Schedulability decision of charging missions in wireless rechargeable sensor networks

Wireless Rechargeable Sensor Networks (WRSNs) have received wide attention in recent years due to their potential to solve the energy problem. With a Mobile Charger (MC), the newly developed charging schemes can be readily applied on a WRSN running traditional protocols. An essential issue in deploying a WRSN is to decide the schedulability of its charging mission. Because one must determine whether the MC can guarantee that no sensor node will stop working within a target lifetime, before designing any specific charging schemes. To tackle the decision problem, this paper proposes an optimistic and a pessimistic condition that can efficiently determine the schedulability of a charging mission. Both of the decision conditions are derived from a generalized formulation of charging schedules. If the MC meets the optimistic condition of a charging mission, a simple and efficient charging scheme can be immediately applied to keep continuous working of the WRSN. While if the pessimistic condition of a charging mission is not met, no valid charging schedule exists. Three methods can be considered when schedulability of a charging mission is still undetermined.