Hybrid Type-II ARQ Schemes with Adaptive Modulation Systems for Wireless Channels

| In this paper, we proposed and analyzed a scheme for wireless channels which is a combination of a hybrid type-II Automatic Repeat reQuest (ARQ) scheme and an Adaptive Modulation System (AMS). In hybrid type-II ARQ schemes, the transmission of redundancy bits for error correction is adapted to the channel variations. Additionally, in the proposed AMS, the modulation is gradually changed from a large constellation to small constellations when the channel bit error probability is high. This is done without any knowledge of the channel at the transmitter. The proposed scheme can provide a signiicant gain in the throughput performance in an eecient and exible way. Simulation results are presented and they con-rm that the proposed scheme considerably improves the performance.