[SI-LIST] Re: StatEye]
- From: Raymond Anderson <Raymond.Anderson@xxxxxxx>
- To: "'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 13 May 2004 08:48:15 -0700
I'm forwarding Tom's message regarding StatEye to the list as he has
problems posting to si-list from his address.
-Ray
-------- Original Message --------
Subject: RE: [SI-LIST] Re: StatEye
Date: Thu, 13 May 2004 08:00:16 -0700
From: Tom Waschura <tom_waschura@xxxxxxxxxxxxxxxxxxxxx>
To: gedlund@xxxxxxxxxx
CC: Raymond.Anderson@xxxxxxx
Greg,
In Anthony Sander's paper, you'll also see reference to "Q" as in
"Q-factor". This was some of the early work on correlating eye opening and
noise content to bit error rate and is based on a simple bi-modal
distribution of gaussians (the classic probability of a bit error in a
threshold-level decision circuit you see in every communications text).
Early papers on Q-factor came out of Bell Labs (search for Neal Bergano's
paper in IEEE optical transactions I think).
From my perspective, the innovation in the StatEye work was really the
convenience of getting between differential s-parameters to impulse
responses to eye diagrams--nicely done. Note the same thing could be done
with TDR (regrettably I have not read it yet, but I believe there is a paper
on the subject at Picosecond Pulse Labs).
Q-factor was important because it allowed quality metrics that relate back
to bit error rate to be performed on live data. I believe Neal's
application was in undersea fiber optic cables where monitoring was
important. In this case, real bit error rate testing was not an option as
it was an invasive test that replaces the live data with test data. It
would be preferred to actually measure bit error rate in live data
(something that can now be done with today's technology) as 10^10 bits can
me measured every second allowing easy accumulation of very deep PDFs
without the need for simulation or extrapolation. This allows for finding
the extremely rare events that simulation won't turn-up in reasonable time.
(I should also note that Q-factor only dealt with degradation in the
voltage-axis; however, the same theory with twists applies in the
time/jitter axis).
Similarly, StatEye is important because simulation tests for ICs need to be
devised that include the effects of lossy backplanes. Once again, it would
be ideal to actually measure bit error rate (something Anthony did in his
technology validation step) however simulating long bit error rate tests is
impractical. Questions that still need to be resolved surround the receiver
in these setups. Imperfections in the models for digital samplers (ie.
limit amps and d-flip flops) are not measured by the S-parameter data taken
on backplanes which means correlation between StateEye and bit error rate in
real-world application are still not quite on target yet. Bit error rate
tester developers, like myself, work very hard to have perfect detectors but
Murphy doesn't always go in our favor.
Best Regards,
Tom Waschura,
Chief Technical Officer
SyntheSys Research, Inc.
www.synthesysresearch.com
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Gregory R Edlund
Sent: Thursday, May 13, 2004 5:43 AM
To: si-list@xxxxxxxxxxxxx; Raymond.Anderson@xxxxxxx
Subject: [SI-LIST] Re: StatEye
Ray,
I heard a paper on StatEye by Sanders, Resso, and D'Ambrosia at DesignCon
East last month, and I was intrigued by the idea. In particular, the
paper seemed to be making a theoretical connection between bit error rate
and eye opening, which I've never seen before. Since I'm pretty new to
the serial link world I could use a very high-level explanation of the
technique. It seems to depend on replacing the familiar SI phenomena
(crosstalk, ISI, PDN noise) with statistical entities and then finding the
response of a complete link (transmitter+interconnect+receiver) to the
convolution of these individual statistical entities. Did I get this
right?
Is there someone out there on the OIF that would care to explain the
"general idea" in a couple of paragraphs?
Thanks in advance.
Greg Edlund
Senior Engineer
Signal Integrity
IBM Engineering and Technology Services
3605 Hwy. 52 N, Dept. HDC
Rochester, MN 55901
gedlund@xxxxxxxxxx
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