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
[mailto:elbarrak.soum...@gmail.com]>:
---------- Forwarded message ----------
From: Soumaya el barrak <elbarrak.soum...@gmail.com
[mailto: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 [mailto: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
[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
[mailto: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
[mailto: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 [tel:+39%20327%20198%205064]
_______________________________________________ Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org [mailto:Discuss-gnuradio@gnu.org]
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[https://lists.gnu.org/mailman/listinfo/discuss-gnuradio]
_______________________________________________ Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org [mailto:Discuss-gnuradio@gnu.org]
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[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 [tel:+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 [tel:+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 [tel:+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
