Research On Device-free Localization Algorithm Based On Sensor Grid Array And Ellipse Measurement Model In Wireless Sensor Networks

With the continuous development of The Wireless Sensor Networks(WSNs),WSNs are widely used in environmental perception,target monitoring and so on.Conventional localization method almost is Device-base Localization,the object must be bound to the electronic device or tag,in the conditions of limited environment is not high applicability.In recent years,the concept of using the Received Signal Strength Indication(RSSI)for Device-free Localization has been proposed:The electromagnetic wave around the object will change due to the absorption,reflection or refraction,so the value of RSSI will also change.According to this changing,the location of the object can be estimated.Device-free Localization makes the object out of the limitations of carried electronic devices,with greater flexibility and applicability.Therefore,algorithm has become the focus of Device-free Localization research.The thesis first summarizes WSNs and Device-free Localization,classifies and compares various types of location algorithm models,focuses on the RSSI-based Device-free Localization algorithm.Then the Device-free Localization Algorithm based on Sensor Grid Array and Ellipse Measurement Model is presented in conjunction with the existing model of the algorithm.The algorithm first divides the monitoring area by using the wireless link between nodes,then through the amount of relative change of the RSSI to select the link and draw the elliptical ring,final the position of the object is determined according to the elliptical intersection.After determining the process of algorithm,the parameters of Ellipse Measurement Model should be adjusted to adapt to the algorithm.Thus in this thesis,we conduct location experiment through the ZigBee experimental platform which using CC2530 chip as the core.By collecting and analyzing error data,to achieve reverse derived parameters and confirm the final form of an algorithm.When the algorithm is determined,we re-conducted Device-free Localization experiment on the original experimental platform,which the number of sensor nodes and the area of the monitoring area are changed The experimental data is collected and simulated by MATLAB.The feasibility of the algorithm is verified.By the error analysis and algorithm comparing,it can be found that the Device-free Localization Algorithm based on Sensor Grid Array and Ellipse Measurement Model compared to Grid algorithm has similar accuracy with the lower sensor node density,but the edge effect is generated.Compared with the Scanning Imaging Algorithm,the Device-free Localization Algorithm based on Sensor Grid Array.and Ellipse Measurement Model has higher locating accuracy with lower node hardware cost.