Hi Amrit, Well, usrp_spectrum_sense is a hopping observer, and GSM is a hopping system: your probability of intercept is rather low.
Your probability of intercept is in fact, really zero, if your phone doesn't do GSM (2G), but uses 3G (UMTS) or 4G (LTE): these use other frequencies altogether. So, make sure your phone really does do GSM. You also don't even have to look at the GSM900 uplink at all: Telefonica (which Aldi resells) doesn't use that band at all. The spectrum sense application is really badly suited for this kind of task, as it hops: Instead, simply look at the whole band at once. A simple GNU Radio Companion flow graph connecting the USRP source (samp rate = total uplink bandwidth) to a Qt GUI Frequency Sink would make more sense. A word of secondary advice: If you're planning to experiment with 2G networks of your own, or doing something about the basic properties of microwave propagation and so on, observing spectrum of GSM is a worthwhile thing to do. Just be warned that it will be increasingly hard to find GSM signals "in the wild": T-Mobile will switch off GSM end-of-2020, and thus, up to then, all phones that can do both LTE and GSM will be instructed to use LTE whenever possible. Since there won't be much Machine-to-Machine GSM-only (which I assume are the primary users that won't be able to switch) user equipment in cities, you'll see that increasingly many phones don't use GSM anymore at all – even if the network still exists; the calculation is very simple: The amount of spectrum necessary to let a single user do a GSM phone call is worth MB/s for a lot of LTE users. Thus, everybody not using GSM is desirable for network operators. Best regards, Marcus On Mon, 2018-06-18 at 11:25 +0200, Amrit Zoad wrote: > Greetings everyone, > > I hope everyone is having a good day. > > I have installed GNURadio 3.7 and I wanted to see the GSM signals of my phone > (when I call someone) with the application "USRP Spectrum Scanner (FFT)". > But, I was unable to see any fluctiations in the spectrum from 890 MHz to 915 > MHz & 1710 MHz to 1785 MHz. My location is in Germany and I own a sim card of > Aldi Talk (MEDIONmobile). > > Then I tried with my phone's Bluetooth 5.0 and I could see the frequency > hopping from 2.4 GHz to 2.44 GHz along with the light Wi-Fi signals in the > spectrum. > > I have the Etttus Research USRP B210 with Bandwidth of 56 MHz (of the > front-end filter) and thus I am setting the sampling rate to 40 MHz. The > antenna also works from 850 MHz to 6.5 GHz. so no problem with that as well. > > What could be reason for me not able to see my phone's GSM signals in the > spectrum scanner? > Your help would be very valuable. > > Best regards, > Amrit Zoad > +49 177 8474550 > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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