Re: [Discuss-gnuradio] OFDM Transmiter and receiver by using USRP1

[Tom Rondeau]

On Oct 18, 2011, at 11:18 AM, "Marcus D. Leech" <address@hidden> wrote:

>> 
>> hi Marcus,
>> 
>> I am attaching the screen shots and also block diagram of transmitter..
>> right now i am just trying to look for transmission of OFDM signal via
>> usrp1. As i mentioned earlier in the fft scope plot in gnu radio i see the
>> typical ofdm signal but on the other hand in usrp sink on the spectrum
>> analyser i saw only simple sine wave peak. please have a look and let me
>> know if there is something else do i need to do to generate the proper ofdm
>> signal on the spectrum analyser.
>> 
>> /home/hp/Desktop/spectrumoutput.jpeg 
>> http://old.nabble.com/file/p32675018/spectrumoutput.jpeg spectrumoutput.jpeg 
>> 
>> 
>> 
>> Block diagram in GNU radio
>> /home/hp/Documents/finaltesting.grc
>> http://old.nabble.com/file/p32675018/finaltesting.grc finaltesting.grc 
>> 
> Your flow-graph appears to be badly confused about bandwidths and
> interpolations and sample rates
>  --an interpolation ratio on your USRP1 sink of 100e6 is almost
> certainly *not* what you had in mind.
> 
> You probably need to learn more about all of that, and get some better
> notions of how the OFDM
>  modulator block works.  At the very least you'll need to
> fractionally-interpolate the baseband
>  up to some sample rather that *can* reasonably be further interpolated
> by the USRP1 hardware.
> 
> Given how simple this graph currently is, I'd *strongly* suggest that
> you upgrade your "world" to UHD,
>  since your investment in the "old world" is still rather small.
> 
> 
>> 
>> 
> -- 
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium

As of last night, the 'next' branch of GNU Radio (if you are using git) has the 
OFDM code and examples rewritten using UHD. 

Tom