Performance analysis and code optimization of low densityparity-check codes on Rayleigh fading channels

摘要

A numerical method has been presented to determine the noisenthresholds of low density parity-check (LDPC) codes that employ thenmessage passing decoding algorithm on the additive white Gaussian noisen(AWGN) channel. In this paper, we apply the technique to thenuncorrelated flat Rayleigh fading channel. Using a nonlinear codenoptimization technique, we optimize irregular LDPC codes for such anchannel. The thresholds of the optimized irregular LDPC codes are verynclose to the Shannon limit for this channel. For example, at ratenone-half, the optimized irregular LDPC code has a threshold only 0.07 dBnaway from the capacity of the channel. Furthermore, we compare simulatednperformance of the optimized irregular LDPC codes and turbo codes on anland mobile channel, and the results indicate that at a block size ofn3072, irregular LDPC codes can outperform turbo codes over a wide rangenof mobile speeds