Wifi and cordless phone conflicts

What uses what:

802.11b and 802.11g use various frequency bands within 2.4GHz

802.11a uses various frequency bands within 5.8GHz

Cordless phones currently appear to come in 900MHz, 2.4GHz, or 5.8GHz.
Note that some "5.8GHz" phones will transmit in one direction using
5.8GHz, but in the other direction using 2.4GHz.

Very nice table describing radio frequency allocation:

http://www.commandline.net/Radio%20Frequency%20Chart1.htm

The more things you have operating in a given frequency band, the more
problems you'll have.  Cordless phones trounce Wifi communications,
Wifi communications may interfere with the sound on Cordless phones,
the more cordless phones you have operating at the same frequency the
more likely you are to have bad reception/transmission, and the same is
true of having a lot of computers/laptops/tablets/PDA's operating in the
same frequency band.  Also, with b and g, bands can overlap significantly.

Most 2.4GHz cordless phones are "spread spectrum' - in other words,
they stomp all over the range of spectra that your 802.11b and 802.11g
want to use - and these wifi technologies more cooperatively use one
portion of the 2.4GHz spectrum (generally user-selectable).

I haven't heard of a way of restricting 2.4GHz cordless phones from
stomping on 802.11b/g, unfortunately.  There should be a way of teaching
them to use a more limited range of the spectrum.

Some alternatives for resolving this (in whole or in part):

1) If you use only 802.11[bg], then switch to either a 900MHz phone,
or a 5.8GHz phone (but note that you may want 802.11a someday, in which
case, see below).

2) If you use only 802.11a, then switch to either a 900MHz phone, or to
a 2.4GHz phone.

3) It is not clear to me at this time, whether 802.11a will conflict with
a 5.4GHz phone.  5.8GHz phones are more likely to conflict with 802.11a

4) If you have a sufficiently flexible access point, then you might try
reducing various wifi parameters, to see if you can reduce conflicts.
EG on a linksys wrt54g running openwrt, this -may- help:
      iwconfig eth1 \                           
              essid "`nvram get wl0_ssid`" \
              key restricted "`nvram get wl0_key1`" \
              mode Master \                           
              nickname "Linksys WRT54G with OpenWRT" \
              rate auto \                             
              rts 100 \
              frag 300 \
              channel "`nvram get wl0_channel`"

5) If you have a sufficiently flexible access point -and- sufficiently
flexible wireless client devices, then you may be able to switch to an
unusual wifi band like "13" or something (usually only goes to 11).

6) Try band 11 with 802.11b/g.  It tends to conflict less with 2.4GHz phones.

A university and their efforts to prevent such collisions:
http://networking.smsu.edu/faq/20010417_WirelessApplication.htm

On band conflicts and what uses what:
http://techrepublic.com.com/5206-6286-0.html?forumID=11&threadID=117834&start=0

Just to clarify kirk's statements, 802.11a operates in the 5.8GHz band,
going from 5725MHz to 5850MHz. 802.11b and 802.11g operate in the 2.4GHz
band, ranging from 2.4GHz to 2.4835GHz, and hence afford compatibility
between the standards (that's why most cross-standard equipment offer
b and g compatibility).

For interference design, the most important thing to understand is
channel selection. 802.11 b and g only has 3 non-overlapping channels,
1 6 and 11. You might be able to get away with slight overlap using 1 4
8 and 11. The nice thing about 802.11a is that it has 8 non-overlapping
channels, giving much better overlapping yet non-interfering coverage.

Use of a spectrum analyzer to find (relatively) quiet bands is highly
recommended!

http://www.boingboing.net/2005/04/11/my_new_favorite_cord.html

I don't think I've ever had a cordless phone I really like. The 2.4 GHz
models interfere with my Wi-Fi setup, and 5.8 GHz phones are a scam,
if you ask me, because they can't penetrate walls as well as phones that
use lower frequencies. For this reason, I always use 900 MHz phones.

Great page about cordless phone features, but I'm not sure I believe
that 5.8GHz never conflicts with 802.11a - it's conceivable the page
was written by someone who wasn't familiar with a.

http://www.officemax.com/max/solutions/microsite/categories/categoryArticle.jsp?edOID=537032268&BV_UseBVCookie=yes&cat=Phones

Another very good page about cordless phones

http://telecom.hellodirect.com/docs/Tutorials/5.8GHzFrequency.1.031903.asp

Very nice page comparing the features and attributes of 802.11[abg]
and bluetooth.  Doesn't cover power drain though, which is important on
mobile systems.

http://compnetworking.about.com/cs/wireless80211/a/aa80211standard.htm

I hear that bluetooth is also 2.4GHz