Complexity reduction in BICM-ID systems through selective log-likelihood ratio updates

Bit-interleaved coded modulation with iterative decoding (BICM-ID) performs well under a variety of channel conditions. Based on a factor graph representation of BICM-ID, we propose a modification of the BICM-ID receiver that can reduce the computational complexity significantly without BER degredation. The basic idea is to avoid updates of code bit log-likelihood ratios whose magnitude is already sufficiently large. Simulation results illustrate the excellent performance-complexity trade-off of our method.