North American Emergency Services

1. North American Emergency Services Brian Rosen Emergicom

2. 9-1-1 Calls • Single universal number for all networks throughout North America (wireline, wireless, …) • Answered at one of ~6,134 Public Safety Answering Points • Dispatched to tens of thousands of police/fire/emergency medical agencies • A function of LOCAL government, not significantly controlled by state/federal governments • Often City or County • But often there are multiple PSAPs per county • Please don’t ask us to fix this, it’s been tried

3. PSAP Boundaries • Every PSAP has a service area • All calls from within that boundary must go to that PSAP • PSAP boundaries do not necessarily lie on neat (e.g. City, County) boundaries • The DEFINITION of a PSAP boundary is currently done on a street/number basis, which has been manually translated into a point/polygon form also • Dealing with non-trivial boundaries is the big problem in routing calls

4. E911 TANDEM OFFICE SUBSCRIBER SRDB END OFFICE ANI PSAP COMMONEQUIPMENT ALI HOST ATTENDENT POSITIONS 7 1 2 7 6 5 5 3 4 Wireline Calls

5. Wireline Calls • Caller Dials 9-1-1 • End Office detects emergency calls and forwards to Selective Router tandem • Caller phone number is looked up in SR DB to determine which PSAP to direct call to • PSAP looks up caller phone number in ALI DB to display location and to determine Emergency Services Zone (combo of police, fire and EMS services)

6. ERDB & ALI DB • Translates phone number to location & routing data • Maintained by a designated service provider • Carriers process service orders into ALI (and SR DB) for new/changed customers • Location (to be associated with phone number) is VALIDATED against the Master Street Address Guide prior to entry in the ALI

7. MSAG • Validation Database for locations • Lists every address (actually an address range) in the area served by the local 9-1-1 system • Maintained by the local 9-1-1 authority. Normally one MSAG per local authority (which often covers more than one PSAP), but there are exceptions • Contains the ESN (code for ESZ) • Indirectly specifies the PSAP to which the call is sent • Implies the S/R (MSAG coverage doesn’t normally cross S/R service areas, but they do sometimes).

8. MSC ESNE (Selective Router) Cellsite Ai Di (ISUP) CAMA CRDB PSAP E12 E3 (ANSI-41) (ANSI-41) E11 (LSP) PDE MPC ESME (ALI Database) E5 E2 (ESP) MSC Mobile Switching Center MPC Mobile Position Center CRDB Coordinate Routing Database PDE Position Determining Entity Wireless (Phase II) Calls

9. Wireless Phase II calls • Mobile Switching Center (MSC) queries Mobile Positioning Center (MPC) for routing • MPC uses position information from PDE and CRDB to determine which PSAP • Given which PSAP, the call is forwarded to the correct Selective Router based on a route code obtained from the CRDB • A key (ESRK), which looks like a phone number, is assigned to the call • The key has an entry in the SR DB and ALI that causes the S/R to route the call to the correct PSAP • The location in the ALI for that key is updated dynamically to have the actual location (as well as the call back number, since the ALI is the key and not the calling party number • The location is provided as lat/lon, not street address. The PSAPs deploy a Geographic Information Service that translates geo to civil; dispatch is always civil • Location can be updated during the call. The PSAP asks (bids) and the ALI database responds

10. NENA “i2”

11. NENA “i2” • Gateway’s VoIP to selective router via a gateway (ESGW) • Uses SIP with PIDF-LO to send location • VoIP Positioning Center (VPC) queries a database (ERDB) with location to obtain a routing token (ESRN) and an ALI/SR DB key (ESQK) • ESRN token will cause the call to go to the right port on the gateway, which means to the correct S/R • ESQK will cause the call to go to the right PSAP • ESQK location will be updated as with wireless Phase II to display the actual location