[opendtv] Patent application on 8-VSB equalizer
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 6 Jul 2006 15:45:02 -0400
Last week, I mused:
> I'm stuck on the idea of using the frequent segment sync to
> assist in training. These occur every 77.3 or so usec, so
> very frequently, and much more frequently than the GI. But
> they are short, only 4 symbols.
>
> What if the segment training sequences were not all
> identical, but instead were a known series of PN symbols. A
> number of these could be combined by a receiver, perhaps, to
> be used as a reasonably good training sequence. I don't know
> how many it would take, but even if you need to accumulate
> 511 of these symbols, that would still occur more than
> twice as often at the existing training segment.
The business about the changing segment sync symbols related
(potentially) to Chinese upgrades of 8-VSB, but I was surprised to run
into this patent application from 2003:
http://cxp.paterra.com/uspregrant20030223519.html
If I understand the obtuse patent-ese, they are proposing something
along these lines. In addition to using the basic training segment,
which occurs once in every "field" (313 segments), store all the segment
sync patterns, the standard ones in A/53, which occur within a field, to
assist in training. That gives you an extra 4 * 312, or 1248 symbols,
per "field."
(I was also proposing to use the randomized data symbols for amplitude
equalization, although without benefit of phase info, as Doug
suggested.)
This is the crux of what the patent describes:
[0018] "In order to achieve the above and/or other aspects, an aspect of
the present invention comprises an equalizer for a VSB receiver for use
in compensating distortions of a VSB broadcast signal which occur in
transmission channels and which include field synchronization
information including synchronization information as to each field of
the VSB broadcast signal and segment synchronization information
including synchronization information of each data segment within the
field, the equalizer including an extraction part to extract the segment
synchronization information included in the VSB broadcast signal, a
storage part to store the extracted segment synchronization information,
and an equalization part to equalize the VSB broadcast signal based on
the segment synchronization information stored in the storage part."
Basically, they are proposing that in dynamic echo situations, you'd use
some number N of these stored segment sync symbols, where N is less than
1248, for training.
Sounds familiar, eh?
And again, this is no doubt not as advanced as A-VSB, but it doesn't
change the transmission standard.
Bert
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