Multicorrelator signal tracking and signal quality monitoring for GNSS with extended Kalman filter

Abstract

GNSS signals may present anomalies that degrade \nthe positioning performance of GNSS receivers. Signal Quality \nMonitoring (SQM) is normally used to detect and to characterize \nthese anomalies. This is required for the GNSS operators \nand integrity services to determine when a satellite should be \nconsidered as faulty and draw conclusions about the type of \nthe fault. In this paper, we present a new SQM algorithm that \ntracks the GNSS signal and possible channel deformations by \nusing a novel methodology based on the Extended Kalman Filter \n(EKF). The EKF is designed such that the measurement update \nis performed in post-correlation and using multiple correlators. \nAfter the estimation of the channel response, we add a detection \nstep to determine if the channel deviates from the nominal \nsignal transmission scenario (i.e., the single path propagation). \nResults suggests that the performance of the delay estimation \nwith the proposed EKF structure outperforms the classical \nDelay-Locked-Loop (DLL) estimation, especially in the presence \nof distortions. Furthermore, it can reliably detect anomalous \nsignal deformations as specified by ICAO threat model.