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针对无线光通信中低密度奇偶校验码(LDPC)置信传播(BP)译码算法复杂度高及置信度振荡造成译码错误等缺点,基于对数BP算法提出了一种改进的译码算法。改进的译码算法在校验节点运算时,判断输入到校验节点消息的最小值与某个门限的大小,根据比较结果,分别用消息最小值或若干个最小值进行运算,在损失很少性能的情况下降低了运算复杂度;同时在比特节点采用振荡抵消处理运算,提高了算法的性能增益。最后在对数正态分布湍流信道模型下,分别对比特充分交织和交织深度为16的情况进行了仿真实验。仿真结果表明,改进的译码算法与BP算法相比,大幅度降低了计算复杂度,而且译码性能有一定的优势,收敛速度损失很少;而相对于最小和算法,改进的算法虽然译码复杂度有所增加,但误码率性能有明显的优势,并且收敛速度也优于最小和算法。因此,改进的译码算法是无线光通信中LDPC码译码算法复杂度和性能之间一个较好的折中处理方案。
Aiming at the shortcomings of high decoding complexity of low density parity check code (LDPC) belief propagation (BP) decoding algorithm and decoding error caused by belief oscillation in wireless optical communication, an improved decoding algorithm is proposed based on logarithm BP algorithm . The improved decoding algorithm judges the minimum value of a message input to the check node and the size of a certain threshold when verifying the node operation. According to the comparison result, it is calculated using the minimum message value or the minimum values respectively, The performance of the case to reduce the computational complexity; the same time in the bit node oscillation compensation processing operation, improve the performance of the algorithm gain. Finally, under the logarithm normal distribution turbulence channel model, the simulation experiments are carried out on the condition that the bit is fully interleaved and the interleave depth is 16 respectively. Simulation results show that compared with BP algorithm, the improved decoding algorithm greatly reduces the computational complexity, and the decoding performance has some advantages, and the convergence speed loss is very small. Compared with the minimum and the algorithm, the improved algorithm The code complexity is increased, but the bit error rate performance has obvious advantages, and the convergence speed is also better than the minimum and algorithm. Therefore, the improved decoding algorithm is a good compromise between the complexity and performance of the LDPC code decoding algorithm in wireless optical communication.