Research On Scheduling Strategies For Mobile Charging Devices In Rechargeable Sensor Networks

In wireless sensor network(WSN),since sensor node’s battery is limited,the traditional WSN is limited by its lifetime,which obstructs the application range of the network seriously.With the introduction of wireless rechargeable sensor network(WRSN),the development of wireless energy transfer technology provides a promising solution to the self-sustainability of the WSN.To prolong the network lifetime and power rechargeable sensor nodes,this thesis will utilize the wireless charging vehicle(WCV)with the wireless energy transfer technology to provide theoretical support for the future wide application of WSN.In the WRSN,how to schedule the WCV to charge sensor nodes efficiently is an urgent problem.Currently,some achievements have been made in WCV path scheduling.However,most existing works do not consider some practical factors,such as,the imperfect charging channel quality,the uneven energy consumption.Corresponding designed charging strategies without considering above factors cannot achieve desired goals in the practical implemention.To maximize the network lifetime,this thesis takes mentioned factors into consideration comprehensively and proposes corresponding improved algorithms which can further improve charging efficiency and network lifetime.At the same time,to further improve the energy efficiency of data transmission,a mobile vehicle scheduling strategy of combining energy replenishment and data collection is also studied.The contents of this thesis can be concluded as follows.(1)Considering the limited battery capacity of the WCV and the imperfect charging channel quality between sensor nodes comprehensively,an efficient WCV scheduling strategy is proposed.To maximize the energy efficiency of the WCV,the metric named as waste rate is proposed.Then the problem of maximizing energy efficiency of the WCV is modeled as minimizing the waste rate.Through analysis on the optimized problem,an efficient algorithm is proposed to find the optimal set of to-be-charged sensor nodes.Then,the shortest travel path of the WCV can be found through the nearest neighbor node algorithm.Simulation results show that our proposed solution can reduce the energy waste of the WCV and the total charging time.(2)In the practical wireless sensor network,considering the different importance of sensor nodes in the data transmission and uneven energy consumption of different sensor nodes,a novel charging model is proposed.Under the novel model,maximizing the network lifetime is modeled as minimizing the normalized dead time.An efficient minimum dead time algorithm is also proposed to minimize the normalized dead time through achieving the optimal charging timeslot sequence.The simulation indicates that our algorithm can reduce the death time of network significantly.(3)It can be found that the energy consumption can be reduced significantly when sensor node just senses data.Based on that,this thesis proposes a novel charging model,which is,schedule to-be-charged sensor node with short residual lifetime to go into sleep to save energy and improve the corresponding residual lifetime.At the same time,through reassigning the charging order of to-be-charged sensor nodes,an efficient WCV scheduling strategy is designed to reduce the energy cost on traveling.Corresponding algorithms are also given.Simulation results show that proposed algorithm can reduce the energy consumed on traveling while the network lifetime can be ensured.(4)To improve the work efficiency and the energy efficiency of the data transmission,this thesis also proposes the scheduling strategy of the WCV combining energy replenishment and data collection.Considering the data overflow and the delay of the delay-sensitive data comprehensively,a new data collection strategy is proposed.At the sasamw time,efficient algorithms are also proposed to determine optimal data collecting clusters and corresponding data collecting time,the sum of normalized saved energy can be maximized.Finally,considering practical complex network environment and the limitation of moving vehicle,UAV-aided data collection strategy is further proposed to improve the amount of data collection.Simulation results show the total normalized saved energy and the network lifetime can be maximized and the energy efficiency of data transmission can be improved.At last,the key of our work is concluded and the future work is prospected.