Table of Contents:

Definition and Overview

1. The Business Challenge: Meeting Consumer Expectations

2. The Current 9-1-1 Landscape

3. Technical Challenges

4. Current Approaches and Limitations

5. New Industry Standards

6. Recommended Approach

7. Implementation Considerations

PDF of this tutorial

In an effort to help VSPs deploy viable E9-1-1 solutions, NENA has worked with the telecommunications and public safety communities to develop recommended call flows. In each of the recommendations currently being deployed, the burden is on subscribers to keep their location information upto- date.

In the I1 stage of deployment, the VoIP 9-1-1 call is delivered to a 24x7 administrative line without the caller’s location; the caller’s phone number is only provided when caller ID is available on the receiving PSAP phone. This approach is detailed in the diagram below.

VoIP E9-1-1 I2 Call Flow

In the I2 stage of deployment, the VoIP 9-1-1 call is delivered to the correct PSAP via a selective router infrastructure solution. In this call flow, the caller's location and callback number are automatically delivered to the PSAP without any required hardware or software upgrades to the existing PSAP E9-1-1 infrastructure. The I2 approach is detailed in the diagram below.

VoIP E9-1-1 I2 Call Flow

The following table summarizes the location, routing, and delivery mechanisms employed by landline, cellular, and VoIP E9-1-1 services:

	Location	Routing	Delivery
Landline	Provisioned in ALI database; takes 24 - 48 hours to be activated; based on where the phone is installed, so it is highly accurate; does not allow for mobility	Routing based on exact location of landline phone; call is routed through the selective router; the PSAP is associated with the caller's location prior to the call	Call back number, voice channel and subscriber's location are delivered to the PSAP across established emergency services trunks
Cellular Phase I	Based on cell tower location; is not the caller's precise location; margin for error can range from a few city blocks to several miles	Routing based on cell site location; call is routed through the selective router; PSAP is identified as part of the call flow; accuracy is dependent upon the placement of the cell tower	Call back number, voice channel and closest cell tower location information are delivered to the PSAP across established emergency services trunks
Cellular Phase II	Precise location based GPS or network-based calculation; accuracy 300 meters or less; location derived in seconds or less	Routing based on precise location; call is routed through the selective router; PSAP is identified as part of the call flow; defaults to cell site if precise location is not determined quickly enough	Call back number, voice channel and caller's precise location information are delivered to the PSAP across established emergency services trunks
VoIP I1	Provided by VoIP subscriber prior to the 9-1-1 call; subscriber must update location each time they move in order to be accurate	Routing is based on subscriber-provided location; PSAP is identified as part of the call flow; call is routed to a 10-digit administrative line	Voice channel is delivered to the PSAP via a 10-digit admin line; no location is delivered; call back number is visible if the phone is equipped with caller ID
VoIP I2	Allows for calculation of exact location of the caller; current solutions rely on location provided by VoIP subscriber prior to the 9-1-1 call	Routing is currently based on subscriber-provided location; call is routed through the selective router; PSAP is identified as part of the call flow	Call back number, voice channel and caller's precise location information are delivered to the PSAP across established emergency services trunks