Re: OFDM demodulation problem / example video

GNU Radio
1

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

2

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 ® 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 A.
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