Codeless processing of binary offset carrier modulated signals

Advanced and unexpected applications are recently raising new interest in Global Navigation Satellite System (GNSS) codeless techniques that can be used, for example, for signal authentication and spoofing detection. Moreover, the presence of a subcarrier in modern GNSS signals introduces new challenges and opportunities. To take advantage of modern signal structures, codeless processing needs to be modified to recover the subcarrier which can subsequently be used for signal quality monitoring. In this study, codeless tracking is modified for processing binary offset carrier (BOC) modulated signals where a subcarrier lock loop is used to remove the subcarrier component. The performance of the suggested architecture is thoroughly analysed and theoretical results are supported by Monte Carlo simulations. An open-loop, multi-correlator codeless architecture is also proposed to monitor the BOC subcarrier correlation function. The effectiveness of the proposed codeless framework is demonstrated using real data collected from the Galileo in-orbit validation satellites. The analysis supports the validity of the proposed architecture which enables quality monitoring of encrypted GNSS signals.