- Mike Altman resumed
previous
presentation (http://ieee802.org/3/ap/public/signal_adhoc/altmann_s1_1004.pdf)
concentrating on slides #11, #12 related to the treatment of
aggressors.
-
NEXT,
FEXT
- [John
S.] One way to
deal with NEXT and FEXT is to simulate the forward and crosstalk paths.
From these simulations you can get PDFs and by convolving them a
resulting PDF could be generated that could be used to analyze the
system.
- [Mike
A.] Would the
results not be Gaussian?
- [John
S.] Probably
not, because the number of interfering signals is
small.
- [Rich
M.] It’s
probably OK to limit the number of interferers.
- [Mike
A.] That would
almost imply treating them as deterministic signals then, not Gaussian.
How does StatEye deal with xtalk?
- [?]
It has both deterministic and random components.
- [Adam
H.] StatEye convolves the
pdf of xtalk and signal
- [Mike
A.] So, for
our purposes, it would be OK to consider xtalk as having Random and
Deterministic components?
- [Dimitri]
All the time we have tried to describe xtalk as a deterministic effect we
have had poor results.
- [?]
Especially in a multilane situation where you may have many
interferers.
- [Mike
A.] I would
like to conduct a straw poll to determine if we feel that there is a need
to consider a mixed random/deterministic scenario. The three alternatives
to consider are: (A) xtalk is random, (B) xtalk is deterministic, (C) has
both random and deterministic components.
- [Petri]
If we are looking for worst case, treating xtalk as a deterministic signal
will yield worst case results.
- [Brian]
Sometimes we look for worst case, sometimes we look for statistics. I
sometimes get confused when the two things are combined. Mike, how would
you see it treated?
- [Mike
A.] My idea
was simple: given an eye at the equalizer input, deterministic components
of xtalk will subtract from the height of the eye, while the random
components will add on to noise.
- [Rich
M.] Is this
discussion really justified? If one signaling scheme turns out to be a
clear winner, it probably makes no difference.
- [John
d’A] Are assuming that
all aggressors are of the same data type (as opposed to considering 1G, 3G
etc)
- [Joe
A]
These are lower frequency so should not have an
effect.
- [Mike
A.] Signal
types that are not part of the 802.3ap standard are to be considered as
part of the environmental noise (TTL, USB, FC etc.). The most likely
source of xtalk are the three signaling schemes described in the
802.3ap.
- [John
S.] I would
support that. For example in ATCA NEXT should be of the same nature as the
one under test, but one of the FEXT aggressors could be one of the other
two signal natures.
- [Fulvio
S.] What about
equalization assumptions in the transmitters associated with these aggressors?
Should all be equal? What if one of the aggressors is of different
nature?
STRAW POLL #1: Next/Fext treatment should be : A. Random, B. Deterministic, C.
Both
STRAW POLL #2: Should
we use Next/Fext mask to determine total xtalk effects (yes) or should we use
measured data (no)?
-
Yes:
2
-
No:
21
-
Abstained:
2
Straw Poll #3 :
dropped
Straw Poll #4 :
Aggressor signaling types:
-
A. aggressors are
10 G serial (14)
-
B. aggressors are
802.3ap types (5)
-
C. treat Next/Fext
to encompass wider signal universe (1)
- Abstained (1)
-
[Fulvio S.]
As for the transmitter
equalization assumptions I propose we use same setting as forward
path.
-
[John
S.]
Alternatively we could use max boost settings.
-
[John
d’A] In general I
have observed that adjacent channels are pretty
similar
Straw Poll #5: For
the purpose of Next/Fext transmitter definition use same equalization settings
as forward path (A) or something else (B):
- Thermal noise
discussion
- [Vivek]
the 1.4 nv/sqrt[Hz] seem too low.
- [John
S.] the number
is accurate for 100 ohm resistor, but is it what we want to
use?
- [Vivek]
in 10GBT we have use 31.6 nv/sqrt[hz] or 140
dbm/Hz.
Some more discussion ensued but
since the time is over, Mike A. decides to table the discussion for the next
signaling ad-hoc call.
Attendance:
Joe |
Abler |
Michael |
Altmann |
Majid |
Barazande-Pour |
Amir |
Bar-Niv |
Joe |
Caroselli |
John |
D'Ambrosia |
Doug |
Day |
Ali |
Ghiasi |
Healey |
Adam |
Mike |
Lerer |
Cathy |
Liu |
Mary |
Mandich |
Richard |
Mellitz |
Charles |
Moore |
Pravin |
Patel |
William |
Peters |
Petre |
Popescu |
Shannon |
Sawyer |
Brian |
Seemann |
Jimmy |
Sheffield |
Jeffrey |
Sinsky |
Fulvio |
Spagna |
Apoorv |
Srivastava |
John |
Stonick |
Dmitri |
Taich |
Vivek |
Telang |
Schelto |
van Doorn |
Brian |
Von Herzen |
Chris |
Wittensoldner |