Determination of PSAP and routing of emergency calls in IP multimedia subsystem

Abstract

A fundamental part of the IMS, Emergency Service provides the user an ability to originate calls in emergency situations and get the help rendered by the nearest Public Safety Answering Point (PSAP). Various implementations of Emergency services use Location to Service Translation (LoST) server or Emergency Call Server (ECS) as the Routing Determination Function (RDF) to determine which PSAP the call shall be routed. In this paper, we propose to implement the PSAP selection logic of RDF at the E-CSCF itself. This paper presents a way to fetch the contact information and responsibility area of PSAP from PSAP directly and then select the appropriate PSAP for routing the emergency calls.