A Distance Education Conferencing System Utilizing Voice and Text Data Over a Low Bandwidth Communications Link

This dissertation addresses the technical utilization of multimedia computer technology to increase the effectiveness of distance education. Text-based conferencing using computers has been in use for more than ten years but suffers from interaction speeds paced by the participant\u27s keyboarding proficiency. Multimedia computers capable of rendering voice and graphics can increase information delivery by an order of magnitude. Constraining the development of multipoint conferencing system are the low bandwidth communications infrastructure, the absence of a data bridge, and effective multimedia compression and multiplexing techniques for the diverse user platforms. Many applications are reviewed that can, in part, perform at least some of the functions required. Research is presented describing current implementations of group conferencing systems which use both high-power workstation computing equipment and high-speed communication connections. Implementations of voice point-to-point connectivity, found in the numerous internet phone applications, are surveyed. A key component of each system is a technique to address the high data rates required for voice data. Voice data compression can use differing techniques, depending on the computing hardware and auxiliary compression hardware available. An analysis of software voice compression techniques is performed noting that computing power for encoding and decoding are not always symmetrical. Unlike standard data driven systems, a voice conferencing application is time-sensitive. Network behaviors, such as queuing, or multitasking operating systems which are not deterministic can introduce significant delays during transmission. Additionally, multitasking operating systems which are not deterministic can also introduce delays. These delays can render voice transmission unusable, introducing sudden stops and starts in the voice reproduction. Techniques for design of a time-sensitive system will be developed. The dissertation develops an implementation of a group conferencing system combining the capabilities of text-data and voice multiplexing, compression, and bridging. The system will be designed to adapt to the many diverse hardware platforms, selecting the compression algorithm to maximize performance on the client system