H.6 eCall over IMS
23.1673GPPIP Multimedia Subsystem (IMS) emergency sessionsRelease 17TS
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 |
PS on another PS RAT if available with EMS=Y and ECL=Y or 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 |
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|
VoIMS = Voice over IMS over PS sessions support as indicated by IMS Voice over PS session supported indication as defined in TS 23.401 [28] and TS 23.502 [49]. EMS = IMS Emergency Services supported as indicated by Emergency Service Support indicator as defined in TS 23.401 [28] and TS 23.501 [48] and TS 23.502 [49]. ECL = eCall Over IMS support as indicated by the eCall support indicator defined in TS 23.401 [28] and TS 23.501 [48]. NOTE 1: As an implementation option, when the first attempt uses PS and fails for reasons other than related to IMS, the second attempt may use PS with a different 3GPP RAT. In this case the UE, can make a third attempt using CS. |
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NOTE: If the E-UTRAN and NG-RAN cells available to the UE have different settings, the UE assumes "PS Available" and "ECL" apply to whichever cell is indicated (as defined in TS 23.401 [28] and TS 23.501 [48]) as providing eCall over IMS support. When support by more than one cell is indicated, a UE may select any cell to attempt eCall over IMS according to the UE implementation.
Annex I (normative):
IMS Emergency Services Using HRPD/EPC Network