Cross‐correlation codeless processing of BOC modulated signals

Abstract

Encrypted global navigation satellite system signals (GNSS) can be tracked using codeless techniques that do not require the knowledge of the spreading code used for signal generation. These techniques can also be applied to binary offset carrier (BOC) modulated signals whose unknown code sequence can be removed through squaring. In this study, an alternative codeless approach based on the cross-correlation principle is considered. Cross-correlation codeless processing is commonly used for tracking signal components on different frequencies, such as the global positioning system (GPS) L1 and L2 P(Y) signals, and it is adapted here to BOC modulations broadcast on a single frequency. A cross-correlation codeless framework is proposed where the BOC signal is split into two data streams that are cross-multiplied to remove the unknown code sequence. Two architectures, open-loop and closed-loop processing, are proposed and analysed. The codeless cross-correlation function is introduced and open-loop processing is used to reconstruct it from the received samples. Closed-loop processing based on cross-correlation phase lock loop (PLL) and delay lock loop (DLL) are used to estimate the signal parameters. The proposed cross-correlation framework is thoroughly analysed theoretically, through simulations and using real data. The analysis shows the effectiveness of the cross-correlation framework.