Constellation rearrangement and spreading code rearrangement for hybrid ARQ in MC-CDMA

Abstract

This paper presents two techniques that rearrange the data between retransmissions and can enhance the diversity gain from hybrid ARQ (hybrid automatic repeat request). One is constellation rearrangement that rearranges the signal constellation of QAM signals between retransmissions. The other is spreading code rearrangement that changes the spreading code with which the same symbol is transmitted in each retransmission. Simulation results show that those proposed schemes outperform type-H hybrid ARQ with packet combining, or chase combining.