gNB-CU
gNB-CU implements the higher layers of the NR protocol stack (RRC, PDCP, and the SDAP control functions) as an independent, scalable network function, connecting northbound to the 5GC and southbound to one or more gNB-DUs over the standard F1 interface.
Key features
- Split CU-CP / CU-UP deployment per 3GPP option 2 (E1 interface)
- RRC and PDCP layer termination with dual connectivity (EN-DC / NR-DC) support
- F1AP-based control of multiple gNB-DUs from a single CU
- O-RAN aligned northbound interfaces for O-RAN SMO / non-RT RIC integration
- Elastic scaling of CU-UP independent of CU-CP for high-throughput sites
- Native carrier aggregation and mobility (Xn-based handover) support
Governing 3GPP & O-RAN specifications
These are the primary specifications this product implements or interoperates against. NgRAN tracks each release train and updates products as specifications evolve.
| Specification | Title / scope |
|---|---|
| 3GPP TS 38.401 | NG-RAN architecture description — CU/DU functional split |
| 3GPP TS 38.470 / 38.473 | F1 general aspects & F1AP (CU ↔ DU) |
| 3GPP TS 38.460 / 38.463 | E1 general aspects & E1AP (CU-CP ↔ CU-UP) |
| 3GPP TS 38.331 | Radio Resource Control (RRC) protocol specification |
| 3GPP TS 38.323 | Packet Data Convergence Protocol (PDCP) specification |
Specification titles are summarised for reference. Full texts are maintained by 3GPP (3gpp.org) and the O-RAN ALLIANCE and are not reproduced here.
Architecture & interfaces
gNB-CU follows the 3GPP 38.401 functional split, hosting RRC and PDCP above the F1 interface while radio-time-critical layers remain on the DU. CU-CP and CU-UP can be scaled independently across the E1 interface, letting operators grow user-plane throughput without re-provisioning control-plane capacity, and vice versa — the core principle of disaggregated RAN.
Reference interfaces
Deployment model
Cloud-native CNF on COTS x86/ARM servers, container-orchestrated, O-Cloud / O-RAN SMO compatible.