For short and middle length LDPC codes

the oscillation of LLR owing to cycles degrades the performance of BP algorithm. In order to minimize the oscillation of LLR during BP decoding process

an improved BP algorithm with serial update scheduling using weighted average message to update the message of checktovariable node is proposed. Currently computed message of checktovariable node and the message of old checktovariable node are weighted and then added up to update the message of checktovariable node. By higher weighted currently computed message of checktovariable node than the message of old checktovariable node

the improved algorithm effectively minimizes oscillation of LLR

at the same time

keeps normal BP message propagation and low compute complexity. Simulation results show that

for short and middle length LDPC codes

the improved algorithm achieves more noticeable error performance than CSBP algorithm at middle to high signal to noise ratio.