---------- 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/ examples/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*
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