[opendtv] Re: 20060616 Free Friday Fragments (Mark's Monday Memo)
- From: "Albert Manfredi" <bert22306@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sat, 17 Jun 2006 15:46:52 -0400
Doug McDonald wrote:
>>In other words, if a given PN1023 sequence is very, very good for
>>training, then use 2000 data symbols instead. What's the big deal?
>
>Self-orthogonality, that's what. 2047 ... or even 1023 ... training
>symbols in the form of a self-orthogonal training sequence is worth
>about 200,000 random symbols. While it is very easy to get
>amplitude information from random symbols, phase information is
>much harder. It's not terribly hard to track the phase info, one it is
>obtained from a training sequence.
So you're saying that you'd still want to use the PN511, at least, to begin
tracking phase info.
I keep thinking, though, that you know a priori that any Q info carried by
the 8-VSB symbols is distortion. That knowledge has to be worth something,
comparing this equalizer design with one that has to work with QAM.
If you diddle with the equalizer coefficients and get a flat amplitude at
the output, but with some Q energy, you know right now that the phase
correction is wrong. You don't need to wonder what the actual phase info
should be, except to create an output with no phase variation.
So maybe you're back to John Shutt's recursive methods, but again with a
continuous supply of "training sequences," I don't see that as being such a
problem.
Bert
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