Study on system impacts of IP Multimedia Subsystem (IMS) emergency sessions over Wireless Local Area Network (WLAN)
The present document studies the mechanisms needed to support IMS Emergency sessions over WLAN (both in the Trusted -S2a - and in the untrusted -S2b- cases)
The study is split up into 2 phases corresponding to 2 SID (FS_SEW1 and FS_SEW2).
Topics to be studied in phase 1 (FS_SEW1) are:
- Providing access to EPC over WLAN in order to support an emergency session only in case of "Valid" UEs as in the case 1 in clause 4.3.12.1 of TS 23.401 [3]: the support of emergency session is only studied for UEs which (a) have valid credentials to access EPC over WLAN and (b) are authorized to connect to EPC over WLAN in the location where they initiate an emergency session.
- Providing Location information (in particular for untrusted WLAN). Only existing location determination mechanisms are considered i.e. location determination mechanisms that should not require standard effort. No location accuracy requirements are considered in phase 1.
Phase 1(FS_SEW1) will not consider solutions that imply specification activities in other SDO(s).
Topics to be studied in phase 2 (FS_SEW2) correspond to all the features not covered by phase 1, e.g.:
- Support of other cases for the access to EPC over WLAN (e.g. the UE is authenticated but is in a location where it is restricted from regular service, or is unauthenticated or has no USIM).
- Roaming cases (user not in his / her home country).
- Support of session continuity of emergency sessions at inter-access mobility.
- TWAN access.