Re: [Discuss-gnuradio] debugging uhd_corr_and_sync example

[Ernest Fardin]

Hi,

I think this behaviour may be due to the level into the Polyphase Clock
Sync block. The block expects a signal amplitude of 1 as explained in [1].

An AGC between the Correlate and Sync and the Polyphase Clock Sync blocks
might do the trick.

Cheers

Ernest

[1] https://destevez.net/2017/08/agc-for-gr-satellites/


On Wed, Jul 10, 2019 at 6:22 AM Achilleas Anastasopoulos 
wrote:

> Hi all,
>
> I am not very successful in running the uhd_corr_and_sync_tx/rx.grc
> example in the gr-digital examples directory (3.7.13.5) using usrps.
>
> In an effort to debug it, i merged the two graphs and eliminated the uhd
> sink/sources (see attached) and so I am running a simulation without the
> usrps. I also eliminated the FLL block as I do not have any frequency error
> and not even any noise.
>
> The behavior I see is as follows:
>
> The transmission seems fine (a nice rrc spectrum followed by silence
> periodically on and off).
> On the reception side the blocks seem to be working fine producing
> appropriate tags (one every 20Ksamples as expected) which means that the
> "correlate_and_sync" block works as expected.
>
> When I plot the output of the "polyphase_clock_sync" I expect to see three
> clear points:  +/- A and 0. Indeed this is what I see at first.
>
> Now I do the following: I increase the noise for a while to a large number
> (~10dB) and then I take it back almost to 0 (-20dB). From that point on,
> although the "correlate_and_sync" block works as expected (I see the tag
> offsets back to normal) the picture does not contain three clear points but
> is blurred indicating that the "polyphase_clock_sync" does not work
> appropriately and I can never recover from this.
>
> I was hopping that since the "correlate_and_sync" block recovers and adds
> the appropriate tags to the stream, the downstream block can recover as
> well. However the behavior is not as robust as I expected.
>
> Can someone shed some light into this.
>
> thanks
> Achilleas
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[Discuss-gnuradio] debugging uhd_corr_and_sync example

[Achilleas Anastasopoulos]

Hi all,

I am not very successful in running the uhd_corr_and_sync_tx/rx.grc example
in the gr-digital examples directory (3.7.13.5) using usrps.

In an effort to debug it, i merged the two graphs and eliminated the uhd
sink/sources (see attached) and so I am running a simulation without the
usrps. I also eliminated the FLL block as I do not have any frequency error
and not even any noise.

The behavior I see is as follows:

The transmission seems fine (a nice rrc spectrum followed by silence
periodically on and off).
On the reception side the blocks seem to be working fine producing
appropriate tags (one every 20Ksamples as expected) which means that the
"correlate_and_sync" block works as expected.

When I plot the output of the "polyphase_clock_sync" I expect to see three
clear points:  +/- A and 0. Indeed this is what I see at first.

Now I do the following: I increase the noise for a while to a large number
(~10dB) and then I take it back almost to 0 (-20dB). From that point on,
although the "correlate_and_sync" block works as expected (I see the tag
offsets back to normal) the picture does not contain three clear points but
is blurred indicating that the "polyphase_clock_sync" does not work
appropriately and I can never recover from this.

I was hopping that since the "correlate_and_sync" block recovers and adds
the appropriate tags to the stream, the downstream block can recover as
well. However the behavior is not as robust as I expected.

Can someone shed some light into this.

thanks
Achilleas


uhd_corr_and_sync_tx_rx.grc
Description: Binary data
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Re: [Discuss-gnuradio] OFDM Mod Block - how is it working?

[rear1019]

On Tue, 09 Jul 2019 at 17:42:11 +0200, lilijobo1 lilijobo1 wrote:
> The thing is that I dont really get how the parameters 
> occupied tones and the FFT length work in that case. 
> Is the occupied tones equal to the numer of subcarriers? If yes where do get 
> to know the subcarrier spacing because if Im right this is different for 
> LTE or 802.11a .
>
> And what about the parameter FFT length?

Occupied tones determines the number of used (occupied) carriers, i.e.
the number of carriers which contain data and pilots. The number of
carriers which can be used at most is determined by the FFT length.

Carrier spacing Δf_c is determined by Δf_c = 1/T_s where T_s is the
length of the OFDM symbol (cyclic prefix not included). Assuming a
sampling rate of f_s you get Δf_c = 1/(N·(1/f_s)) = f_s/N where N is the
required length of the FFT.

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[Discuss-gnuradio] OFDM Mod Block - how is it working?

[lilijobo1 lilijobo1]

Hi,

 

I'm working with grc and a LimeSDR board and saw that there is the "OFDM Mod" Block available that I thought I could use to generate a broadband signal that is similar to a channel in LTE.

In detail I want to generate a signal with a known bandwidth like 5MHz  and analyze how the LimeSDR works with that for different frequencies and gains. Therefore I just took a random source the OFDM Mod block and the Limesuite sink ( Gr-limesdr Plugin from Myriad) to generate such a signal. 

The thing is that I don't really get how the parameters "occupied tones" and the "FFT length" work in that case. Is the occupied tones equal to the numer of subcarriers? If yes where do get to know the subcarrier spacing because if I'm right this is different for LTE or 802.11a .

And what about the parameter "FFT length"?

I would appreciate any help or suggestions.

 

Thank you in advance

 

Greetings

Johannes

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Re: [Discuss-gnuradio] JIT integration and undefined symbol

[Ron Economos]

This is just a guess, but the DVB-T Viterbi decoder uses SSE2 intrinsics 
for performance. In gnuradio/gr-dtv/lib/CMakeLists.txt, the flag 
"-msse2" is added to CMAKE_CXX_FLAGS.


Ron

On 7/9/19 05:39, Corentin Basler wrote:


Hello everyone,

I'm actually doing my bachelor thesis about Just In Time compiler and 
I want to integrate this technology in GNURadio. I've already created 
OOT module with integrated JIT functionality. I'm now trying to add an 
in-tree module. I'm trying to do that by copying the dvbt viterbi 
decoder block. The JIT compiler that I use is : ClangJIT 
 . For testing, I 
use the example dvbt_rx_8k. I’m working from the maint-3.7 branch. I 
added my new block and replace the originalviterbi decoderin the 
example. Unfortunately, when running the application, I have the 
following error :


Traceback (most recent call last):

File "/home/pacco/TB/gnuRadio_perf/dvbt_rx_demo_8k_jit.py", line 21, 
in 


from gnuradio import dtv

File 
"/opt/gnuradioClangJit/lib/python2.7/dist-packages/gnuradio/dtv/__init__.py", 
line 34, in 


from dtv_swig import *

File 
"/opt/gnuradioClangJit/lib/python2.7/dist-packages/gnuradio/dtv/dtv_swig.py", 
line 17, in 


_dtv_swig = swig_import_helper()

File 
"/opt/gnuradioClangJit/lib/python2.7/dist-packages/gnuradio/dtv/dtv_swig.py", 
line 14, in swig_import_helper


return importlib.import_module(mname)

File "/usr/lib/python2.7/importlib/__init__.py", line 37, in import_module

__import__(name)

ImportError: 
/opt/gnuradioClangJit/lib/libgnuradio-dtv-3.7.13.5.so.0.0.0: undefined 
symbol: 
_ZN2gr3dtv29dvbt_viterbi_decoder_jit_impl28dvbt_viterbi_get_output_sse2IXdtdefpT12d_ntracebackEEEhPDv2_xS4_Ph


I’ve already search in the mailing list for solution, but all the 
solution that I’ve found are for OOT module.


When running c++filt, I get the following result :

unsigned char 
gr::dtv::dvbt_viterbi_decoder_jit_impl::dvbt_viterbi_get_output_sse2<(*this).d_ntraceback>(long 
long __vector(2)*, long long __vector(2)*, unsigned char*)


Which is the result I wanted to see.

I use the following cmake command when building from source :

cmake -DCMAKE_C_COMPILER=/opt/release/llvm/bin/clang 
-DCMAKE_CXX_COMPILER=/opt/release/llvm/bin/clang++ 
-DPYTHON_EXECUTABLE=/usr/bin/python2 
-DPYTHON_LIBRARY=/usr/lib/x86_64-linux-gnu/libpython2.7.so 
-DCMAKE_INSTALL_PREFIX=/opt/gnuradioClangJit -DJIT_ENABLE=ON 
-DENABLE_GR_UHD=OFF ../


CMAKE_C_COMPILER and CMAKE_CXX_COMPILER points to the llvm version 
with clangJIT (see link above). JIT_ENABLE enable the flags for the 
JIT compiler.


Every change that I’ve made are on the following git (and commit ): 
https://github.com/Pacco1217/gnuradio/commit/14d656e5aecc998bb1cda9259de8a639dabf6d04 



About the computer :

Kernel : 4.18.0-25-generic

OS : Ubuntu 18.10

Does anyone has already faced the same difficulties or having a 
possible solution to this problem ?


Thanks in advance for your answers,

Basler Corentin


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[Discuss-gnuradio] Digital pre-distortion

[Simona Sibio]

Dear Sir/Madam,

I am writing to you regarding the digital pre-distortion  technique.
I would use this DPD on GNU radio, I read that there is available only a
part.
How can I do?
Is it necessary a particolar hardware?
I am using GNU radio on N310 ettus research.
Thank you for your time and every help.

Best Regards,

Simona
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[Discuss-gnuradio] JIT integration and undefined symbol

[Corentin Basler]

Hello everyone,
I'm actually doing my bachelor thesis about Just In Time compiler and I want to integrate this technology in GNURadio. I've already created OOT module with integrated JIT functionality. I'm now trying to add an in-tree module. I'm trying to do that by copying the dvbt viterbi decoder block. The JIT compiler that I use is : ClangJIT . For testing, I use the example dvbt_rx_8k. I’m working from the maint-3.7 branch. I added my new block and replace the original viterbi decoder in the example. Unfortunately, when running the application, I have the following error :
 
Traceback (most recent call last):
 File "/home/pacco/TB/gnuRadio_perf/dvbt_rx_demo_8k_jit.py", line 21, in 
 from gnuradio import dtv
 File "/opt/gnuradioClangJit/lib/python2.7/dist-packages/gnuradio/dtv/__init__.py", line 34, in 
 from dtv_swig import *
 File "/opt/gnuradioClangJit/lib/python2.7/dist-packages/gnuradio/dtv/dtv_swig.py", line 17, in 
 _dtv_swig = swig_import_helper()
 File "/opt/gnuradioClangJit/lib/python2.7/dist-packages/gnuradio/dtv/dtv_swig.py", line 14, in swig_import_helper
 return importlib.import_module(mname)
 File "/usr/lib/python2.7/importlib/__init__.py", line 37, in import_module
 __import__(name)
ImportError: /opt/gnuradioClangJit/lib/libgnuradio-dtv-3.7.13.5.so.0.0.0: undefined symbol: _ZN2gr3dtv29dvbt_viterbi_decoder_jit_impl28dvbt_viterbi_get_output_sse2IXdtdefpT12d_ntracebackEEEhPDv2_xS4_Ph
 
I’ve already search in the mailing list for solution, but all the solution that I’ve found are for OOT module.
When running c++filt, I get the following result :
 
unsigned char gr::dtv::dvbt_viterbi_decoder_jit_impl::dvbt_viterbi_get_output_sse2<(*this).d_ntraceback>(long long __vector(2)*, long long __vector(2)*, unsigned char*)
 
Which is the result I wanted to see.
I use the following cmake command when building from source :
 
cmake -DCMAKE_C_COMPILER=/opt/release/llvm/bin/clang -DCMAKE_CXX_COMPILER=/opt/release/llvm/bin/clang++ -DPYTHON_EXECUTABLE=/usr/bin/python2 -DPYTHON_LIBRARY=/usr/lib/x86_64-linux-gnu/libpython2.7.so -DCMAKE_INSTALL_PREFIX=/opt/gnuradioClangJit -DJIT_ENABLE=ON -DENABLE_GR_UHD=OFF ../
CMAKE_C_COMPILER and CMAKE_CXX_COMPILER points to the llvm version with clangJIT (see link above). JIT_ENABLE enable the flags for the JIT compiler.
 
Every change that I’ve made are on the following git (and commit ): https://github.com/Pacco1217/gnuradio/commit/14d656e5aecc998bb1cda9259de8a639dabf6d04 
 
About the computer : 
Kernel : 4.18.0-25-generic
OS : Ubuntu 18.10
Does anyone has already faced the same difficulties or having a possible solution to this problem ? 
 
Thanks in advance for your answers,
Basler Corentin


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[Discuss-gnuradio] [GSoC19] Block header parsing tool: Blog update

[Arpit Gupta]

Hello everyone,
I have updated the blog  for the Week
6 updates and the tasks for week 7. Here
 is the link to the updated
Github project.

Week 6 updates:
- Write unit-tests to check for valid Blocktool Exceptions.
- Modify the directory structure as discussed with the mentors.
- Fix Bugs for the issues in the PR.

Tasks for Week 7:
- Split long python unit-tests.
- Simplify the cli structure by reducing the subcommands.
- Refactor the Exception handling of the blocktool.
- Fix the issues specified in the PR.
- Work on a way to output the io_signature in the blocktool generated YAML
files acceptable by the GRC.

Link to the parser branch  in
the forked repository.

Thanks,
Arpit Gupta
Indian Institute of Technology Roorkee
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[Discuss-gnuradio] DQPSK /QAM modulation and demodulation from gnu radio tutorial for IQ signal generation.

[Md. Atiqur Rahman]

Hello Guys,
I am very much new in gnu radio and trying to do the tutorial that gnuradio
published for PSK demodulation. I am using constellation modulator to
modulate the signal and demodulate it by  constellation demodulator block.

I have managed that successfully for 4 sps for psk but now I want to modify
it 8/16/32 sps(samples/symbol) for QAM.  Unfortunately, I do not get the
same result(synchronized input and output ). I think its may the Channel
model or time recovery block is not set correctly.  I am still confused the
term delay block though.

I  have to complete this task to generate the IQ signal of 32sps for the
SDR board. I have installed all the driver that needed but still couldn't
figure out how
 to use it in my task. I want to run this IQ signal to my SDR board to see
how it works (means is it working perfectly on the sdr board or not). If
you have something to share for this matter, I will be glad.

I attach my .grc file in this mail. Please have a look. Looking forward to
hearing from you guys.

Sincerely,
Atiq


stage6_32_samples.grc
Description: Binary data
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