Size-based and direction-based TCP fairness issues in IEEE 802.11 WLANs

  • Authors:
  • Naeem Khademi;Mohamed Othman

  • Affiliations:
  • Department of Informatics, University of Oslo, Oslo, Norway;Department of Communication Technology and Network, Faculty of Computer Science and Information Technology, Universiti Putra Malaysia, Serdang, Selangor D.E, Malaysia

  • Venue:
  • EURASIP Journal on Wireless Communications and Networking
  • Year:
  • 2010

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Abstract

Cross-layer interaction of Distributed Coordination Function (DCF) of 802.11 MAC protocol and TCP transport protocol leads to two types of unfairness. In a mixed traffic scenario, short-lived TCP flows suffer from poor performance compared to the aggressive long-lived flows. Since the main source of Internet traffic is small file web transfers, this issue forms a major challenge in current WLANs which is called size-based unfairness. In addition, when sharing an access point bottleneck queue, upstream flows impede the performance of downstream flows resulting in direction-based unfairness. Proposed solutions in the literature mostly rely on size-based scheduling policies. However, each proposed method is able to solve any of these two mentioned aspects, none of them can provide both size-based and direction-based fairness in a unique solution. In this paper, we propose a novel queue management policy called Threshold-Based Least Attained Service-Selective Acknowledgment Filtering (TLAS-SAF). We show analytically and by simulation that TLAS-SAF is capable of providing both direction-based and size-based fairness and can be taken into account as a unique solution to be applied at access point buffers.