Improved min-sum decoding algorithms for irregular LDPC codes

In this paper, we apply two improved min-sum algorithms, the normalized and offset min-sum algorithms, to the decoding of irregular LDPC codes. We show that the behavior of the two algorithms in decoding irregular LDPC codes is different from that in decoding regular LDPC codes, due to the existence of bit nodes of degree two. We analyze and give explanations to the difference, and propose approaches to improve the performance of the two algorithms.