E  Emergency support in different IP-CANs  Word‑p. 43

Support for emergency services in the IP Multimedia Core Network can be provided by certain IP-CANs according to Table E.1, which shows the level of possible emergency support in this version of the specification. The UE may be able to use also other IP-CANs that are not included in Table E.1 to access emergency services in the IP Multimedia Core Network, but the support of such access technologies is out of scope of this specification.

Table E.1: Support for IMS Emergency Services by Different IP-CANs

IP-CAN	Normal Access	Emergency support	Insufficient Security Credentials
GPRS (UTRAN)	X	X	X
Fixed Broadband	X	X	X
cdma2000 HRPD/PDS	X	X	X
cdma2000 HRPD/EPC	X	X	X
EPS (UTRAN and E-UTRAN)	X	X	X
WLAN access to EPS	X (Note 1)	X	–
5GS (NG-RAN)	X	X	X
non-3GPP access to 5GC	X (Note 1)	X	–

The term "normal access" in Table E.1 means that the IP-CAN is not made aware of the UE intent to establish an emergency services session and therefore provides no special emergency support e.g. call priority.

The term "emergency support" in the table means that the IP-CAN is made aware of the UE intent to establish an emergency services session, or at least of the priority nature of the access, so that the access network is able to handle the emergency call with appropriate priority.

The term "insufficient security credentials" in the table means that the IP CAN is able to allow a UE with no UICC card or a UICC card with insufficient credentials to obtain IP bearer access for emergency services in the IP Multimedia Core Network.

F (Normative)  IMS Emergency Services Using HRPD/PDS Network  Word‑p. 44

F.1  cdma2000 HRPD/PDS Options |R8|

The following options from the normative clauses of this TS are applicable in cdma2000 HRPD systems with a PDS core network:

1. Clause 7.1.1, step 4 "The IP-CAN may support a UE indication that this request is for an emergency service".

The following options from the normative clauses of this TS are not applicable in cdma2000 HRPD/PDS systems:

1. Clause 4.1 "The P-CSCF serving the emergency call is the IMS network entity which may retrieve the location identifier from the IP CAN".

F.2  Requirements on the HRPD Network as an IP-CAN |R8|

For an emergency call over HRPD, the requirements on the IP CAN are specified in 3GPP2 X.S0060 [25].

F.3  Information Flows |R8|

The informational flows for emergency calls over HRPD are provided in 3GPP2 X.S0060 [25].

G  TEL URI provisioning considerations for IMS emergency call back |R8|  Word‑p. 45

In order to support emergency call-back from the PSTN or CS Domain:

• For a single or multiple device subscription that contain both a SIP URI and TEL URI in at least one implicit registration set for each device (including subscriptions that share SIP-URIs and TEL URIs between devices), IMS emergency sessions can already be supported. If the user registers with a temporary public user identity (e.g. the subscription has a device containing a USIM) ensure that a TEL URI is provisioned in the same implicit registration set as the temporary public user identity.
• For a multiple device subscription that has TEL URIs for some devices but has one or more devices that are not assigned an implicit registration set containing a TEL URI (e.g. because these devices in the subscription are not allowed to use a TEL URI in normal originations), the existing TEL URIs in the subscription cannot be shared between all devices for the purposes of IMS emergency sessions.

H (Normative)  IMS emergency services using UTRAN, E-UTRAN and NG-RAN radio access network |R9|  Word‑p. 46

H.1  General

This annex includes additional requirements and clarifications when the IP-CAN is a PS Domain supporting UTRAN, E-UTRAN or NG-RAN radio access network.

If a PLMN supports other emergency numbers than those listed in TS 22.101, the UE is connected to the PLMN using UTRAN, E-UTRAN or NG-RAN radio access network and the UE needs to know these other emergency numbers, then such emergency numbers shall be provided to the UE via the mobility management procedures as described in TS 24.301, TS 24.008 and TS 24.501.

For registration requests received from an emergency PDN connection or emergency PDU session, the P-CSCF shall reject any IMS registration which is not for the emergency purpose.

eCall is supported with E-UTRAN and NG-RAN. UE configured for eCall Only Mode can receive a PSAP call back for a limited duration following the termination of the eCall due to its specific mobility management procedures requirement as defined in TS 22.101.

H.2  UE specific behaviour

For the specific case where the UE has selected to make an emergency call over EPS, GPRS or 5GS the UE shall use the following procedures:

• A UE shall establish an emergency PDN connection or emergency PDU session and perform an IMS emergency registration before initiating a UE detectable emergency session via UTRAN, E-UTRAN or NG-RAN.
• A UE shall not establish an emergency PDN connection or emergency PDU session if the UE initiated a non UE detectable emergency session and is subsequently informed by the network that the ongoing session is an emergency session.
• If the UE initiates a non UE detectable emergency session, and the session initiation request is rejected by the P-CSCF with an indication that this is an emergency session, the UE shall select a domain according to the requirements for domain priority and selection in clause H.5 when applying the requirements in clause 7.1.2.
• A UE in 5GS shall not initiate establishment of an IMS emergency session over Non-3GPP access unless the emergency session could not be established via 3GPP access.
• If the UE has not been authenticated in the PS domain, the UE shall initiate an IMS emergency session establishment without registration according to clause 7.4.
• The UE shall include the latest available Cell Global Identification (CGI) in the IMS emergency request establishing the emergency call.
• If the UE is required to include an equipment identifier (according to clause 4.1 and clause 6.1) the equipment identifier shall be the IMEI.
• For the media supported during IMS emergency sessions in TS 22.101, clause 10.4, media codec and format support is specified in TS 26.114.
• UE shall only perform eCall procedure over IMS as specified in clause 7.7.1 when it detects the "eCall supported" indication as defined in TS 23.401 and TS 23.501.
• When PS access is available, but the UE does not detect the "eCall supported" indication as defined in TS 23.401 and TS 23.501, and there is no CS access available, the UE shall establish a regular IMS emergency call.
• If the broadcast indicators in an E-UTRA cell connected to 5G and EPC as defined in TS 23.501 indicate only one core network (EPC or 5GC) supports emergency services then the UE shall register to the core network which supports emergency services when the UE initiates emergency services. If broadcast indicators indicate that both 5GC and EPC support emergency services then the UE initiates emergency services to either EPC or 5GC according to the UE implementation.

H.3  High Level Procedures for IMS emergency calls  Word‑p. 47

For the high level procedures (as described in clause 7.1.1) the following statements apply for UE detected emergency calls when PS domain with UTRAN, E-UTRAN or NG-RAN access is used:

• the bearer registration to the IP-CAN is the PS attach or PS Registration procedure;
• the IP-CAN bearer resource is the PDP context for GPRS, EPS Bearer for EPS and QoS Flow for 5GS, and TS 23.060, TS 23.401 and TS 23.501 respectively describe how to indicate that the request is for emergency;
• the release of reserved bearer resources is the release of a PDP context, an EPS Bearer or a QoS Flow.

For the high level procedures (as described in clause 7.1.2) the following statements apply for Non UE detectable emergency calls when PS domain with UTRAN, E-UTRAN or NG-RAN access is used:

• The P-CSCF rejects the session initiation request with an indication that this is an emergency session; or
• the P-CSCF allows the session initiation request to continue and the E-CSCF informs the UE that it is an emergency session. Such a session will not use an emergency PDN connection or emergency PDU session and will not have SRVCC or SRVCC for IMS emergency session support.

For the IMS Emergency Session Establishment without Registration (as described in clause 7.4), P-CSCF retrieves the additional subscriber related identifier(s) from IP-CAN via PCC in TS 23.203 when PS domain with UTRAN and E-UTRAN access is used.

H.4  Location handling

The applicable location solutions are specified in TS 23.271 for control plane with UTRAN and E-UTRAN access, in TS 23.501 and TS 23.502 for control plane with NG-RAN access and in SUPL 2.0 (OMA AD SUPL [15], OMA TS ULP [16]) for user plane. For SUPL, SUPL Initiation Function using UDP/IP (OMA AD SUPL [15]) shall be supported by the SET.

If the operator policy requires network provided location using PCC-based solutions for the UE location (e.g. serving cell), the P-CSCF retrieves location information from the access network and includes it in the emergency service request, as described in TS 23.228. The UE location is marked as being network provided to distinguish it from location information that the UE provided.

If the operator policy requires network provided location using the LRF-based solution for the UE location (e.g. serving cell), the P-CSCF forwards the emergency request to E-CSCF. The E-CSCF retrieves location information from LRF as described in clause 6.2.2.

Operator policies in the P-CSCF and E-CSCF should be aligned to ensure that the E-CSCF doesn't attempt to retrieve location information from the LRF if network-provided location information is present in the initial emergency request. However, as described in clause 6.2.2, the E-CSCF may request the LRF to retrieve additional location information (e.g. the UE's geographical location information).

H.5  Domain Priority and Selection Rules for Emergency Session Attempts  Word‑p. 48

This clause details the domain priority and selection (see clause 7.3) for UE that attempts to make an emergency session for UTRAN, E-UTRAN or NG-RAN radio access networks based on the UE attach status to CS or PS domains and the network support for IMS emergency and IMS voice over PS.

The following table (Table H.1) defines these rules based on the UE (last 2 columns) for different initial conditions (first 4 columns) when an emergency session is initiated and when the UE is not in limited service state.

For NG-eCall (eCall over IMS) domain selection in clause H.6 applies. This clause is not applicable for NG-eCall.

Table H.1: Domain Selection Rules for emergency session attempts for UTRAN, E-UTRAN or NG-RAN radio access networks

	CS Attached	PS Attached	VoIMS	EMS	First EMC Attempt	Second EMC Attempt
A	N	Y	Y	Y	PS	CS if available and supported (Note 7)
B	N	Y	N	Y	PS or CS if the emergency session includes at least voice. PS if the emergency session contains only media other than voice.	PS if first attempt in CS CS if first attempt in PS (Note 7)
C	N	Y	Y or N	N	PS if ESFB is "Y" (Note 5). Else CS or PS for another 3GPP RAT with EMS or ESFB set to "Y" if available and supported and if the emergency session includes at least voice. Else PS for another 3GPP RAT with EMS or ESFB set to "Y" if available and supported if the emergency session contains only media other than voice.	PS if first attempt in CS CS if first attempt in PS Note 7)
D	Y	N	Y or N	Y or N	CS if the emergency session includes at least voice. PS if available and EMS or ESFB is "Y" and emergency session contains only media other than voice.	PS if available and EMS or ESFB is "Y"
E	Y	Y	Y	Y	If the emergency session includes at least voice, follow rules in TS 22.101 which say to use the same domain as for a non-EMC (Note 2) PS if the emergency session contains only media other than voice.	PS if first attempt in CS CS if first attempt in PS
F	Y	Y	Y or N	N	PS if ESFB is "Y" (Note 5). Else PS for another 3GPP RAT with EMS if available and supported or CS, if the emergency session includes at least voice.	CS if first attempt in PS PS for another 3GPP RAT if available and supported and EMS or ESFB is "Y" if first attempt in CS.
G	Y	Y	N	Y	CS if the emergency session includes at least voice. PS if the emergency session contains only media other than voice.	PS
EMC Emergency Session. EMC includes also normal calls initiated in the CS domain that are treated by the CS CN as emergency calls. VoIMS Voice over IMS over PS sessions support as indicated by IMS Voice over PS session supported indication as defined in TS 23.401, TS 23.060 and TS 23.502. EMS IMS Emergency Services supported as indicated by Emergency Service Support indicator as defined in TS 23.401, TS 23.060, TS 23.501 and TS 23.502. ESFB Emergency Services Fallback for 5GS as defined in TS 23.501 and TS 23.502.

H.6  eCall over IMS |R14|  Word‑p. 51

This clause details the domain priority and selection (see clause 7.3) for a UE that attempts to make an eCall over IMS session using E-UTRAN or NG-RAN radio access networks based on the availability of the CS or PS domains and the network support for IMS emergency, eCall over IMS and IMS voice over PS.

The following table (Table H.2) defines these rules based on the UE (last 2 columns) for different initial conditions (first 4 columns) when an eCall over IMS session is initiated and when the UE is not in limited service state.

Table H.2: Domain Selection Rules for eCall over IMS session attempts for E-UTRAN or NG-RAN radio access networks

	PS Available	VoIMS	EMS	ECL	First eCall Attempt	Second eCall Attempt
A	Y	Y	Y	Y	PS	CS if available
B	Y	Y	Y	N	CS if available	PS (UE establishes IMS emergency session)
C	Y	Y or N	N	N	CS if available	PS on another PS RAT if available with EMS=Y or EMS unknown
D	Y	N	Y	Y	PS or CS if available	CS if first attempt in PS PS if first attempt in CS
E	Y	N	Y	N	CS if available	PS (UE establishes IMS emergency session)
F	N		-	-	CS if available
VoIMS Voice over IMS over PS sessions support as indicated by IMS Voice over PS session supported indication as defined in TS 23.401 and TS 23.502. EMS IMS Emergency Services supported as indicated by Emergency Service Support indicator as defined in TS 23.401 and TS 23.501 and TS 23.502. ECL eCall Over IMS support as indicated by the eCall support indicator defined in TS 23.401 and TS 23.501.

---