Rate allocation for HARQ in relay-based cooperative transmission

We analyze HARQ transmission over a fading channel with the help of a relay node. In the absence of the channel state information (CSI) at the transmitters, we establish the problem of maximizing the overall throughput of HARQ transmission by optimizing the variable transmission rate. We present a closed form of the throughput with respect to the transmission rates and use the well-known Dynamic Programming technique along with the necessary simplifications on the problem to find the optimal set of transmission rates for both the Source node and the Relay node in source-relay-destination scenario. We show that such an approach yields a significant increase in throughput compared to fixed-rate HARQ.