Energy Loss Minimization for Wireless Power Transfer Based Energy Redistribution in WSNs

By enabling energy redistribution among nodes in Wireless Sensor Networks (WSNs), the Wireless Power Transfer (WPT) technology provides a new approach to prolong life time of WSNs or a fundamental block for building perceptual WSNs. In this paper, we attempt to deal with the underlying WPT based Energy ReDistribution (WPTERD) problem, which is targeted for finding an energy transmission schedule that satisfies the nodes' energy expectations, meanwhile achieves minimum energy loss and shortest time span. In this paper, we propose a two-step approach for WPTERD by splitting it into two sub-problems named WPTERD-Egy and WPTERD-Time, which focus on the optimization in energy loss and in time span respectively. Basing on some proved properties, we transform WPTERD-Egy to a Linear Programming problem and thus can obtain an optimal time-length list of the nodes' energy transmissions leading to minimum energy loss. Finding that WPTERD-Time is NP-hard, we propose an approximate algorithm to solve the WPTERD problem by exploiting the concurrent energy transmission opportunities. The algorithm is named as Greedy Energy ReDistribution Scheduling (GERDS) algorithm, which is proved to finish in limited loops. Simulations validate the algorithm's ability in minimizing energy loss, and meanwhile return near-optimal schedules with time span in range 100 similar to 125% of the optimal value. Simulation results also show that GERDS outperforms a typical flow-based algorithm in terms of the tested performance metrics.