Performance analysis of IEEE 802.11 WLANs with saturated and unsaturated sources

This paper proposes a comprehensive but tractable model of IEEE 802.11 carrying traffic from a mixture of saturated and unsaturated (Poisson) sources, with potentially different QoS parameters, TXOP limit, CWmin and CWmax. The model is used to investigate the interaction between these two types of sources, which is particularly useful for systems seeking to achieve loadindependent ''fair'' service differentiation. We show that, when the TXOP limit for unsaturated sources is greater than one packet, batches are distributed as a geometric random variable clipped to TXOP limit. Furthermore, we present asymptotic results for the access delay distribution, which indicates that it is infeasible to obtain real-time service in the presence of 8 or more saturated sources regardless of the real time traffic load given that all stations use CWmin of 32.