Improved hybrid ARQ scheme using adaptive modulation in cooperative relay networks

Hybrid ARQ has been shown to be an effective strategy to improve the performance and capacity in wireless networks. In this paper, we present novel and simple feedback hybrid ARQ schemes with adaptive modulation for cooperative wireless networks. The proposed scheme combines the retransmission mechanisms, incremental relay and adaptive modulation. For more tractable analysis, we derive closed-form expressions with the combined signal noise ratio at the destination for Rayleigh fading conditions. Verified by simulations, the scheme can obtain significant spectral plus by the strategy in low average SNR region and the performance can further improve when more relays are selected.