A Novel and Efficient Mapping of 32-QAM Constellation for BICM-ID Systems

Bit-interleaved coded modulation with iterative decoding (BICM-ID) is a bandwidth-efficient technique for both additive white Gaussian noise and fading channels. The asymptotic performance of BICM-ID is strongly determined by how the coded bits are mapped to the symbols of the signal constellation. In this paper an explicit mapping method is presented for 32-QAM using two criteria: (i) maximization of the minimum Euclidean distance between the symbols with Hamming distance one, and (ii) minimizing the number of symbols which have jointly the minimum Hamming distance and the minimum Euclidean distance from each other. Our method is much simpler than the previously-known methods. Compared to previously-known best mapping, the mapping obtained by our method performs significantly better in a BICM-ID system implemented with hard-decision feedback, while its asymptotic performance is almost the same in a BICM-ID system using soft-decision feedback.