On the joint power and rate optimization in multihop relay networks with HARQ

We consider a linear multihop relay network adopting Chase-combining type Hybrid ARQ strategy in Rayleigh fading channels. The total number of (re)transmissions is assumed to be not limited, i.e., we consider delay-tolerant applications. We aim at maximizing the average throughput by jointly optimizing the transmit powers and data rates over all hops, while limiting the sum of transmit powers of all nodes. However, it is hard to find the jointly optimal power allocation and rate selection strategy in this problem. In this paper, we propose an iterative algorithm in order to obtain the optimal transmit powers and transmission rates for all the nodes including source and relays. Numerical results show that the proposed algorithm which controls both power and rate yields the best throughput performance among the conventional link adaptation schemes including the schemes that adapt either power or rate.