Analysis of Signal Authentication and OSNMA Performance in Urban Scenarios

This work evaluates the availability and performance of GNSS authentication in a challenging urban environment using Open Service Navigation Message Authentication (OSNMA) and Assisted Signal Authentication Service (A-SAS). OSNMA allows to authenticate the I/NAV navigation message transmitted on the Galileo E1BC signal. Signal authentication validates the pseudoranges of the Galileo E1 and E5 signals by comparing them with the ones from the encrypted E6C signal. The evaluation of these two methods has been conducted on an E1/E6 recording from an urban drive in Nuremberg, which has then been replayed on a GNSS hardware receiver using different receiver settings. OSNMA achieved consistent authentication after KROOT initialization, with an average of four authenticated satellites per subframe. Signal authentication successfully acquired sufficient satellites for a potential authenticated Position, Velocity, and Time (PVT) in 82.8% of snapshots, with a 0.26% false alarm rate when using live data. After initialization, authenticated PVT was available for 91.3% of the time relative to non-authenticated PVT. These results indicate that authenticated PVT is feasible in urban scenarios, with initialization and parameter tuning being the primary practical constraints.