UAV-Assisted RF Energy Transfer

Limited battery capacity is one of the major hurdles towards perpetual operation of wireless sensor networks (WSNs). In this work, a framework for Unmanned Aerial Vehicle (UAV) based wireless charging of sensor nodes using radio frequency energy transfer (RFET) is presented. First, RFET zone is conceptualized where energy transfer is possible such that the received power is above a sensitivity level of power harvester. Next, two novel strategies Static Charging Time Allocation (SCTA) and Optimal Charging Time Allocation (OCTA) are proposed for charging the sensors. The UAV remains static in SCTA, whereas in OCTA it hovers above each sensor node and replenishes depleted energy of the sensors that are within its RFET zone. Further, a model for evaluating the energy consumption of UAV is presented in order to determine the number of rounds required by the UAV for charging. Different gas sensors are planted emulating a practical deployment scenario, and with this arrangement charging time with the proposed strategies are evaluated. Our numerical results justify applicability of the UAV-assisted RFET.