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Fixed Point Analysis of Single Cell IEEE 802.11e WLANs: Uniqueness and Multistability

Ramaiyan, Venkatesh and Kumar, Anurag and Altman, Eitan (2008) Fixed Point Analysis of Single Cell IEEE 802.11e WLANs: Uniqueness and Multistability. In: ACM Transactions on Networking, 16 (5). pp. 1080-1093.

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We consider the vector fixed point equations arising out of the analysis of the saturation throughput of a single cell IEEE 802.11e (EDCA) wireless local area network with nodes that have different backoff parameters, including different Arbitration InterFrame Space (AIFS) values. We consider balanced and unbalanced solutions of the fixed point equations arising in homogeneous (i.e., one with the same backoff parameters) and nonhomogeneous networks. By a balanced fixed point, we mean one where all coordinates are equal. We are concerned, in particular, with 1) whether the fixed point is balanced within a class, and 2) whether the fixed point is unique. Our simulations show that when multiple unbalanced fixed points exist in a homogeneous system then the time behavior of the system demonstrates severe short term unfairness (or multistability). We provide a condition for the fixed point solution to be balanced, and also a condition for uniqueness. We then extend our. general fixed point analysis to capture AIFS based differentiation and the concept of virtual collision when there are multiple queues per station; again a condition for uniqueness is established. For the case of multiple queues per node, we find that a model with as many nodes as there are queues, with one queue per node, provides an excellent approximation. Implications for the use of the fixed point formulation for performance analysis are also discussed.

Item Type: Journal Article
Publication: ACM Transactions on Networking
Additional Information: Copyright 2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Keywords: Performance of wireless LANs;saturation throughput analysis of EDCA;short term unfairness.
Department/Centre: Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited: 08 Jul 2009 07:37
Last Modified: 19 Sep 2010 04:54
URI: http://eprints.iisc.ac.in/id/eprint/16831

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