Research On Multi-station Positioning Technology In Outdoor NLOS Environment

With the rapid development of mobile communication technology,such as the gradual commercial use of 5G technology,people have more and more demand for Location Based Service(LBS).Outdoor positioning based on existing mobile communication networks is also important,and it does not need to deploy other dedicated positioning systems.The mainstream of outdoor positioning technology based on microcellular networks is to use Line-of-Sight(LoS)signals for positioning,but the outdoor environment is complex,and the LoS path from the target to the base station is sometimes blocked.Therefore,it is of great significance to study positioning in the NonLine-of-Sight(NLoS)environment.In addition,the phase error existing in the network makes the absolute Time-of-Flight(ToF)of the signal unavailable,so the NLoS positioning under the cellular network is great challenge.For this reason,this thesis proposes an outdoor NLoS positioning method based on the scatterer model.Several typical scatterer models are analyzed,and the model matching algorithm is studied,and then a multi-base station joint positioning model is proposed on this thesis.Specifically,the main research contents of this thesis are as follows.First of all,the realization of target positioning in the NLoS environment must rely on the surrounding reflection path.Therefore,this thesis analyzes the parameter probability density function(PDF)of the typical ring scatterer model,disk scatterer model and Gaussian scatterer model.In order to select the appropriate model according to different environments,the reference templates of the three models are constructed with different characteristics of the parameters.And the scatter template to be matched is constructed in combination with the actual scatterer distribution.Then the Earth Move Distance(EMD)algorithm is used to carry out the model matching research,and the simulation verification is carried out.Secondly,on the basis of model matching,the multi-base station positioning technology in outdoor NLoS environment based on scatterer model is studied.The Ao A of the target is reconstructed from the Angle of Arrival(Ao A)of the multipath signal,and the influence of phase error in the Orthogonal Frequency Division Multiplexing(OFDM)signal is eliminated by differential ToF.Then,the location equation is established by using the geometric relationship among base station,scatterer and target and combining with the difference ToF,and the target constraint interval is introduced to transform the location problem into the least square problem.Finally,Levenberg Marquardt(LM)algorithm with constraints is used to solve the least squares problem to obtain the initial position of the target,and the location is performed by using distance difference with multiple base stations.Finally,the influence of the parameters on the positioning performance is analyzed on the Matlab simulation platform.At the same time,REMCOM's Wireless Insite software is used to model the outdoor scene in three dimensions,which can accurately simulate the location and size of each base station,obstacles,and the surrounding geographic environment.The Wireless Insite software can simulate the Signal propagation characteristics based on the principle of ray tracing algorithm in microcellular network environment.Wireless Insite software is used to obtain the data and verify the positioning method.The results show that the positioning error of 50%confidence is 11.02 m,the positioning error of 67% confidence is 15.25 m and the positioning error of 80% confidence is 18.64 m.