Enhanced Authentication Based on Angle of Signal Arrivals

In the scope of vehicular communication networks, the nature of exchanged safety/warning messages renders itself highly location dependent, as it is usually for incident reporting. Vehicles are required to periodically exchange beacon messages that include speed, time, and GPS location information. Reported position information must be accurate and authentic. To mitigate the potential risk of location spoofing/falsifying attack, this paper presents Angle-of-Arrival (AoA) estimation as a physical layer authentication scheme for cross verification of the reported location information. We consider a multi-antenna road side unit under location spoofing attack. Within the considered vehicular communication settings, fundamental limits of AoA estimation are developed in terms of its Cramer-Rao Bound and existence of efficient estimator. The problem of deciding whether the received signal originated from the claimed GPS location is formulated as a two-sided hypotheses testing problem whose solution is given by Wald test statics. We give correct decision P-D and false alarm P-F probabilities in a closed form. To offset the gap between information theoretical studies and practical implementations of physical layer security architectures, theoretical results presented in this paper are further supported by detailed hardware implantation using software-defined radios and field experimental results. We show that the keystone for obtaining reliable AoA measurements is the accurate characterization of the array response vector. Our hardware measurements showed that, unlike idealized models, hardware imperfections leave the actual array response vector of non-structured form. To address this problem, we introduce the method for obtaining the actual array response vector empirically, which led to accurate and stable AoA measurements. Field experimental results shows the feasibility of the proposed AoA authentication scheme.