Research On Mobile Charging Planning Method For Wireless Rechargeable Sensor Networks

As an important means of obtaining information nowadays,sensor network has been widely concerned by the society.However,the energy problem has always been an important constraint and challenge restricting its wide application.With the breakthrough and development of wireless charging technology,the problem of energy limitation of sensors and node death can be effectively solved and the service life of sensor network can be extended by charging the sensor with wireless charging equipment.Mobile charging of wireless sensors is one of the more mature energy replenishment methods.At present,most of the existing mobile charging schemes use the "mobilecharging" mode for energy supplement,that is,WCV moves to the sensor node and then charges it.This mode is intended to reduce the WCV's mobility delay or charging delay to reduce the charging completion time.However,this mode usually ignores the charging opportunity during the WCV's mobility--WCV can charge the sensor during the mobility.Therefore,based on the charging opportunity in the WCV moving process,this paper proposes a variable speed scheme when the WCV speed is variable.The charging completion time minimization problem of WCV was converted into tsp-vs,and the linear programming method was used to solve the problem.Simulation experiments were carried out in various scenarios,and the proposed variable speed scheme was compared with other charging schemes.The experimental results show that,compared with the existing charging schemes,the variable speed scheme proposed in this paper can effectively shorten the completion time of charging,and the maximum completion time of charging is reduced by 23.9%.With the increase of the number of sensor nodes,the range of improvement of charging efficiency of WCV in the proposed variable speed scheme decreases until it is no longer improved.Therefore,in view of the shortcomings of the variable speed scheme in large-scale network application scenarios,this paper proposes a different charging mode.After upgrading the charger hardware platform of WCV,a single WCV can carry multiple low-cost and detachable chargers to charge the sensor nodes.By placing separate chargers in multiple charging locations,the WCV can charge multiple sensors almost simultaneously(regardless of the time it takes to place the charger),greatly improving the charging efficiency of the WCV.Based on this charging mode,this thesis studies the charging scheduling problem of WCV in two different application scenarios.When the remaining life of the sensor is negligible,a 3+?-approximation algorithm for solving the shortest charging path is proposed.This approximation algorithm is suitable for scenarios that are insensitive to the remaining life of the sensor node,such as structural stability monitoring of buildings.When the remaining life of the sensor is not negligible,a heuristic algorithm for minimizing the cost of the charging service is proposed to find the shortest charging path of the WCV while ensuring the minimum dead time of the sensor.This heuristic algorithm is suitable for scenarios that are sensitive to sensor data changes,such as forest fire warnings.Finally,the performance of the proposed approximation algorithm and heuristic algorithm is evaluated by experiments.The experimental results show that the proposed heuristic algorithm(calculated when K = 2)can reduce the maximum and average dead time of sensor nodes by 52.2% and 40.7% respectively compared with the existing EDF algorithm,and can extend the lifetime of sensor networks more effectively.