Assessing Spoofer Impact on GNSS Receivers: Tracking Loops

In the context of global navigation satellite systems (GNSSs), synchronization is crucial for successfully decoding the navigation message and accurately estimating pseudoranges. Synchronization of each received GNSS signal typically involves at least two tracking loops: a delay lock loop (DLL) and a phase lock loop (PLL). The reception of a spoofed signal disrupts the synchronization process, potentially leading to erroneous pseudorange estimation or loss of service. This paper investigates the impact of spoofing on code, carrier phase, and frequency tracking estimates and proposes a transformation-based strategy to characterize the joint DLL and PLL under spoofing, focusing on the system’s stable equilibria (SE), linearity and interdependence, transient response, and noise impact. The study reveals the nonlinearity and interdependence of the tracking loops (i.e., the PLL and DLL cannot be considered separately) and shows the emergence of multiple SE, leading to potential chaotic behavior and bifurcation.