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Re: [Discuss-gnuradio] regarding fft-ifft processing

From: pankaj kumar
Subject: Re: [Discuss-gnuradio] regarding fft-ifft processing
Date: Wed, 7 Mar 2007 05:15:04 -0800 (PST)

"Brett L. Trotter" <address@hidden> wrote:
Trond Danielsen wrote:

> I read in an earlier thread that you want to do the (I)FFT processing
> in the FPGA. This is not how it is intended to be used. GNU Radio is a
> software radio framework, and the goal is to move as much of the
> signal processing as possible onto the host computer. Moving the FFT
> back to the FPGA would therefore be a step backward in the software
> approach. This is just my personal opinion, so feel free to spank me
> with a 10 foot monopole if your view is different :)

An interesting debate. FPGA is indeed hardware, but I'd argue that if
the (I)FFT can be done faster on the FPGA and can use the appropriate
window sizes, etc (eg on-the-fly reconfigurable) that it would still
technically meet the definition of 'software'. If it frees up USB
bandwidth somehow or frees up host-CPU and lets the host have more
resources left to do its job and we're not really doing a mode-specific
function that locks us into MIMO or GMSK or OFDM, etc that it would be
OK by me as a consumer.

That Cyclone FPGA was awfully full last I checked- I don't know enough
about this type of thing to say it wouldn't fit, but it seems at least
possible that the amount of real-estate required to do the FFT might be
more than the current generation USRP could handle?

IANAE (expert), but I thought the debate was interesting enough to risk
embarassment :)

yes, as Brett said that the FFT can be done on FPGA faster. Because it will provide us the benefit that we can process task parallaly in the host computer(DSP) and FPGA...  earlier we were trying to use a Xilinx board but later saw USRP with more features compared to xilinx one...

 so we thought of implementing OFDM processing function,
Thats why we thought, lets start with mainly, Up conversion, Downconversion and FFT /IFFT... 

but things does not look so easy, because in this the first task is to change the RBF file generated for our purpose and accordingly we need to make change in the USRP documentation, for example Python and C program...

but really we have got stucked to this point... so if you people can help us...

Thank you


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