Research On Distributed And Cooperative Localization For Wireless Sensor Networks

Wireless sensor network(WSN)is an important part of the underlying network of the Internet of things(IoT).It is a wireless communication network composed of a large number of sensor nodes deployed in the working area by means of multi-hop self-organization.The node localization is the prerequisite for the implementation of monitoring tasks and final decision making.The development of wireless sensor network technology will lead to more location based protocols and applications.Therefore,the acquisition of node location information has always been the focus of research in WSN.The difficulty of this field lies in the contradiction between the positioning precision and the cost,as well as the serious problem of high computational complexity.In this paper,new distributed and cooperative positioning algorithms are proposed based on the distance measurement model to solve or improve the above problems.Compared with centralized algorithm and non-cooperative algorithm,the proposed algorithms can make full use of the advantages of distributed computing and inter node cooperation,and further improve the positioning performance.The main work is summarized as follows.(1)In order to solve the problems of traditional algorithm in WSN location,such as the huge computation and complexity,and the degradation of positioning accuracy caused by measurement errors,a distributed location algorithm based on closed form solution of ranging model is proposed.Based on distance modeling and data processing,the quadratic equation is obtained from the received signal strength indicator(RSSI)measurement modeling linearization caused by additional variables and unknown node coordinates.Then,the weighted least squares(WLS)criterion and analytical calculation are used to obtain the closed form solution of the node position estimation.Theoretical analysis and simulation show that the algorithm can approximate the optimal solution of Cramér-Rao lower bound(CRLB)with low computational complexity in the estimation performance.(2)Considering the influence of energy consumption and wireless environment in the range model,the measurement accuracy is reduced and the location is inaccurate.To circumvent this problem,the joint power and location estimation algorithm is presented.For the quadratic equation that is related to the extra variables and the transmitted power and the unknown node coordinates obtained from the linearization of ranging model,the non Bayesian method and the closed form solution are applied to get the optimal solution of location and transmit power approaching CRLB in the estimation performance.Theoretical analysis and simulation results prove its effectiveness.(3)Aiming at the contradiction between accuracy and cost in localization algorithm,a new distributed anchor node and pseudo anchor cooperative localization algorithm is proposed based on data processing in location process.The dynamic parameters of the RSSI model and distances are obtained by periodic measurement,and the distance error is corrected by the observation information between the anchor nodes.Location nodes that meet certain requirements are upgraded to anchor nodes to participate in other nodes' location calculation,which improves the coverage and robustness of location.Simulation results show that the localization performance of the algorithm is close to the Taylor series expansion algorithm based on the actual coordinates,and the positioning accuracy is improved rapidly with the decrease of ranging error.(4)In order to make use of the information between unknown nodes in the network to improve the location performance,a new distributed location algorithm of cooperative location for non-anchor nodes is developed.On the basis of selecting anchor nodes to participate in location calculation,the closed form algorithm is adopted to get the node coordinates.According to the Euclidean distance and the measured distance information between the unknown nodes,the location error is reduced by the cooperative positioning between the non-anchor nodes.Numerical simulation proves that the proposed algorithm has a great advantage over non cooperative positioning in location performance.(5)To tackle the problem of low accuracy in RSSI location algorithm,a multimode cooperative location algorithm is proposed,which makes full use of the redundant observation information between anchor nodes and non-anchor nodes.The weighted distance correction is carried out by using the observation information between anchor nodes.The anchor nodes with high quality positioning information are selected to participate in the location calculation.By using the regional weighted coordinate correction implemented by the collaboration between anchor nodes,and the cooperation algorithm between the non-anchor nodes improves the positioning accuracy and enhances the adaptability to the application environment.Simulation results demonstrate its effectiveness.