Performance analysis of the MAP turbo-equalizer and mapping optimization for BICM

In this paper, we consider a bit interleaved coded modulation (BICM) scheme over a frequency selective channel. At the receiver, a turbo-equalizer composed of a maximum a posteriori (MAP) equalizer and a MAP decoder is used. We derive an upper bound of the bit error probability (BEP) at the output of the equalizer. We give an analytical approximate expression of this BEP when the a priori information provided by the decoder is reliable. Based on this expression, we make an optimization of the mapping between the coded bits and the transmitted modulated symbols.