Re: [Discuss-gnuradio] 802.11 and Bluetooth

[John Clark]

Dheeraj S. Aralumallige schrieb:
> Hi !!
>
> Thank you very much for the help!!!
>
> But still I have one question. (See the highlighted part)
>
> Is there any example program to just detect the presence of wi-fi or 
> Bluetooth.
>
> I’m just interested in detecting the presence of any of these signals 
> in the environment. I don’t want to transfer any data/packets using 
> SDR. I just need to detect the presence or absence of a signal.
>
> Please help me regarding this.
You can 'sweep' the range 2.4 Ghz range that 802.11/Bluetooth exist on. You
can probably detect transmitter energy. You may even be able to see the 
'shape'
of spectrum associated with either DSS or OFDM, and probably be able to 
distingish
that from say a Microwave oven in operation.... But to specifically say
this energy is from a 802.11/Bluetooth device, is not possible without 
attempting
to decode the transmitted packet data.

In 802.11 each channel is 20 Mhz wide, since I'm just tuning into 
GNURadio, the USRP,
I don't know what it's operational limits are. From my experience looking at
spectra given by more expensive spectrum analyzers in the 2.4 GHz band, 
the energy
envelope is identifiable, but not identifiable to the point of knowing 
that it is
an 802.11 signal, unless I'm also controling the interface card, and 
know I'm transmitting
on a particular 802.11 channel.

Other divices such as Bluetooth, or cordless phones that operate in the 
band, I'm not
familiar with, as that is not my usual area of work. If Bluetooth 'hops' 
across the full
ISM 2.4 GHz band, then one can only see an occasional burst of energy, 
and maybe make
some estimate given a limited window, or sweep through the band, but 
dwelling in a
particular frequency range long enough to 'catch' a hopper pattern.


John Clark.