A Charging Scheme for Large-Scale Suburban WRSNs Based on the Collaboration of UAVs and Mobile PADs

Unmanned aerial vehicles (UAVs) are ideal mobile chargers (MCs) for energy-starved sensor nodes in wireless rechargeable sensor networks (WRSNs). Recently, the power access docker (PAD) is developed to extend the operating range of the UAV in large-scale WRSNs by recharging the UAV in the air. Existing research on WRSNs with PADs assumes that PADs have unlimited energy, implying that PADs are connected to consistent long-term energy supplies wherever they are deployed. However, this assumption may be achievable in urban WRSNs, but it is overly strict in suburban WRSNs, where only a few locations have reliable energy supplies. Consequently, the deployment of PADs in suburban WRSNs is constrained and cannot support UAV coverage of the entire surveillance area. Our work addresses this issue by introducing a vehicle-borne mobile PAD to large-scale suburban WRSNs. The mobile PAD may drive to places that the predeployed PADs cannot cover to recharge the UAV, allowing it to function across the whole area. To the best of our knowledge, this is the first work to consider the energy constraint of PAD deployment. To minimize the nodal charging delay, we investigate the problem of periodic charging with the collaboration of the UAV and the mobile PAD in the proposed new scenario. To address this problem, we propose the active rendezvous charging scheme (ARCS), which divides nodes into two types, plans the UAV’s travel path, and schedules the rendezvous between the UAV and the mobile PAD. Simulation results show that ARCS can effectively address the energy problem in large-scale suburban WRSNs.