Multi-relay cooperation with self-energy recycling and power consumption considerations

We focus on the problem of rate-optimal beamforming for wireless powered cooperative communications systems. We consider the case of systems employing multiple wireless powered Amplify and Forward self-energy recycling relays and relay selection. By employing a generic piecewise linear energy harvesting model, that can adapt to the characteristics of different non linear energy harvesting measurements and models, we present the solution to the rate-optimal beamformer design problem. Our solution is based on solving a set of simple optimization subproblems where the solution of each one of them can be found in a simple closed form. Moreover, for the first time we combine such a realistic energy harvesting model with an equally realistic power consumption model at the self-energy recycling relays that not only accounts for the transmit power but also for other sources of power consumption (e.g. the power consumption of the relay circuits). By means of simulations we quantify the gains that multiple relays can bring validating that significant gains can be delivered for a variety of relay placements.