I have my AP set on channel 1.  Occasionally when I pick up my 2.4ghz
phone it'll knock me of my wlan.  All I have to do is hit the channel
button on the phone and it'll pick right back up.  If I pick up the
phone, and it uses channel 2, it's only partially overlapping my signal
(as you may recall, WLANs use 3 channels or 22mhz wide swaths of
bandwidth) it'll drop my throughput/signal quality to 5.5mbps.

I think what is happening is that the cordless phone detects a strong
signal on channel 1, and selects it to xmit on that channel.

I really should get rid of that phone and get a FHSS or a 900mhz.
900mhz is much better for cordless phones anyway (Better range)...



-----Original Message-----
From: tcwug-list-admin at tcwug.org [mailto:tcwug-list-admin at tcwug.org] On
Behalf Of Chris Elmquist
Sent: Tuesday, July 02, 2002 10:20 PM
To: tcwug-list at tcwug.org
Subject: Re: [TCWUG] Bluetooth

On Tuesday (07/02/2002 at 09:10PM -0500), Matthew S. Hallacy wrote:
> On Tue, Jul 02, 2002 at 05:03:16PM -0500, Joel R. Helgeson wrote:
> > For the most part, Bluetooth and 802.11a will coexist quite
> > neither stomping on each other.
> I think you need plain vanilla 802.11, such as the 3mbit breezecom 
> equipment (FHSS), unless there's something in the 802.11a specs that I
> heard about =p

I'm quite curious about the coexistance statements being made now
about Bluetooth and 802.11b since apparently something has changed.

About four years ago the literature (RF Design, Microwaves and RF,
were full of stories about early Bluetooth devices wiping out 802.11b
systems due to fundamental overload.  My greatest recollection was
as I mentioned in my earlier post regarding large 802.11b installations
making sure no Bluetooth devices (of which there were few on the market)
where used on the premis because they would take down the wireless
nodes in close proximity.  The scenario was someone sitting across the
conference table from you, using a Bluetooth headset with his cellphone,
and keeping you from accessing the corporate network over 802.11b.

Which piece changed? The Bluetooth or the 802.11b?  and how?

I find this reference, which suggests some approaches to coexistance
(like turning on system off while the other is operating) yet definitely
highlights the interference problems:


"When both technologies are operating at the same time, but are
separated by
more than 3 meters, they don't typically interfere with one another to a
great degree. However, within 3 m, and especially within one-half a
they can degrade each other's performance significantly. This is
relevant to devices such as laptops or Internet appliances enabled with
technologies, as they will have far less than one-half a meter
the two."


Chris Elmquist   mailto:chrise at pobox.com   http://www.pobox.com/~chrise
Twin Cities Wireless Users Group Mailing List - Minneapolis/St. Paul,
tcwug-list at tcwug.org