A new relay assisted Hybrid ARQ scheme

In this paper, we propose a new relay assisted Hybird-ARQ scheme where the two transmitting nodes (source and relay) and the two received signals (from first transmission and retransmission) are viewed as a virtual MIMO and thus the source can send new codeword when the relay is retransmitting the old codeword. Moreover, to take advantage of time varying channel conditions, the retransmission of relay can be scheduled to a time slot with better channel condition. Simulation results show that the proposed method can improve the retransmission efficiency significantly.