CU-UP

srsRAN Project CU-UP implementation.

The CU-UP, or Central Unit - User Plane, is responsible for the handling of user plane messaging. Specifically the user plane aspect of the PDCP and SDAP protocols. In the implementation of the CU-UP, there are four main components and four main interfaces. The CU-UP communicates directly with the UPF in the 5G Core (via the N3 interface), the CU-UP (via the E1 interface), the DU-high (via the F1-u interface) and can also be connected to the near-RT RIC (via the E2 interface).

Return to top level architecture diagram.

Components:

• UE Manager: Custom component for managing connected UEs in the CU-UP. Responsible for adding and removing UEs and providing relevant UE information to other processes. Communicates information to/from the CU-CP, DU and Core.

• GTP-U: The GPRS Tunneling Protocol - User Plane (GTP-U) is responsible for transporting User Plane traffic to and from the UPF of the 5G Core via the N3 interface.

• SDAP: The Service Data Adaptation Protocol (SDAP) is responsible for adaption and mapping of Quality of Service (QoS) requirements on User Plan traffic.

• PDCP: The Packet Data Convergence Protocol (PDCP) is responsible for handling the User Plane data before/ after it enters the DU-high.

Interfaces:

• E2: Interface with the near-RT RIC.

• E1: Interface with the CU-CP.

• F1-u: User plane interface with the DU.

• N3: User plane interface with the 5G Core (UPF).

---