[opendtv] Re: Let the games begin

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Fri, 10 Nov 2006 12:38:28 -0400

At 8:47 PM -0500 11/9/06, Albert Manfredi wrote:
Let's compare. You can transmit 4.5 Mb/s over normal 8-VSB with 15 dB of C/N margin, and send along HDTV or a couple or three of SDTV channels to boot, not just one NTSC.

Really? Can you provide the parameters to do this? By my calculations, you would use the entire 6 MHz channel to send 4.5 Mbps of robust data - and that would leave ZERO room for SDTV or HDTV. In the example used in the paper I referenced, the high quality 8-VSB payload is reduced by ~4.5 Mbps to accommodate SRS and ONE 1.5 Mbps robust channel.

I would note that we demonstrated mobile reception at NAB in 2000 with an OFDM constellation that provided a robust channel and nearly 18 Mbps for the high quality bits.

You get on a slippery slope real quick trying to compare these standards. The reality is that you need a system that is flexible enough to handle whatever service mix is needed at any given point in time, unless you are going to use ALL of the bandwidth for a single service, as is the case for MediaFlo. As defined today, U.S. broadcasters will be required to deliver at least one program at NTSC quality or higher to legacy ATSC receivers. If that one program is HDTV there won't be much room left for robust A-VSB channels.

Regards
Craig



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