[opendtv] Re: Let the games begin

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Mon, 13 Nov 2006 16:09:07 -0500

Bob Miller wrote:

> There is no argument in Europe over their modulation. Only
> discussion over how to get from SD to HD. The UK will
> upgrade from their 2K to 8K and most of their receivers
> are ready for that.

I think you are missing what has to happen in the UK.

Yes, the newer receivers should have no trouble going from 2K to 8K, the
older ones will go dark.

But why the move to 8K? 8K does not add spectral efficiency by itself.

The move to 8K is to tolerate more echo range. And the reason they need
to tolerate more echo range is to install SFNs. And the reason they need
to install SFNs is that they need to migrate from 16-QAM to 64-QAM to
support the HD bit rate, and don't want to go to high power big sticks
in doing so. They want to use low power big sticks instead.

So the move to HDTV is not so simple. And, besides that, they still need
to broadcast the SD simulcasts, assuming they want shows to be available
to SD and HD viewers alike, as we do here.

> For example the VSB modulation that the Chinese will not
> use is only another step up the ladder from A-VSB. The
> difference is that with A-VSB we have the argument that it
> could be used in such away that all legacy receivers could
> theoretically receive all broadcast while we know that in
> reality it will be used in such a way as to make all
> legacy receivers obsolete.

The Chinese VSB scheme is probably better at high spectral efficiency
settings than 8-VSB, although proper LG prototype-like receivers are
apparently very good anyway. And could be made better, e.g. by doing the
Viterbi and Reed Solomon FEC differently and by improving the way
training is done. But I doubt the Chinese system is any better at the
very robust modes than A-VSB. When you get close to the Shannon limit,
as A-VSB does with diversity antenna, the message is that you can't do a
whole lot better.

Why this apparent need to consider A-VSB to be a pointless kludge?

Bert
 
 
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