基于重复累积码的BICM系统译码算法

Decoding of Repeat Accumulate code based on Bit-Interleaved Coded Modulation

重复累积码(RA)由于其编译码复杂度低、性能接近香农限的优点,目前得到学术界的广泛关注。文中研究了RA码及其译码算法,并将其应用于比特交织编码调制(BICM)系统。针对低信噪比下基于RA码的编码调制系统误码率较高的问题,提出了一种改进算法,该算法通过在解调器和译码器之间引入迭代处理,利用译码器输出的外信息改善解映射结果,从而降低了系统误码率。仿真结果表明,在加性高斯白噪声(AWGN)信道、瑞利(Rayleigh)衰落信道下,BICM系统使用迭代的译码算法与原算法相比,误码性能有较明显提高。

Repeat Accumulate(RA) codes have attracted great research interests because of their low coding and decoding complexity and good performance close to the Shannon limit.This paper introduces RA codes and their decoding algorithms,and then proposes the RA Bit-Interleaved Coded Modulation(RA-BICM) scheme.An improved scheme with iterative process between demodulator and decoder has been brought forward to reduce the bit error ratio of the system,especially in the low SNR environment.Simulation results show that the iterative scheme bears distinct performance improving both AWGN and Rayleigh fading channels compared with the former system.