Re: [Discuss-gnuradio] USRP2 - 25MS/s

[Matt Ettus]

Douglas Geiger wrote:
>  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.
>
>   

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