Mobile Charging And Low Delay Data Gathering Strategy In Wireless Sensor Networks

In wireless sensor networks(WSNs),the combination of mobile wireless charging and mobile data gathering improves the balance of node energy distribution and prolongs the lifetime of WSNs.However,the limitation of the speed of the mobile device leads to data gathering delay.Aiming to optimize data gathering delay on the premise of guaranteeing the network lifetime,delay optimization problem on charging sensors and collecting data with multipurpose mobile device(MPMD)was studied.An optimal mobile charging and low delay data gathering strategy was proposed.The strategy was analyzed theoretically and verified by simulation.The main work is as following:(1)Mobile charging and low delay data gathering problem in WSNs was studied.MPMD was introduced in WSNs for wireless charging and data gathering.The low delay mobile data gathering problem was proposed on the premise of guaranteeing the network lifetime.(2)The low delay mobile data gathering problem in WSNs was translated into the shortest path problem under the relay hop constrains(SPRH).Through analyzing and deducing theoretically the relation among the receiving data/charging time,the moving time,the length of moving path,the data gathering time,the maximum data gathering delay,energy constrains and the relay hop,the low delay mobile data gathering problem in WSNs was translated into SPRH problem.(3)The node charging weight based greedy heuristic algorithm(NCWG)was designed for solving SPRH problem.SPRH was proved to be NPC problem.The node charging weight was designed according to the restrictive relation between the relay hop and the length of moving path,and charging node set and moving path were acquired by greedy algorithm depend on node charging weight.(4)The node charging weight optimization based heuristic algorithm(NCWO)was acquired by improving NCWG algorithm.Considering the node charging weight would change if the effect degree of moving path increment and relay hop decrement was changed,adjustable node charging weight was designed,and the optimal node charging weight was found by particle swarm optimization.The charging node set and moving path were determined with the optimal node charging weight.The length of moving path is shorter than NCWG's.(5)A mobile charging and low delay data gathering strategy was proposed for MPMD in WSNs.The charging node set was established depending on the energy state of nodes and NCWG or NCWO althorithm;virtual clusters in which charging nodes were regarded as virtual cluster heads were built and data were transmitted in them;MPMD collected data within each cluster in turn along the moving path.Simulation results verify that the strategy can reduce data gathering delay effectively while maintain network work.The length of MPMD moving path and data gathering time are analyzed with some factors,such as charging power,the rate of data transmission and acquisition,the speed of MPMD.