Achievable delay performance in CSMA networks

We explore the achievable delay performance in wireless CSMA networks. While relatively simple and inherently distributed in nature, suitably designed backlog-based CSMA schemes provide the striking capability to match the optimal throughput performance of centralized scheduling mechanisms in a wide range of scenarios. 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 CSMA operation of these schemes, or caused by the specific kind of activation rules. We first establish lower bounds for the delay in the case of fixed activation rates. The bounds indicate that the delay can dramatically grow with the load in certain topologies. We also discuss to what extent the bounds apply to backlog-based activation rules. Simulation experiments are conducted to illustrate and validate the analytical results.