Collaborative mobile charging policy for perpetual operation in large-scale wireless rechargeable sensor networks

In this paper, we present a mobile charging policy for perpetual operation of large-scale wireless rechargeable sensor networks (WRSNs). In these networks, dedicated mobile chargers (MCs) move throughout the network and supply energy for power-limited sensors. The MCs not only charge the sensors but also charge each other. We develop a hop-based mobile charging policy (HMCP) minimizing the number of required MCs. The HMCP considers both the sensors' unbalanced energy consumption rate and the MCs' limited energy capacity. The minimum number of MCs is is formulated as an integer programming problem. We first verify the existence of an optimal solution, and later design an algorithm to obtain the optimal solution. Based on HMCP, we propose HMCP+ for the case that only one MC can recharge sensors in each region. HMCP+ plans MCs' paths to decrease mobile energy consumption by MCs. Finally, performance of the proposed polices is validated through the simulation results.