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.