Biomedical Engineering Reference
In-Depth Information
Videoconferencing—the real-time, one-to-one and one-to-many broadcasting of video and audio—is
often configured to use the telephone lines for audio and the Internet or other network for the video
channels. This is because brief interruptions in the packets of data passing through the Internet
result in annoying dropouts in the audio signal, even though the interruption may not be noticeable
with video because of the persistence of the image to the human eye. When there is ample network
bandwidth available, videoconferencing may be extended to multimodal conferencing, that is some
combination of electronic whiteboard, a text forum, audio communications, and multiple-channel
videoconferencing—as a means of enabling real-time collaboration.
From a practical perspective, the limitations on the level of collaboration possible as a function of the
bandwidth of the communications channel can best be appreciated by exploring the relationship
between the level of interactivity versus the maximum number of simultaneous users that can be
supported by a system. As illustrated in Figure 10-4 , because e-mail is asynchronous, it can support
a large number of users, but with little interactivity. Online text forums, which may involve real-time
communications, offer more interactivity but can support fewer simultaneous users. As the user
capacity of the text forum system is approached, interactivity will drop as a function of the available
server resources.
Figure 10-4. Interactivity versus Maximum Number of Users for
Collaborative Technologies. The typical tradeoff is of interactivity versus
the number of collaborators that can be accommodated.
Shared authoring tools, such as the Chimera Collaboratory Extension or a general-purpose shared
document editor, offer highly interactive levels of collaboration, but can only support a relatively
limited number of participants. Multimedia conferencing, which integrates applications such as video
conferencing, electronic whiteboards, screen-sharing applications, and shared authoring tools, offers
the greatest flexibility in collaboration and the highest potential level of interactivity. However, it also
demands the most of the communications infrastructure, and typically supports the fewest number of
collaborators. Groupware that enables multimedia conferencing is often limited more by the
bandwidth of the underlying network than by any inherent limitations in the application software or
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