[opendtv] Re: C/N comparison analysis
- From: "Albert Manfredi" <bert22306@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sun, 15 Jul 2007 14:11:13 -0400
Tom Barry wrote:
Agreed. The explanations of 8vsb today appear equally
independent of real world implementations. ;-)
Winks aside, that's why I'd like to see a good, up to date retest. It seems
obvious that as the receivers of both systems get better, the theoretical
differences should become more sharply defined.
The other thing is that STMicroelectronics, some time ago, developed a DVB-T
receiver with a good equalizer. I'd love to see that one tested as well, to
see the improvement in C/N margin compared with a stanadrd DVB-T design.
Matter of fact, here's a quote from the 1999 article that addresses exactly
this point:
"Other techniques are available for decoding the COFDM signal without using
the in-band pilots [12, 13], which could significantly improve the spectrum
efficiency. Unfortunately, those techniques were not fully developed when
the DVB-T standard was finalized."
With these better equalizers, if backfit today into DVB-T, you should see
some improvement in those receivers. But as long as the transmitters need to
transmit active pilots, the peak to average ratio will contiue to be higher
in DVB-T.
He also goes into SFN advantages and molbile reception of COFDM, but again,
he talks about the cost of doing these things. Both require a further
reduction in spectral efficiency.
Yiyan Wu makes the point in the article that "nothing comes for free," or
words to that effect. Meaning, simple to implement multipath tolerance comes
at a cost.
Bert
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