A Broadcast Protocol for File Transfers to Multiple Sites

Abstract

A retransmission protocol for a broadcast connection (point-to-multipoint) is proposed and its performance characteristics are considered. The protocol is designed for transfers of large files over a satellite channel that is time-shared to carry both the data from the broadcasting transmitter and the set of acknowledgments from the multiple receiver sites. A mathematical model of the transmission system that includes separate error processes for uplink and downlink errors on data transmissions, and similar processes for errors on the acknowledgment frames as well, is used to analyze the performance of the scheme. Exact analytical expressions for the relative throughput of the channel are obtained for two special cases: 1) the uplink is error-free; and 2) the acknowledgments are error-free. For the general case, upper and lower bounds are derived and are shown to be virtually indistinguishable for many practical sets of system parameters. The results demonstrate that the broadcasting of large files to multiple receivers can be done both efficiently and reliably. Copyright © 1981 by The Imtitute of Electrical and Electronlcr Engmeers. Inc.