[opendtv] Re: Forwarded on behalf of Bob Miller - 3 posts
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Mon, 15 May 2006 11:14:05 -0400
Bob Miller wrote:
> But Doug's technique would make all current receivers
> obsolete, the ultimate sin, I believe. The saving
> grace for A-VSB is that while current receivers cannot
> receive the robust signal they can still receive the
> non robust signal. That is E-VSB and A-VSB both only
> obsolete part of the spectrum for current receivers
> while also throwing a chunk away not available to
> either current receivers or new fangled A-VSB
> receivers.
There may be a misunderstanding about which of "Doug's techniques" we're
talking about. There was one, replacing the PN511 training sequence with
a new PN1023, that Doug, Al, and CB Patel collaborated on, that may have
obsoleted any receiver which used the PN511 sequence. At the time, I
think there were none, though. That may no longer be the case, but I
don't know for sure.
The more recent and interesting approach is to basically say this. Who
needs to develop a special-purpose training segment with pseudo-noise
characteristics when 8-VSB is *already* randomizing the regular old data
symbols to be noise-like? Why not just use data symbols as your training
sequence?
That's what the nice, flat spectrum of 8-VSB offers. And the nice thing
is, because the symbol duration is so short, you can accumulate enough
symbols to do a good job of training in a relatively short time. Rather
than waste spectrum by introducing a special 8-VSB segment every so
often, which you would want to do as infrequently as possible to avoid
wasting bandwidth, you allow the receiver to train itself as fast as its
processor can manage.
Bert
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