Analysis Of GNSS-multipath In Closed Loop Simulation Framework For Collaborative Positioning

Multipath reception and the limitation of satellite availability remain dominant issues in Global Positioning System(GPS)application in dense urban areas.Unlike other error sources such as atmospheric delay which can be modeled and significantly corrected by differential techniques,multipath effects have been proven to be much more difficult to mitigate.This thesis aims to improve the positioning performance in dense urban areas by detecting and mitigating the Non-Line-Of-Sight(NLOS)measurements,and collaborating with multiple vehicles in a vehicular network.A large part of this thesis is dedicated to aspects of NLOS detection and mitigation.To enhance the understanding of the multipath propagation,the thesis contains an overview of multipath environment,typical characteristics,multipath signal model and its effect description.Then the NLOS detection algorithm based on the concept of consistency checking is proposed and verified to substantially mitigate the NLOS degradation.A ray-tracing tool has been developed to characterize the multipath signals under different simulated dense urban environments.Additionally,in an attempt to improve GPS positioning performance in urban areas,this thesis tries to provide a comprehensive insight into integrating NLOS detection into collaborative positioning on a basis of Extended Kalman Filter(EKF).By getting multiple vehicles involved in a vehicular network,NLOS detection in collaborative positioning(ND-CP)manages to achieve an accurate positioning solution in simulated dense urban areas using the satellite information and vehicle information transmitted through V2 X channel.To further evaluate the NLOS detection in collaborative positioning(ND-CP)algorithm,three algorithms are applied for comparison,including single point positioning(SPP),collaborative positioning(CP)and NLOS detection in single point positioning(ND-SPP).In this thesis,ND-CP is proven to outperform the other three algorithms,and produce high-accurate positioning solution by improving satellite availability and measurement reliability.