Key Techniques Of Localization In Wireless Sensor Networks Under Complex Environment

Localization is one of the most fundamental techniques and services in WirelessSensor Networks (WSNs). Many applications in WSNs, such as information collection,targets tracking, information management, environment monitoring, geographic routingand so on, all require accurate position information of sensors. Under complexenvironment, networks are characterized by3D distribution, link indeterminacy,environment heterogeneity and unstructured deployment properties. These factors bringgreater challenges to localization theories and algorithms. Currently, most localizationstudies assume that the communication model and network deployment environment areidealized, and they ignore the effects of various factors on the localization algorithms.As a result, these models and algorithms will become inefficient or useless in practicalapplications. To overcome the defects of existing work and to relax the challenge ofcomplex environment localization, four distributed localization solutions whichsatisfy the practical requirements of high precision, low overhead, high efficiency andlow cost in complex environment, are proposed in this dissertation. The maincontributions of this dissertation are listed as follows:1. Flood boundary control based error-correction localization strategyTo solve the problem of model impropriety, large accumulated errors and matrixmulticollinearity form directly extending the traditional hop-based localization schemeto3D complex concave/convex surface with obstacles, a new hop-basederror-correction localization scheme called3DPHDV-Hop is proposed.3DPHDV-Hopuses the scheme of projection plane selection, hop control in N subareas from interestarea, hop distance correction and measurement correction to achieve fine-grainedlocalization with high accuracy and low error. Experiment results show that3DPHDV-Hop has higher localization rate than APIS,3D DV-Hop and3D-MDS, withthe ratio of45.2%,35.4%and32.3%, respectively.2. Concave/convex decomposition localization mechanism based on spatialgeometric segmentation.To solve the problem of large localization error and energy consumption on thetopology of3D complex concave/convex surface with obstacles, a new concave/convexdecomposition localization mechanism called3D-CCD, which is based on spatial geometric segmentation, is proposed.3D-CCD utilizes the logical delamination andconcave/convex decomposition to divide the complex, irregular area to subareasaccording to the concave/convex topology. It only utilizes RSSI used by mostlocalization schemes to reach high accuracy, low consumption fine-grained localization.Experiments show that, compared with SV and COLA,3D-CCD reduces thelocalization error by10%and17%respectively, and reduces the energy consumption by31%and22%respectively.3D-CCD offers a brand new research method on3Dcomplex concave/convex surface localization.3. Triangulation based localization algorithm based on fractal networktopologyIn order to solve the problem that it is expensive and difficult to deploy anchornodes on3D complex concave/convex surface, a new triangulation localizationalgorithm (called3DT-ST) which is based anchor free and applies to complex3Dterrainis presented.3DT-ST only utilizes network connection and special nodes (specialport nodes, SPN) to triangulate and model. It establishes local relative maps in everytriangle areas, then combine triangle together to get global map of the network.Experiments show that when comparing with SV,3DT-ST reduces the localization errorby85.3%, and localization is an iteration-free process with only the information ofnetwork connection. It improves the localization accuracy, lowers the localization error,andsaves the cost of network deploying as well. It provides a new method on energysaving localization research over complex networks.4. Mobile anchor sensor routing planning of localization based on graphtheory.To address the problem that fixed anchor sensors has the disadvantage of lowexpansibility and high cost in3D concave/convex uneven surface networks, a newmobile anchor sensor routing planning of localization3DT-PP is proposed. It leveragesthe routing planning of mobile anchor sensor, locating sensors in complex3D terrain,planning the accessible route and traversing the entire monitored area with optimal routeto quickly locate the sensors in entire network. Experiments show that compared withMDS-MAP and Landscape-3D, the proposed method lowers the localization error by91%and8.7%respectively and reduces the computation overheads by75%and1.3%respectively. It can localize all nodes in a very short time with high performance, reducethe number of anchor nodes and isolated nodes, relieve the impact of obstacles and lower the cost of network establishment.In summary, this dissertation takes efforts on WSNs localization in complexenvironments. A series of experiments show that the proposed four solutions satisfy thepractical requirements of high precision, low overhead, high efficiency and low cost.Therefore they not only have important theoretical value, but also have extensiveapplication potential.