Maintaining sensor networks perpetually via wireless recharging mobile vehicles

The emerging wireless energy transfer technology based on magnetic resonant coupling is a promising technology for wireless sensor networks as it can provide a controllable and perpetual energy source to sensors. In this paper we study the use of minimum number of wireless charging mobile vehicles to charge sensors in a sensor network so that none of the sensors runs out of its energy, subject to the energy capacity imposed on mobile vehicles, for which we first advocate an flexible on-demand wireless charging paradigm that decouples sensor energy charging scheduling from data routing protocols design. We then formulate an optimization problem of scheduling mobile vehicles to charge lifetime-critical sensors with an objective to minimize the number of mobile vehicles deployed, subject to the energy capacity constraint on each mobile vehicle. As the problem is NP-hard, we devise an approximation algorithm with a provable performance guarantee for it. We finally evaluate the performance of the proposed algorithm through experimental simulations. Experimental results demonstrate that the proposed algorithm is promising, and the solution obtained is fractional of the optimal.