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VoIP: A Step Forward for the Deaf

May 3, 2004

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We have definitely entered a new age in telecommunications. The momentum behind VoIP, or Voice over IP, has turned into reality for many enterprises and service providers. Sales of IP-based PBX systems continues to grow and is doing so at an incredible rate. However, the one aspect of VoIP technology that is most difficult for the deaf person to use is "voice." Fortunately, VoIP is just a marketing term. It does not mean that the technology is limited to voice. In fact, it encompasses a whole suite of multimedia services, including voice, video, and other real-time information.

So how does this all relate to the deaf?

The deaf and hard of hearing have always had problems communicating over telephone networks, which are designed for people who can hear. While the telephone was invented in the late 1800s, the first device to allow a deaf person to communicate over the public telephone network was not invented until 1964.

Since then, a number of competing protocols have been developed to transport text over telephone networks. There are roughly six major "textphone" protocols used throughout the world, some with multiple variants. Consequently, deaf people have long had a difficult time communicating. Even today, an international call is very difficult to make due to interoperability problems between so many textphone protocols.

VoIP offers us a unique opportunity to significantly improve communication, not only for those of us who can hear, but for the deaf. With VoIP, we have the possibility to transport text simultaneously with voice and video. Deaf users can use their "natural" language (sign language) to communicate via video. Text can also be used to augment or serve in the absence of video. Not only that, but with this new technology, we have a unique opportunity to bridge the gap that has long-existed between PSTN textphone users in different countries.

The standards required to support the needs of the deaf have been slow to evolve. Today, textphones can be used over IP networks using standards developed by the IETF and ITU-T. However, in addition to providing reliable delivery of text, we must also enable disparate devices to communicate with each other, such as a person using a hand-held computer to communicate with a person on a legacy, PSTN textphone. This capability is being actively developed by people in both the IETF and ITU-T.

The ITU-T is creating a new standard, V.151, built on the work done in the IETF (RFC 2793), that allows a gateway connected to the PSTN to transport legacy textphone analog signals over IP networks as "real" text. This standard makes it possible for the for world to have a single, standard means of transporting text between legacy, PSTN networks and new, IP-based systems. Further, V.151 uses the same mechanisms to transport Unicode characters as IP-only devices use to exchange real-time text, allowing all devices to interoperate with one another and support all languages.

Bridges will soon be in place to allow the deaf to cross from the old, legacy, PSTN networks into the Next Generation Networks (NGN) currently being developed and deployed around the world. Not only that, but the door will be opened to allow deaf users to take advantage of technologies that combine voice, video, and text. All of the NGN systems will hopefully utilize a single mechanism for transporting text, thereby removing the barriers to interoperability faced by legacy textphone devices of the past.