Re: [Discuss-gnuradio] Coarse Frequency and related stuff

[Vanessa Gardellin]

> Dear all,
>>
>> I am trying to use the alamouti code implemented by trondeau.
>> Studying the gr_ofdm_frame_acquisition I found several concepts that
>> are not clear to me:
>
>
> Wow, this code is pretty old, and we never did finish it. I hope you get it
> working! I'd love to see the results.

Yes I know... I am trying to implement alamouti and this is the only
thing that I have found... do you know about newer code? and/or
working one?

>
>>
>> 1)  d_phase_count: what does it mean?
>
> We have a look up table for various phase rotations to use in the
> calculations instead of recalculating them every time. This is the index
> into the LUT.

In the code you never used "d_phase_lut"... so this explain a lot of things...

>
>>
>> 2) coarse_freq_comp(int freq_delta, int count): which is the meaning
>> of this function?
>
> If the frequency offset is larger than a subcarrier spacing, we want to
> correct for that. Once the number of subcarrier offset is found, we use this
> function to recenter it. The fine frequency correct has already been taken
> care of to center the signals to the center of a subcarrier.
>
>>
>> 3) what "-M_TWOPI*freq_delta*d_cplen/d_fft_length" represents?
>
> This is the integer number of subarriers (freq_delta) and the phase
> correction per subcarrier.
>
>>
>> Thank you
>>
>> Vanessa
>
> Tom
>

Thanks

Vanessa

-- 
Vanessa GARDELLIN, Ph.D.
Researcher
Institute for Informatics and Telematics (IIT),
Italian National Research Council (CNR)
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