Joint Online Transmission and Energy Transfer Policies for Energy Harvesting Devices with Finite Batteries

One of the main concerns in traditional Wireless Sensor Networks (WSNs) is energy efficiency. In this work, we analyze two techniques that can extend network lifetime. The first is Ambient Energy Harvesting (EH), i.e., the capability of the devices to gather energy from the environment, whereas the second is Wireless Energy Transfer (ET), that can be used to exchange energy among devices. We study the combination of these techniques, showing that they can be used jointly to improve the system performance. In particular we focus on the online optimization process, solving a dynamic programming problem with a Markov approach. We derive the performance upper bounds that can be achieved with and without ET. Moreover, we show that if one of the two devices receives much more energy than the other, then it is possible to use ET to increase the system performance. Finally, we present simulation results based on realistic energy arrivals in indoor and outdoor environments, discussing how ET can be used in such environments.