[opendtv] Re: Thomson readies solutions for U.S. Digital TV broadcast transi
- From: "Albert Manfredi" <bert22306@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sat, 13 May 2006 18:10:24 -0400
Al Limberg wrote:
>I am unaware of any effort having been made to determine
>whether this is better than four- or five-thousand-symbol
>signature analysis using DFT techniques for handling dynamic
>multipath, as proposed some years ago by Doug McDonald,
>the patent for which should soon issue. Doug's technique
>does not chew up data capacity or intrude into packet
>structure like A-8VSB would.
When John Shutt described the extra training sequences, I wondered exactly
the same thing. How does that compare with using any grouping of the symbols
themselves, as Doug suggested?
Doug's idea seems far more elegant, in that it doesn't chew up any
bandwidth, it's completely backward compatible, it can be applied to in
varying amounts by any given receiver manufacturer, depending on their
processing power and the intended use of the box, and it has a
philosophically pleasing attribute of puitting the very short symbol
durations of the n-VSB modulation scheme to very good use. Turning a
liability into a feature.
Aside from the other enhancements in the A-VSB scheme, it seems to me that
what Doug proposes should work at least as well as the more brute-force
method of adding more training sequences?
Another thing I was wondering was whether there's any benefit to using the
three PN63 sequences along with the PN511, in the existing training segment.
They were meant for use by short equalizers, but is there a way for a long
equalizer to treat the 700 symbols as one long training sequence?
(Not that this would reduce the 24 msec time between these training
sequences. And there's the complication added by the reversing of the middle
PN63 sequence every other segment.)
Just wondering, since you guys were proposing a PN1023 scheme.
Bert
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