Hello Georg, On Fri, 24 Sep 2010 19:19:06 +0200, "Georg Hofstetter" <[email protected]> wrote: > > Okay - you will loose realtime processing with most machines. > Separating several ARFCNs, demodulating, brute force and decoding on the > same machine may be kind of problem :) > But there is room for optimization. e.g. freq xlat in channel separator > only for "used" ARFCNs after they were assigned by the channel assignments.
There is one problem with the USRP1: You don't have enough USB bandwidth to cover all hopping channels at once, at least not for a general scenario where the hopping channels are spread over the whole band (especially bad with GSM-1800). And the FPGA is too small to do the channelisation, at least for lets say 16 channels (with some trick it might be possible somehow, but this is surley nothing which could be done in a few days). And even than you might have cells which use more channels for hopping. So you need an USRP2, for uplink/downlink you need two of them. > For portable realtime processing one just would have to take two laptops > like the dell precision or XPS series with a decent GPU. Let the one > preprocess the USRP signal, demodulate and feed the L1 bitstream to the > second which buffers this stream and decodes the communication. > So a demonstration in a studio or on symposia is still possible. GPU code is work in progress. But anyone who is willing to spend money in the range of 15.000 EUR can buy hardware which is ready to capture uplink and downlink and do the required channelisation without the need for any FPGA adjustments. With such a setup only the Airprobe adjustments for hopping and uplink capture is currently missing (another work in progress thing). And this price tag is extremly cheap compared to commercial equippment doing the same. > But the most "interesting" part for criminals would be SMS communication > (intercepting homebanking TANs and such stuff). > And in my hopping cells, I haven't seen a hopping SDCCH yet. Did anyone? > Not sure if they are possible at all :) It is possible, one of my "official" cells here does SDCCH hopping. Best regards, Dieter -- Dieter Spaar, Germany [email protected] _______________________________________________ A51 mailing list [email protected] http://lists.lists.reflextor.com/cgi-bin/mailman/listinfo/a51
