Performance Evaluation of Multimodal Detection Method for GNSS Intermediate Spoofing

Abstract

With the appearance of Global Navigation Satellite Systems spoofers, anti-spoofing has become a pressing issue. Intermediate spoofing is performed at a power only slightly higher than that of an authentic signal; therefore, it is quite difficult to detect counterfeit signals in real time via current detection methods. Multimodal detection is a well-known method for detecting counterfeit signals. However, it is often used in the acquisition stage, and thus, its effective time is very short. In this paper, we define the searching process as when the acquisition module does not need to find new signals. In addition, we utilize multimodal detection to detect intermediate spoofing in the acquisition module when performing the searching process, which is almost real time and can address the condition of arbitrary signal intervals. The acquisition module is used to monitor the signals that are being tracked; if we find at least two peaks above a threshold, we declare that counterfeit signals are detected. Then, we define an evaluation standard and provide a theoretical performance calculation method. An empirical formula is proposed to calculate the method's performance. By analyzing the effect of five influencing factors, we better understand the empirical formula and obtain the conclusion that, by decreasing the code phase's search step, we can obtain better detection results. The results are desirable for designing anti-spoofing receivers.