Requirements for Accessibility
The requirements to support rich communications for the hearing- or speech-
disabled can be divided into generic requirements targeted for SIP and specific
needs of the impaired users. We can thus break up the requirements into com-
munication requirements and application requirements.
The generic requirements for SIP based communications for impaired
users are:
- Connection without difficulty in setting up SIP sessions and adding/
removing media streams during a session. - Users must be able to communicate their abilities and preferences dur-
ing a session for such features as text, voice, video; simplex or duplex. - Redirecting specific media stream to transcoders, for example, for
speech-to-text conversion. - Roaming or SIP service mobility as discussed in Chapter 15, “SIP Appli-
cation Level Mobility.” A user should, for example, be able to use his or
her service profile while visiting an Internet cafe that provides general-
purpose PCs for communications. - Anonymity: Not revealing the user is speech or hearing impaired, even
if transcoding is inserted into the session so as to avoid possible dis-
crimination or prejudice. - Inclusive design: Users must be able to connect to other impaired per-
sons that still use legacy protocols and devices via IP-PSTN gateways. - Personal resource management: Users must be informed of the media
options and their price differences. - Confidentiality and security of similar quality as for nonimpaired users.
- Real-time flow of all media.
The video application requirements for impaired persons have been docu-
mented in detail in [3]. Video is used for lip reading and signing in different
flavors:
■■ Sign languages enable the communication of concepts, partial sen-
tences, grammar, and nouns. Rapid hand movements and short blinks
of the eyes carry grammatical information.
■■ Finger spelling is a subset of using a sign language where every letter
corresponds to a unique hand position, as shown in Figure 17.1.Accessibility for the Disabled 289