Gamma-Gamma 信道下 LDPC 码译码算法性能分析

为降低低密度奇偶校验(LDPC: Low-Density Parity-Cheek)码译码算法的复杂度, 同时提高通信系统性能, 在研究对数似然比置信传播(LLR-BP: Log-Likelihood Ratio Belief Propagation)算法及其简化的译码算法基础上, 提出了一种基于归一化最小和(NMS: Normalized Min Sum)算法的改进算法。 深入研究了 Gamma-Gamma 分布 模型, 并将 Gamma-Gamma 分布作为仿真的信道模型, 应用 Matlab 仿真比较了 LLR-BP 及其简化算法在不同湍 流强度信道下的性能。 仿真结果表明, 无论在 AWGN(Additive White Gaussian Noise)信道还是不同湍流强度的 Gamma-Gamma 信道下, 改进算法在几种算法中都有较好的译码性能, 尤其是在中湍流和强湍流信道下改进算 法的性能优势更为明显。 通过码长对 BER(Bit Error Rate)影响的仿真结果表明, 适当增加码长可有效改善算法 的性能。

Performance Analysis of LDPC Decoding Algorithm under Gamma-Gamma Channel

In order to reduce the LDPC (Low-Density Parity-Cheek) complex ity of decoding algorithm, studied the LLR BP (Log-Likelihood Ratio Belief Prop agation algorithm) and its simplified decoding algorithm, and an improve d algorithm based on NMS (Normalized Min Sum) algorithm is proposed;studied the Gamma-Gamma distribution model and Gamma-Gamma distribution as the channel mo del are studied.The performance of LLR-BP and its simplified algorithm under different turbulence intensities are compared with Matlab, the simulation resul ts show that both in the AWGN (Additive White Gaussian Noise) or different turbulence intensity Gamma-Gamma cha nnel, the improved algorithm has better performance in decoding algorithms in pa rticular, the performance advantages of the improved algorithm in strong turbule nce is more obvious.The simulation results show that the increase of the code l ength can improve the performance of the BER (Bit Error Rate).