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Re: [10GBT] Symbol rate

Title: Message

At the March meeting, some of the discussion on leaving the door open to the higher baud rates was aksing to have time to run simulations with the higher baud rates to validate the optimal DFE results presented.

The MATLAB code has been available on the 802.3an web site for a while now – I assume others have now seen that the ANEXT model we agreed to (49.5-15log10(f/100)) is within a couple dB of the insertion loss at 650 MHz – which means that the penalty for signaling at rates over 500 MHz, where the SNR gets pinched off, is extreme. (to run this case, use: parameters: solarsep_varlen7a(-10.5,650,4,55,6,1,6,2) ).


What these curves tell you is simply that at more than 1Gbaud, you are simply signaling faster than the channel can support, and thus starting out in an SNR hole in building a 10GBASE-T system.


Hopefully at the meeting we can agree to constrain the baud rates and begin to focus our analysis.



-----Original Message-----
From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG] On Behalf Of Booth, Bradley
Tuesday, May 11, 2004 10:36 AM
Subject: Re: [10GBT] Symbol rate




The objectives do require that we provide one PHY that meets at least 100 meters on Class F and at least 55 to 100 meters on Class E.  A proposed PHY must meet both these distance requirements.  To take this a step further, a PHY or port type has traditionally referred to one PCS, one PMA and one PMD.  So this could be seen as one PHY which has only one PCS, one PMA and one PMD is required to meet both the distance objectives.


In the past, the Working Group has asked the Task Forces to make the tough decisions and to choose only one PCS, PMA and PMD to meet the objective.  If the Task Force chooses PAM5, then the decision is made.  If the Task Force chooses PAM10, then the decision is made.  If the Task Force chooses PAM5 and PAM10, then the Working Group will likely send the specification back to us to make a decision.


To quote the movie Highlander, "There can be only one."




-----Original Message-----
From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG] On Behalf Of Sanjay Kasturia
Sent: Tuesday, May 11, 2004 12:12 PM
Subject: [10GBT] Symbol rate

At the March meeting, there was a motion to bound the range of symbol rates. The motion, moved by George Zimmerman, suggested  a symbol rate that would range from 714Msym/sec per pair to 1000Msym/sec per pair.

This motion failed to get the requisite 75% yes vote. Some of the people who voted against this proposal were in favor of schemes that would require higher symbol rates - e.g. 1250Msym/sec per pair but were probably not very familiar with 802.3 operation. With 802.3 voters in the room, the motion would have passed. See the vote tally appended below from the meeting minutes.

As I understand it, the PAM 4 type schemes that would use the much higher symbol rate would NOT meet our distance objectives but offered some value in that they could enable much lower power transceivers for shorter distances than called for in our objectives.

Should these schemes, which do not meet our distance objective, but could still be valuable for customers who want shorter reach and lower power be considered in separate class - possibly in a different forum than 802.3an?

Can our chair, Brad Booth, give us his opinion on this?

Vote count from minutes of March meeting

TF Voters Y: 24 N: 15 A: 19

802.3 Voters Y: 21 N: 5 A: 9


Sanjay Kasturia


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