GNSS-dependent positioning, navigation, and timing synchronization procedures have a significant impact on everyday life. Thus, such an extensively used system progressively become an attractive target for illegal exploitation and attacks. Position and timing solutions provided by GNSS receivers can be threatened by structural interference such as spoofing threats. This paper provides an overview of recent research work on GNSS signal authentication utilizing spatial processing methods. Different spatial processing approaches for spoofing detection, classification and mitigation are characterized and compared. Three different processing methods, namely antenna array processing, moving receiver and cloud based spoofing countermeasure are analyzed in details. The benefits and disadvantages of each are discussed.

Several terrestrial communication systems use the same frequency spectrum as Global Navigation Satellite Systems (GNSS) or bands close to it. Pseudolites constitute one such system that generally uses the GNSS spectrum for signal propagation. The signals from pseudolites in the operating region play a crucial role in augmenting satellite based user navigation. These signal transmitters are deployed at ground stations for the majority of their applications. In the near region, pseudolites are overpowered and cause impediments to normal receiver operation due to an increase in the noise floor. Interference and jammers form another source of GNSS disruption. Interference could result from intentional jammers or unintentional signal disturbances from in-band or out-of-band high power sources. A GNSS user can experience interference from near region pseudolites as well as from other interferers. These interference sources may have directional coexistence with pseudolites or GNSS satellites. Such disruptions might completely block signal acquisition and lead to processing failure. The capability of antenna array space-time processing to counter the above mentioned scenario is demonstrated herein. In addition to interference mitigation, pseudolite signal recovery in the near region and subsequent enhancements are shown. Results that demonstrate improvement in measurement geometry for various antenna array configurations and different processing modes are also shown.