An Approach to Increase Channel Utilization in the IEEE 802.11 Networks by Improving Fairness at the Medium Access Control Sub-Layer




Kamath, Vikram V

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The IEEE 802.11 Standard, serves as an access mechanism for multiple stations to exchange data over the wireless medium. This standard made it possible to provide Internet- based services to untethered stations. With the undisputed success of IEEE 802.11 Standard over the contemporary short-range wireless networks, this technology is being quickly adopted by the cellphone manufacturers, for their hand-held devices. In future, this will mean, a large number of devices will be capable of transmitting over IEEE 802.11 protocol. This access method however, results in collisions when two or more stations try to transmit simultaneously. Furthermore, the probability of collision, increases with the number of stations sharing the medium. The Binary Exponential Back off (BEB) mechanism, in Carrier-Sense Multiple Access/Collision Avoidance (CSMA/CA), reduces this probability of collision to some extent. However, under saturation conditions, the behavior of BEB is somewhat unfair, which leads to degradation of average channel utilization. Also, this degradation increases linearly with the number of stations contending for the channel. A new scheme, Enhanced Binary Exponential Back off (EBEB) is proposed, which enhances the average channel utilization by improving degree of fairness for BEB at the Medium Access Control sub-layer. EBEB scheme can blend with all flavors of the IEEE 802.11 Standard. Also, EBEB stations can coexist with the existing BEB stations. In this thesis, analytical and simulation models for both schemes are developed, followed by comparison of analytical and simulation results for both schemes.



EBEB, Medium Access Control, Fairness, BEB, 802.11