[opendtv] Re: Backward Compatibility of Robust DTV Transmissions

  • From: "Allen Le Roy Limberg" <allimberg@xxxxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 7 Nov 2006 17:54:20 -0500

The training wheels (i.e. extra parity) help new receivers.  The information
content in the robust transmission is carried in standard 8VSB data
segments, which legacy receivers can usefully receive.

In the EVSB, ASB, Philips and ETRI proposals the information content is
coded in such a way that it is not possible for legacy receivers to decode
it.  This means information content has to be transmitted twice if legacy
receivers are to receive it and new receivers are to receive it with full
robustness.  This is a major waste of code capability.

The original goal in the Request for Proposals from ATSC was to ruggedize
HDTV broadcast or multi-cast SDTV.  The various proposals seem to focus on
replacing HDTV with other services that halve or quarter code rate.  Perhaps
this is a tacit concession to business opinion that HDTV broadcast and
multi-cast SDTV will disappear from terrestrial transmitter service.

Al

----- Original Message ----- 
From: "John Shutt" <shuttj@xxxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>
Sent: Tuesday, November 07, 2006 11:37 AM
Subject: [opendtv] Re: Backward Compatibility of Robust DTV Transmissions


> Al,
>
> Once a receiver is built, how much can be done ex post facto to improve
the
> performance?  With so many receivers designed around "blind equalization"
> exclusively, I don't understand what sort of "training wheels" can be
added
> to ATSC to help them.
>
> I can see how one could create pseudo-training sequences ala A-VSB that
> could help new receivers improve their performance without upsetting
> existing hardware, but I think the best one can hope for with legacy
> receivers is similar to the Hippocratic oath, "first do no harm."
>
> John
>
> ----- Original Message ----- 
> From: "Allen Le Roy Limberg" <allimberg@xxxxxxxxxxxx>
> To: <opendtv@xxxxxxxxxxxxx>
> Sent: Tuesday, November 07, 2006 8:25 AM
> Subject: [opendtv] Backward Compatibility of Robust DTV Transmissions
>
>
> > Actually, backward compatibility has been given short shrift in
proposals
> > for robust 8VSB.  These proposals time division multiplex robust
> > transmissions with ordinary 8VSB, but no portion of the robust
> > transmission
> > is usefully received by legacy receivers.  In short, training wheels
> > approaches have been ignored.
>
>
>
>
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