[opendtv] Re: China writes its own digital TV standard
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 27 Jun 2006 11:04:08 -0400
Frank Eory wrote:
> "Accept both" was always the best idea. BTW, putting
> time domain PN training signals in the guard interval
> of an OFDM signal is a brilliant idea, although I'm
> not sure it's actually a new idea.
But it changes how COFDM is used, yes? Meaning, instead of the guard
interval acting as an easier mechanism to combat ISI (inter-symbol
interference), without resorting to fancy equalizers, this approach uses
the GI to provide room for a training sequence, so that fancy equalizers
*can* be used.
The nice thing is, the training sequences are added without extracting a
further penalty in spectral efficiency. The negative aspect is that (I
think), now you need fancy equalizers because the GI is no longer dead
time.
Or is the PN sequence in the GI somehow not a problem for simple
receivers?
The philosophical equivalent of this would be for 8-VSB to use the
segment sync, somehow, to assist in the training function.
Bert
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