It may be integrated into a Location Server (e.g., GMLC) or an LRF (Location Retrieval Function).
Its primary purpose is to provide the proper outgoing address to the E-CSCF (Emergency Call Session Control Function) for routing emergency requests toward a PSAP (Public Safety Answering Point).
Workflow:
When an emergency call is initiated (e.g., 911 call), the RDF determines the appropriate PSAP address.
It considers various factors, such as network configuration, policies, and location information.
The allocated outgoing address is then used by the E-CSCF to route the emergency request to the correct PSAP.
Interfaces Supported:
For 2G/3G networks, the RDF supports MAP-based 3GPP Lg and Lh interfaces.
For 4G networks, it supports 3GPP Diameter SLg and SLh interfaces.
In 5G, the RDF interfaces with the AMF (NL2), NEF (NL5), and UDM (NL6) using the Ngmlc_Location service.
Communication with Location Clients uses the Le interface, which supports a subset of the OMA Mobile Location Protocol (MLP).