Novel method for counting short cycles of Tanner graphs
Zhou Li-hua · Journal of Xidian University · 2010
Short cycles have an important influence on iterative decoding for low-density parity-check(LDPC) codes.By using tree expanding of Tanner graphs and the analysis of the influence of invalid cycles and duplicate cycles,a formula for counting short cycles of LDPC codes is derived.With the derived formula,an algorithm for counting short cycles of Tanner graphs based on tree expanding is proposed.The proposed algorithm can count short cycles with arbitrary lengths,and thus overcomes the disadvantage of existing algorithms that count short cycles with given lengths.Numerical results of counting short cycles of some typical LDPC codes show the correctness of the proposed algorithm.