Re: [Discuss-gnuradio] OFDM Frequency Spacing

[CEL]

Hi ARob,

You're right to presume that – because that's how the math behind the
DFT works out! So, no, you can't change that.

What you can do, of course, make a system with the correct resulting
sampling rate (as calculated from desired spacing times number of
bins), and just resample that to the rate you need.
Alternatively, and that's what you probably want: Calculate the FFT
length so that you get your desired channel spacing giving your
sampling rate, and use the carrier map to just use the (typically
center, aside from DC) ones that you need.

Best regards,
Marcus
On Wed, 2019-02-27 at 13:00 -0600, Alex Roberts wrote:
> Hello GNURadio Users,
> 
> Is it possible to specify the frequency spacing of the carriers in the OFDM 
> Transmitter Block or Carrier Allocator block? My assumption is the carrier 
> spacing is calculated from the sampling rate and the FFT length (e.g, if 
> sampling rate is 640k and fft length is 64, is the frequency spacing 10 kHz). 
> It would be nice to have the capability to manually define the frequency bin 
> spacing. 
> 
> Thanks,
> ARob
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