Collaborative Vector Tracking of GNSS Signals with Ultra-Wideband Augmentation in Degraded Signal Environments

Augmented GNSS has played an ever increasing role in situations where GNSS signals cannot be reliably tracked; such augmentation may involve the use of inertial sensors, odometers, vision, Wi-Fi localization and Ultra-Wideband (UWB) ranging, to name a few. Although these augmentation techniques improve the positioning availability and accuracy of GNSS receivers, the signal tracking performance of GNSS receivers remains largely unaffected. On the other hand, vector-based GNSS receiver architectures have sought to improve the signal tracking performance of GNSS receiver by accounting for the receiver dynamics when generating the local replica signal. This is done by driving the receiver's numerically-controlled oscillator (NCO) using the navigation solution of the receiver. Although a vector-based architecture can greatly improve the tracking performance of the GNSS receiver, it too is limited if it cannot track enough satellites to compute a navigation solution, or if its solution is poor. Given the limitations of current vector-based GNSS receiver architectures and augmented GNSS receivers, this paper describes a collaborative vector-based GNSS receiver architecture for improving weak signal tracking. This system consists of two (but conceivably more) GNSS receivers coupled with UWB ranging transceivers. By taking advantage of differential GPS (DGPS) observations between two nearby receivers as well as UWB range observations, it was possible to allow the collaborative vector-based receiver to achieve a more accurate navigation solution and better predict the satellite signal characteristics. The work presented in this paper shows that the more accurate navigation solution from the collaborative vector-tracking architecture improved the frequency and phase tracking performance of the GNSS receiver while in an indoor environment.