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ptrkrysik / gr-gsm

Gnuradio blocks and tools for receiving GSM transmissions
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grgsm_scanner performance with uhd4 & gnu radio 3.8 #584

Open mirastyle opened 3 years ago

mirastyle commented 3 years ago

I have been using an older build of the grgsm_scanner with USRP B210 for a while with UHD3.12 drivers and gnu radio 3.7 and everything was working great.

Recently I have updated to gnu radio 3.8 with UHD4 drivers and while everything builds and works, I am experiencing issues with performance. When doing a GSM900 scan for basestations with both configurations, exact same conditions, I am getting only fraction of detected basestations with the UHD4 + GR3.8 setup just 3-4 BTS's where the original setup would detect 20+. The basestations. Moreover, the basestations that are discovered usually are missing a lot of info as if some SiBs weren't decoded properly.

Has anybody experienced something similar? Thank you

Mirek

velichkov commented 3 years ago

Hi @mirastyle,

Can you be a bit more specific? What Linux distribution do you use and what version (both before and now)? How did you install UHD, volk and gnuradio and the exact versions (both before and now)?

uhd_config_info --version
volk-config-info --version
gnuradio-config-info --version

Do you experience performance issues with the other gr-gsm's tools (grgsm_livemon, grgsm_livemon_headless, grgsm_decode)?

mirastyle commented 3 years ago

Dear Vasil,

Thank you for looking into this. I am using ubuntu 16.04 (I know it is a bit dated) and I have built uhd and both volk and gnuradio from sources. Regarding the configurations, I am using following versions:

Original setup uhd: 3.12.0 volk: 1.4 gnuradio: 3.7.14.0

New setup uhd: 4.0.0 volk: 2.0 gnuradio: 3.8.3.1-2-g18f86220

Regarding the other tools, I unfortunately can't tell as I am only using the scanner. I can check...

Thank you BR Mirek

velichkov commented 3 years ago

What CPU do you have and does it supports AVX2 instructions? Provide the output of cat /proc/cpuinfo | grep flags

volk: 2.0

In volk 2.0 there is a kown issue in volk_32fc_s32fc_x2_rotator_32fc that for sure affects gr-gsm. You should either update volk to its latest version or make sure the gnuradio gets build with APPLY_BROKEN_ROTATOR_WORKAROUND flag.

Alternatively you may try exporting the following variable to disable all VOLK SIMD optimizations.

export VOLK_GENERIC=1

See also https://github.com/gnuradio/gnuradio/pull/3062 https://github.com/gnuradio/gnuradio/issues/3308 https://github.com/gnuradio/gnuradio/pull/3311

mirastyle commented 3 years ago

Dear Vasil, Thank you for the hints. I'm running on a i7-4770 and the avx2 are listed as available. Regarding the volk 2.0 rotator workaround, when looking through the CMakeLists, it seems that it actually gets applied automatically when volk 2.0 is detected on the gr-3.8 maint branch so it must have previously been compiled with it.

That being said, when I tried to build after setting the VOLK_GENERIC variable, I am getting far better results with more than 15 basestations fully decoded.