Multipath mitigation and NLOS detection using vector tracking in urban environments

Abstract

Multipath interference and non-line-of-sight (NLOS) reception are major error sources when using global navigation satellite systems in urban environments. A promising approach to minimize the effect of multipath interference and aid NLOS detection is vector tracking. Therefore, the objective of this research was to assess vector tracking in a dense urban environment to determine its effect on multipath interference and NLOS reception. Here, a vector delay lock loop is implemented using an adaptive extended Kalman filter. This replaces the individual code-tracking loops and navigation filter, but retains conventional carrier frequency tracking. The positioning and tracking performance of the conventional and vector-tracking implementations with and without a strobe correlator are compared using intermediate frequency signals recorded in the Koto-Ku district of urban canyon Tokyo city environment. Both static and dynamic tests were performed. It is shown that vector tracking reduces the root-mean-square positioning error by about 30 % compared with an equivalent conventional receiver in urban environments and is capable of detecting long-delay NLOS reception for a GPS receiver without any external aiding .