Teletext-like information delivery using broadcast polling

Abstract

Teletext is an information system that uses the continuous one-way broadcast of information pages as a delivery mechanism. Teletext systems are simple to operate and, because their performance is insensitive to user loads, can accomodate an unlimited number of users. This, however, is achieved at the expense of having to undertake superfluous transmissions, i.e., page broadcasts that do not satisfy any outstanding requests. In this paper, we first derive an expression representing the proportion of superfluous transmissions in a teletext system for any given cyclic sequence of page broadcasts. Next, we propose a broadcast polling information delivery scheme. This scheme insures that no superfluous transmissions take place, at the expense of requiring a two-way communication network, and incurring a polling overhead. We investigate, through the use of simulation, the response time performance of the broadcast polling scheme and how it relates to that of a teletext system.