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An Adaptive Contention-window Adjustment Technique Based on Individual Class Traffic for IEEE 802.11e Performance  

Um, Jin-Yeong (동국대학교 컴퓨터학과)
Oh, Kyung-Sik (동국대학교 컴퓨터학과)
Ahn, Jong-Suk (동국대학교 컴퓨터학과)
Publication Information
Journal of KIISE:Computing Practices and Letters / v.14, no.2, 2008 , pp. 191-195 More about this Journal
Abstract
This paper proposes a technique for improving IEEE 802.11e EDCA's performance by dynamically adjusting each class's contention window size based on each class's traffic amount. For providing differentiated service differently from 802.11, 802.11e EDCA maintains four classes each of which specifies different static minimum and maximum contention window sizes. Since the initial window sites significantly affect the 802.11e performance, several window adjustment schemes have been proposed. One of the schemes known as CWminAS (CWmin Adaptation Scheme) dynamically and synchronously determines the four windows' site based on the periodically measured collision rate. This method, however, can lower the send probability of high priority classes since it can't differentiate their collisions from those of low priority classes, leading to the channel underutilization. For solving this problem, we propose ACATICT(Adaptive Contention-window Adjustment Technique based on Individual Class Traffic) algorithm which adapts each class window size based on each individual collision rate rather than one average collision rate. Our simulation experiments show that ACATICT achieves better utilization by around 10% at maximum.
Keywords
IEEE 802.11e; QoS; EDCA; backoff algorithm; contention window (CW);
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