Forum: GNU Radio Re: OFDM demodulation problem / example video

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C369ebbe1655201988e376af57460f23?d=identicon&s=25 Achilleas Anastasopoulos (Guest)
on 2006-04-05 01:56
(Received via mailing list)
Jens,

I used a complete ad-hoc method for automatic frequency estimation:
tracing the minimum ratio of the power of DC over the total power of the
remaining channels, averaged over all symbols in a frame.
Your estimate seems quite good!

I atatch the .m file

I have not tried anything with the timing yet...

Achilleas
3d1bbca20dabfeca5cce1687c1e70660?d=identicon&s=25 Jens Elsner (Guest)
on 2006-04-05 17:41
(Received via mailing list)
Achilleas,

my estimate is based on frequency domain correlation. Just count the
offset of the maximum (o). Then estimate the fractional offset (fo) by
taking the
value left (l) and right (r) of the maximum and calculate fo =
(r-l)/(r+l).
To compensate substract the resulting frequency offset (o+fo) from the
received signal. Works as long the channel doesn't interfere too much.

Jens


On Tue, Apr 04, 2006 at 07:52:58PM -0400, Achilleas Anastasopoulos
wrote:
>
> Achilleas

> d_re = fread(fid, 1000000, 'float32',4);
> e = d_re + j*d_im;
>
>     [m offset] = max(xc);
>         glob_max = m
>
>
> % first OFDM symbol is used for synchronization - no data.
>     %dem=dem./abs(dem);
> data_l = data;
>
>
> end
>
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