[opendtv] Re: 20060616 Free Friday Fragments (Mark's Monday Memo)

Doug's original signature analysis technique calculates the equalizer
coefficients from scratch, not by incremental adaptation.  Noise is averaged
out by integrating successive coefficient determinations.  So, when there is
a concealed-path / revealed-path change in the echo spectrum, the equalizer
can update very rapidly without having to wait for errors to accumulate.

Later work uses a parallel equalizer approach, with decision feedback being
used to reduce long post-echoes.

Allen
----- Original Message ----- 
From: "John Shutt" <shuttj@xxxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>
Sent: Friday, June 16, 2006 3:32 PM
Subject: [opendtv] Re: 20060616 Free Friday Fragments (Mark's Monday Memo)


> That might work as long as the change in multipath isn't very great from
> snapshot to snapshot.  Calculating taps is a recursive process and if
there
> were drastic changes from "look" to "look" it would require several
> iterations to recalculate the proper taps to cancel out the new echo
> ensemble.  That eats up both time and energy.
>
> John
>
> ----- Original Message ----- 
>
> > Once synchronized, the receiver comes on about 2000 symbols prior to its
> > allocated time slot, or 186 usec prior, to train itself. Right after
> > this training it receives the data, then goes back to sleep mode.
> > Perhaps once in awhile, the receiver looks for the training segment
> > again, to correct its internal clock.
> >
> > That should save a lot of power.
>
>
>
>
>
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