Re: [Discuss-gnuradio] 802.11 and Bluetooth

[Shravan Rayanchu]

> Nevertheless, there is a spectrum sweep example
> (gnuradio-example/usrp/usrp_spectrum_sense.py). This application can
> sense a large bandwidth, but not in real time! It can do a sweep over
> a very large frequency range, but it will very likely not be able to
> detect bluetooth (since it is frequency hopping) nor 802.11b/g since
> this will most likely just look like noise. Anyway, it is difficult to
> just detect wi-fi without trying to decode it, since it is not a
> continuous signal, i.e., packet oriented. Therefore, you won't have a
> nice peak in your fft, compared to a radio broadcast channel.

Actually, you get a reasonable plot. Although you can only sense a
maximum of ~6 Mhz at once, doing so in steps of frequency gives a fair
idea. I made some changes to the spectrum_sense example, so as to a
fftshift and remove outer 25% of the bins. I used a frequency step of
0.5 Mhz and also passed it through the log10 block. Attached are the
plots for entire spectrum (spec.pdf) and channel 1 (0.5m.pdf).

Although, I am not sure what the "UNITS" are, they should give a sense
of the relative powers at different frequencies.  (Would they end up
in dB as I passed it through the log10 block? I couldnt particularly
understand Eric's code i.e. what is passed to the log10 block)

Thanks,

Shravan

0.5m.pdf
Description: Adobe PDF document

spec.pdf
Description: Adobe PDF document