Scheduling of ERD-Assisted Charging of a WRSN Using a Directional Mobile Charger

For the capability of concentrating radiation energy along a direction, using Directional Mobile Chargers (DMCs) for charging the nodes in a Wireless Rechargeable Sensor Network (WRSN) via wireless power transfer has become a research hotspot. However, existing research neglect cooperative Energy ReDistribution (ERD) among nodes, handering energy charging efficiency. This motivated us to focus on the scenario of charging a WRSN using a DMC and address the underlying ERD-Assisted Directional Charging Schedule (ERADCS) problem. This problem involves determining a charging schedule with minimal energy loss and minimum time span. We first proved the NP-hardness of ERADCS and then proposed a Directional Charging Schedule algorithm Based on Greedy Strategy (DCSBGS) to solve it. In DCSBGS, to tackle the infinite charging directions, we created cMFRDS algorithm to determine a minimum-size representative direction set functionally equivalent to the original infinite directions, and proved its optimality. Subsequently, we assumed Virtual Mobile Chargers (VMCs) fixed to the representative directions, transformed ERADCS into a charging schedule problem using the VMCs, solving it using a two-step framework. We also established key properties of DCSBGS and its sub-algorithms. Furthermore, we extended DCSBGS for ERADCS involving a DMC with multiple charging beams. Our simulation results validate the superiority of DCSBGS over other typical algorithms.