Delays and mixing times in random-access networks

Abstract

We explore the achievable delay performance in wireless random-access networks. While relatively simple and inherently distributed in nature, suitably designed backlog-based random-access schemes provide the striking capability to match the optimal throughput performance of centralized scheduling mechanisms. The specific type of activation rules for which throughput optimality has been established, may however yield excessive backlogs and delays. Motivated by that issue, we examine whether the poor delay performance is inherent to the basic operation of these schemes, or caused by the specific kind of activation rules. We derive delay lower bounds for backlog-based activation rules, which offer fundamental insight in the cause of the excessive delays. For fixed activation rates we obtain lower bounds indicating that delays and mixing times can grow dramatically with the load in certain topologies as well.