What is O-RU / O-DU / O-CU?
O-RU, O-DU, and O-CU are the O-RAN compliant versions of the Radio Unit, Distributed Unit, and Centralised Unit in the disaggregated 5G RAN architecture. The ‘O-‘ prefix indicates that these components follow Open RAN standards defined by the O-RAN Alliance, enabling multi-vendor interoperability through open, standardised interfaces. This disaggregation allows operators to mix and match components from different vendors, promoting competition, innovation, and cost reduction in RAN deployment.
How Does O-RU / O-DU / O-CU Work?
The O-RU handles lower-PHY processing and RF functions: it converts digital signals to/from radio waves, performing operations like beamforming, IFFT/FFT, and cyclic prefix insertion/removal. The O-DU handles upper-PHY, MAC, and RLC layer processing: scheduling, HARQ, channel coding, and modulation. The O-CU handles PDCP, SDAP, and RRC: ciphering, header compression, mobility management, and QoS mapping. The open fronthaul interface (defined in O-RAN WG4) connects O-RU to O-DU using eCPRI or RoE over Ethernet. The F1 interface (3GPP) connects O-DU to O-CU. Additionally, the O-RAN architecture includes the RIC (RAN Intelligent Controller) connected via E2 (near-RT RIC) and A1 interfaces, enabling AI/ML-based RAN optimization.
Use Cases
Open RAN multi-vendor 5G deployments, greenfield operators building cost-efficient networks, brownfield operators diversifying their vendor ecosystem, rural coverage expansion with lower-cost RAN solutions, and enterprise private 5G with flexible architecture.
3GPP / Standards Reference
O-RAN Alliance specifications (WG1 Architecture, WG4 Open Fronthaul, WG3 Near-RT RIC), 3GPP TS 38.401 (CU/DU split)
Related Terms
Open RAN | O-RAN | C-RAN | Fronthaul | BBU
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This glossary entry is part of the 5GWorldPro Complete 5G Glossary. To go deeper into 5G architecture and technology, explore our 5G Training courses.
