Efficient Power Allocation for Hybrid-arq Relay Networks

Spatial diversity is an inherent nature of wireless communications. This nature can be exploited to make communications more reliable by Multiple-Input-Multiple-Output (MIMO). However the use of multiple co-located antennas is constrained by the dimensions of modern devices. To overcome this drawback cooperative relaying shares antennas between different network nodes thus realizing a Virtual antenna arrays (VAA). In this paper we study a single user relay network aided Hybrid-ARQ (H-ARQ) type I consisting of a source, a relay and a destination. We provide the closed form expressions for the outage probability and delay. We use a numerical method based on relative distance between nodes to estimate the optimum amount of power to be allocated to source and relay. The numerical results show the accuracy of our analytical expressions. In addition proposed allocation strategy outperforms the equal power allocation.