Forum: GNU Radio USRP2 - 25MS/s

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Douglas G. (Guest)
on 2008-12-05 22:41
(Received via mailing list)
Question about the USRP2 - I just received my order earlier this week,
and got them up and running with no problems.  However, I have a
question about the transfer rate out of them. When I run usrp2_fft.py,
or usrp2_rx_cfile.py I am able to get 25MS/s out of them (using -d 4)
with few or no S's. However, now that I'm playing around with looking at
802.11b packets, and trying to use the USRP2 with the (modified for
hier_block2) BBN code, I cannot run it at that rate without filling the
screen with S's. I can imagine the BBN codeis more cpu intensive than
writing to the file, but does it make sense that usrp2_fft.py has no
problem? Any suggestions on where to start looking for possible
bottlenecks?
 I am able to get some results with -d 8 (i.e. 12.5MS/s), however all
the packets I'm receiving have CRC errors (the transmitter is only ~3 ft
away). In case it helps, I'm running on a Core2 Duo @ 2Ghz.

--
Doug G.
Research Assistant
Communications and Signal Processing Lab
Oklahoma State University
http://cspl.okstate.edu
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Matt E. (Guest)
on 2008-12-06 00:06
(Received via mailing list)
Douglas G. wrote:
>  I am able to get some results with -d 8 (i.e. 12.5MS/s), however all
> the packets I'm receiving have CRC errors (the transmitter is only ~3 ft
> away). In case it helps, I'm running on a Core2 Duo @ 2Ghz.
>
>

25 MS/s is a very high data rate to keep up with.  If you were to just
run a 40 tap FIR filter you would easily be eating up half of a
processor.  I haven't looked at it, but the 802.11b code is bound to use
more processing than the fft display does.

Does the bbn code accept other decimation rates?  you could try 5 or 6.

Matt
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