Time-constraint Multiple Mobile Chargers Scheduling Method for Large-scale Wireless Rechargeable Sensor Networks

Using multiple mobile chargers (MCs) to collect data and charge simultaneously can provide sustainability and energy efficiency for large-scale wireless rechargeable sensor networks (WRSNs) working in single hop mode. One focus of the research is how to reasonable scheduling a limited number of MCs to improve network performance and deployment cost. However, the timeliness of data upload is rarely considered in the existing work. In this paper, we consider a new deployment scheduling problem for the WRSNs in a two-dimensional space, that is, how to minimize the number of employed MCs for energy replenishment of sensor nodes (SNs) and optimize their scheduling with the constraints of non-overtime upload requirement. Furthermore, the problem is defined as a Time-constrained Minimum Number of MCs Problem (TMinMCP), and is NP-hard. To solve this problem, two methods, a Heuristic algorithm based on shortest Hamiltonian loop (HA-SHL) and a Heuristic algorithm based on distance weight (HA-DW), are proposed, and their execution process and time complexity are analyzed. Then a large number of numerical simulation results are introduced to compare the number of MCs deployed by the two methods. The results show that, compared with HA-SHL, the number of MCs deployed by HA-DW can be reduced by 0.56%-10.79% respectively, and thus the HA-DW method is recommended for the TMinMCP.