Log-Likelihood Ratios for LDPC Codes with Pilot-Symbol-Assisted BPSK Transmission over Flat Rayleigh Fading Channels

Abstract

We derive the exact log-likelihood ratio (LLR) for iterative decoding of low-density parity-check codes for pilotsymbol-assisted BPSK transmission over flat Rayleigh fading channels. The bit-error rate (BER) performances of this metric are studied for various interleavers and different pilot spacings. We further compare this metric with the approximate metric, which has been commonly used in the literature. Simulation results show that the newly derived LLR metric results in better BER performances. In addition, the effect of signal-to-noise ratio estimation error is investigated and our new LLR shows more robustness.