On Wed, Sep 15, 2010 at 10:42:22AM +0200, Fabio Pietrosanti (naif) wrote: > On 14/09/10 16.15, sascha wrote: > > On Tue, Sep 14, 2010 at 12:49:29PM +0200, Љубомир Самарџић wrote: > > > >> Hello people, > >> > >> Is it possible to record several ARFCNs at once? Or record some narrow band > >> (5 - 10 Mhz wide) and extract offline data for specific frequency from > >> band? > >> > > yes its possible but airprobe currently does not support hopping. It is > > on the todo list, though. > > > > mmmm but frequency hopping would mean following the ARFCN after the > information into the paging request. > So the listening would still be on a 200khz single channel.
if you look at the numbers in the datasheet of the USRPs then you will find that it takes a few hundred usec to tune the daughterboard to a new frequency, so it should be possible to hop, but it will require exact timing. IMHO you would have to puffer the frequency change in the FPGA and execute it at a specific clock time, meaning the USB/GBE communication would not be precise enough. You would also have a certain period in which you try to crack Kc and do not know where to hop. Then after you have Kc you can find out the channel assignment and try to retune to the hopping sequence. Because of these problems, method 2 below will be done first. > > Instead would be very useful to be able to get the whole spectrum > available from the USRP (so multi-ARFCN) being it 8mhz or 25mhz. > > The ability of airprobe to decode a single capture file that include > more tha one ARFCN would open the capability to get immediately > multiple-ARFC (without freq hopping) and stacking-up multiple USRP2 to > catch the whole GSM spectrum. That is work in progress. _______________________________________________ A51 mailing list [email protected] http://lists.lists.reflextor.com/cgi-bin/mailman/listinfo/a51
