School of Specs 23.501v20.2.0

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

5.16.3.6 Terminating domain selection for IMS voice

Taught in 21. Emergency calls, messages, voice and location (The 5G system architecture, in depth).

When requested by IMS, the UDM/HSS shall be able to query the serving AMF for T-ADS related information. T-ADS is a functionality located in the IMS and is performed as specified in TS 23.221 [23].

The AMF shall respond to the query with the following information unless the UE is detached:

  • whether or not IMS voice over PS Session is supported in the registration area (s) where the UE is currently registered;
  • whether or not IMS voice over PS Session Supported Indication over non-3GPP access is supported in the WLAN where the UE is currently registered;
  • the time of the last radio contact with the UE; and
  • the current Access Type and RAT type.