3GPP 23.501 v20.2.0 — the document's own text

5.3.3.2.3 CM-CONNECTED state

Taught in 9. Registration, reachability and paging (The 5G system architecture, in depth), 4. Knowing who you are and where you are (The 5G system architecture, overview).

A UE in CM-CONNECTED state has a NAS signalling connection with the AMF over N1. A NAS signalling connection uses an RRC Connection between the UE and the NG-RAN and an NGAP UE association between the AN and the AMF for 3GPP access. A UE can be in CM-CONNECTED state with an NGAP UE association that is not bound to any TNLA between the AN and the AMF. See clause 5.21.1.2 for details on the state of NGAP UE association for an UE in CM-CONNECTED state. Upon completion of a NAS signalling procedure, the AMF may decide to release the NAS signalling connection with the UE.

In the CM-CONNECTED state, the UE shall:

enter CM-IDLE state whenever the AN signalling connection is released (entering RRC_IDLE state over 3GPP access or when the release of the UE-N3IWF connectivity over untrusted non-3GPP access or the UE-TNGF connectivity over trusted non-3GPP access is detected by the UE), see TS 38.331 [28] for 3GPP access.

When the UE CM state in the AMF is CM-CONNECTED, the AMF shall:

enter CM-IDLE state for the UE whenever the logical NGAP signalling connection and the N3 user plane connection for this UE are released upon completion of the AN Release procedure as specified in TS 23.502 [3].

The AMF may keep a UE CM state in the AMF in CM-CONNECTED state until the UE de-registers from the core network.

A UE in CM-CONNECTED state can be in RRC_INACTIVE state, see TS 38.300 [27]. When the UE is in RRC_INACTIVE state the following applies:

UE reachability is managed by the RAN, with assistance information from core network;
UE paging is managed by the RAN.
UE monitors for paging with UE's CN (5G S-TMSI) and RAN identifier.