Re: [Discuss-gnuradio] Working at 20 MS/s

[frankist]

Hi,

In fact I have underruns in the transmitter which means according to the
website you gave me, my transmitter is not producing data fast enough. I
guess I need a better computer for that.

Just one more question:
Are sampling rates of 20 and 25 MS/s too much for devices, more
especifically, for cognitive radio?


Josh Blum-3 wrote:
> 
> 
> 
> On 05/01/2012 08:55 AM, frankist wrote:
>> 
>> Hi,
>> 
>> I was interested in working with detectors for OFDM 802.11b in my USRP2.
>> I've read on the internet about this and it seems that there are people
>> able to use sampling rates of 20 MS/s.
>> 
>> However, when I try to send an OFDM signal with 20 MHz of bandwidth, at
>> the USRP2 receiver board the FFT plot shows the signal blinking.
>> 
> 
> I think you are seeing the result of an FFT over a sample discontinuity.
> This discontinuity is due to overflow, in other words, your computer is
> not able to process at this rate.
> 
> http://files.ettus.com/uhd_docs/manual/html/general.html#overflow-underflow-notes
> Are you seeing overflow (O's are being printed)?
> 
> Are there any warnings printed by the driver?
> (Answering some of those warnings can help with performance)
> 
> Usually running an FFT display on RX data is not a big performance hit.
> Any information about your PC that you can share? CPU? OS?
> 
> -Josh
> 
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> 

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