中文摘要：

采用BPSK调制方式的系统发生跳周现象后，输入LDPC译码器的信息序列符号与原序列符号相反，导致译码器失效。提出了基于置信传播算法的抗跳周LDPC译码算法。该算法通过增加一次迭代译码的运算量。根据校验节点与变量节点之间传递的信息对初始似然比信息进行修正，可以消除跳周对译码器的影响。仿真结果表明在不发生跳周时．抗跳周LDPC译码算法与传统译码算法性能相同，即抗跳周LDPC译码算法对初始似然比信息的修正不会导致译码性能损失。在跳周发生时，传统译码算法失效。对校验节点奇数度的码字采用抗跳周译码算法可以完全克服跳周带来的影响，译码性能与无跳周发生时相同。

英文摘要：

When cycle-slip occurs in BPSK modulation system, sign of information sequence which is input of LDPC decoder is opposite to the original one. This problem will lead to decoder failure. Anti-cycle-slip LDPC decoding algorithm based on belief propagation was proposed. Modified algorithm modifies initial likelihood ratio information according to information between check nodes and variable nodes by an iterative decoding computation. Modified algorithm can eliminate the influence of cycle-slip and ensure normal function of LDPC decoder. Simulation result shows that modified decoding algorithm has the same performance with traditional decoding algorithm without cycle-slip, which means that the modification of initial likelihood ratio doesn＇t lead to decoding performance loss. When cycle-slip happens, traditional decoding algorithm fails. Decoding LDPC of odd check node degree by anti-cycle-slip algorithm will overcome the impact of cycle-slip totally. Modified algorithm has the same decoding performance no mater cycle-slip happens.