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4
Performance Study of IEEE 802.11 DCF
and IEEE 802.11e EDCA
Giuseppe Bianchia, Sunghyun Choib and Ilenia Tinnirelloc
4.1 Introduction
One of the key factors for the wide acceptance and deployment of IEEE 802.11 Wireless
Local Area Networks (WLANs) is the simplicity and robustness of the Medium Access
Control (MAC) protocol. Based on the well-known carrier sense paradigm, with an
exponential backoff mechanism devised to minimize the probability of simultaneous
transmission attempts by multiple stations, the protocol is able to work in presence of
interference, which is very critical for networks operating in unlicensed spectrum. In fact,
interfering sources are simply revealed by the carrier sense mechanism in terms of channel
occupancy times, or by the acknowledgement mechanism in terms of collisions. However,
the simplicity and the robustness have often been traded off with the efficiency of the
access protocol, in terms of radio resources which are wasted or underutilized.
In this chapter, we provide a detailed analysis of the 802.
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