Enhanced GNSS frequency tracking in multipath environments

A novel configuration for improving the frequency tracking performance of GNSS signals in multipath environments is proposed. The proposed technique is based on combining the weakly correlated outputs of Early, Prompt and Late match filters to exploit the inherent time-delay diversity when severe multipath conditions prevail. By observing more code-phase offsets simultaneously, the loop is more resilient to fading than the conventional loop. The proposed configuration is implemented in a GPS software-receiver and tested on GPS signals collected through an extensive measurement campaign in an urban canyon in downtown Calgary. The test results demonstrate the effectiveness of the proposed technique in mitigating multipath fading and improving the robustness of frequency tracking under severe multipath conditions.