Qi-ferry: Energy-constrained wireless charging in wireless sensor networks

Using the technology of wireless energy transfer, the paper proposes Qi-ferry which physically carries energy, roves a wireless sensor network, and wirelessly charges sensor nodes to extend their lifetime. To optimize the usage of the entire energy reserve on a Qi-ferry, both the movement of the Qi-ferry itself and its wireless charging of sensor nodes share the same pool of battery energy reserve, resulting in a tradeoff between how many sensors the Qi-ferry could charge and how far it could travel. The paper formulates an energy-constrained Qi-ferry wireless charging problem in wireless sensor networks, which maximizes the number of sensors wirelessly charged by a Qi-ferry subject to an energy constraint limiting the total energy consumed by the Qi-ferry for both moving and charging. Due to the NP-hardness of the problem, the paper proposes heuristic solutions based on the meta-heuristics of Particle Swarm Optimization. Evaluation results validate the effectiveness of the solutions.