Broadcast Delivery

This paper is concerned with the architecture and performance of systems that use a broadcast channel to deliver information to a community o f users. lnformation 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 environ-ment because a single transmission o f a page wi l l satisfy all pend-ing 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 broadcasthwo-way interaction. An important design issue is the scheduling o f page transmissions such that the user response time is minimized. For each architecture, existing scheduling algo-rithms are described, and their mean response time performance evaluated. Properties o f scheduling algorithms that yield optimal mean response time are discussed. A comparative discussion o