Normalized Switch Schemes for Low Density Parity Check Codes

This paper addresses switch schemes for switch type hybrid hard decision iterative algorithms decoding finite length low density parity check (LDPC) codes. After piecewise analysis for extrinsic transfer information (EXIT) chart family and exploration of fixed points, one general switch scheme named normalized switch scheme, for which majority based (MB) algorithms and Gallager´s decoding algorithm B (GB) are extreme cases, is proposed. Several specific normalized switch scheme, named expanded optimal switch scheme and tail-cut (TC) optimal switch scheme, are given and their convergence properties are analyzed. Simulation shows that compared with GB that holds optimality for infinity length codes, proposed switch schemes show performance improvements while enjoying less sensitivity to channel parameter underestimations for finite length codes