On Tuesday (07/02/2002 at 10:19PM -0500), Chris Elmquist wrote:
> 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 peacefully,
> > > 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 haven't
> > 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, others)
> 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:
> http://www.planetanalog.com/features/OEG20010226S0036
> "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 meter,
> they can degrade each other's performance significantly. This is particularly
> relevant to devices such as laptops or Internet appliances enabled with both
> technologies, as they will have far less than one-half a meter separating
> the two."

Just to keep beating this horse...

here is another reference that goes into the gory technical details of
how and why the interference between these two systems is likely:


it should be noted that Mobilian are (or have) developed a hybrid
PHY that can handle both 802.11b and Bluetooth simultaneously in
the same silicon.  They are pushing this as a solution to the close-in
coexistance problem.  They did a good analysis of the interference
issue in this paper though, IMO.


Chris Elmquist   mailto:chrise at pobox.com   http://www.pobox.com/~chrise