Many hail voice-over-IP calling as the future of voice communications, but one of the primary technical hurdles for VoIP providers is getting access to the emergency 911 system — a priority for regulators and often a prerequisite for customers considering VoIP as a primary-line alternative.

Currently, there is no standard method connecting VoIP calls to public service access points (PSAPs), which were designed to work with legacy, circuit-switched networks. As a result, most 911 services from VoIP providers direct emergency calls to a PSAP's administrative office instead of connecting directly to a 911 dispatcher.

This patch creates potentially costly time delays in responding to a caller in crisis, but there are also other problems. A VoIP phone is mobile and can be used anywhere there is a broadband connection, so the phone number associated with the device cannot be used to determine the nearest PSAP to the caller's location.

With this in mind, Nortel Networks last month offered a proposal at the National Emergency Number Association Technical Development Conference that is designed to tackle these VoIP-related 911 problems by using the infrastructure created to solve 911 challenges in another mobile area: connecting wireless phone users to the current 911 architecture.

“We want to keep the investment to PSAPs to a minimum, if not negligible, compared to their existing budgets,” said Mark Lewis, senior consulting engineer for Nortel Networks and leader of the VoIP migratory working group for NENA. “This proposal leverages their existing E911 wireless networks.”

Specifically, the proposal calls for the addition of a location gateway server (LGS) that would serve as a conduit between a VoIP network and a PSAP's network, according to Lewis.

Feeding location information into the LGS would be a location information server (LIS), which would deliver the location information — most likely an IP address or GPS coordinates — that can be cross-referenced with a street address database within the LGS, Lewis said. The LGS would transmit the location information to the PSAP network in the most appropriate format, such as the street address for older PSAPs and latitude/longitude data for upgraded PSAPs.

Simultaneously, the LGS would deliver the location information to the call server, so it can route the 911 call to the PSAP that is best suited to help the caller — even if the server that routes the call is not in the same area, Lewis said.

Under this proposal, the only new pieces are the LGS and its connections to the LIS and the call server — all of which are expected to be in the VoIP network, with the network provider or the VoIP application provider bearing the costs, Lewis said.

With a location gateway server, “We don't have to worry about smaller VoIP providers having huge start-up costs,” Lewis said, noting that an independent VoIP application company could contract with the network provider or pay for its own LGS.

Lewis emphasized that this proposal is designed to handle 911 calls during the transition period as VoIP calling and circuit-switched calling coexist. NENA has a separate plan for the day when all calls are executed on an IP network.

Several experts have predicted an all-IP 911 has an opportunity to be rich with features, such as giving first responders automatic access to medical records or building information.