LDPC编码调制系统中基于反馈LLR均值的迭代解调/译码算法

该文针对LDPC码编码的BICM系统，提出一种对LDPC码译码器输出外附信息的计算方法进行改进的迭代解调/译码算法。与传统的解调/译码算法不同在于，该算法对每次BP迭代中译码器输出的各编码比特的外附LLR分别求均值后，再将其作为先验信息反馈给软解调器开始下次的迭代解调/译码。采用该方法可有效地减轻LDPC码在BP迭代过程中某些比特LLR值的振荡现象，从而使得传递给软解调器的外附信息更准确。仿真结果表明，和传统的两种迭代解调/译码算法相比，该算法能进一步提高LDPC编码BICM迭代系统的译码性能，而复杂度并无明显增加。

Improved Decoding for LDPC Coded Modulation Systems Using Averaged Log-Likelihood Ratios

In this paper, an improved iterative decoding algorithm based on averaged Log-Likelihood Ratio (LLR) is proposed for LDPC coded BICM systems. The extrinsic information delivered by every BP iteration is averaged and the averaged LLR values are used as a prior LLR fed back to the input of demodulator for the next iteration. This method can alleviate the LLR oscillation of certain variable nodes during BP iterations and thus make the extrinsic output of decoder is more credible. Simulation results show that, compared with the two conventional iterative decoding algorithms, this improved algorithm achieves noticeable error performance improvement with only modest increase in computation complexity.