5 General architecture

38.4013GPPArchitecture descriptionNG-RANRelease 17TS

5.1 General

The protocols over Uu and NG interfaces are divided into two structures:

– User plane protocols

These are the protocols implementing the actual PDU Session service, i.e. carrying user data through the access stratum.

– Control plane protocols

These are the protocols for controlling the PDU Sessions and the connection between the UE and the network from different aspects (including requesting the service, controlling different transmission resources, handover etc.). Also a mechanism for transparent transfer of NAS messages is included.

5.2 User plane

The PDU Session Resource service is offered from SAP to SAP by the Access Stratum. Figure 5.2-1 shows the protocols on the Uu and the NG interfaces that linked together provide this PDU Session Resource service.

Note 1: The radio interface protocols are defined in TS 38.2xx and TS 38.3xx.

Note 2: The NG interface protocols are defined in TS 38.41x.

Figure 5.2-1: NG and Uu user plane

5.3 Control plane

Figure 5.3-1 shows the control plane (signalling) protocol stacks on NG and Uu interfaces.

Note 1: The radio interface protocols are defined in TS 38.2xx and TS 38.3xx.

Note 2: The protocol is defined in TS 38.41x. (Description of NG interface).

Note 3: CM, SM: This exemplifies a set of NAS control protocols between UE and 5GC. The evolution of the protocol architecture for these protocols is outside the scope of the present document.

Figure 5.3-1: NG and Uu control plane

NOTE: Both the Radio protocols and the NG protocols contain a mechanism to transparently transfer NAS messages.