Re: [Discuss-gnuradio] ofdm_sync_sc_cfb_impl.cc and sync methods used in practical

[Marcus Müller]

Hi Sumit,

well, being a part of the industry, I can certainly say that GNU Radio
happily encourages usage of Schmidl&Cox (SC).

If you look at it closely, SC is pretty cool because, heck, timing AND
frequency correction with just two training symbols?! The paper was von
1997, which means that any standard drafted before that can't include
it. And there were reasons to not use the time-domain-identical-halves
preamble symbol SC demands in IEEE802.11a-1999, so that's why (I
presume) SC wasn't originally in WiFi standards.

Anyway,

> which method is used dominantly
> Auto-correlation based or Cross-correlation based. 

Well, yeah, and SC is an auto-correlation based timing estimator, isn't
it, if you look closely at eq. (5) in the SC paper.

> I went thru a couple of papers which states pros and cons of both the
> methods, however it is not clear to me which method is dominant and why ? 
So you did the right thing and found out what is true in most cases in
engineering:
If there's multiple solutions to a problem in existence, all of them
have their niche and you can't find one dominant solution that fits all
use cases, so discussion must always work with the pros and cons of each
method.

Best regards,
Marcus


On 08.11.2016 01:33, sumitstop wrote:
> Hello,
>
> I was going thru the implementation of ofdm_sync_sc_cfb_impl.cc. As it says,
> it implements 
>
> [1] Schmidl, T.M. and Cox, D.C., "Robust frequency and timing
> synchronization for OFDM", Communications, IEEE Transactions on, 1997.
>
> with modified normalization. 
>
> However I was wondering that in industry, which method is used dominantly
> Auto-correlation based or Cross-correlation based. 
> I went thru a couple of papers which states pros and cons of both the
> methods, however it is not clear to me which method is dominant and why ? 
>
> Sumit 
>
>
>
> --
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