23.1673GPPIP Multimedia Subsystem (IMS) emergency sessionsRelease 17TS
When a UE performs an emergency registration or initiates an emergency session over WLAN access to EPC the UE provides location information that is further defined in TS 23.228 .
If the operator policy requires network provided location using PCC-based solutions for the UE location, the P-CSCF may retrieve location information from the access network as defined in TS 23.203  and includes it in the emergency session request, as described in TS 23.228 .
Annex K (normative):
Support of IMS emergency sessions for roaming users in deployments without IMS-level roaming interfaces