Efficient k-Shot Broadcasting in Radio Networks

摘要

The paper concerns time-efficient fc-shot broadcasting in undirected radio networks. In a k-shot broadcasting algorithm, each node in the network is allowed to transmit at most k times. Both known and unknown topology models are considered. For the known topology model, the problem has been studied before by Gasieniec et al. [14], who established an upper bound of D + O(kn~(1/(k-2)) log~2 n) and a lower bound of D + Ω((n - D)~(1/2k)) on the length of k-shot broadcasting schedules for n-node graphs of diameter D. We improve both the upper and the lower bound, providing a randomized algorithm for constructing a k-shot broadcasting schedule of length D + O(kn~(1/2k) log~(2+1/k) n) on undirected graphs, and a lower bound of D + Ω(k · (n - D)~(1/2k)), which almost closes the gap between these bounds. For the unknown topology model, we provide the first fc-shot broadcasting algorithm. Assuming that each node knows only the network size n (or a linear upper bound on it), our randomized k-shot broadcasting algorithm completes broadcasting in O((D + min{D · k, log n}) · n~(1/(k/1)) log n) rounds with high probability. Moreover, we present an Θ(log n)-shot broadcasting algorithm that completes broadcasting in at most O(D log n + log~2 n) rounds with high probability. This algorithm matches the broadcasting time of the algorithm of Bar-Yehuda et al. [3], which assumes no limitation on the maximum number of transmissions per node.