A robust bias detection method in the frequency domain for code delay estimation applied to modern navigation modulations.

The present paper develops an innovative method in the frequency domain for code delay false lock detection and resolution, applicable to GNSS receivers compatible with subcarrier navigation modulations. This novel technique is based on the cross-spectrum estimation between the cross-correlation of received and locally generated spreading codes, and its well-know theoretical non-shifted auto-correlation. The code delay bias is then obtained back in the time domain, and subtracted in closed loop from the output of the numerically controlled oscillator that generates the delayed code replicas in a classical early-prompt-late GNSS receiver architecture. Parametrical optimization pending, this novel technique already shows an entire reduction of systematic errors on the estimated code delay in AWGN channels for BOCcos(10, 5) on Galileo E6a and BOCcos(15, 2.5) on Galileo E1a, with virtually no additional performance degradation in terms of code delay jitter.