Generalized BICM for Block Fading Channels

In this paper, we propose a novel form of bit interleaved coded modulation (BICM) that we call generalized BICM (GBICM) for block fading channels. The achievable diversity order on block fading channels is limited by the channel itself and not by the code used. Conventional BICM attempts to maximize the Hamming free distance of the underlying convolutional code. Although this maximizes diversity on independently fading channels with ideal interleaving, its effect on block fading channels is not clear. In this paper, we analyze code performance on block fading channels and seek to optimize it by suitably modifying the BICM paradigm. The resulting GBICM system is just as simple and as flexible as BICM is when coding for different modulations and different kinds of channels. In fact, the same decoder can be used to decode both BICM and GBICM. We show code design principles and analysis techniques with examples. Simulation results supporting the arguments are shown.