[opendtv] Re: Backward Compatibility of Robust DTV Transmissions

  • From: "John Shutt" <shuttj@xxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 7 Nov 2006 16:51:23 -0500


----- Original Message ----- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>

Hmmm. Since blind equalization works best with a strong signal, why
wouldn't it help these legacy receivers if the 8-VSB transmissions
included some variable number of "bogus" segments, each of which is, for
example, always modulated at 100 percent (i.e. all large amplitude
symbols)?

Because if you did this, then you would be eating into the precious 19.4 Mbps payload of ATSC. Also, you'd violate the data interleaver which worked so diligently to make sure that there was equal energy in each symbol, thus making the 8-VSB waveform as close to a nice gentle sinewave as possible, limiting the energy to the FCC mask.

But the Samsung does play tricks with the interleaver so that a recurring pattern of symbols occurs periodically, and these are the pseudo-training signals used by the A-VSB receiver.

http://www.tvtechnology.com/features/On-RF/2006.06.14-f_Doug_Lung.shtml

John





----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:

- Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word 
unsubscribe in the subject line.

Other related posts: