[opendtv] ATSC for Brazil

From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>
Date: Thu, 9 Mar 2006 17:16:05 -0500
Here's what I think the ATSC/FCC could offer that might appeal to the
Brazil Ministry of Communications. This would meet their stated interest
to develop a DTT system optimized for their own needs.

Offer to provide grants to universities and industry in Brazil to
participate in development of a robust variant of ATSC. Something like
4-VSB and H.264 image compression, so as to achieve even better long
range capability and still capable of carrying SD and eventually HD
multicasts.

4-VSB carries 2 bits per symbol, or about 20 Mb/s baud rate over a 6 MHz
channel, or a net of about  13 Mb/s with 2/3 code convolutional FEC.
Keeping the same block FEC as here, and the same 6 MHz channels, the C/N
margin would be on the order of 10.9 dB of C/N.

(The Shannon limit for 13 Mb/s in a 5.38 MHz channel is 6.37 dB C/N, and
then I'm degrading that by the same 4.5 dB as 8T-VSB degrades its 10.47
dB Shannon limit.)

But H.264 is just about right to compensate for the missing channel
capacity.

Alternatively or concurrently, work on better use of the Reed-Solomon
and convolutional FECs to lower the C/N margin even without lowering the
channel capacity. This is a great university math project. You might be
able to approach that 10.9 dB of C/N of 4-VSB even with 8-VSB, and lower
the C/N margin of 4-VSB even more.

This would be a cool program. Brazil gets to develop their own content
in the standard, which optimizes ATSC for the huge distances to be
covered by Brazil's DTT. The simpler constellation should even help with
dynamic echo tolerance, with similar levels of equalizer sophistication
as US ATSC has developed. And what's more, since 4-VSB modulation was
originally contemplated as one of the settings of the "VSB Mode" field
of the VSB data segment, these Brazilian receivers could be made to
accept 2-VSB, 8-VSB, or 16-VSB as well, for added flexibility.

So here the ATSC would actually be leveraging one of its weaknesses. The
lack of adjustability of US ATSC is used to attract a customer who wants
to participate in the development of their standard. What a deal.

Then we can benefit from the work here in the US too.

Bert
 
 
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[opendtv] ATSC for Brazil

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