Broadcast delivery

The architecture and performance of systems that use a broadcast channel to deliver information to a community of users are discussed. Information is organized into units called pages, and at any instant of time, two or more users may request the same page. Broadcast delivery is attractive for such an environment because a single transmission of a page will satisfy all pending requests for that page. Three alternative architectures for broadcast information delivery systems are considered. They are one-way broadcast, two-way interaction, and hybrid one-way broadcast/two-way interaction. An important design issue is the scheduling of page transmissions such that the user response time is minimized. For each architecture, existing scheduling algorithms are described, and their mean-response-time performance evaluated. Properties of scheduling algorithms that yield optimal mean response time are discussed. A comparative discussion of the performance differences of the three architectures is also provided.>