中文摘要：

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。

英文摘要：

Due to high complexity of belief propagation （BP） decoding algorithm for low-density parity- check（LDPC）codes and bite errors caused by oscillation of magnitudes of a posterior log-likelihood- ratios （LLRs） and ex-LLRs of some bits every iterations, a modified algorithm which reduced complexity of the updates of check nodes and corrects oscillation （OSC） of bit nodes updating for decoding LDPC codes was proposed. With the log-normal model under the turbulence channel, simulations were given with full interleaving and interleaving depth fading ratio （IDFR） of 16. Simulation results show that the proposed algorithm can reduce the computational complexity and improve the decoding performance of conventional BP algorithm. Compared with Min-Sum algorithm, the proposed algorithm has better bit error rate（BER）performance and less average iterations with little loss in the complexity in computation. Therefore, the proposed algorithm is a good trade-off between the decoding complexity and error performance.