[opendtv] Re: News: DTV Boxes Could Cost $1 Billion

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 27 Jul 2004 16:11:17 -0400

John Shutt wrote:

> I am still in violent disagreement with you here, Bert.  The digital
> transition would have been much better off if the Sinclair
> petition were accepted in 2000.

I will actually *agree* with you there. The optimism we have
seen this past week would have been there years ago.

But, as I offered plenty of times, we can either whine or
make the best of this. There are advantages to single carrier
schemes, for this sort of application, that we can in the long
run benefit from.

Think of this as a hybrid between what a satellite broadcast
system would choose as modulation scheme vs what a Wi-Fi or
cellular telephone system would choose. DTT needs long range
and high spectral efficiency as well as good multipath
and mobile performance. You can argue from either side. It's
not all bad, either way.

> 8-VSB, perhaps just the current ATSC implementation of it,
> still produces a net negative atmospheric pressure.

Oh, so *that's* why my ears keep popping.

> They do not reproduce 2004 COFDM performance,=20
> and by the time
> they can (if ever), Moore's law predicts that COFDM would=20
> have moved the
> goalposts back even farther.

John, on this we will continue to disagree.

In the ultimate, 8-VSB will come out ahead. Why? Simple.
COFDM has some 6700 carriers, several hundred of which
are *not* suppressed. (I'm too lazy to check, but it's
a sizable number of unsuppressed carriers.) They are
used as pilots. In addition to this, COFDM has at least
a 1/32 guard interval. So this combination results in
extra demands for power and a little less spectral

The end result is that as equalizers tend to more
perfection, and they inevitably will, with COFDM you will
still be transmitting those pilots and taking up precious
time with guard intervals that will not strictly be
required anymore.

I showed you the CRC tests done in 2002, and reported in
2003. At that time, at the ~20 Mb/s bit rate, it was
virtual parity. You can keep asking yourself which system
would be best at any given bit rate, but I'm positive that
in the back of your mind somewhere, something is saying
that the answer will flip over 180 degrees sooner rather
than later.

The software glitches you're finding are certainly not a
function of modulation scheme, although they are a function
of clearly written standards. I will grant you that. If you
haven't done your trial by fire with DVB-T, I'm not sure
what can be concluded. Perhaps DVB-T is more bulletproof in
that regard, I just don't know. You don't hear horror
stories on DVB-T until way after the fact.

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