The National Emergency Numbering Association (NENA) has approved an interim E911 standard for VoIP services.

The standard is called the NENA Interim VoIP Architecture for Enhanced 9-1-1 Services, or i2 for short. It defines an architecture that will allow IP telephony service providers to deliver full-fledged emergency calling services through the existing E911 infrastructure, until a planned all-IP E911 system becomes available nationwide.

Providing E911, or enhanced 911, service requires connecting a caller who dials 911 to the proper nearby emergency dispatcher, and supplying the dispatcher with the address and phone number of the caller. Their inability to do so for all of their customers has become a major stumbling block for VoIP providers as they try to expand their business.
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Earlier this year, the FCC ruled that, as of November 28, VoIP providers could no longer market to or sign up new customers to whom they could not provide such service. Nuvio Corp. challenged the ruling, but an appeals court denied its request to delay the deadline. (See Appeals Court Upholds E911 Deadline.)

The regulatory agency did, however, rescind an earlier decision that VoIP companies would have to stop serving customers to whom they could not provide E911 service. (See FCC Backs Off On VoIP E911 Enforcement.)

Two functions are critical to providing E911 service. One is finding out the address from which the emergency call originates. The second is forwarding the call, along with the address and the phone number of the caller, to the proper public safety answering point (PSAP), which can then dispatch emergency services to the caller’s location.

A number of vendors and service providers are working on ways to get the address information to the right PSAPs. (See Intrado Lays the Groundwork for Nationwide VoIP E911.) A bigger problem, however, is how to make sure the address is correct.

The difficulty lies in the fact that VoIP is a so-called nomadic service. Users can unplug their IP phones from their registered addresses and plug them in anywhere they can find a broadband Internet connection, keeping the same phone number. Although they are supposed to register the new address when they do so, they often do not.

That isn’t a major issue when customers are buying IP telephony as part of a bundle of services from cable companies, since the telephone is generally plugged into non-portable cable modem or set-top box equipment. But it’s trickier if all they need to move is an IP phone or adapter.

AT&T’s solution for its CallVantage VoIP service is to force users to register new addresses, or reconfirm existing ones, every time their IP phone adapter gets unplugged, on the assumption that it may have been moved in the meantime. (See How the FCC Helps VoIP Providers Help Themselves.)

If AT&T can’t provide E911 connectivity at the new address, it won’t provide phone service either. And therein lies the plan’s greatest weakness: that users may not tell the truth about their new locations, if it means losing service.

Because of such possibilities, the new interim NENA standard calls for VoIP providers to find ways to automatically determine the locations of IP phones making emergency calls, rather than depending on users to provide the information, according to Roger Hixson, technical issues director for the standards organization.

One way to do so would be for VoIP phone companies to work with broadband Internet providers to identify the specific DSL or other link to which a specific IP phone or softphone is connected, and to register the address information before the user makes a call.

Another method under discussion is using signals from TV towers to triangulate the IP phone’s position. The technique would be more precise than is possible using GPS positioning, another oft-discussed possibility.

According to Hixson, the i2 standard is only a temporary measure meant to allow VoIP networks to work with existing E911 services. The i3 standard, also called next-generation or NG911, will be entirely IP-based, he says.

That future standard is scheduled for public review in early 2006, according to Patrick Halley, the organization’s government affairs director.