A Hybrid Charging Scheme for Minimizing the Number of Energy-Exhausted Nodes in Wireless Rechargeable Sensor Networks

In wireless rechargeable sensor networks (WRSNs), researchers address the energy problem in wireless sensor networks (WSNs) by introducing fixed chargers or mobile chargers (MCs) to recharge energy-starving nodes. The majority of existing studies on WRSNs investigate either the deployment of fixed chargers or the scheduling of MCs to charge sensor nodes. In this work, we investigate the hybrid charging problem, i.e., the problem of recharging nodes by fixed chargers and MCs cooperatively, in scenarios with arbitrary node distribution, with the goal of minimizing the number of energy-exhausted nodes. We deduce the problem into two subproblems, namely, the fixed chargers deployment problem (FCDP) and the mobile charger path planning problem (MCPP). We present the definitions of these two subproblems and prove that both of them are NP-hard. Then, we propose a hybrid charging scheme that comprises two algorithms to address these two subproblems one by one. Extensive simulation experiments confirm the scheme’s effectiveness and the results show that the proposed scheme outperforms the existing methods (i.e., TCA-MCPPA, FCDA-JERDC, and MSC) in minimizing the number of energy-exhausted nodes. In the uniform node distribution, they are reduced by 79.62%, 88.2%, and 95.01%. In the triple Gaussian node distribution, they are reduced by 99.90%, 99.71%, and 99.98%.