Analysis of Non-Persistent CSMA Protocols with Exponential Backoff Scheduling

This paper studies the performance of Non-persistent CSMA/CA protocols with Exponential Backoff scheduling algorithms. A multi-queue single-server system is proposed to model multiple access networks. The input buffer of each access node is modeled as a Geo/G/1 queue, and the service time distribution of head-of-line packets is derived from the Markov chain of underlying scheduling algorithm. The main results include the complete analysis of the throughput and delay distribution, from which we derived the characteristic equation of network throughput and obtained stable regions with respect to the throughput and bounded mean delay of the Exponential Backoff scheme. We show that the stable throughput region of Exponential Backoff can be obtained even for an infinite population. Since the variance of service time of Exponential Backoff can be unbounded due to the capture effect; thus, its bounded delay region is only a sub-set of its stable throughput region, and the maximum achievable throughput of the network within this region is slightly smaller than the absolute maximum throughput. Analytical results presented in this paper are all verified by simulation.