A Slowly Varying Spoofing Algorithm for Tightly-Coupled GNSS/IMU with Multiple Anti-spoofing Techniques

Satellite navigation user terminals will be seriously affected if they are not specially protected against signal interference and even spoofing. GNSS spoofing technology has gradually become the focus of jamming technology research because of its great threat and high concealment. In the face of navigation users increasingly adopt coupling GNSS and IMU to varying degrees and configuring a variety of anti-spoofing technologies to detect spoofing, even if the spoofing is carried out slowly, if the spoofing strategy is unreasonable, it will lead to the estimated parameters of the coupled filter output, or the spoofing measurement does not meet the reasonable range, which will lead to the detection of spoofing and greatly increase the difficulty of spoofing. In view of the above problems, in order to effectively counteract the unidentified object equipped with tightly-coupled navigation system by using spoofing technology, this paper establishes the GNSS spoofing model, based on the analysis of the influence mechanism of spoofing on tightly-coupled GNSS/IMU positioning, a slowly varying spoofing algorithm is proposed to spoof tightly-coupled GNSS/IMU system for configuring the least squares residual RAIM and verification and inspection of reasonable range of parameters, the algorithm gives a measurement deviation determination method to avoid a variety of anti-spoofing technologies. The algorithm can gradually pull the positioning results of the tightly-coupled system, and successfully avoid the detection of a variety of anti-spoofing technologies to achieve the purpose of spoofing. The experimental results show that the algorithm can gradually change positioning of tightly-coupled GNSS/IMU within 72 s, and the north displacement completely achieves purpose of spoofing, the east and down displacement basically achieve purpose of spoofing, the errors with the expected offset are 2.3 m and 13 m respectively. At the same time, it avoids the detection of the above anti-spoofing techniques. The mean value of test statistics for tightly-coupled is reduced by 83.1% and does not exceed alarm threshold, so as to achieve the purpose of spoofing, so that the spoofing algorithm has high concealment and application value.