NENA’s 11 th Annual Technical Development Conference

1. NENA’s 11th AnnualTechnical Development Conference A proposal to support E911 calls on Voice over IP Networks Martin Dawson – Nortel Networks

2. The existing emergency network interfaces Selective Router CAMA Wireline LEC ISUP PAM ALI Cellular E2+ ESP Local ALI National Voice N/Ws Emergency Services N/W

3. E911 – Key functions of location information The idea of the subscriber’s location is important to E911 call handling in two key aspects: • ROUTING • The dialed digits, 911, do not contain any explicit routing information. • The call needs to be delivered to the Public Safety Answering Point specific to the jurisdiction from which the call is originating. • This is necessary to facilitate notification of the correct local emergency response unit. • LOCATION DELIVERY & DISPLAY • Ideally a PSAP operator can obtain a display of the location of a caller in conjunction with the call itself. • Allows emergency teams to be dispatched to the destination quickly without depending on the caller to provide the location – which they may not know. • Could be a “Civic Address” or “Geodetic” (lat/lon) location.

4. Routing – Local wireline calling LocalExchange SelectiveRouter Incoming local line and CLID provides an indication of the fixed location and, therefore, correct destination PSAP for the caller. PSAPs

5. ZDB Routing – Cellular calling PSAP chosen on ESRK SelectiveRouter SelectiveRouter PSAPZone B SelectiveRouter PSAPZone A SMLC S/R chosen on cell ID GMLC Lat-Lon LocationDetermination • Cellular • No association between CLID and Location. • Selective Router chosen based on Serving Cell location. • PSAP selected based on Lat/Lon (or cell). • MSC has dedicated trunks to all Selective Routers in service area. BSC ESRK MSC

6. ALI Delivering Location – Local wireline PSAP CAMA LocalExchange SelectiveRouter CLID PAM Address The PSAP can query the ALI database with the caller’s CLID and receive a civic address in return. The CLID and street address have an explicit association.

7. ALI Location Delivery – Cellular E2+ESP LocBid(pANI|ESRK) PAM LocResp(LocInfo) esposreq(lat-lon + Phase1 loc*) ESPOSREQ(ESRK+CLID) PSAP CAMA SelectiveRouter GMLC SMLC BSC MSC The ESRK generated by the positioning systems becomes a key to the call in progress. A location bid from the PSAP is converted to an ESPOSREQ to the cellular network to have the location associated with that call returned. * Phase 1 Location: Nominally the street address of the serving BTS

8. Voice over IP (VoIP) – Special challenges • VoIP networks have much in common with cellular networks in terms of the challenges presented by E911. • VoIP clients can be nomadic or, even, fully mobile. • There is no location association between a CLID nor, even, the call server providing service and the client. • How to support VoIP without impacting the emergency network? • Routing – the concept of a routing key (ESRK) can be reused. • Location Delivery – the E2 interface already supports queries for dynamically determined location. • For “fixed VoIP subscribers” a mechanism also exists for delivering civic address, if that is more appropriate than geodetic location. CallServer

9. Wireline LEC Cellular VoIP Goal - adding a new voice networkWithout impacting existing emergency network interfaces Selective Router CAMA ISUP PAM ALI E2+ ESP Local ALI National Voice N/Ws Emergency Services N/W

10. Wireline LEC PSAP selectedbased on ESRK Cellular S/R selectedbased on ESRK ECReq(ClientID) ECRsp(ESRK) LGS* ECTerm(ESRK) * LGS – Location Gateway Server ROUTINGReusing the ESRK for VoIP Selective Router CAMA ISUP IP TrunkMG CallServer PAM ALI E2+ ESP Local ALI National Voice N/Ws Emergency Services N/W

11. Considerations for Routing In both local wireline and cellular, the switching entities have dedicated trunks to the Selective Routers • For carrier VoIP networks • There is a similar assumption that every subscriber service area will include Point of Presence (PoP) with a Trunk Media Gateway. • The Trunk Media Gateway supports the dedicated S/R trunks. • Carriers may elect to share the PoP resources for emergency services • In the absence of a PoP and for enterprise VoIP • Direct dial numbers for PSAPs may be used in place of the ESRK. • Routing is performed based on the direct dial number in the Called Party Number of the ISUP signaling. • The LGS provides the direct dial number in addition to the ESRK. • Such an approach may not be scalable for PSAPs, may be less reliable (call tandemed through the PSTN), and may not allowenhanced 911 service. But it is a viable fallback.

12. Wireline LEC Cellular ESPOSREQ(ESRK) esposreq(Location) LOCATION DELIVERYReusing the E2 Interface for VoIP Selective Router CAMA ISUP IP TrunkMG CallServer PAM ALI E2+ ESP Local LGS ALI National Voice N/Ws Emergency Services N/W

13. Wireline LEC Cellular ECReq(ClientID) ECRsp(ESRK) LIS* PLR(ClientID) PLR(Location) Access specific positioning methods * LIS – Location Identification Server Determining LocationThe LIS – access specific location determination Selective Router CAMA ISUP IP TrunkMG CallServer PAM ALI E2+ ESP Local LGS ALI National Voice N/Ws Emergency Services N/W

14. Geodetic Location vs Civic Address The E2 interface allows a “Location Description” to be provided in addition to the geodetic location: • Geodetic Location • Required for clients which are arbitrarily mobile, where a specific address is not applicable or relevant • Coded in WGS-84 coordinate system. Effectively the latitude and longitude of the client – plus an uncertainty radius* • Can be determined dynamically by the LIS using appropriate technology (Port wire map, WiFi triangulation, GPS) • Delivered in Position Information parameter of esposreq* • Civic Address • May be more relevant for fixed/wired clients (e.g. desktop phone form factor devices) • Provides a conventional street address* • Can be determined by LIS against static port (switch, DSLAM, etc.) datafill • Delivered in ESP “Location Description” parameter of esposreq* * See NENA Standard for the Implementation of the Wireless Emergency Service Protocol E2 Interface.

15. ZDB eLGS DHCP Using DHCP to support a distributed implementation with roaming Home Network EmergencyNetwork Call Server Selective Router TrunkMG ISUP 3 Visited Network ECReq(LIS-ID) CAMA 2 EmergencyCall Init(eLGS-ID, LIS-ID) Access Network 1 • The visited network may be: • Another carrier for a roaming subscriber • The local VoIP carrier for an enterprise network • Permits enterprise to use direct trunking instead of direct dial routing. LIS LIS-IDeLGS-ID

16. Where to now? What does this proposal need: • VoIP Standards – short term • Call Server to LGS messaging • EC Request/Response/Terminate. • SIP based? • LGS to LIS messaging • Perform Location Request/Response • SIP based? • E2+ - New code points for IP position source, Use of Locn Description for Civic Address • Location determination - short term • LIS implementations which can work with • Legacy client devices • Legacy access networks • VoIP Standards – longer term • Enhanced LIS messaging (e.g. LIS-Client for A-GPS requests) • Enhanced Client to Call Server messaging • Immediate location delivery to call server • LIS-ID and emergency LGS-ID delivery • DHCP support • Delivery of local LIS and LGS identities to client on initialisation • Location determination – longer term • Advanced positioning for IP clients – WiFi triangulation, Assisted GPS • Mid-call position updates for fully mobile clients (already supported on E2) The E911 support imperative is very pressing. The question is how to best, and most quickly, get a solution in place.

17. Thankyou Contact details: Martin Dawson Nortel Networks mdawson@nortelnetworks.com