L.2 UE specific behaviour

23.1673GPPIP Multimedia Subsystem (IMS) emergency sessionsRelease 17TS

Procedure for determining the list of emergency numbers:

– In addition to the emergency numbers and associated types stored either on the USIM or on the user equipment specified in clause 10.1.1 of TS 22.101 [8], the UE shall use the stored Local Emergency Numbers List received from the 3GPP network to detect that the number dialled is an emergency number.

– If a UE has a SIM/USIM and has received a list of emergency numbers and associated types or URN information via mobility management procedures as described in TS 24.301 [33] and TS 24.008 [13] when connected to the PLMN using GERAN, UTRAN, E-UTRAN, or TS 24.501 [52] when connected to NG-RAN or non-3GPP access connected to 5GC, or, for a UE supporting access to EPC via WLAN, as specified in Annex J, the UE shall use this list to determine if the dialled digits correspond to an emergency call as long as the UE has determined that the list is valid (see clause 4.1).

NOTE: How the UE uses two lists (a list of emergency numbers and associated types or URN information received via mobility management procedures and , for a UE supporting access to EPC via WLAN, a list as specified in Annex J) is a stage 3 decision.

– The list of downloaded emergency numbers shall be deleted at country change or, if the particular list is only valid for a PLMN (see clause 10.4.1 of TS 22.101 [8]), at successful registration with a different PLMN.

For the specific case where the UE has selected to make an emergency call over non-3GPP access to 5GC (hence the UE has detected that the target URI or dialled digits correspond to an emergency sessions), the UE shall use the following procedures:

– The UE shall establish an emergency PDU session over non-3GPP and shall perform an IMS emergency registration before sending an IMS emergency session request.

– The UE shall include any available location information in the IMS emergency session request. This is further detailed in TS 23.228 [1].

– For the media supported during IMS emergency sessions, media codec and format support is specified in TS 26.114 [34].

A UE shall not establish an emergency PDU session over non-3GPP access if the UE initiated a normal (i.e. non-emergency) session and is subsequently informed by the network that the ongoing session is accepted by the network even though it is an emergency session.