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1.2 COMPUTER AND INFORMATION SCIENCE
In this paper we experimentally evaluate the capability of the EDCA mechanism to support voice traffic in a mixed voice/data transmission over 802.11e WLANs. In particular we investigate how real-time voice transmission can be supported by tuning four EDCA parameters, namely AIFSN, CWmin, CWmax and TXOP and how this impacts on background data transmission. The experimental set-up involves fifteen VoIP terminals sending bi-directional traffic between wired and wireless subnets and another station injecting various types of heavy background load to the wireless subnet. End-to-end voice transmission quality is predicted from time-varying transmission impairments with the use of the latest Appendix to the ITU-T E-model. Our experimental results show that the AIFSN parameter more effectively protects voice calls against background data traffic than CWmin. We also demonstrate that tuning of the TXOP parameter does not improve the quality of voice transmission. To the best of our knowledge this is the first experimental investigation regarding tuning of MAC layer EDCA parameters in a real 802.11e WLAN network form the perspective of end-to-end voice transmission quality and end user satisfaction.
Narbutt, M. & Davis, M. (2007) The capability of the EDCA mechanism to support voice traffic in a mixed voice/data transmission over 802.11e WLANS: an experimental investigation. IEEE Conference on Local Computer Networks (LCN'07), Dublin, Ireland, October, 2007.