A novel evil waveforms threat model for new generation GNSS signals: Theoretical analysis and performance

With the advent of new Global Navigation Satellite Systems (GNSS) and signals, Satellite Based Augmentation Systems (SBAS) will rely also on them to provide higher position accuracy. For services based on such systems it is fundamental to protect the user against potential signal distortions in order to ensure the required integrity and performance. SBAS systems usually implement signal deformation monitors which are capable to recognize payload imperfections affecting the received signals in order to discard the corrupted information. The advent of new GNSS signals introduces the necessity to extend already accepted failure models to the new modulations techniques. This paper considers in particular the 2nd-Order Step threat model adopted by the International Civilian Aviation Organization (ICAO) for GPS signals. Starting from the ICAO model, a general threat model affecting the signal generation and transmission hardware is here proposed for Binary Offset Carrier (BOC) signals, and then extended also to Multiplexed Binary Offset Carrier (MBOC), and to Alternate BOC (AltBOC) modulated signals. As a first analysis, the correlation peaks affected by the proposed threat model are shown for the aforementioned signals, and some evaluations on the parameters space are carried out. In order to evaluate the effect of deformations on the performance of a GNSS receiver, the tracking error behavior is studied for two types of discriminator (early late, double delta) and different correlators´ spacing.