Adaptive and conjoint scalar-vector tracking loops for GNSS tracking robustness and positioning integrity

Abstract

Maintaining robust tracking and positioning integrity in harsh environments is a real challenge for GNSS receivers. This paper considers three possible tracking and navigation solutions to address this challenge. Firstly, a vector tracking loop (VTL) capable of using correlator-based multipath detectors and other signal quality indicators to exclude contaminated satellites from the PVT calculation is proposed. Secondly, an adaptive scalar-vector tracking loop (STL-VTL) that continuously switches between STL and VTL modes based on the state of signal quality indicators is considered. Lastly, a conjoint scalar-vector tracking scheme which maintains STL and VTL modes simultaneously then chooses the measurements to be fed to the navigator based on the state of quality indicators is suggested. To evaluate the performance of the proposed solutions, the trajectory and environment simulator developed by the German Aerospace Center (DLR) is used to simulate GPS signals in harsh suburban and urban conditions. The exclusion of multipath contaminated satellites from PVT calculation improves PVT accuracy and tracking performance. The adaptive and conjoint STL-VTL schemes allow, each in its way, to exploit the advantages of both STL and VTL regarding positioning reliability and tracking robustness.