Detection of synchronous spoofing on a GNSS receiver using weighed double ratio metrics

Spoofing signal detection is an essential process in GNSS anti-spoofing. The detection probability of the existing metrics degrades significantly for many specific combinations of relative code phases and carrier phases of the spoofing signal relative to the authentic signal. To improve detection, we propose a four-complex-correlator metric, called weighted double ratio (WDR), which first constructs a metric named RatioQ exploiting the quadra-phase correlation outputs and then combines two pairs of complex correlators separated by a large correlator spacing and weighted according to their noise levels to form a WDR. Theoretical analysis and simulation results show that the detection coverage rate, the receiver operating characteristic, and the detection probability versus different carrier to noise ratios are significantly improved. The experiment using the Texas spoofing test battery data in all eight cases demonstrates that the proposed method outperforms the existing metrics, especially for high spoofing-signal-ratios and the unlocked-frequency mode.