User guide

AirMagnet Spectrum XT User Guide
Chapter 10: Device Detection 121
Impact on 802.11b/g WLAN
Because the 2.4-GHz radio band is unlicensed (free to all), there are numerous Bluetooth-
enabled devices by different manufacturers available on the market. The following is a short
list of such devices:
•Laptops
•PDAs
•Headsets
• Headphones
•Mice
•Keyboards
• Dongles
•Adapters
• Speakers, etc.
These Bluetooth devices are becoming increasingly popular in homes and businesses where
802.11b/g WLANs are deployed and have been recognized as a source of RF interference to
802.11b/g WLANs. You may tackle these interfering Bluetooth devices by identifying and
locating them in your WLAN.
Recommended Courses of Action
Once interfering Bluetooth devices are successfully located, the following actions are
recommended to minimize or eliminate the RF interference they cause to your 802.11b/g
WLAN:
• Change your WLAN from 802.11b/g to 802.11a or upgrade it to 802.11n standard and
set it up to run in the 5-GHz channels or frequencies, which will not only avoid RF
interference from Bluetooth devices operating in the crowded 2.4-GHz band but also
offer greater throughput.
• Try to use Bluetooth devices that are based upon Bluetooth specification version 1.2 or
later which uses Adaptive Frequency Hopping (AFH) which limit the use of
pseudorandom frequencies by Bluetooth devices when interference is detected. It
helps prevent Bluetooth devices from interfering with other transmissions in the 2.4-
GHz band.
Digital Cordless Phones
Most digital cordless phones on the market today operate in either the 2.4-GHz or 5.8-GHz
radio band, which happen to be the channel or frequencies used by 802.11b/g or 802.11a
wireless LANs (WLANs). The problem is that the two are completely different systems that
do not understand each other. As a result, radio signals from the two different systems will
collide and cause mutual RF interference. This is especially the case when 2.4-GHz FHSS
digital cordless phones are involved. Because they use FHSS modulation, their radio signals
hop from one frequency to another across the entire 2.4-GHz band, in searching for the best
channel or frequency to use. This hopping behavior will cause persistent RF interference to the