Simple Modeling for QoS Management of IEEE 802.11 DCF

摘要

As widely seen in various private networks and public wireless hotspots, the spread of wireless LAN based on IEEE 802.11 has reached a peak, and its IEEE standard continues to be improved toward 802.1 In. On the other hand, the quantitative method of evaluating wireless LAN has not caught up with the evolution of its technology and is still under development. Indeed, some design or management know-how, such as a placement design of access points (APs) aimed to avoid radio interference or traffic congestion, has been accumulated, while some analytical approaches based on a strict mathematical model are studied. However, we cannot say that they are practical and sufficient for actual network management situation. In this paper, a simple and practical performance evaluation model of IEEE 802.11 DCF based on the M/M/1/K queue, to contribute to establishing efficient QoS management of wireless LAN networks is presented. The relationship between the packet loss ratio, which is one of the important metrics in QoS management, and the MAC retry ratio, whose measurement is comparatively easier, is demonstrated in this model. Some numerical examples are described, and their effectiveness is discussed. In addition, some experimental evaluations corroborating the numerical analysis, are presented.