Hi Marcus,
I understand the usb bandwidth limitations, but I have to experience this spectrum scanning in the Raspberry pi 3. I used 8 MS/s, fft-size equal to 512 and tune-delay equal to 0.25s. I followed your recommendation, and I scanned only 48 Mhz per time. The energy levels obtained are logic, but while switching from one center frequency to another, almost 3.6 Mhz are dropped, I don’t receive anything along this bandwidth, it scans almost 2 Mhz and drop 3.6 Mhz. I don’t understand what is the reason behind those results and how can I improve them. Please if you have any ideas, give me a hand! Best Regards Soumaya 2017-01-16 14:24 GMT+01:00 Soumaya el barrak <elbarrak.soum...@gmail.com>: > > ---------- Forwarded message ---------- > From: Soumaya el barrak <elbarrak.soum...@gmail.com> > Date: 2017-01-16 12:48 GMT+01:00 > Subject: Re: [Discuss-gnuradio] usrp_spectrum_sense.py input parameters in > USRP B200 > To: Marcus Müller <marcus.muel...@ettus.com> > > > Dear Marcus, > > > Thank you again for your explanations, but I installed Gnuradio on a > Raspberry pi 3, model B board, so the usb ports are USB2 not 3. That’s why > I cannot use a high sample rate. I got an error because of the USB > bandwidth limitations. If you can guide me to the right parameters to > choose with this kind of host machine? > > Also, Can you please explain for me what does this parameter refer to : > $((2**16)) > > > The script which I use is this one: > > https://github.com/gnuradio/gnuradio/blob/master/gruhd/examp > les/python/usrp_spectrum_sense.py. > > > Thank you in advance > > Kind Regards > > Soumaya > > 2017-01-16 12:28 GMT+01:00 Marcus Müller <marcus.muel...@ettus.com>: > >> Hi Soumaya, >> >> while tuning, there will simply be transients, mostly of oscillator >> energy leaking into the receiver. You cannot use the data that you get >> while tuning. >> >> You might want to define "strange power values"; 2.4 GHz is an ISM band, >> so a lot of traffic is to be expected there, and that traffic is also >> probably very bursty, so that your observed values might temporarily vary a >> lot, since your observation time is much longer than the bursts in e.g. >> WiFi, your observed power is basically the product of number of burst, >> burst energy of the individual transmitter, and path loss between your >> receiver and the transmitter. >> >> Still, why are you using such small sampling rates as 8 MS/s? With a good >> USB3 controller and a reasonably fast computer, you should easily be able >> to do 40 MS/s with the usrp_spectrum_sense program. In fact, on my >> throttled thinkpad X240, I'm currently doing >> >> ./usrp_spectrum_sense.py -s 40e6 -g 76 -F $((2**16)) 2.4e9 2.5e9 >> >> and it works just fine. >> >> Best regards, >> >> Marcus >> On 01/16/2017 10:32 AM, Soumaya el barrak wrote: >> >> Hi Marcus, >> >> >> Thank you so much for your reply, I followed your recommendations, I used >> a sample-rate of 8MS/s and FFT-size 1024 and I kept the tune-delay and >> dwell-delay at 0.25 s. But I still receive some strange power values while >> scanning the 2.4 GHz band. >> >> >> I also obtained high power picks while tuning from one center frequency >> to another. Could you please explain for me where I am mistaken? And what >> is the explanation of those power picks? >> >> >> Best.. >> >> Soumaya >> >> 2017-01-13 14:46 GMT+01:00 Marcus Müller <marcus.muel...@ettus.com>: >> >>> Hi Soumaya, >>> >>> the B200 tunes slower and might need up to half a second when tuning >>> further. >>> >>> You should hence minimize the amount of tuning, and instead of 4MS/s use >>> a higher rate, a larger FFT size, and tune less often. >>> >>> The power normalization is truly, 100%, arbitrary. Since these dB are >>> all "relative to digital 1", they only have linear relation with real-world >>> powers. >>> >>> >>> Best regards, >>> >>> Marcus >>> >>> On 01/13/2017 11:40 AM, Soumaya el barrak wrote: >>> >>> Dear all, >>> >>> I am working with USRP B200 for spectrum sensing, I want to scan the >>> band from 2.4 to 2.5 Ghz, I use fft size 256, and sample_rate 4M, and tune >>> _delay 0,001s. I am not sure if the parameters are correctely chosen >>> because when I try to scan another band without wireless activities, I >>> still receive hight power levels. Can anyone has any idea about where I am >>> mistaken ? >>> >>> Also, in the formula used to calculate the PSD : >>> >>> Power_dB = 10*math.log10(m.data[i_bin]/tb.usrp_rate); >>> >>> Normally it is the magnitude squared averaged , I want to know why it is >>> averaged by the usrp_rate ? >>> >>> >>> Thank you in advance ! >>> >>> Soumaya >>> >>> -- >>> >>> *EL BARRAK Soumaya* >>> >>> *Telecommunication & Networking Engineer / Phd Student* >>> >>> *Innovative Technologies Laboratory* >>> >>> *National School of Applied Sciences of Tangier - (ENSA Tanger)* >>> >>> *Abdelmalek Essaâdi University - Morocco* >>> >>> *Tel : (+212) 6 65 9 625 40/ (+ 39) 327 198 5064 >>> <+39%20327%20198%205064>* >>> >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing >>> listDiscuss-gnuradio@gnu.orghttps://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >>> _______________________________________________ Discuss-gnuradio >>> mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/ >>> listinfo/discuss-gnuradio >> >> -- >> >> *EL BARRAK Soumaya* >> >> *Telecommunication & Networking Engineer / Phd Student* >> >> *Innovative Technologies Laboratory* >> >> *National School of Applied Sciences of Tangier - (ENSA Tanger)* >> >> *Abdelmalek Essaâdi University - Morocco* >> >> *Tel : (+212) 6 65 9 625 40/ (+ 39) 327 198 5064 <+39%20327%20198%205064>* >> >> > > > -- > > *EL BARRAK Soumaya* > > *Telecommunication & Networking Engineer / Phd Student* > > *Innovative Technologies Laboratory* > > *National School of Applied Sciences of Tangier - (ENSA Tanger)* > > *Abdelmalek Essaâdi University - Morocco* > > *Tel : (+212) 6 65 9 625 40/ (+ 39) 327 198 5064 <+39%20327%20198%205064>* > > > > -- > > *EL BARRAK Soumaya* > > *Telecommunication & Networking Engineer / Phd Student* > > *Innovative Technologies Laboratory* > > *National School of Applied Sciences of Tangier - (ENSA Tanger)* > > *Abdelmalek Essaâdi University - Morocco* > > *Tel : (+212) 6 65 9 625 40/ (+ 39) 327 198 5064 <+39%20327%20198%205064>* > -- *EL BARRAK Soumaya* *Telecommunication & Networking Engineer / Phd Student* *Innovative Technologies Laboratory* *National School of Applied Sciences of Tangier - (ENSA Tanger)* *Abdelmalek Essaâdi University - Morocco* *Tel : (+212) 6 65 9 625 40/ (+ 39) 327 198 5064*
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