The Effect of the Choice of The Mapping on the Performance of Map Equalizer

Abstract

In this paper, we propose to study the effect of the
choice of the mapping on the performance of iterative receivers
for frequency selective channels. We use at the transmitter a
BICM (Bit Interleaved Coded Modulation) based scheme
obtained by the concatenation of a binary code and a modulator
separated by an interleaver. Because of the interleaving, the
optimal receiver is too complex. We consider here an iterative
receiver composed of a Maximum A Posteriori (MAP) equalizer
and a MAP decoder. During the iterations, the equalizer and the
decoder exchange extrinsic information and use them as a priori
in order to improve their performance. An optimization of the
mapping is required to obtain a gain by using the iterative
receivers. In order to make the mapping choice easier, we
propose to perform an analysis based on the Gaussian
approximation. This analysis relies on only one simulation of the
equalizer