1. Phase 4 : Call Presentation Four Phases of Emergency Calling
Emergency Calling for VoIP Wonsang Song and Jong Yul Kim Internet Real-Time Lab, Columbia University
Phase 4 : Call Presentation
Project Overview
Develop a prototype system that routes emergency calls over SIP based VoIP networks.
Use embedded location information delivered via the SIP protocol to make routing decisions.
Provide opportunities to enhance 911 system:
More robust
Additional services like multimedia, video, etc.
Better integration with first responders and public safety
Cheaper to build and operate.
Four Phases of Emergency Calling
Phase 1 & 2 : Identifying Emergency Calls & Determining Caller Location
Why is VoIP Emergency Calling Interesting?
Where is the user calling from?
Users can be nomadic or mobile
Many solutions (user entry, GPS, DHCP, CDP etc)
How do you determine the PSAP nearest to the caller?
Location is given as geo coordinates / civic address
Civic addresses : DNS NAPTR records
Geo coordinates : DNS map polygon data
No address : Route to default PSAP
What kind of additional features are possible?
Streaming instructional video to caller (e.g. CPR how-to)
Language-based calltaker routing
Auto-answering similar incidents based on time/location
3rd Party Call Control Flow
Phase 3 : Routing to Correct PSAP
Project Participants
Columbia University
Texas A&M University
University of Virginia
State of  Texas Commission on State Emergency Communications
State of Virginia Commission on State Emergency Communications
University Corporation for Advanced Internet Development
Brazos County Texas E911 District
National Emergency Numbering Association
Cisco Inc.
Nortel Inc.
The original grant proposal can be found in For drafts and papers, see