Hi Joshua, I followed installation instruction with almost no errors. But, when running Wireshark, I get nothing displayed with the GSM interface. My BTS signal is very high, and I located the offset of the frequency correction burst (which is by the way almost the same as your default one). Any suggested checking point ?
Firas, Joshua Lackey-2 wrote: > > gssm-v0.1 > > Groupe Special (Software) Mobile > > or > > The Global Software System for Mobile communications > > --- > > SUMMARY > > Okay, calling gssm "The Global Software System for Mobile > communications" is a bit of a stretch as all it does is monitor GSM > control channels. > > What this package does is use the USRP and various daughterboards to > capture live data, GNU Radio and custom modules to demodulate and decode > the GSM packets, and then Wireshark to display the data. > > > Get it here: http://thre.at/gsm > Install instructions: http://thre.at/gsm/index.html#install. > Talk about it here: [EMAIL PROTECTED] > More here: http://wiki.thc.org/gsm. > > --- > > WHAT > > This package monitors GSM base station control channels. It uses the > USRP and various daughterboards to capture live data, GNU Radio and > custom modules to demodulate and decode the GSM packets, and then > Wireshark to display the data. > > This version of gssm decodes most of the control channels. The control > channels contain the information necessary for a mobile to communicate > with a base station. The control channels gssm currently decodes are: > > FCCH The frequency correction channel. > SCH The synchronization channel. > BCCH The broadcast control channel. > PCH The paging channel. Downlink only, used to page mobiles. > AGCH The access grant channel. Downlink only, used to > allocate an SDCCH or directly a TCH. > SACCH Slow associated control channel. > SDCCH Stand-alone dedicated control channel. > > gssm displays the decoded data using Wireshark. Not only does this give > us a very nice graphical front end to examine the dissected packets, but > Wireshark already has quite a bit of code to dissect GSM data. > Unfortunately, the current implementation of Wireshark does not dissect > packets unique to the wireless interface. Up to now, there was no reason > to include code to dissect these packets. I include a patch for > wireshark-0.99.5 which adds partial Um packet dissection capability > and a new custom ethertype to interface with the USRP. > > While gssm has basic functionality now, it really is alpha-quality > software and there are a number of enhancements which must be made > before it becomes truly useful. > > 1. The Mueller and Muller clock recovery method doesn't always > handle the quarter-bits present in a GSM burst. A more reliable > method must be implemented. Until then, this software will > suffer from a large number of receive errors even with a high > signal-to-noise ratio. > > 2. Wireshark dissects most GSM packets except those specific to > the Um interface, the wireless interface between the mobile and > the BTS, the Base Transciever Station. > > a. I've only implemented a small portion of the Um > interface. Much more work must be done to complete this. > > b. Only the Bbis frame type is implemented. When packets > arrive in Wireshark which are "malformed" or with > strange protocol descriptors, it is because they were > sent using some other frame type. > > c. The interface between gssm and Wireshark is extremely > hacky, to say the least. It would be nice to eventually > standardize a GNU Radio interface for Wireshark. I also > want to clean up my Um interface and submit that there > as well. > > 3. You need to find your local GSM tower by hand. Once you've > found it, you need to edit the python script and enter the > information by hand. It would be very nice if this information > were automatically generated. > > 4. The code is designed to support all frequency bands but I > haven't implemented anything but U.S. support. > > 5. This code is receive-only and currently can only monitor > tower to mobile transmissions. > > 6. Lots more. > > --- > > WHERE > > This code is being adopted by the GSM Scanner Project and any updates to > this code will be found there. Questions and suggestions can certainly > be sent to me, but they also should be directed to the mailing list -- > [EMAIL PROTECTED] Also, check out the wiki at > http://wiki.thc.org/gsm. > > The current version of this code can be found here: > http://thre.at/gsm/gsm-v0.1.tar.bz2. Updates and bug-fixes will be > located at the GSM Scanner Project, http://wiki.thc.org. > > > -- > Joshua Lackey, Ph.D. ([EMAIL PROTECTED]) > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- View this message in context: http://www.nabble.com/software-implementation-of-GSM-tf3862520.html#a10995762 Sent from the GnuRadio mailing list archive at Nabble.com. _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio