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A Collision Avoidance Mechanism for IEEE 802.11e EDCA Protocol to Improve Voice Transmissions in Wireless Local Area Networks

Enhanced distributed channel access (EDCA) is the basis protocol in IEEE 802.11e protocol suite. It is used for providing differentiated quality of service (QoS) in IEEE 802.11e standard wireless local area networks (WLANs). One of the main drawbacks in EDCA is the small values used for minimum and maximum contention window (CW) sizes for the AC_VO access category, the queue designated for voice transmission. The AC_VO queues of the QSTAs are very aggressive in transmitting their packets on to the channel due to their small CW sizes. This leads to degradation in the actual voice throughput performance even when the network size is small. This work proposes a new modification to the collision avoidance mechanism used by AC_VO queues without seriously effecting the performance of other traffic categories such as video and data. Extensive simulations are carried out to verify the performance of the proposed enhancement to the original collision avoidance mechanism.