Research On NLOS Base Station Identification And Location Technology In MLAT

With the rapid development of civil aviation industry,air traffic management is becoming more and more important.As a new surveillance technology,multilateration(MLAT)is getting more and more attention.Due to the occlusion of buildings,non-line of sight(NLOS)propagation path will exist,which seriously affects the positioning accuracy of MLAT.The positioning method in NLOS environment has become the focus of research.Aiming at different wireless channel environments,the positioning algorithm of MLAT system is studied,especially the positioning algorithm in NLOS environment.Starting from the positioning technology of time of arrival(TOA),it is extended to the positioning technology of time difference of arrival(TDOA).The main innovations are summarized as follows:(1)To improve the positioning accuracy of the TOA positioning algorithms in the LOS environment,an algorithm named error correction of ranging positioning(ECRP)is proposed.ECRP algorithm constructs the model of offset circle using range residuals.The target position error is corrected by estimating the center of the offset circle.The simulation results show that ECRP algorithm has strong adaptability to the layout of base stations,and has strong adaptability under different ranging accuracy.(2)Focusing on the problem of improving the positioning accuracy of TDOA positioning methods in the NLOS environment,an algorithm named residual test based on arc-edged convex hull(RTAC)is proposed.RTAC uses the minimal arc-edged convex hull to group and identify the base stations to realize the exclusion of all NLOS base stations in the system.The simulation results demonstrate that RTAC algorithm can correctly identify NLOS base stations with low computational complexity and has better location performance.(3)The methods to improve the positioning accuracy in LOS environment and in NLOS environment based on TDOA technology are proposed respectively.An algorithm in the LOS environment named error correction of ranging difference positioning(ECRDP)is proposed by extending the offset circle model to TDOA technology.Based on ECRDP algorithm,an algorithm in the NLOS environment named residual test based on enclosing circle(RTEC)is proposed.The RTEC uses the model of enclosing circle to group and identify base stations.The simulation results show that RTEC algorithm has higher correct identification rate of LOS base stations,higher positioning accuracy and higher computational efficiency.