Sunday, March 14, 2010

multimedia applications

With the rapid growth in the popularity of multimedia applications, such as voice-over-IP and video conferencing, the demand for high bandwidth and Quality-of-Service (QoS) in WLANs is increasing dramatically. There are many inherent QoS limitations in Distributed Coordination Function (DCF) and the system efficiency is considerably affected by various overheads referred to as control frames, backoff, and inter-frame space. To mitigate the impacts of the overheads, a new standard IEEE 802.11e EDCA is specified and the mechanism of burst transmission based on the Contention Free Bursting (CFB) has been specified in the IEEE 802.11e standard. IEEE 802.11e EDCA support QoS by providing differentiated classes of service in the medium access control (MAC) layer. With the CFB scheme, multiple data frames are transmitted in a burst once a station obtains a transmission opportunity (TXOP) after winning the contention for channel access to improve the channel utilization.

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