Perhaps the most difficult task in wireless networking is trying to visualize what is really going on. Radio waves are invisible and undetectable to humans without the aid of sophisticated tools, such as a spectrum analyzer. Such devices aren't cheap, ranging from several hundreds to tens of thousands of dollars, depending on their capabilities. Obviously, such devices are well beyond the reach of the average networking aficionado. And even if they weren't, a spectrum analyzer only gives you a visualization of what is going on at the physical radio layer; it doesn't give you any indication of what is happening with the actual network data.
Fortunately, every 802.11 networking device can not only transmit data, but can listen as well. Combined with sophisticated (and generally free) software, this can turn an average laptop or handheld into a powerful monitoring tool. This chapter shows how to use standard hardware to detect wireless networks and clients, generate statistics on their usage, and gather valuable insight into how your network is being used by sifting through the deluge of available radio information. Using these tools can help you coordinate networking efforts with people in your local vicinity to make the most efficient possible use of the available radio spectrum.
Bluetooth, Mobile Phones, and GPS
Network Discovery and Monitoring
Wireless Network Design
Appendix A. Wireless Standards
Appendix B. Wireless Hardware Guide