A new framework for QoS provisioning in WLANS using p-persistent 802.11 MAC

  • Authors:

  • Kiran Anna;Mostafa Bassiouni

  • Affiliations:

  • School of Electrical Engineering and Computer Science, University of Central Florida, Orlando, FL 32816, USA;School of Electrical Engineering and Computer Science, University of Central Florida, Orlando, FL 32816, USA

  • Venue:
  • Computer Communications
  • Year:
  • 2008

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Abstract

In this paper, we propose a new framework which consists of three components viz., a p-persistent 802.11-based core MAC layer which provides optimum channel utilization, a scheduler that provides service differentiation between different classes of traffic in the contention phase of 802.11 and an admission control which provides statistical QoS guarantees. The current 802.11e EDCF protocol uses the same set of parameters viz., CW"m"i"n, CW"m"a"x, CW, AIFS, and PF for both channel access and service differentiation. We show that using these parameters to achieve a specific desired throughput differentiation is a very cumbersome task. We present detailed performance results of our framework using the NS2 simulator to demonstrate the effectiveness of the scheduler and the core MAC layer. Compared to 802.11 adaptive EDCF, our scheduler consistently achieves the desired throughput differentiation and easy tuning. The core MAC layer achieves better delays in terms of channel access, average packet service time and one hop delay and also achieves higher system throughput than the AEDCF for a given service differentiation ratio. We also develop an analytical model for the p-persistent 802.11 in the core MAC layer under unsaturated load conditions and present closed forms for the average packet service time and one hop delay. We consider both the ''no retry limit'' and ''finite retry limit'' cases and validate the analytical model by extensive simulation results.