置信传播即BP译码算法，在每一次迭代过程中,都要对全部比特和校验信息进行更新,存在计算量大、译码效率低的问题,故提出了单边传播信息的迭代BP算法-Belief Propagation that BP decoding algorithm, in each iteration, we must check for all the bits and update the information, there is a large amount of calculation, low coding efficiency problem, it also suggests an iterative algorithm BP unilateral dissemination of information