Spoofer Detection and Suppression in GPS Using Auto-regressive Spectrum Estimation in the Code Domain

Spoofing in the Global Positioning System (GPS) is a major concern in an increasing threatening environment. Existing spoofer mitigation techniques rely on having multiple antenna elements that identify spoofers based on their direction-of-arrival (DoA). But these techniques often require an antenna array at the receiver and/or assume a single spoofer. It is desirable to have a technique that is more robust to multiple spoofers, regardless of their DoA. In this paper, we propose a simple, single antenna technique using auto-regression spectrum estimation (ASE), with respect to the GPS codes, not DoA. The method is based on a previously proposed ASE technique for detecting synchronous codes in the forward link of code division multiple access (CDMA) systems. The ASE method shows, via a ‘code spectrum’, which GPS codes are present in the environment. The magnitudes of the spectral peaks allow us to easily determine whether the code is a signal-of-interest (SOI) or a spoofer. Demodulation using only valid codes allows for spoofers to simply be ignored. Asynchronous spoofers and multipath components are similarly ignored. Simulations show that we can detect codes with a probability of detection <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(P_{D})\approx 99\%$</tex> at an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$E_{chip}/N_{0}$</tex> of -10 to -13 dB, with a false alarm rate of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$P_{FA} &lt; 0.003$</tex>, when the spoofer power is just 1 to 2 dB greater than that of the GPS SOIs, if the spoofer power gradually increases.