I see.. so the problem is not only on the pc but even on the fpga for the frequency hopping.. on the pc side is known how to follow the hopping sequence on an unencrypted call ? I mean the list of the frequencies can be easily decoded at the start of the call ? as far I know for encrypted a5\1 calls there is a signal burst on the the next channel that is going to be used.. so the stream can be rebuild after capture of the entire frequency band.
And another very important question.. let's say we have an FPGA on USRP that can follow the hopping sequence.. an usrp1 or usrp2 board could capture both side of the conversation, or there are other hardware limitations on USRP boards that prevent from this ? Alvin ________________________________ Da: Fabian van den Broek <[email protected]> A: Alvin Liebe <[email protected]> Cc: [email protected] Inviato: Ven 15 gennaio 2010, 10:01:04 Oggetto: Re: [A51] just a simple question A USRP1 *could* be enough to fully decode one side of the conversation (either up or down link). The problem of frequency hopping kicks in if a BTS has too many frequencies. Even if everything is in the clear, then you would still need to interpret the hopping sequence and follow it fast enough. That seems hard. Either that or capture the entire frequency band, which will probably be too much data for the USB throughput. To get past the data-bandwidth trouble you'd need to implement some kind of pre-selection (like following the hopping sequence) on the USRP1's FPGA and I don't think the FPGA will manage. But if you're listening in on BTSs that transmit on only very few frequencies, then you could listen in on one side of the conversation. Fabian On Fri, Jan 15, 2010 at 12:41 AM, Alvin Liebe <[email protected]> wrote: > Hi all > according your experience an Usrp1 board would be enough to fully decode > a call with only a5\0 encryption (not encrypted) ? > or there are bandwidth issues ? > > > > _______________________________________________ > A51 mailing list > [email protected] > http://lists.lists.reflextor.com/cgi-bin/mailman/listinfo/a51 > >
_______________________________________________ A51 mailing list [email protected] http://lists.lists.reflextor.com/cgi-bin/mailman/listinfo/a51
