Probabilistic quorum systems in wireless Ad Hoc networks

Abstract

Quorums are a basic construct in solving many fundamental distributed computing problems. One of the known ways of making quorums scalable and efficient is by weakening their intersection guarantee to being probabilistic. This article explores several access strategies for implementing probabilistic quorums in ad hoc networks. In particular, we present the first detailed study of asymmetric probabilistic biquorum systems, that allow to mix different access strategies and different quorums sizes, while guaranteeing the desired intersection probability. We show the advantages of asymmetric probabilistic biquorum systems in ad hoc networks. Such an asymmetric construction is also useful for other types of networks with nonuniform access costs (e.g, peer-to-peer networks). The article includes a formal analysis of these approaches backed up by an extensive simulation-based study. The study explores the impact of various parameters such as network size, network density, mobility speed, and churn. In particular, we show that one of the strategies that uses random walks exhibits the smallest communication overhead, thus being very attractive for ad hoc networks.