Power Allocation and Relay Selection for AF Cooperative Relay Systems With Imperfect Channel Estimation

In this paper, we investigate power-allocation and relay-selection algorithms for amplify-and-forward (AF) cooperative relay systems under imperfect channel estimation. Based on maximizing a tight capacity lower bound, a closed-form formula for optimal power allocation under a given relay is first derived and then used to establish an optimal relay-selection algorithm. By exploring the asymptotic behavior of the capacity lower bound, a suboptimal but reduced-complexity relay-selection algorithm is further presented. Simulation results demonstrate that significant capacity gains can be achieved by using the proposed optimal and suboptimal algorithms.