Intermediate frequency level GPS multipath/NLOS simulator based on vector tracking and ray tracing

Abstract

Recent years have witnessed a great advancement of urban global positioning system (GPS) positioning performance. In specific, a lot of efforts have been put on the issue of multipath and/or non-line-of-sight (NLOS) signals. Therefore, there's an increasing demand of ground truth of the multipath/NLOS signals for better assessment of the algorithm that mitigates or reduces the multipath/NLOS effects. This paper proposes a novel intermediate frequency (IF) level GPS multipath simulator based on vector tracking and ray tracing techniques. Unlike existing multipath simulators that generates signals from scratch, the proposed simulator generates multipath/NLOS signals in urban canyon based on the IF data that collected in an open-sky area. The parameter conversion of signal parameters like code delay, carrier phase and frequency, etc., is, therefore, the most innovative part of the simulator. To enhance the parameter estimation for the open-sky IF data, the advanced tracking, i.e., vector tracking, is employed for processing. Ray tracing technique is also used to obtain the additional code delay, incident angle, and the frequency change of the reflected signal. An experiment was conducted in Hong Kong. The results show that the proposed simulator can generate multipath/NLOS signals with controllable parameters.