Using the Receiver Clock Offset Abnormal to Prove the Existence of Spoofing Signal

Abstract

To make the receiver get wrong positioning, the existence of spoofing signal causes the change of pseudorange and results in the abnormality of the receiver clock offset. Based on the relationship equation of satellite position, receiver position, receiver clock offset and pseudorange, Taylor expansion is made at two different points for the equation, and the least square method is used to solve it, then receiver clock offset calculated value can be obtained. We can get current receiver clock offset reference value by using second-order polynomial fitting and extrapolation for the previous data. The difference between the calculated value and the reference value is used as the influence of spoofing signal on the receiver clock offset. Combining the parameter matrix from two times Taylor expansion and the difference of receiver clock offset, we can get each satellite corresponding pseudorange bias value. Then we can use the bias values to modify the pseudorange, and use the least square iterative method to solve it and get the receiver's real position. From four schemes, including whole-satellite repeater deception jamming, whole-satellite generated spoofing, part-satellite repeater deception jamming and part-satellite generated spoofing, we verify the performance of the algorithm. The simulation results show that pseudorange bias values caused by the spoofing signal can be estimated effectively by the algorithm, and the existence of spoofing signal can be proved. Also, we can determine the signal's type, and get the receiver's real position by modifying the pseudorange.