无线可充电传感器网络中能量饥饿避免的移动充电

无线可充电传感器网络（wireless rechargeable sensor networks，简称WRSN）中，如何调度移动充电器（mobile charger，简称MC），在充电过程中及时为传感器节点补充能量，尽量避免节点能量饥饿的同时降低MC充电代价及节点平均充电延迟，成为无线充电问题的研究挑战.大多数现有WRSN充电策略或是不能适应实际环境中传感器节点能量消耗的动态性和多样性，或是没有充分考虑节点及时充电问题和MC对充电响应的公平性，导致节点由于能量饥饿失效和充电策略性能下降.当网络中请求充电的节点数量较多时，节点能量饥饿现象尤为明显.为此，研究了WRSN中移动充电的能量饥饿问题，提出了能量饥饿避免的在线充电策略（energy starvation avoidance onlinecharging scheme，简称ESAOC）.首先，根据各节点能量消耗的历史统计和实时值计算当前能量消耗率.接着，在调度MC时，根据当前能量消耗率计算各请求充电节点的最大充电容忍延迟和当某节点被选为下一充电节点时各节点的最短充电等待时间，通过比较这两个值，始终选择使其他待充电节点饥饿数量最少的节点作为充电候选节点以尽量避免节点陷入能量饥饿.仿真分析表明：与现有几种在线充电策略相比，ESAOC不仅能有效解决节点的能量饥饿问题，同时具有较低的充电延迟和充电代价.

Energy Starvation Avoidance Mobile Charging for Wireless Rechargeable Sensor Networks

In wireless rechargeable sensor networks (WRSN), it is very challenging to schedule the mobile charger (MC) to replenish energy for sensor nodes timely to avoid node energy starvation in the charging process, and reduce the charging cost of MC and the average charging delay. However, most of existing WRSN mobile energy replenishment schemes either cannot adapt to the dynamic and diversity energy consumption of sensor nodes in actual environment or leave out of consideration of the timeliness and fairness of charging response, which may result in both sensor node failure due to energy starvation and low charging performance. The node energy starvation issue will be worse when there is a large number of request nodes in the networks. This paper explores the energy starvation issue in mobile charging for WRSN and proposes an energy starvation avoidance online charging scheme (ESAOC). To avoid node energy starvation, ESAOC first calculates the current energy consumption rate of each node based on both its history statistics and real time energy consumption. Then, to each request node, ESAOC calculates the maximum tolerable charging delay and its shortest waiting time for charging under the assumption that only one node would be selected as the next charging node. By comparing these two values, it always chooses the nodes which make the least number of other request nodes that could suffer from energy starvation as the charging candidates. Simulation results demonstrate ESAOC can effectively solve the energy starvation problem with lower charging latency and charging cost in comparison with other existing online charging schemes.