Mapping Rearrangement for HARQ Based on Low-Order Modulation

In this paper we consider hybrid automatic repeat request transmission based on binary phase shift keying modulation. Our objective is to improve the performance of the retransmissions, keeping at the same time the complexity and the performance of the first transmission unaltered. We conclude that the so-called mapping rearrangement (MR) may considerably improve the performance if multi-dimensional modulation is applied. We evaluate the theoretical limits of bit-interleaved coded modulation with MR, verify the functioning of the practical coding scheme, and propose to improve the performance via iterative detection-decoding (BICM-ID) which brings considerable gains. In particular, for high coding rates, a 4 dB SNR gain over transmission without MR may be achieved.