[opendtv] Re: VSB equal to COFDM?
- From: "John Willkie" <jmwillkie@xxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 4 May 2004 18:23:43 -0700
-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx]On
Behalf Of John Shutt said (in part, quoting Doug Lung):
'He also said that new technology from French company DiBcom allows
substantial improvement in reception of DVB-T broadcasts. Investigating
DiBcom, I found a paper by Yannick Levy, CEO of DiBcom and Gerald Pousset,
VP of Marketing at DiBcom - A Revolution for Indoor DVB-T portable reception
and Outdoor DVB-T mobile reception -- that described how DiBcom uses a
diversity receiver to give 3 to 9 dB more margin and twice the Doppler
frequency capability while reducing problems with ingress noise and short
echoes. Refer to the paper for details on the testing. Many of the tests
used 64-QAM 8K COFDM. While adding the second front end necessary for
diversity reception increases costs, that cost is offset by the need for
fewer transmitters and the ability to use higher data rates. Barry added,
"Recent improvements in chip algorithms are said to be able to meet similar
results with single antennas."'
The canard in the paragraph above is "fewer transmitters." A U.S.
broadcaster with fewer transmitters would have none. Fewer transmitters
means higher effective signal level, and that's great.
In the ATSC countries and Australia, that's not much of a selling point.
If they wanted to, they could use these technologies to expand service areas
with the same number of transmitters (pie-baking), but we're told that the
advantage is to make the pies smaller.
I can see the outline: eliminate tv, except when serving 120x160 screens.
But, here in the U.S. the model is not "fewer transmitters" but "more TV
stations." Diversity of service availability will come from multiple
stations in the same market carrying much of the same content.
John Willkie
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