ETD

• 5g
• anomaly detection
• flexric
• ntn
• o-ran
• openairinterface
• regenerative payload
• security
• xapp

Connecting the world through satellites and aerial networks is becoming increasingly important for 5G. These systems face very different security challenges than traditional ground-based networks; ensuring their security has become a critical priority.

In this work, we investigate the impact of Buffer Status Report attacks in 5G NTN environments, where malicious UEs forge a BSR request to illegitimately exhaust PRBs, thereby disrupting service for legitimate users. To mitigate this threat, we propose a security monitoring xApp built on the O-RAN architecture that continuously validates what users claim they will send against what they actually transmit. Since satellite connections experience variable signal quality, we designed the system to dynamically adjust its detection sensitivity based on real-time channel conditions.

We validated our approach using experimental testbed equipment that emulates a satellite network environment. The results demonstrate that our monitoring system reliably identifies attacks across different signal conditions while maintaining an optimal balance between detecting threats and preserving legitimate user traffic. This work underscores the potential of xApps tailored to protect 5G NTN resources without requiring modifications to existing 3GPP protocol standards.