SAS draft specification R14b - Query on section Reference receiver device

John Dunn John_Dunn at
Wed Jun 25 08:12:11 PDT 2008

* From the T10 Reflector (t10 at, posted by:
* "John Dunn" <John_Dunn at>
 I suspect the equation used to describe the equaliser has a bug.
Section 3.1.55 defines 'decision feedback equalizer (DFE)' as 'A
nonlinear equalizer that uses a feedback loop based on previously
DECODED symbols'
 Section has an equation for the equaliser that ends in
This seems to be saying you are using the sign of the previous UNDECODED
raw data to improved the signal that is about to be decoded
Surely if you can correctly detect the sign of the incoming data
already, then it does not need improving?
And if you can't, your equaliser will make false alterations that will
degrade the incoming signal rather than improving it.
 I believe the equation should be corrected to end in 'sgn(Yk-i)'. You
are then using the previuosly DECODED data, which makes more sense and
agrees with the statement in Section 3.1.55
John Dunn
Senior Hardware Engineer
Storage Infrastructure
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