[10GBT] PMA Training signal
Hi all,
I apologize. I discovered an error with my PMA training signal proposal in slide 8-10
of my startup presentation entitled "Startup protocol for 10GBASE-T", thanks to comments from Brett at SolarFlare.
In my original proposal, training seaquense is generated
from side-stream scrambler as follows
Syn[0] = Scrn[0]
Syn[1] = g(Syn[0])
Syn[2] = g(Syn[1])
Syn[3] = g(Syn[2]) when loc_rcvr_status = NG
Syn[3] = g(Syn[2])^Syn[0] when loc_rcvr_status = OK
g(x)=x^3+x^8
These 4 bit seaquense are mapped into 2PAM symbol.
I misunderstood that we can distinguished between pair A,B,C and D through try and error
even when channel skew and pair swaps are present.
Because I misunderstood that there is only one pair combination wicth satisfy following relationship
Ry(n)[1]+Ry(n-3)[0]+Ry(n-8)[0]=0
Ry(n)[2]+Ry(n-3)[1]+Ry(n-8)[1]=0
Ry(n)[3]+Ry(n-3)[2]+Ry(n-8)[2]=0 when loc_rcvr_status = NG
Ry(n)[3]+Ry(n-3)[2]+Ry(n-8)[2]+Ry(n)[0]=0 when loc_rcvr_status = NG
Ry(n)[x]: PAM2 demapping deta of lane x
However, Brett found the relationship between pair D and pair A when loc_rcvr_status = NG.
That relationship is Sy(n+1)[0]+Sy(n-3)[3]+Sy(n-8)[3]=0.
So, I realize that my original proposal can't distinguish ABCD(normal) from BCDA, CDAB, and DABC
when channel skew is present.
On the other hand, 1000BASE-T had a mechanism to easily identify pair A.
This was done by transmitting the inverse of Syn[1],Syn[2] and Syn[3] during time n+1.
Below are a detail explanation by Brett,
"In 1000BASE-T 3PAM was used for training.
The 4 scrambler sequences were used to generate 2-level sequences, but the 2 levels were (0,-2).
An additional polarity scrambler randomly flipped the polarity of the -2 to get a 3-level signal.
The important thing to note is that although the scrambler sequences were used to directly generate
the 2-level sequences for pairs A, pair B,C & D was different.
At even time periods (n = 2*k, for integers k) pair A is the same as the scrambler sequence).
At odd time periods (n = 2*k+1, for integers k) pair A is the inverse of the scrambler sequence from time n-1.
From this construction, pair B,C & D will always have a 1,0 or 0,1 at times n=2*k and 2*k+1.
From this pair A can be identified."
I didn't apply 1000BASE-T approach, because pair B,C and D are the inverse of the scrambler sequence
from time n-1 at odd time periods. In this case, these signals has higher transmitting PSD at high freaquency.
So, these signal should be scrambled by another scrambler such as polarity scrambler in 1000BASE-T.
This might bring us increasing complexity in polarity correction, deskew and pair swapping by 2PAM training signal.
On the other hand, 1000BASE-T can correct polarity due to its 3PAM training signal.
So, I would like to modify my proposal so that pair D is distinct from pairs A,B,C
according to Brett's advice.
Original:
Syn[3] = g(Syn[2]) when loc_rcvr_status = NG
Syn[3] = g(Syn[2])^Syn[0] when loc_rcvr_status = OK
Modified:
Syn[3] = g(Syn[2])^Syn[0] when loc_rcvr_status = NG
Syn[3] = g(Syn[2])^Syn[1] when loc_rcvr_status = OK
From this, my modified proposal can determine the order of A, B, C & D.
Anyway, my proposal is just an idea to start discussion about PMA training signal.
I am welcome refinement to my proposal and other more efficient proposal.
To: Brad
Could you take a vote on providing corrected presentations on the website
during Friday's closing session?
Regards,
Seki
Katsutoshi SEKI
k.seki@necel.com
-----Original Message-----
From: "Booth, Bradley" <bradley.booth@INTEL.COM>
Sent: Wed, 15 Sep 2004 16:59:30 -0700
Subject: Re: [10GBT] Reminder: Presentation submittal deadline
This is a multi-part message in MIME format.
A clarification so that there is hopefully less confusion on this:
Addition of supporter names is permitted after the presentation
submission deadline. Technical additions or corrections to the
presentation are not permitted after the presentation submittal
deadline. What is posted on the website on Thursday should be
technically complete and must be used in the meeting. If there are
errors discovered in the presentation after the submission deadline,
post a notice to the reflector as soon as the errors are discovered.
During Friday's closing session, if there are any presentations with
errors that the authors would like to have corrected, I will take a vote
on providing corrected presentations on the website.
=20
Thanks,
Brad