RE: [Discuss-gnuradio] 802.11 and Bluetooth

[Tom Rondeau]

> -----Original Message-----
> From: Eric Blossom [mailto:address@hidden
> 
> On Wed, Dec 06, 2006 at 12:01:03AM -0500, Tom Rondeau wrote:
> > I've seen a number of questions about these issues in the past couple of
> > days, so I'm addressing this from my own knowledge.
> >
> > Can we detect Bluetooth and WiFi with GNU Radio?
> >
> > I'm making two assumptions: we're using the USRP and WiFi/802.11 is
> > specifically addressing 802.11a/b/g.
> >
> > The answer is no. The bandwidth is too large for the system to currently
> > handle. If you tune the GNU Radio to the center frequency of an 802.11
> > channel, you'll see what looks like a rise in the noise floor (and,
> under
> > these conditions, it really is a rise in the noise) when there is a
> > transmission.
> >
> > Bluetooth signals hop from 2.402 - 2.480 MHz; 79 1 MHz channels at a
> rate of
> > 1600 hops per second. The GNU Radio cannot look a the entire band all at
> > once, so if you look at a particular slice (~4 MHz) of spectrum, you
> might
> > catch a glimpse of a signal every now and then, unless you can plug in
> the
> > right frequency hopping sequence (I think I have both MATLAB and C++
> code to
> > do this, buried somewhere, but then you'd need the master address (easy)
> and
> > its clock (difficult) to do it; and I'm not sure if the USRP's can
> change
> > frequency and settle fast enough for this).
> >
> > If you have some 1 or 2 Mbps 802.11 devices to use, the BBN guys have
> done
> > work on receiving those (search the list, it's been addressed a number
> of
> > times in the past).
> >
> > Hope this clears a bit up,
> > Tom
> 
> Actually, I think you should be able to detect Bluetooth without too
> much trouble.  If you just stare at a single point in the spectrum you
> should be able to reliably detect 7 1 MHz channel's worth of data.
> 
> IIRC the hopping sequence is known, and thus you should be able to
> determine if what you are seeing is bluetooth or not, even though you
> are seeing only 7 out of 79 channels.
> 
> Eric

I was thinking that, too, but you'll just see short blips on the screen.
Actually, if I get another second to breathe today, I'm going to see if I
can make it happen and see what can be seen.

Tom