Though their reviewer found some fault with the documentation and packaging, Enterprise Networking Planet found that Zap, an open source wireless performance tool from Ruckus, provides some really useful insight into how a WLAN can be expected to perform. A bit more polish, they conclude, and Zap will be more than welcome in every network admin's arsenal.
"Zap" is a wireless performance tool, previously used for internal development and testing by Ruckus Wireless. Ruckus has released the Zap source code under a modified BSD license to provide the tool to the world, and hopefully spur development of this and other related analysis tools. Zap measures performance, statistically, to provide insight into the true nature of how a network can perform.
Before Zap, a wireless network administrator might have done some manual calculation to determine a best-guess baseline of how a network would perform. Check to make sure there aren't too many overlapping channels that may cause interference, carefully plan the layout, and hope. When testing time comes, we might run a large file copy with rsync or even use TTCP, which will tell us, on average, how fast the data transferred. This is fine for bulk transfers, and it may highlight an obvious problem in the network, but network-intensive applications today require more certainty.
Testing wireless is difficult because the tester has no ability to control the environmental factors. We might run a crude test, like a file copy, multiple times and get multiple answers. Those answers can vary by MegaBits per second, which isn't exactly precise.
Read "Zap Provides Open Source Wireless Testing" at Enterprise Networking Planet