中文摘要：

光通信系统中低密度奇偶校验（Low-densityParity-check，LDPC）码采用对数似然比置信传播（Log-likelihood Ratio Belief Propagation，LLR-BP）算法进行译码时，在高信噪比区域迭代译码过程中会出现变量节点外部信息振荡不收敛而导致译码纠错性能的降低。为满足光通信系统的要求，提出了一种削弱外部消息振荡的改进LLR-BP译码算法。该算法通过引入加权系数平衡前后两次迭代之间变量节点传递的外部信息，明显减缓了外部信息的振荡现象。仿真结果表明：与传统LLR-BP译码算法相比，该改进LLR-BP算法具有更佳的误码性能，同时降低变量节点外部信息振荡现象并加快了译码的收敛速度。

英文摘要：

The oscillation phenomenon usually appears in the extrinsic message of the variable node of low density parity check（LDPC） codes for optical communication systems in the iteration decoding process of the high signal to noise ratio（SNR） region when using the log- likelihood ratio belief propagation（LLR-BP） algorithm. The oscillation phenomenon will lead to the non-convergence of the decoding algorithm and decrease the error-correction performance. An improved LLR-BP decoding algorithm to reduce the extrinsic message oscillation phenomenon is proposed to meet the requirements of optical communication systems. The proposed algorithm can significantly reduce the extrinsic message numbers by introducing a weighted coefficient to balance the extrinsic message of the variable node between the twice iterations before and after. The simulation results show that the improved LLR-BP decoding algorithm has a better error correction performance compared with traditional LLR-BP decoding algorithm, furthermore, the proposed decoding algorithm can reduce the oscillation phenomenon of the variable node extrinsic message and enhance the decoding convergence.