Scheduling Time-Constrained Communication in Linear Networks

Abstract

We study the problem of centrally scheduling multiple messages in a linear network, when each message has both a release time and a deadline. We show that the problem of transmitting optimally many messages is NP-Hard, both when messages may be buffered in transit and when they may not be. For either case, we present efficient algorithms that produce approximately optimal schedules. In particular, our bufferless scheduling algorithm achieves throughput that is within a factor of 2 of optimal. We show that buffering can improve throughput in general by a logarithmic factor (but no more), but that in several significant special cases, such as when all messages can be released immediately, buffering can help by only a small constant factor. Finally, we show how to convert any of our centralized, offline bufferless schedules to a fully distributed online buffered schedule of equal throughput. Most of our results extend readily to ring-structured networks.