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Re: [10GBT] Updated Tables



Sailesh,

Following is my results of your requested simulation. Note that the purpose of the simulation is to repeat what you did so that we can talk with the same language. Although I am not sure why PAM12 has penalty in coding gain, I used 10.2dB coding gain for PAM8 and 9.8dB for PMA12. I think these are what you used (Correct me if I am wrong). I also added your numbers in red for “BGN for 0dB margin” for the comparison.

 

Model 1, CAT7 100m

PAM Level

TX Digital Shape

Assumed Coding Gain

TX Power

Assuming 2Vpp with simple LPF at Fs/2

SNR

Noise margin with BGN =  

- 150dBm/Hz

BGN for 0dB margin

Difference between PAM8 and PAM12

PAM8

0.75+0.25/z

10.2dB

3.3dBm

25.4dB

5.5dB

-137.4dBm/Hz

 

2dB worse

NONE

4.8

25.6

25.5

5.7

5.6

-135.4

-133.2(Sailesh)

Normalized to 0dB

PAM12

NONE

9.8

4.6

29.7

29.6

5.9

5.8

-136.1

-134.2(Sailesh)

0.7dB worse

1.0dB worse

Note: Red is from Sailesh results

 

Model 2, CAT6 55m

PAM Level

TX Digital Shape

Assumed Coding Gain

TX Power

Assuming 2Vpp with simple LPF at Fs/2

SNR

Noise margin with BGN =  

- 150dBm/Hz

BGN for 0dB margin

Difference between PAM8 and PAM12

PAM8

0.75+0.25/z

10.2dB

3.3dBm

26.0dB

6.1dB

-124.9dBm/Hz

 

2.2dB worse

NONE

4.8

26.0

26.0

6.1

6.1

-122.7

-120.7(Sailesh)

Normalized to 0dB

PAM12

NONE

9.8

4.6

29.1

29.1

5.3

5.3

-124.7

-123.1(Sailesh)

2dB worse

2.4dB worse

 

 

I, intentionally remove your final columns because it is not CORRECT. We will discuss later on the subject.

 

First of all, SNR and noise margin matched very closely, within 0.1dB error, however, BGN for 0dB margin are off by about 2dB. We have to find out why but “Difference between PMA8 and 12” are about same. Yours are a little more than what I got but they are off only 0.3 to 0.4dB. At this stage, I agree with you that tolerable BGN is bigger for PAM8. However, note that PAM8 is the simple one without 0.75+0.25/z that you are proposing. Your proposal with 0.75+0.25/z filter is the worst. Albert is now getting similar results witn mine in time domain simulation and he is going to release it soon. In anyway, at this stage, I am not claiming simple PAM or with digital filter and let us assume simple PAM for both cases to compare. The important issue is whether that is 1~2dB or 2~4dB. Let’s discuss the issues of intentionally removed columns in which you integrated to fs/2. You assumed that “ERXTERNAL NOISE” is fitting just fs/2 for both systems. That is not correct. The “EXTERNAL NOISE” could be at the higher frequency up to 1GHz or higher. Let’s assume that we test performance with single tone at 450MHz in which PAM12 can tolerate a lot better than PAM8. What I am saying that in order to argue EMI tolerance, we need to define the spectral content of the “EXTERNAL NOISE”.

 

 

We have had four models for the system comparison back in March meeting. Those models do not have any “EXTERNAL NOISE” other than A-crosstalk. We assumed 10GBaseT is the self-crosstalk limited system. We believed that is reasonable and we did intensive study with the good IC considerations. As everyone agreed, PAM12 is the best noise margin solution in those criteria. Now, Sailesh raised the issue “Immunity for the EXTERNAL NOISE” at the last meeting.

 

I am very positive to improve IEEE standard within a reasonable time frame. If A-crosstalk is not the biggest impairment or EMI noise is as big as that, let’s redefine that and create 5th model on the top of the existing four models. Dan made a good point in his mail today. Will you be able to get a data of the frequency content of the EMI noise that everyone is comfortable with? I myself want to take a quick look at that even if you can not claim that is the general universal conditions. That should tell how many dB PAM8 is better in EMI tolerance (or non issue) and people can judge both A-crosstalk immunity and EMI tolerance at the same time.

 

Hiroshi Takatori

Keyeye Communications, Inc.

 

 

 

-----Original Message-----
From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG] On Behalf Of sailesh rao
Sent: Monday, July 19, 2004 11:16 AM
To: STDS-802-3-10GBT@listserv.ieee.org
Subject: [10GBT] Updated Tables

 

10GBT'ers:

 

In the attached, I've updated the 3 tables in our July presentation based on

the following:

 

1. Change PAM12 symbol rate to 825Ms/s from 820Ms/s.

2. Delete PAM10 entry.

3. As Luc pointed out, add a 1.2dB emissions penalty for PAM12 due to its

higher transmit PSD.

4. As Jose pointed out, subtract 0.4dB from the PAM12 emissions penalty due

to the THP peak voltage adjustment.

 

Next, I integrated the WGN for 1E-12 BER over the Nyquist frequency range to

get a "wideband noise tolerance" measure for the two proposals. Finally, I

summed the noise immunity penalty and the emissions penalty for the PAM12

proposal to form a "Total EMI Penalty" metric over the PAM8 approach.

 

In Models 1 and 3, the penalty works out to be 2.6dB and 2.2dB respectively

for PAM12 over PAM8. However, in Model 2, which represents the existing

cabling infrastructure, the penalty for PAM12 over PAM8 works out to a

whopping 4.0dB!!

 

Regards,

Sailesh Rao.

srao@phyten.com

 

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