Localization Technology For Mobile Wireless Senor Network

Node localization and time synchronization as two key components of any self-organizing location-aware wireless sensor network(WSN),has always been the focus of the research and application topics.With the further promotion of WSN in the application domain,demands for high precision positioning is greatly increasing,and the higher accuracy of localization is,the more demands for network time synchronization is.The problem of both node clock synchronization and high precision node localization can be put together to study.To solve the node clock synchronization problem,can provide further support for node localization in a variety of different environments.Ultra-wideband(UWB)technology as a new communication technology with non-carrier,has a nanoscale time resolution,in recent years it has been widely used in high precision positioning system,the technical foundation is provided for the project implementation of the high precision localization algorithm.Based on the existing TOA and TDOA location method,the clock synchronization algorithm with the position of anchor known is proposed in this paper,the basic concept of the anchor blink is mainly introduced,the key concepts of both anchors' frequency difference(ie.the relative clock skew)and anchors' clock difference(ie.the relative clock offset)are introduced.The relative clock skew and the relative clock offset of anchor pairs can be jointly estimated by using the least square method,and can be used to compensation original TDOA which comes from tag positioning,the purpose of anchor clock synchronization can be achieved at the time of the positioning calculation.Monte Calro simulation results show that the algorithm performance is superior in positioning calculation,the accuracy of clock synchronization can achieve 910-s,and the clock synchronization problem of high precise positioning has been effectively solved,which has provided a strong support to solve the high precision positioning of node under the different positioning conditions.Based on the methods of clock synchronization compensation in the previous section,this paper also put forward the mobile WSN localization algorithm with the position of anchor unknown.The least squares estimation(LSE)for the relative clock skew of anchor pairs is firstly obtained;based on the relative clock skew estimation,the relative position of anchor can be calculated by the way of the maximum likelihood estimation(MLE),and the establishment of a 2D coordinate system;based on the least squares estimation for the relative clock skew and the relative clock offset of anchor pairs,The precise positioning results of tag can be obtained by the way of the maximum likelihood estimation.Monte Calro simulation results show that the position estimation error of both anchor and tag is small,GDOP simulation diagram of the algorithm verify the positioning accuracy and effective positioning range of the algorithm,This algorithm,which can effectively solve the problem of tag localization in the case of the anchors' position or moving distance unknown,provides a theoretical basis for the engineering application.Based on the existing UWB communication module,a positioning platform is built,and a positioning software is also designed according to the mobile WSN localization algorithm.Through the analysis of positioning data packet,anchor and tag are positioned respectively according to different TOA information,and the positioning results are finally displayed in the user interface,you can visually see the tag positioning results,tag positioning accuracy reachs centimeter level.Project implementation,which further validates the positioning performance of the algorithm proposed in this paper,provides a specific reference for the practical application of the algorithm.