Solving wireless problems can be tricky, but it’s not rocket science. Granted, there are a few basic concepts to understand -- but your success most likely will depend on your own observations and detective skills. The majority of problems can be traced to RF interference, misaligned antennas, poorly placed access points, dead spots, and suboptimal channel selection.
With wireless systems it is very difficult to predict the propagation of radio waves and detect the presence of interfering signals without the use of test equipment. Radio waves don't travel the same distance in all directions -- instead walls, doors, elevator shafts, people, and other obstacles offer varying degrees of attenuation, which cause the Radio Frequency (RF) radiation pattern to be irregular and unpredictable. In order to achieve optimal reliability and throughput for a WiFi (802.11) wireless network it is necessary to detect and identify sources of interference that affect network performance.
A variety of tools are available for detecting and identifying sources of RF interference and which provide information that allows optimal configuration of a WiFi network -- they each have their strengths and weaknesses. These include network discovery tools (also known as WiFi scanners), WiFi and RF spectrum analyzers, channel analyzers, and WiFi connection analyzers. The progression from network discovery, to RF spectrum analysis, to channel analysis, and finally to connection analysis provides a natural flow and conceptual path when contemplating how to approach a WiFi problem. The progression breaks what might initially seem like a hopeless problem into smaller, more easily solvable pieces -- with the ultimate goal being the application of a quantifiable metric that allows you to optimize the performance of your wireless network and determine the best channel.
Four things to keep in mind as you tackle a WiFi-related problem:
1. It is most likely caused by RF interference, the existence of dead spots, or poor reception that can be corrected by better locating/aligning an antenna.
2. The beacon strength of an access point is not a measure of performance. Nor do you want to necessarily associate with the access point with the strongest beacon signal.
3. In 802.11 b/g you have a choice of channels (11 channels in North America, 13 channels in Europe) where each channel is a range of frequencies. Furthermore, there is tremendous overlap among adjacent channels (take a quick look at the image at the bottom of this page). It’s important to make note of the overlap because a wireless device that transmits in the frequency range of channel 1 not only interferes with channel 1 but probably also is wrecking havoc on channels 2, 3, etc.
4. When interference is the cause of poor performance, then the most common solution is to reconfigure your access point to use a different channel. In certain situations you may need to track down the source of interference, but more often than not it will be coming from a source or location you have no control over. So, the simplest (and, often, only) solution is to identify a channel that isn’t subject to RF interference and reconfigure your wireless network to use that channel.