Research On Cost Balanced Energy Replenishment Strategy For Rechargeable Sensor Networks

Multiple Mobile Wireless Chargers(MWC)are typically employed in large-scale Wireless Rechargeble Sensor Networks(WRSNs)to meet the demand of their energy replenishement.However,due to the limitations of velocity,charging power as well as battery capacity of MWC,it is necessary to develop an effective collaborative charging strategy of Mutiple MWCs while ensuring the sustainable operation of the networks.To realize the effective energy utilization of MWC and reduce the waiting time of sensor nodes for being recharged,three aspects of to-be-charged nodes selection,charging task allocation and charging mode optimization are studied in this thesis.The main work and contributions of this thesis are descirbed as follows.1.In order to solve the problems of low energy efficiency in periodic recharging algorithms and the unreliability in on-demand recharging methods,a selection mechanism for the nodes to be charged is proposed according to their residual lifetimes.Based on the minimum lifetime of all nodes,the relationship among each recharging slot,the energy supplement period of nodes and the scheduling period of MWC is established.Thus,the set of nodes to be charged in each recharging slot is formed.2.Aiming at reducing the energy consumption of MWC on moving and the waiting time of nodes for being recharged,a trajectory allocation strategy is proposed in this thesis.Constrained by the moving distance and energy consumption of MWC,the TSP based trajectory constructed by the set of nodes to be charged is split into several cost balanced paths for recharging.3.Due to the limited capacity of MWC's batteries,we design an adaptive charging mode for the MWC.The amount of energy replenished to nodes are adjusted without changing their recharging frequency.It ensures that each MWC has sufficient energy to complete the charging task on its trajectory and returns back to the base station.Simulation results show that,the proposed algorithm can effectively dispatch multiple MWCs to accomplish the charging tasks while ensuring that no nodes die.Compared with Periodic algorithm and C-MCC algorithm,methods in this paper can effectively balance the charging tasks between MWCs.As a result,it reduces the difference degree of energy consumption between MWCs by 65.35% and 55.74%,and it also increases the efficiency of energy utilization by 48.22% and 43.35%.Furthermore,the average waiting time for nodes can be reduced by 55.72% and 30.7%,respectively.