Learn to do a wireless LAN site survey with this tutorial

While a wireless site survey using the tools described above are great, they're not great at factoring in Radio Frequency (RF) interference from non-802.11 devices that use the 2.4 or 5.8 GHz range. For that, you need a true Spectrum Analyzer to measure RF activity from any radio-emitting device such as microwave ovens, wireless cordless phones, or wireless video surveillance cameras. Dedicated hardware analyzers can cost several thousand dollars, but laptop owners have a new, cheaper way of measuring RF activity using commodity laptop computers. AirMagnet offers a new line of Spectrum Analyzersthat come in the form of software and a PCMCIA card that can map RF activity in both the 2.4 and 5 GHz range.

Strategies for avoiding interference

To avoid these interference issues with WLANs, here are some best practices to consider:

• Measure for excessively noisy 2.4 and 5 GHz using a spectrum analyzer and get rid of them. If you can't afford one, you can still do the following to minimize interference issues.
• Stick with newer 5.8 GHz digital spread spectrum cordless phones.
• Stick with wired video cameras. For any fixed devices that don't need to move around like a laptop or PDA, CAT-5 cabling is the best way to go because not only does it transmit data, but also electricity to power the device, so that you don't need to use an AC adapter and a thick power cord.
• If you must use a wireless camera because it's not feasible to run CAT-5 cabling, use an 802.11 camera (preferably 802.11a if possible) because they use less radio spectrum.
• Analog 2.4 GHz cordless phones are also notorious for being spectrum hogs, and cordless 2.4 GHz analog video cameras are also in the same category.
• In most cases, you'll find that newer, well-made microwave ovens will produce less noise than an older model that can easily overwhelm a 802.11 b/g WLAN with sheer power.
• Bluetooth devices can also cause interference in the 2.4 GHz range, but their power levels are usually limited especially with the newer Bluetooth 1.2 standard that's designed to play nicer with 802.11.