IMS Network Element - Emergency Service (E-CSCF+LRF)

IMS Network Element - Emergency Service (E-CSCF+LRF) Overview

UE (SIP: UA)
- Initiates e-calls, if necessary also e-registration
- May receive callbacks from PSAP

P-CSCF (SIP: Outbound Proxy)
- Detects whether call is subject to emergecny treatment
- Rejects e-calls if UE should e.g. use CS domain
- Allow and Forwards e-calls to the E-CSCF

E-CSCF
- Routing to PSAP (based on e-URN, location information, etc.)
- Query LRF (Location Function in 3G network) for user location information

MGCF / MGW (Interworking between IMS / CS)
- No additional requirements due to e-calls
- Based on the local policy if an incoming call from the PSTN is for the purpose of PSAP call-back

LRF (PS: Le is used between an AS and a GMLC on LCS)
- Consist of a RDF and a LS
- provide the correct PSAP destination address to the E‑CSCF for routing the emergency request
- Responsible for retrieving the location information of the UE
- Information provided by the LRF to the E‑CSCF (includes the routing information and other parameters like ESQK, ESRN, LRO in NA, or location number, PSAP SIP‑URI or TEL‑URI in EU)

PSAP: No 3GPP specific requirements

S-CSCF (SIP: Registrar, Home Service Proxy)
- Registration of the user and always locates in users home network
- Call-backs from PSAP take place via home network

P.S. E-SCC AS (TBD Later)

Furthr Information: https://docs.google.com/fileview?id=F.309cf55c-be6a-4557-931a-2e8e50138ea7