Video-conferencing and data traffic over an IEEE 802.11g WLAN using DCF and EDCA

In this paper we study the ability of an IEEE 802.11g WLAN to support video-conferencing and data applications. We evaluate the number of simultaneous video-conference calls that can be supported, subject to user perception-based quality requirements, and compare the performance of two MAC protocols: the default distributed coordination function (DCF) protocol and the enhanced distributed channel access (EDCA) protocol. We also assess the effect of the presence of data traffic generated by Web browsing and file transfer applications and the physical size of the network on the number of video conference calls that can be supported. The analysis of the network is carried out by means of simulation; great care is taken to accurately represent the applications and the network, requiring several modifications and additions to the widely-used ns-2 network simulator. At the application layer, traffic is generated using realistic models or real traces, and user perception-based quality metrics (for example, the mean opinion score for voice) are used to assess the network´s performance. Within the network, we use accurate representations of the MAC protocols, and use a wireless channel model which incorporates the effect of frequency-selective fading. We find that the presence of data traffic does not reduce the number of video-conference calls that can be supported when EDCA is used; this is not the case with DCF, Furthermore, the performance of both data applications considered is slightly improved by the use of EDCA.