An adaptive coded modulation scheme associated with improved HARQ

In this paper, an adaptive coded modulation scheme associated with improved HARQ is proposed. In the scheme, non-uniform constellation Gray encoding for the modulation with alphabet size M>4 is adopted in the retransmissions. Combining with the symbol bits rearrangement before modulation mapping and non-uniform constellation for retransmission in HARQ scheme, the reliability of each bit inputting to the turbo decoder is averaged and improved. As a result, the system throughput is increased effectively, and it is noticed that the throughput of 1/2 code rate 8PSK with the improved HARQ is shown to be better than 3/4 code rate QPSK with conventional HARQ. So instead of 3/4 code rate QPSK, a novel adaptive coded modulation scheme associated with improved HARQ is proposed, and the system throughput gets a significant performance improvement.