.