Measuring Wireless LANs

Wireless local area networks (WLANs) have appeared in many venues, including academic and corporate campuses, residences, and wireless ‘‘hotspots.’’ It becomes increasingly important to understand how these networks are used, as they continue to appear in more numerous and varied environments. Measuring and collecting data from production WLANs in a usage study is one way of fulfilling this need for understanding. Wireless usage studies and usage data are valuable for many aspects of wireless network research. Understanding how and where clients use the network, what applications clients are using, and how applications are using the network can help with network provisioning and deciding where to expand or augment coverage in an existing WLAN. Models of wireless application workloads can aid the design of future network protocols. Measurements of client mobility in a WLAN can help with the design of location-aware applications, or for developing and improving mobile handoff algorithms. Collecting data on a WLAN can be difficult, however. There are many technical and nontechnical logistical hurdles involved in collecting high-quality wireless measurements. We have been continuously monitoring a campus WLAN for over 3 years in the course of conducting two of the largest wireless measurement studies to date [9,13], and we have encountered many of these hurdles. In this chapter we describe some of the tools that the research community has used for measuring WLANs, and provide hints for their effective use obtained from our real-world experiences. We also discuss some of the usage studies that have been conducted using these tools, both on our own campus and elsewhere. In particular we concentrate