Prolonging WSN lifetime with an actual charging model

Abstract

Recent breakthroughs in wireless power transfer make it possible to charge sensors over a long distance. Existing works have mainly focused on maximizing network lifetime, optimizing charging efficiency, and optimizing charging quality. All these works use a linear superposition charging model, which may not be accurate in real life situations. We use the actual charging model, which has a nonlinear super-position and we consider the charging scheduling problem (CSP): given multiple chargers and a group of sensor nodes, how can the chargers be optimally scheduled so that the total charging time is minimized and each sensor node has at least energy E? We prove that CSP is NP-hard, and propose a weight-greedy algorithm to solve the problem. Unlike the algorithm proposed before, ours does not need to calculate all charger groups utility in advance, which reduces the complexity. Extensive simulations demonstrate that the performance of our algorithm with sparse network is almost as good as the optimal algorithm. In general cases, our algorithm outperforms the random algorithm. Furthermore, our algorithm obtains the best solution in two special cases.