The Charging Strategy Combining With the Node Sleep Mechanism in the Wireless Rechargeable Sensor Network

The utilization of mobile wireless charging vehicles (WCVs) is a promising solution to address the problem of the energy shortage in wireless rechargeable sensor networks. Most existing works just scheduled WCVs to replenish energy to keep the continuous operation of the network, without taking any action on sensor nodes. In this paper, an interesting idea occurs to us, can we achieve this goal through scheduling WCVs and sensor nodes simultaneously? Define such scheme as the charging strategy combined with the node sleep mechanism. Note that when sensor node only senses data, the energy consumption will be reduced significantly. We then propose a novel charging model, schedule sensor node whose energy cannot keep it alive before getting charged to go into the sleep mode. Therefore, more energy can be saved and the corresponding residual lifetime can be improved. Under the proposed charging model, two problems are formulated, which are (i) maximizing the lifetime of the network combining with the node sleep mechanism and (ii) minimizing the travel path while the network lifetime can be ensured. Efficient algorithms are also proposed to address these problems. First, considering the residual lifetime, the importance in the connectivity and the coverage of the network comprehensively, to maximize the network lifetime, an efficient charging algorithm is proposed to schedule WCVs with limited energy to charge sensor nodes and schedule some appropriate sensor nodes to be in sleep. After determining the trajectories of WCVs, considering the travel cost, a minimum travel path algorithm is further proposed. Through rearranging the charging sequence of sensor nodes, the travel distance can be optimized. Finally, our algorithms are verified by MATLAB. The simulation results show that proposed algorithms are very promising.