Synchronization Plane in O-RAN: Overview, Security and Research Directions

Under the efforts to transition to an open radio access network (RAN), movements like O-RAN have emerged. One of these movements' goals is opening RAN interfaces (like the open fronthaul (O-FH)), to break the vendor lock-in of RAN resources. However, this raises concerns about RAN's security especially in elements that are bound to latency and performance requirements like the O-FH's synchronization plane (S-plane). In this article, we provide a comprehensive discussion of S-plane threats following O-RAN architecture, considering used synchronization protocols and mandatory security requirements. Further, we discuss the identified threats' impact on S-plane synchronization topologies and comment on possible countermeasures. Finally, we leverage O-RAN properties and benefits to propose future research directions for better S-plane security.