Calculation of the lower limit of the spoofing-signal ratio for a GNSS receiver-spoofer

A receiver-spoofer is one of the most covert global navigation satellite system (GNSS) spoofing attacks and can only be effectively detected by the combination of multiple anti-spoofing technologies. In this paper, an analysis of influencing parameters for receiver-spoofers indicates that the ratio of the spoofing signal amplitude versus the authentic signal amplitude (spoofing-signal ratio) is a key parameter for spoofing results. For a spoofer to ensure covertness, the goal is to maintain a low spoofing-signal ratio. The carrier phase difference and code phase difference between authentic signals and spoofing signals resulted in errors in the position estimation of the target receiver increase the lower limit of the spoofing-signal ratio required for successful spoofing. A spoofing signal alters the phase of local replicate code based on the original balance of a receiver phase discriminator to seize control. Based on this principle, the lower limit of the spoofing-signal ratio that corresponds to various phase discriminator spacings, carrier phase differences, and code phase differences is deduced in this paper. Two tests are designed for the simulation source and authentic navigation signals to verify the deduced formula. The lower limit of the spoofing-signal ratio obtained from these tests matches the calculated results, which proves the validity and effectiveness of the derived algorithm.