[opendtv] Re: Mobile DTV
- From: Albert Manfredi <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Sat, 22 Dec 2007 18:30:01 -0500
Al Limberg wrote:
> U. S. Pat. No.6,166,667 issued 26 December 2000 and
> owned by Samsung Electronics has an interesting claim 1
> that reads as follows.
>
> "A channel encoding method in a mobile communication
> system, comprising the steps of: selecting one of a
> convolutional encoding scheme and turbo encoding scheme
> according to a service type of data to be transmitted; encoding
> the data to be transmitted utilizing said selected encoding
> scheme; and transmitting the encoded symbols on a
> transmission channel."
To me, that sounds an awful lot like ideas that morphed into part of A-VSB.
A-VSB, in two of its modes, uses turbo coding layered over the convolutional
trellis code. In that patent, it sounded like they wanted instead to select
either turbo coding or the trellis code.
But I prefer working on the standard 8T-VSB symbol stream, as you mentioned
previously. The standard stream already contains two well-known 2-VSB symbol
sequences -- the training sequence and the segment sync sequences -- that can
be used to obtain the absolute amplitude levels of the symbols. And 8T-VSB
already transmits a well-randomized and high rate of symbols, which generates a
very flat spectrum very quickly. This should allow for very rapid dynamic
equalizer response to dynamic fading.
The previous Sinclair testing and NAB demo of mobile 2-VSB, which contained no
convolutional FEC at all apparently, would have been far more successful if
only they had used a diversity antenna. The biggest flaw in reception was,
reportedly, when the van stopped at traffic lights. And moving the van just a
few inches or feet restored reception. So the benefit of a diversity antenna is
clear.
It just seems to me that very credible mobile 8T-VSB should be achievable
without violating any laws of the universe.
Bert
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