WM Setup

To capture wireless frames, we used three network sniffers, each comprising a PC running Linux with the 2.4.19 kernel. Each sniffer had a Prism2 chipset-based wireless network interface card; two sniffers had Demarctech DT-RWZ0-200mW-WC cards, and the third had a Linksys WPC11v3 card. To measure traffic, we used the Ethereal protocol analyzer (version 0.9.6) with the libpcap library (version 0.7). Each card was placed into `monitor mode', which allowed the card to capture 802.11 frame information on a target channel.

The sniffers captured the first 256 bytes of each observed 802.11 frame, recording the complete view of the frame, i.e., PHY/MAC/LLC/IP/Above-IP information. PHY information, such as MAC Time and SNR (signal-to-noise ratio), can be captured using Prism2 monitor header, which is not a part of the IEEE 802.11 frame header, but is generated by the firmware of the receiving card.