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Lalu Naick B.,Narasarao Pet Engineering College | Suvarna B.,Vignan University
IEEE-International Conference on Advances in Engineering, Science and Management, ICAESM-2012 | Year: 2012

Voice over Internet Protocol is an important service with strict quality of requirements in Wireless Local Area Network (WLANs). The IEEE 802.11e Standard has been introduced recently for providing Quality of Service (QoS) capabilities in the emerging wireless local area networks. The IEEE802.11e is an approved amendment to the IEEE802.11 standard that defines a set of Quality of Service enhancements for Wireless LAN applications through modifications to the medium access control layer. This 802.11e introduces a contention window based that is Enhanced Distribution Channel Access (EDCA) technique that provides a prioritized traffic to guarantee minimum bandwidth needed for time critical applications. However this EDCA technique resets statistically the contention window of the mobile station after each successful transmission. This static behavior does not adapt to the network state hence reduces the network usage and results in bad performance and poor link utilization whenever the demand for link utilization increases. For that purpose a new adaptive differentiation technique has been proposed for IEEE 802.11e wireless local area networks that take into account the network state before resetting the contention window. The proposed approach is based on adapting the values of CW depending on the channel congestion level. In IEEE 802.lIe the value of CW is incremented whenever a station fails to transmit due to a collision. This would imply that when the channel is highly congested CW would acquire values distant from CW min and close to CW max• Similarly, when the channel is free, CW values would be close to CW min and distant from CW max. Hence, it is feasible to estimate the channel congestion level by taking into consideration the current value of CWo The performance of the proposed technique is evaluated and compared with the original IEEE 802.lIe technique. Preliminary results show that the proposed adaptive technique enhances the channel utilization and increases throughput. © 2012 Pillay Engineering College.

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