openIn urban environments any GNSS receiver is subjected to frequent sudden losses of the line-of-sight (LOS) signal and to the multipath phenomenon, which drastically reduce the accuracy, robustness and availability of the GNSS service.
This thesis evaluates the implementation of a tracking loop for robust tracking of GNSS signals in hostile scenarios, developed in collaboration with Qascom and addressed to their software defined GNSS receiver, the QN400.
After an initial analysis of the state of the art in robustness enhancement techniques, it was decided, together with Qascom's Advanced Navigation team, to integrate a Kalman filter inside the common tracking loop structure.
More specifically, the proposed tracking loop integrates a fourth-order Kalman filter and an outage detection algorithm into the standard structure, with the overall goal of improving tracking performance in terms of robustness to multipath effects and signal's interruptions.
The proposed design was extensively tested with Qascom's semi-analytical simulator in Matlab, both with simulated scenarios, based on the DLR land mobile multipath channel model, and more realistic ones based on live recordings of a GNSS receiver mounted on a vehicle moving in Bassano del Grappa.
The proposed solution has shown great efficacy in all designed test environments. Specifically, it has demonstrated superior resilience in resisting signal outages when compared to the standard tracking loop
