Optimization of Two-Way Relaying Networks With Battery-Assisted EH Relays

In this paper, we investigate the performance of a two-way relaying (TWR) network with a battery-assisted energy harvesting (EH) relay. The relay uses limited battery energy to augment the harvested energy and aid communication between the two source terminals. Considering a time-switching relaying (TSR) protocol at the EH relay, we investigate the performance of the TWR system in terms of outage, throughput, and ergodic rate. Assuming that the source with a better channel to the relay transfers energy in the EH phase, we investigate statistical and instantaneous channel state information (CSI)-based optimization of the TSR parameter to maximize throughput for a fixed amount of relay battery energy usage. We observe that the instantaneous CSI-based optimization results in higher throughput with less battery energy usage. Furthermore, we investigate the problem of minimization of battery energy consumption for target throughput using the statistical and instantaneous CSI-based optimization of the TSR parameter. We show that battery energy consumption can be drastically reduced by availability of instantaneous CSI. The derived insights are crucial from a designer point of view. Simulation results are presented to confirm accuracy of the derived analytical expressions.