Advanced hybrid ARQ technique employing a signal constellation rearrangement

This paper presents an advanced hybrid ARQ technique applicable to QAM multilevel modulation formats together with type II hybrid ARQ (automatic repeat request) schemes, in which at least part of the initially transmitted bits is repeated in retransmissions. The presented technique averages over retransmissions the variations in bit reliabilities caused by the signal constellation of multilevel modulation formats to improve decoding performance. It is shown that by rearranging the signal constellation for retransmissions a significant gain in hybrid ARQ performance is achieved with only a marginal increase in complexity.