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*
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