Hi Marc, Thank you for joining the conversation, my channel bandwidth is fixed on 6250 Hz, it is the default value in the script, I don't know how can I decrease the frequency step, because received samples during a large band are dropped, and while plotting the results, I couldn't have a continuous distribution of the power.
Thank you again Regards Soumaya 2017-01-18 12:39 GMT+01:00 Marc Pàmies Massip <mpamies...@gmail.com>: > Hi Soumaya, > > Which is your channel bandwidth? According to your message I think you are > not setting this parameter, so I don't know which value the program might > be using. I say that because in line 195 (self.freq_step = > self.nearest_freq((0.75 * self.usrp_rate), self.channel_bandwidth)) the > freq_step is set to discard the bins on both ends of the spectrum, and the > formula used depends on both the sample rate and the channel bandwidth. > Maybe it is related with your problem (or not?). > > I wanted to join this conversation because I am also using > osmocom_spectrum_sense and having some trouble with the frequencies as > well... I don't really understand the way center_freq is set. In my case I > want to find peaks in a band that goes from 925MHz to 960MHz in steps of > 200KHz ((960M-925M)/200K=175steps), but when I execute the program printing > the variables "center_freq" and "freq" at each iteration of the main loop > they don't change as I was expecting. > > I thought that in the first iteration center_freq would be 925.1MHz (to > compute the power in the 200KHz band that goes from 925.0MHz to 925.2MHz), > the second iteration should be cenetered in 925.3MHz and so on until the > 175th iteration where the band from 959.8MHz to 960.0MHz should be analysed > (so freq_center would be 959.9MHz in this last case). However, looking at > the outputs given by the program I see that the center_freq remains the > same for a while while freq goes increasing in intervals of 200KHz (input > parameter of channel_bandwidth), but the value of freq starts far away from > 925MHz so this makes me think that it is not looking at the first band of > the spectrum that I am asking from the command line. > > It doesn't make much sense to me, con anyone explain how it works? > > Thank you in advance, > > Marc. > > PD: In case it helps, here it is the command I am using: > > osmocom_spectrum_sense -a hackrf -s 10000000 -g 20 -b 200000 -F 1024 > 925000000 960000000 > > On 17/01/2017 11:42:06, Soumaya el barrak <elbarrak.soum...@gmail.com > wrote: > > _______________________________________________ Discuss-gnuradio mailing > list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/ > listinfo/discuss-gnuradio > > 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 <+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*
_______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio