STFT-based method applied to GNSS spoofing estimation, mitigation and discrimination from multipath

Spoofing attacks are threatening the global navigation satellite system (GNSS). GNSS receivers are vulnerable to spoofing attacks because the power of received GNSS signals is very low and the details of civilian signals are open to the public. The spoofing attack is potentially more hazardous than jamming since the target receiver is not aware of this threat and it is still providing position solutions which seem to be reliable. The robustness and security of GNSS have attracted worldwide attention, and the anti-spoofing technology of navigation signals is in urgent need. Fast Fourier Transform (FFT) is a parametric multipath estimation method implemented in the frequency domain for BOC signals. Since the correlation function distortion of the authentic and spoofing mixture signals is similar to that of multipath, we find the above method also has a potential ability for GNSS anti-spoofing. Motivated by developing a more feasible spoofing estimation and mitigation technique with acceptable computational load, we extended the method to anti-spoofing by means of the short-time Fourier transform (STFT). Both formulae and simulations are provided to evaluate the anti-spoofing performance. Experiments with recordings in real GNSS spoofing scenarios are also performed to validate the practicability of the approach. Results indicate that the proposed STFT-based anti-spoofing method is capable of estimating the spoofing parameters and then removing the spoofing effect from the tracking loop. In addition, when considering multipath environments, this paper discussed a way to classify the authentic, spoofing and multipath components in the composite signal by analyzing the characteristics of the estimated parameters. Thus, even in the degraded environments, the proposed method is able to identify the potential spoofing attack and minimize the false alarm rate caused by multipath.