Impact of frame size, number of stations and mobility on the throughput performance of IEEE 802.11e

IEEE 802.11e medium access control (MAC) is an emerging supplement to the IEEE 802.11 wireless local area network (WLAN) standard to support quality of service (QoS). The 802.11e MAC defines a new coordination function, namely hybrid coordination function (HCF), which is based on the centrally controlled and contention-based channel accesses. In this paper we evaluate, via simulation in OPNET, the throughput performance of the new 802.11e MAC HCF, and compare it with the 802.11 legacy MAC. We also study the scheduler implementation included by the IEEE 802.11e draft standard. Finally, we evaluate the effect of the "bad link" on the capacity of the network. Different stations in an IEEE 802.11 network can operate with different physical transmission rates based on their distance from the access point. A station transmitting at a lower physical transmission rate brings down the performance of the whole WLAN network. Through our simulation study, we conclude that the transmission opportunity (TXOP) of the IEEE 802.11e can enhance the system performance and provide fairness in time.