Transmission policies in wireless powered communication networks with energy cooperation

Energy Harvesting (EH) has been recognized as one of the most appealing solutions for extending the devices lifetime in wireless sensor networks. Despite the vast literature available about ambient EH, in the last few years Energy Transfer (ET) has been introduced as a new and promising paradigm. With ET, it becomes possible to actively control the energy source and thus improve the network performance. We focus on two particular applications of ET which have been studied separately in the literature so far: Energy Cooperation (EC) and Wireless Powered Communication Networks (WPCNs). In the first case, energy is wirelessly shared among terminal devices according to their requirements and energy availability, whereas, in a WPCN, energy can be purposely transferred from an energy-rich network node (e.g., an access point) to terminal devices. We solve a weighted throughput optimization problem for the two-node case using optimal as well as sub-optimal schemes. Numerically, we explain the role of EC in improving the system performance.