On The Topology Control In Wireless Sensor Networks

Wireless Sensor Network (Wireless Sensor Network) is a kind of application-oriented Network architecture withinwhich a Sensor node is distributed in the target area to monitor a particular object. In the applications of area coverage,wireless sensor network is composed of blanket coverage network and barrier coverage network. Blanket coveragenetwork is that any point over the target area is covered by at least a or k nodes, also known as full coverage ork-coverage network, and barrier coverage refers to that any path passing through the target area is intersected with theregion covered by at least one or k nodes, which is also known as k-barrier coverage.Node deployment, which is divided into non-random layout and random layout, is a very important stage for theformation of wireless sensor network topology structure. In the primeval forest, the deployment of blanket sensornetworks makes early warning of fire, or in the border, the deployment of barrier sensor network makes early warning ofstowaways, they usually choose to drip sensors randomly by plane or throw rockets. Sensor nodes of random drippinghave positional uncertainty, coupled with the redundant features of WSN, and it is necessary to periodically select a partof sensors in working status through the topology control strategy, or to relocate some sensor nodes in order to constructsuitable topology structure.The following problems concerning the present wireless sensor network topology control:1. Maximum coverage. The coverage is the ratio of the region area covered by wireless sensor network to the wholearea. The part of area of the random deployment is unavoidably covered by a sensor node, and therefore, these sensornodes need to be in the active state, or it will reduce network coverage. There is no such mechanism in the currentresearch results to make these sensors in the active state.2. The maximization of1-coverage ratio.1-coverage ratis is the ratio of the region area covered by only one sensor tothe whole area. Except to set the coverage as1, the objectives of the optimization of ideal blanket network topology alsoinclude the maximization of the proportion of1-coverage in order to reduce the number of the active sensors and toprolong the network lifetime. There is no research to the latter as topology control and the optimization target, so therewill effect the network lifetime.3. To minimize the energy consumption for topology control by mobile sensor. Existing research is mainly aimed atminimizing the sum of the node energy consumption as the optimization goal, but ignored the minimization of thevariance of energy consumed by every sensor, leading to the unbalanced distribution of node residual energy, andultimately, it will reduce the network lifetime.4. Full barrier coverage network. It is a full barrier network for the intrusion detection with the probability being1.This network ensures the effect of monitoring target, and improves the reliability of network. For topology control ofnode selection, this condition is ignored and results in the non-full barrier coverage.For the above problem, this project mainly makes research of wireless sensor network topology control, and its aim isto find a network topology structure more close to the expected results to improve the network coverage, to save network energy and to prolong thenetwork lifetime. In this paper, the main research contents and results are as follows:1. Topology control of blanket network based on node selection. It studies high redundancy network topology control,mainly analyzes how to choose the active sensors, to reduce the number of active sensors, and to prolong the networklifetime.(1) CDBANS center algorithm is proposed. It puts coverage degree as parameter, user the two-part graph forselecting the active sensors, and to extend the network lifetime up to the hilt.(2) CBANS distributed algorithm isproposed. The algorithm put the minimization of the overlap area of the adjacent two working node as the optimizationgoal, reduce the number of active sensors, and improve the1-coverage ratio. The simulation results indicates:(1)compared with SSR algorithm, CDBANS algorithm improves20%and5%respectively for network lifetime and1-coveage ratio, and compared with LWS algorithm, CDBANS algorithm have the same network lifetime and thecoveage, but improve13%for1-coveage ratio.2. Topology control of limited-mobile-sensor-based blanket network. It studied the the process of wireless sensornetwork’s converting into a voronoi diagram and the characteristics of the voronoi diagram, mainly analyzing how todetermine the node mobile strategy.The purpose is to improve the coverage. VBMC algorithm is proposed. It aims atvoronoi polygon for the algorithm to determine whether a node itself on the edge of the blind area, and then to determinethe direction of movement according to the polygon vertices, thus achieving the goal of maximizing the networkcoverage with the minimum energy consumption. Compared with MiniMax algorithm, VBMC algorithm reduce80%forenergy consumption, and compared with grid-based algorithm, VBMC algorithm improve13%for network coverage.3. Topology control of barrier coverage which is based on active sensor selection. It studied the key indicators ofmeasuring the performance of barrier coverage, including barrier coverage degree and blind area, with the purpose ofdetermining whether layout ribbon network meet the application requirements to simplify the ribbon network topologycontrol algorithm. SMCS algorithm and LTNWB algorithm are proposed, and they are based on the concept of minimumcut set in graph theory and DFS algorithm, independently. SMCS algorithm determines the barrier coverage and blindarea, and LTNWB algorithm determines barrier coverage degree and belt cover. This article not only theoretically provedthat the convergence and effectiveness of the two kinds of algorithm, and confirmed in the simulation experiment.4. Topology control of barrier coverage based on limited mobile sensor. It studies how to locally determine the barriercoverage degree, to make decision of movement strategy only depmending on the local information, and to improve thebarrier coverage degree. It improved MobiBar algorithm to be VMB_MobiBar algorithm, which can achieve the samebarrier coverage as the MobiBar algorithm, and consume less energy in the process of topology control. Simulationresults indicate that, compared with MobiBar algorithm, the algorithm of VMB_MobiBar has the same barrier coveragedegree, but reduce10%~50%for energy consumption.To sum up, the author studied topology control and optimization of blanket and barrier network in the applications ofwireless sensor network of the random layout. The method adopted is mainly based on the working node selection andlimited mobile sensors. The goal is to guarantee the optimal network performance, including higher network coverageand1-coverage ratio to reduce and balance energy consumption of each node or to extend the network life cycle.