Hierarchical conferencing architectures for inter-group multimedia collaboration

Advances in computer and communication technologies have stimulated the integration of digital video and audio with computing, leading to the development of various computer-assisted collaborations. In this paper, we propose a multi-level conferencing paradigm (called super conferences) for supporting collaborative interactions between geographically separated groups of users, with each group belonging to possibly a different organization. Hierarchical communication architectures are naturally suited for carrying out media transmission in super conferences. We study the performance of hierarchical communication architectures, and present algorithms for bounding end-to-end delays of real-time media traffic in them. We derive some interesting limits on the number of participants in a group and the number of groups within a super conference, so as not to violate bandwidth and delay requirements of multimedia. At the Multimedia Laboratory at the University of California, San Diego, we have implemented a conferencing system on an environment of Sun SPARCstations and PCATS equipped with digital video and audio processing hardware. As an interesting application of the conferencing system, we have developed a tele-presenter by which users can remotely attend lectures in progress. We present our initial experiences with using the system.