Re: [802.3_B400G_ELEC] MLSE

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Colleagues,

Please note that at the 11 January electrical ad hoc meeting, Hossein Shakiba will provide a very brief recap of his contribution from 4 January for the purpose of fielding Q&A on his proposed MLSE approach. His contribution will also be the basis for several MLSE related straw polls that I will take.

-Kent

Electrical Track Chair, IEEE P802.3dj Task Force

From: Lusted, Kent C <kent.c.lusted@xxxxxxxxx>
Sent: Friday, January 5, 2024 5:40 PM
To: STDS-802-3-B400G-ELEC@xxxxxxxxxxxxxxxxx
Cc: Lusted, Kent C <kent.c.lusted@xxxxxxxxx>
Subject: RE: [802.3_B400G_ELEC] MLSE

Thanks, Rich, for kickstarting the MLSE conversation on the email reflector.

At the 4 January 2024 electrical ad hoc meeting, Hossein brought forward a detailed proposal for a specific MLSE approach for the Task Force to consider. (see: https://www.ieee802.org/3/dj/public/adhoc/electrical/24_0104/shakiba_3dj_elec_01a_240104.pdf) Thank you, Hossein. Unfortunately, time constraints prevented us from having a Q&A session at the end of his contribution. Additionally, there was insufficient time to conduct a few straw polls.

From a TF leadership point of view, the most important pieces of the MLSE topic to nail down in Phase 1 are:

Whether the TF is going to assume “MLSE capability” as a technique to close the electrical link budget(s)? (Prior straw polls suggest a strong yes)
Which electrical interfaces and electrical PHYs are assumed to make use of the “MLSE capability”? (prior straw polls suggest yes for CR/KR but unclear for C2C or C2M)
What approach/direction does the TF want to take for the “MLSE capability” in the specification?

There are a few different approaches to consider before selecting a specific proposal
For example, does the TF want to implement the MLSE “algorithm” in COM or does the TF want to take a COM margin “reduction” instead? Or something else?

i. if the TF decides that the MLSE algorithm should be implemented in an Annex as part of the COM reference receiver, Hossein’s contribution could be a candidate solution.

The straw polls that I planned for 4 January were to explore the consensus on items #2 and #3 of the list above so that I know where and how to guide the TF forward. Given the importance of clarity on these items for baseline adoption, I requested to the TF Chair a pair of straw polls to be considered at the January interim meeting.

Here there are in advance to facilitate discussion (and wordsmithing):

SP #x

I would support including MLSE as a capability in the reference EQ for the following 200G/lane electrical interfaces:

CR
KR
AUI C2M
AUI C2C

(Chicago Rules)

SP #Y

For the 200G/lane electrical interfaces having MLSE capability, the MLSE solution approach that I prefer is:

A. Include MLSE COM calculations based on the existing proposal (i.e. shakiba_3dj_elec_01_240104, slide 9)

B. Use MLSE coding gain as a rough estimate (i.e. shakiba_3dj_elec_01_240104, slide 27)

C. Relax COM margin by a constant amount

(choose one)

-Kent

Electrical Track Chair, IEEE P802.3dj Task Force

From: Richard Mellitz <000014533bad0b9c-dmarc-request@xxxxxxxxxxxxxxxxx>
Sent: Thursday, January 4, 2024 2:55 PM
To: STDS-802-3-B400G-ELEC@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_B400G_ELEC] MLSE

John,

I do not believe there have been any decisions about MLSE made in .3dj yet. That said, I’m hoping some folks have experience in the field to access MLSE expectations that can be related in simple terms.

Do you think this reflector is the place to discuss expectations and broaden our understanding? Hopefully, we can move expectations into decisions.

… Rich

Richard Mellitz

Samtec Southeast

Office: 803-908-4411

www.samtec.com

From: John D'Ambrosia <jdambrosia@xxxxxxxxx>
Sent: Thursday, January 4, 2024 2:12 PM
To: STDS-802-3-B400G-ELEC@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_B400G_ELEC] MLSE

Caution: This email originated from outside the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.

Rich

Correct me if I’m wrong please, but I don’t believe any decision has been made yet related to MLSE in the receiver.

Please note I am not speaking for or against – just procedurally.

John

From: Richard Mellitz <000014533bad0b9c-dmarc-request@xxxxxxxxxxxxxxxxx>
Sent: Thursday, January 4, 2024 1:42 PM
To: STDS-802-3-B400G-ELEC@xxxxxxxxxxxxxxxxx
Subject: [802.3_B400G_ELEC] MLSE

I believe it would be helpful to start public discussion about MLSE.

The presentation https://www.ieee802.org/3/dj/public/adhoc/electrical/24_0104/shakiba_3dj_elec_01a_240104.pdf by Hossein Shakiba at the past 1/4/24 IEEE802.3dj electrical ad hoc was quite extensive. There is a lot to digest there and we ran out of time. There are many moving parts. First maybe we can simplify to make progress.

The intent of the presentation seems to illustrate a comprehensive method to compute a delta SNR which equates to a delta COM. I believe the basis is delta SER when MLSE is applied. Perhaps a simple way of moving forward is to address a straw poll as to what delta COM or delta SER folks are likely in the worldwide ecosystem and considering PVT.

Work toward our baseline could then be mediated using the barometer of expectations most folks can easily comprehend.

Thank you,

Richard Mellitz

Richard Mellitz

Samtec Southeast

Office: 803-908-4411

www.samtec.com

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