Joint Time Synchronization And Localization Estimation Methods In Wireless Sensor Networks

Wireless sensor networks have several characteristics: low power consumption,low cost,dynamic topology and low data throughput.Wireless sensor network applications are very broad,including in industrial production,military security,smart agriculture and forestry,health care,environmental detection and control.In the localization of wireless sensor networks,the research direction of low cost and high precision is the most important.The measurement methods of Time Difference of Arrival(TDOA)and Time of Arrival(TOA)are used in this paper.Time synchronization is an important basis for the realization of the two methods.In order to make the positioning process more simple and accurate,a new method of time synchronization and localization for wireless sensor networks is proposed.Time synchronization and localization are two important technologies in wireless sensor networks.First of all,this paper makes a brief introduction to the two technologies of time synchronization and positioning.Then the equations of joint time synchronization and localization are established.By comparing the common algorithms,the linear equation is used to avoid the choice of the initial solution,so as to avoid the local optimization of the results.In this paper,we describe the single source and multi-source localization.Single source location,which is a method of estimating the location of a source node with multiple anchor nodes,is simple,but it can cause large errors and excessive workload.Multi-source localization is used to estimate the location of multiple source nodes with multiple anchor nodes simultaneously.The time information of a large number of anchor nodes and source nodes is transmitted to each other in a real environment.That is to say,the anchor node sends the information to the source node,as well as the active node sends the information to the source node.The information is true and effective,and the source position estimation is made by using the information,which improves the positioning accuracy and reduces the workload.In this paper,we compare the unconstrained weighting least square(UWLS)and the constrained weighting least square(CWLS),the semidefinite programming(SDP)algorithm in the cooperative and non-cooperative localization.Through the simulation analysis,the SDP algorithm is better than the least square method,but the computational complexity is higher.The positioning accuracy of cooperative localization is higher than that of non-cooperative localization algorithm.Joint time synchronization and the proposed algorithm has better positioning accuracy and achieve the Cramer-Rao lower bound.The algorithm proposed in this paper has achieved the low cost and high precision positioning of the wireless sensor network.