Re: [Discuss-gnuradio] OFDM demodulation problem / example video

[Robert McGwier]

Jens Elsner wrote:
> Achilleas,
>
> thanks for taking the time. My goal is to implement COFDM in gnuradio, 
> DAB is a nice start.
>
> To your points:
>
>   
>
> Time sync is not a problem in OFDM - the guard interval takes care of
> that. Nice property. Try playing along with the "start_resamp" value -
> it will work for an offset up to about 504 (this is the length of the guard
> interval).
>
> Jens
>
>
>   


AHA!  Now we are getting some place.  This last paragraph was very 
revealing.  Time sync is not a problem because of the guard interval BUT 
varying depth in to the guard interval will IMMEDIATELY translate into 
phase shifts on each and every bin that will vary with frequency and 
depth into the guard interval.  I am sorry I have not had time to spend 
on the code but I have a lot going at the moment.   There is simply no 
such thing as a free lunch anywhere anytime, not even with OFDM.

Bob


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