Optimal Power Management to Minimize SER in Amplify-and-Forward Relay Networks

This paper studies optimal power allocation to minimize symbol error rate (SER) of amplify-and-forward cooperative diversity networks. First, we analytically solve optimal power allocation problem to minimize SER for three different scenarios, namely, multi-branch single-relay, single-branch multi-relay and multi-branch multi-relay cooperative diversity networks, all subject to a given total relay power consumption. In addition to the total relay power constraint, for the multi-branch single-relay scenario. Next, we assume that every single relay is subject to a maximum power constraint. To this end, we present an iterative algorithm to find the optimal power rates. Finally, we study an off-line scenario in which the relays are energy harvester and equipped with infinite-sized batteries. For this scenario, the maximum SER is minimized over the whole harvesting time slots. We propose a water filling algorithm for the classical relay channel and an iterative algorithm for the multi-branch single-relay cooperative scheme. Through the numerical results, it is shown that optimal power allocation policies enhance the system performance.