[opendtv] Re: HDTV DVB-T on air in 6 Mhz channels in Taiwan
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 22 May 2008 17:10:04 -0400
Olivier Houot wrote:
> Seems to fit right in with the recent historical reminders
> on this list :
"Historical rehashing," more like.
It's all a matter of perspective, and "glass half full, glass half
empty." My perspective is this.
ATSC started out with high expectations for spectral effciency at low
C/N ratios, and the FCC planning factors take that into account. On the
negative side, the ATSC high expectations were not initially realizable
with the receiver designs of the day. Just in the past 3 years or so
they have started to become realized.
DVB-T started out with adjustable spectral efficiency, and a system
which requires somewhat higher C/N margins. Receivers capable of meeting
their expectations were available early on, especially because the
spectral efficiency was dialed down (in the UK) to provide the wanted
coverage and immunity to impulse noise. However now DVB-T2 is being
considered, to bring the spectral efficiency and related C/N margins up
by several dB.
So that's the tradeoff. If the poor ATSC receiver designs initially
available were the cause of low DTT uptake in the US, then one could
legitimately say that the gamble was a bad one. But the truth is, this
had nothing to do with DTT uptake. People had been chasing after the
cable trucks for at least 15 years BEFORE the very first ATSC stations
got on the air.
Bert
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