An efficient ARQ scheme using soft output demodulation in Rayleigh fading channel

An automatic repeat request (ARQ) scheme using rate compatible trellis coded modulation, pilot-symbol aided channel estimation, soft output packet combining, and a retransmission request strategy supporting a variable quality of service within a packet is proposed. Simulation results show that this type II hybrid ARQ has about 3-5 dB SNR gain over its type I ARQ counterpart.