CU-CP

The CU-CP (Central Unit - Control Plane) is responsible for handling control plane messaging, specifically the control plane aspect of the PDCP protocol. The CU-CP communicates directly with the AMF via the N2 interface, the CU-UP via the E1 interface, the DU-high via the F1-c interface, and optionally with the near-RT RIC via the E2 interface. This implementation takes a UE-centric approach.

Components

• CU-UP Processor: Handles each CU-UP connected to the CU-CP. Multiple CU-UPs can be connected to a single CU-CP; the E1AP is instantiated inside the CU-UP Processor for each connected CU-UP.
• DU Processor: Handles each DU connected to the CU-CP. Each connected DU has its own DU Processor with bundled F1AP, PDCP, and RRC procedures. Each connected UE also has its own RRC UE instance containing the PDCP processes.
• UE Manager: Manages connected UEs in the CU-CP. Responsible for adding and removing UEs and providing relevant UE information to other processes. Communicates UE information to and from the CU-UP, DU, and Core.
• Measurement Manager: Manages cell measurement within the gNB.
• Mobility Manager: Manages UE mobility in the CU-CP.

Interfaces

Interface	Connects to
E2	Near-RT RIC
E1	CU-UP
F1-c	DU (control plane)
N2	AMF