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Discontinuity-Based Code Delay Estimator for GNSS Signals

Undoubtedly, accurate line-of-sight (LOS) code delay estimation is encountered among the most challenging synchronization problems in the context of Global Navigation Satellite Systems (GNSSs). However, the way towards achieving high accuracy is seriously hindered by the various error sources affecting the transmitted satellite signal. Particularly, the destructive nature of multipath environments has posed several limitations in the tracking performance, thus increasing the need for estimators, resistant against multipath delays. In this paper, we present a new code delay estimator for binary offset carrier (BOC) and BPSK modulated signals, the so-called DiscTracker, which combines features from both feedback and feedforward approaches. The proposed estimator is tested in multipath static and in multipath fading channels and its performance is compared with a set of state-of-art estimators in terms of root mean square error (RMSE) and mean time to lose lock (MTLL). The simulation results show that DiscTracker is robust in closely-spaced multipath scenarios and resistant to non-zero initial code delay errors.