Thanks for your comment. Please can you let me know what you’re trying to do, so that I can try to help you?

Tyson.

can help?

Unfortunately I have to tell you that we were not able to capture any gsm traffic.
As you can see in my reply above, we were able to get the capture script working for our USRP. But the resulting file had no gsm packets in it.
For the RTL-SDR, we gave up after we found out that the capture_rtl.sh script was bugged, because it did not put any data in the output file we specified. So to be clear, the script created a file, but it was 0 bytes big…

I hope this topic will help people get it working!
Regards, Willem

Though we were able to get the capture script working, we were not able to capture any data. We don’t exactly know why the capture files stay empty. This could be because our USRP did not have a modified clock.

Thank you for your reply. I hope this topic will help others!

The AirProbe tools don’t actually produce a trace file. Instead, they output data using a broadcast UDP socket that just “throws data into the wind”, containing GSM packets with “GSMTap” encapsulation, which can be captured from the loopback interface (or the “any” pseudo-interface in Wireshark).

I hope that helps,

Tyson.

Thanks for your explanation.
Compiling gsm-receiver works fine.
I’ve read somewhere that the tvoid part of airprobe is much like like the receiver, but it does not work, so we went on with the receiver.
Running it still gives us problems though.
When we try to capture traffic with the URSP from our university, by running capture.sh, it complains about being unable to find usrp_rx_cfile. It should be installed with gnuradio, but it isn’t.
We got our hands on an RTL-SDR last friday, so now we tried to run gsm_receiver_rtl.py from the gsm-receiver software collection.
This works and we get nice graphics. Output to file does not work however.

Do you know how to really capture the traffic to an analyzable file?

Thanks for your help!

Regards,
Willem

If I remember correctly, the situation for each source module directory was:

• “A5.1″ – contents of the “C” directory are probably used by other modules; but there’s no Makefile
• “gsm-receiver” – should build successfully using the included Makefile, once GNURadio, and some other bits are installed
• “gsm-tvoid” – couldn’t make this build using the Makefile; but it probably doesn’t hurt to have a semi-built version floating around
• “gsmdecode” – probably a good idea to try and build/install this; needs AutoTools + Make files generating manually; can’t remember if it completely builds without errors/warnings
• “gsmsp” – building it is worth a try; but again, I can’t remember the outcome
• “gsmstack” – no Makefile; contents integrated into other Makefiles, for other modules
• “gssm” – USRP-specific; probably builds – but useless with RTL-SDR devices
• “viterbi-detector” – No Makefile; probably integrated into the build process of other components
• “viterbi_generator” – Probably worth trying to build this – but it doesn’t really do much by itself

I hope that summary helps.

I’ll probably reboot into Ubuntu later, have a look at the state of my last build attempt, and report back, though. I don’t know if there’s a recommended order for installation – but I’m sure that rebuilding each in a bruteforce manner would probably “work”…