Research On Coverage Hole Repair For WSN

With the expanding scope of cross-border integration of global information technology,human beings have started to step into the era of the interconnection of everything.Wireless Sensor Networks(WSN),as an essential means of interaction with the external environment and the primary source of sensory information,are regarded as one of the cores to determine the future development of the information technology industry.WSN,which in acquiring and processing information,has high requirements.The effectiveness of transmitted information and communication quality both have high requirements.As a critical indicator of its service quality,the coverage issue has attracted extensive attention from scholars.However,during the regular operation of the network,coverage holes will inevitably occur due to the failure of sensor nodes.Thus,it is vital to study the repair of coverage holes.In this thesis,a new definition of coverage holes is proposed to avoid the loss of data collected before node failure.Coverage holes are composed of pre-fault nodes that reach the energy threshold,and these nodes no longer communicate with other nodes.However,they will use the remaining energy to transmit the collected data to the aggregation nodes to avoid the loss of essential data.On this basis,for the general and water surface environment,the coverage hole repair problem is studied by minimizing the total time of the coverage hole waiting for repair or the network’s total energy consumption.The specific contents are as follows.For the general environment,a Timeliness Coverage Hole Repair(TCHR)algorithm is proposed to minimize the total time of coverage holes waiting for repair.Firstly,define the maximum sustainable moving time of mobile nodes,and establish the problem model of minimizing the total waiting time for repair.The model is established by considering the transmission time of pre-fault nodes and the moving time of mobile nodes when performing repair tasks.Then,to obtain the optimal solution to the problem,we filter out the set of optional mobile nodes that satisfy the mobility condition.The screening is based on the sustainable maximum movement time of mobile nodes.On this basis,the original problem model is transformed into the allocation model of coverage holes waiting for repair.Finally,the Hungarian algorithm is used to solve the problem and obtain the optimal allocation scheme.The simulation results show that the algorithm can effectively repair all the coverage holes in the network,which minimizes the total time of coverage holes waiting for repair.For the water surface environment,a Timeliness Water Coverage Hole Repair(TWCHR)algorithm is proposed to minimize the total time of coverage holes waiting for repair.Firstly,the maximum drift velocity and position are calculated by considering the gravity,buoyancy and water pressure difference force on the mobile node in the water surface mobile repair process.The problem model of minimizing the total time of water surface coverage holes waiting for repair is constructed.Then,based on the mobile nodes’ maximum sustainable moving time,the optional mobile nodes satisfying the moving conditions are selected.Furthermore,the original problem model is transformed into the allocation model of water surface coverage holes waiting for repair.Finally,the Hungarian algorithm solves and obtains the optimal repair allocation scheme.The simulation results show the effectiveness of the proposed algorithm in minimizing the total time of water surface coverage holes waiting for repair.Based on the above research on water surface coverage hole repair,a Minimum Energy-consumption Water Coverage Hole Repair(MEWCHR)algorithm is proposed to minimize the network’s total energy consumption.Firstly,the problem model of minimizing the network’s total energy consumption is established.The model is established by considering the pre-fault nodes’ transmission power and the mobile nodes’ total distance when they are moving on the water surface for repair.Then,under the constraints of transmission time and power,the Karush Kuhn Tucker(KKT)condition is solved by the Lagrange multiplier method to obtain the optimal transmission power.Finally,the optimal repair allocation scheme is obtained based on the Hungarian algorithm.The simulation results verify the algorithm’s effectiveness,which minimizes the network’s total energy consumption and extends the network’s life cycle.