Assessment of Cyber-Secure GBAS Using Adaptive Beamforming in the Presence of Interference

Kurzfassung

The Ground Based Augmentation System (GBAS) provides integrity-assured differential corrections for aircraft precision approaches. As GBAS evolves toward multi-frequency, multi-constellation operation to increase global availability, its dependence on GNSS signals susceptible to jamming and spoofing becomes a growing cybersecurity vulnerability. This paper presents an experimental assessment of a cyber-secure GBAS architecture that replaces conventional single-element antennas with controlled reception pattern antennas (CRPAs) combined with adaptive beamforming on both the ground and airborne segments. The system, developed within the DLR project CySNAB (Cyber-Secure Navigation for Aviation and Beyond), employs the internally developed GALANT array receiver platform, which ensures carrier-phase stability during beamforming through an additional compensation step. Extensive validation was performed during multi-day flight trials and live jamming/spoofing campaigns at the DLR research airport in Cochstedt, Germany. Three key aspects of resilient GBAS performance are evaluated: tracking stability, integrity monitor behaviour, and ground noise/multipath models. Results demonstrate that the CRPA-based system maintains carrier-phase continuity and code-carrier alignment during active interference, whereas conventional single-antenna receivers exhibit severe code-carrier divergence and ultimately lose track. The code-carrier divergence rates of the resilient system remain within nominal ranges even under jamming, supporting continuous GBAS services. Furthermore, residual ground noise and multipath models derived during interference tests indicate compliance with the most demanding GAD-C (Ground Accuracy Designator) requirements for both L1/E1 and L5/E5a frequencies across GPS and Galileo. In contrast, commercial single-antenna receivers used as reference could, as expected, not compute smoothed corrections during interference tests. These findings indicate that a CRPA-based resilient GBAS can preserve measurement quality and integrity-monitor behaviour under intentional interference supporting the feasibility of continuity and availability of GBAS service during interference, representing one step toward cyber-resilient precision approach operations