Bit-interleaved coded modulation with iterative decoding

Bit-interleaved coded modulation (BICM) was originally suggested by Zehavi (1992) to increase the time diversity of coded modulation over Rayleigh fading channels. In its typical design with Gray signal labeling, BICM causes a degradation over Gaussian channels, compared with the conventional trellis-coded modulation. We show that bit interleaving can actually be used to increase the Euclidean distance between the codewords of a convolutional code. With iterative decoding and careful design of signal labeling and interleaving, BICM can provide great performance even for Gaussian channels.