Formal approach to guard time optimization for TDMA

Abstract

Treating clock drift to avoid message collision and loss is a major challenge when the Time Division Multiple Access (TDMA) protocol is used to schedule communication over a shared medium in networks. We consider clock drift in synchronized networks with tree topology and limited energy, where the root provides the reference clock. We provide a formal approach for analyzing the effect of the slot assignment on the maximal clock drift, given an upper bound on the drift rates of the clocks. We give exact topological characterizations of the slot assignments with largest and least existing clock drift and provide least upper bounds on the clock drift in both cases. We apply our results to derive an optimal, i.e. minimal, safe guard time which effectively avoids message collision or loss due to clock drift.