User guide

AirMagnet Spectrum XT User Guide
Chapter 10: Device Detection 123
Figure 10-4: RF spectrum pattern of a 5.8-GHz FHSS digital cordless phone
Impact on 802.11 WLAN
Because the 2.4-GHz and 5-GHz radio bands are unlicensed (free to all), there are numerous
2.4-/5-GHz digital cordless phones by different manufacturers available on the market. They
are widely used in homes and businesses where 802.11b/g or 802.11a WLANs are deployed.
They have been recognized as a major source of RF interference for 802.11b/g or 802.11a
WLANs. You may tackle these interfering 2.4-/5-GHz cordless phones by first identifying and
locating them in your WLAN.
Recommended Courses of Action
Once interfering cordless phones are successfully located, you can take the following actions
to minimize or eliminate their RF interference to your 802.11b/g or 802.11a WLAN:
• Do not waste your time switching AP channels, because RF signals from digital
cordless phones spread over all channels or frequencies in the band they operate.
Simply adjusting AP channel is not the solution.
• If you have an 802.11b/g WLAN, avoid or stop using 2.4-Ghz FHSS cordless phones.
Instead replace them with 5.8-GHz or even old 900-MHz cordless phones which use
different radio bands and channels.
• If you have an 802.11a WLAN, avoid or stop using 5-GHz cordless phones. Instead
replace them with 2.4-GHz cordless phones.
• If you have an 802.11b/g WLAN and 2.4-GHz cordless phones are a must, try to use
those more expensive but less interfering ones which use Digital Spread Spectrum
(DSS) technology that offer wider range, better security, with less interference.
• If optimal WLAN performance is not an issue, you may continue use your 2.4-/5-
GHz cordless phones along with 802.11b/g or 802.11a WLANs but try to maximize
the distance between APs and cordless phone bases to minimize their RF interference
between each other.
• Consider upgrading your WLAN to 802.11n standard, which not only provides better
RF interference avoidance mechanisms but also offer greater throughput.