ABSTRACT
There is a vast literature on the throughput analysis of the IEEE 802.11 media access control (MAC) protocol. However,
very little has been done on investigating the interplay between the collision avoidance mechanisms of the 802.11 MAC
protocol and the dynamics of upper layer transport protocols. In this paper, we tackle this issue from an analytical
perspective. Specifically, we develop Markov chain models to compute the distribution of the number of active stations in
an 802.11 wireless local area network (WLAN) when long-lived Transmission Control Protocol (TCP) connections
compete with finite-load User Datagram Protocol (UDP) flows. By embedding these distributions in the MAC protocol
modeling, we derive approximate but accurate expressions of the TCP and UDP throughput. We validate the model
accuracy through performance tests carried out in a real WLAN for a wide range of configurations. Our analytical model
and the supporting experimental outcomes show that 1) the total TCP t hroughput is basically independent of the number of
open TCP connections and the aggregate TCP traffic can be equivalently modeled as two saturated flows and 2) in the
saturated regime, n UDP flows obtain about n times the aggregate throughput achieved by the TCP flows, which is
independent of the overall number of persistent TCP connections.
Keywords: MAC protocol, TCP traffic, Throughput, UDP datagrams, WLAN.