Low Complexity LDPC Decoding Techniques with Adaptive Selection of Edges

In this paper, we propose low complexity LDPC decoding algorithms with variable number of edges. The main idea of this paper is to use the bit nodes selectively instead of using all the connected bit nodes. The proposed algorithms choose the bit node selectively when calculating the check node update equation. First, we study the relationship between the number of bit nodes for updating check node and the performance of the BP decoding algorithm. Two selective algorithms are proposed accordingly. The first algorithm (algorithm 1) does not use the bit nodes whose values are highly reliable when calculating the check node update equation. In the second algorithm (algorithm 2), we increase the number of bit nodes to update check node each time we have a decoding failure. These two algorithms have lower complexity with small performance degradation compared to the LLR-BP based decoding algorithm. These algorithms reduce the computational complexity at high SNR more than they do at low SNR.