In recent years, various new portable global navigation satellite system (GNSS) spoofers have emerged that have become an important threat to the integrated inertial navigation system (INS)/GNSS. The spoofing strategies have become increasingly advanced and the spoofer gradually adjusts the counterfeit signals to covertly take over the target receiver. The existing anti-spoofing algorithms based on INS/GNSS integration show the shortcomings of the reduced detection probability, and the inability to mitigate spoofing. In this study, the multipath estimating delay lock loop (MEDLL), originally designed for multipath mitigation is used in conjunction with INS to suppress the spoofing attacks. First, a bank of correlators is employed to estimate the spoofing and authentic signals. Second, a new spoofing validation and mitigation structure is proposed based on the tightly coupled INS/GNSS integrated system. Finally, the INS-aided reacquisition and spoofing suppression method is derived. The simulated INS measurements were used together with Texas Spoofing Test Battery datasets to evaluate the performance of the proposed anti-spoofing algorithm. The results showed that the spoofing attacks were detected within 1 s and the positioning errors decreased from 600 m to 12.9 m. The proposed algorithm can suppress different types of spoofing attacks and ensure reliable positioning and timing results in various complex threat environments.

Global navigation satellite systems (GNSSs) are widely used in various fields to provide high-precision timing. However, their low signal power and open signal structure render GNSS receivers vulnerable to time synchronization attacks (TSAs). In this study, we propose a novel single-antenna-based TSA mitigation algorithm. First, a multicorrelator estimator was adopted to calculate the parameters of the authentic and counterfeit signals. Then, the predicted pseudorange was derived for spoofing validation, and the counterfeit signals were subtracted. Finally, a robust extended Kalman filter was adopted to resist gross errors in the estimation results. A series of Monte Carlo simulations were conducted to evaluate the performance of the proposed method with different relative delays and power advantages of the spoofing signals. The Texas Spoofing Test Battery spoofing datasets were used in the experiments to verify the effectiveness of the proposed algorithm. The results indicated that the timing errors decreased from $2.0~\mu \text{s}$ (600 m) to 53.4 ns (16 m), and the spoofing signals were considerably mitigated. The proposed anti-spoofing algorithm can ensure the availability of GNSS timing under TSAs and only requires a single antenna, greatly simplifying the GNSS receiver installation and reducing costs.

Under harsh propagation conditions, Global Navigation Satellite Systems (GNSS) receivers are susceptible to signal degradation, which can lead to loss of signal lock. Unlocked receivers, when subjected to spoofing attacks, are highly susceptible to false re-acquisition, and their tracking-stage anti-spoofing algorithms may become ineffective, thereby simplifying the execution of spoofing interference. Compared to the traditional scalar tracking loop (STL), the vector tracking loop (VTL) demonstrates superior performance in maintaining Positioning, Navigation, and Timing (PNT) service continuity in complex environments. Therefore, this study designs an enhanced VTL by developing an adaptive loop controller and constructs a composite interference scenario using the Oak Ridge Spoofing and Interference Test Battery (OAKBAT) database to compare the anti-spoofing performance of STL and VTL under various application challenges. In the os2 scenario, the STL’s root mean square (RMS) value of the receiver clock error increases sharply to 601.1 m owing to the re-acquisition, while the VTL is not affected by the signal interruption. In the os4 scenario, the RMS value of its position solution deviation was reduced by 66.35% and 80.83% compared with that of the STL before and after signal interruption, respectively. The study demonstrates that VTL, empowered by an Extended Kalman Filter (EKF) and interchannel cooperation, possesses significant anti-spoofing advantages in adverse environments. These findings highlight the significant advantages of VTL in improving the endogenous security of GNSS receivers and provide key insights for designing anti-spoofing algorithms for challenging environments.