Measuring Traffic on the Wireless Medium: Experience and Pitfalls

Abstract

A number of measurement studies have examined traffic characteristics in wireless networks. Most of these measurements [1], [6], [7] have been conducted from the wired portion of the network. In this paper we argue that such measurements are not sufficient to expose either the characteristics of the wireless medium or how such characteristics impact traffic patterns. While it is easier to make consistent measurements in the wired part of a network, such measurements can not observe the significant vagaries present in the wireless medium itself. As a consequence constructing an efficient and accurate measurement system from a wireless vantage point is important but usually quite difficult. In our work we have explored the various issues in implementing such a system to monitor traffic in an 802.11 based wireless network. We identify different challenges in making such measurements and provide detailed experimental evidence in their supports.Our work shows that the wireless measurement allows us to infer much richer information about the medium characteristics than is possible with a measurements made on the wired part of the network. We apply our measurement technique to study the end-to-end wireless network delay. We show that wireless monitoring can effectively identify the causes of end-to-end delays.

Improving the latency of 802.11 hand-offs using neighbor graphs

“…Sniffing is often used for performance analysis in WLAN, especially for management frames [9] [13] [32]. One advantage of sniffing is its independence from implementations.…”

The changing usage of a mature campus-wide wireless network

“…We are currently extending our sniffing capability to include wireless sniffers, so as to monitor the 802.11 MAC layer. Whilst some researchers have taken 802.11 wireless measurements [21,7,14], these have typically taken place in laboratory conditions, and there is little wireless monitoring of production WLANs. As the quantity of data collected by wireless sniffing is much greater than for wired sniffing, we again intend to only monitor the most popular parts of campus.…”

Lightweight MAC-spoof detection exploiting received signal power and median filtering

“…A complete model is not within the scope of this paper, this is just to give an idea of the problem. If the reader wishes to read more about the topic a good starting point could be [1,16,5]. Signal power is also dependent on other factors directly related to the device, namely the type of wireless card, antenna, driver etc.…”