An Improvement on the Min-sum Algorithm for Low-rate Protograph LDPC Codes
基于原型图的低码率LDPC码最小和译码算法改进方案

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.