O²-RAN: Orbital Open RAN for Non-Terrestrial Networks and Space-Based Edge Computing

Non-Terrestrial Networks (NTNs) are rapidly becoming a foundational element of global connectivity, extending coverage and capacity through the integration of terrestrial, airborne, and spaceborne communication platforms. The Open Radio Access Network (O-RAN) architecture, grounded in disaggregation, open interfaces, and intelligent control, provides a promising foundation for orchestrating heterogeneous and dynamic communication systems. However, applying O-RAN principles to NTNs introduces distinct challenges, including limited onboard compute and energy resources, highly dynamic topologies, and latency-sensitive control across spatially distributed domains. This paper introduces O<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>-RAN, a unified architectural framework designed to support multi-layer, multi-segment NTN deployments. We examine the placement and coordination of key O-RAN components across terrestrial, aerial (e.g., HAPS, UAVs), and orbital (LEO, GEO) segments, and analyze the associated trade-offs, particularly in terms of latency, control distribution, and resource constraints. The discussion highlights architectural strategies for enabling resilient, adaptive, and resource-efficient orchestration across NTN infrastructures, paving the way for scalable and autonomous O-RAN deployments in future NTNs.