[Discuss-gnuradio] USRP and GSM

[Pete Chown]

I have to develop some equipment for receiving GSM 900 and GSM 1800. 
(Fortunately, it doesn't have to receive both at the same time!) It would
be good to do this with GNU Radio and the USRP, but I'm not sure what
performance I can expect.  I hope you don't mind if I ask a few questions.

The spectrum allocated to GSM is split into a number of carrier
frequencies, which are 200kHz apart.  Each of these frequencies can carry
up to eight channels, with a data rate of about 34kbps each.  (This
includes framing bits and so on, so much less useful data is actually
transmitted.)  As this data rate is quite low, presumably it would be well
within the capacity of GNU Radio to decode it in real time?

According to the wiki, the USRP can push about 6MHz of spectrum over the
USB bus.  This is quite a bit lower than the frequency range allocated to
GSM, so I assume it would not be possible to receive all the carrier
frequencies at once.  However, no single base station uses all the
frequencies.  Neighbouring cells must not interfere with each other, so
they must use different frequencies.  So, does my 6MHz have to come from a
single contiguous range of frequencies?  Alternatively, can I ask for a
number of 200kHz bands, with some bands in between that I'm not interested
in?

Thanks for your time and for sharing GNU Radio.

Pete