Robust GNSS Triple-Carrier Joint Estimations Under Strong Ionosphere Scintillation

In this paper, we proposed a tri-frequency joint estimation algorithm to address the loss of lock issues during strong ionospheric scintillations. This algorithm utilizes the frequency dependency to assist the GNSS tri-frequency signal tracking. The tri-frequency measurements are combined in a joint estimator for Doppler estimations so as to perform inter-frequency aiding from uncompensated signals to the interfered signals and mitigate the strong amplitude attenuations. However, as the tri-frequency estimations are coupled together, the bad measurements will deteriorate the strong signal tracking performance. We upgrade the tri-frequency joint estimator with a real time weighting adjustment according to the observed signal strengths on three frequency bands to address the issues. In addition, the algorithm adopts independent tracking on carrier phase, while joint tracking on carrier frequency. Therefore, the phase fluctuation features on each frequency can be preserved for the ionospheric scintillation characterizations and detections. The performance of the proposed algorithm is verified by the simulations. The results show that the tri-frequency joint estimator can effectively suppress tracking errors and recover carrier parameter estimations during strong ionospheric scintillations.