Re: [802.3_ISAAC] NEW Topic - PAM Levels

[Ragnar Jonsson <rjonsson@xxxxxxxxxxx>]

Hi Kamal,

 

Thank you for bringing up this important subject.

 

I am not able to open the figure that you embedded in your email. Could you please share it with me directly?

 

Regarding your specific comments, I like to refer you to presentation I gave in the Hamburg meeting:

https://www.ieee802.org/3/dm/public/0924/jonsson_razavi_3dm_01_09_15_24.pdf

This presentation shows that ACT with Differential Manchester Encoding (DME) in the low data rate direction is superior to the TDD PAM2 and PAM4 modulation used in ASA-MLE. Therefore, I think that we should be careful not to limit our options to PAM2 and PAM4 only for the low data rate direction.

 

For the high data rate direction, we should keep in mind that the switch/network/processor side PHY would in many cases have to be able to support receiving all the high data rates: 2.5Gbps, 5Gbps, and 10Gbps. This will make it preferable to use the same PAM modulation for all the data rates, to simplify the multi rate receiver.

 

There is a lot more that goes into selecting the right modulation, than the simple examples in our emails here. I plan to work with other PHY experts to provide more analysis on this in the coming meetings.

 

Ragnar

 

From: Kamal Dalmia <kamal@xxxxxxxxxxxxxx>
Sent: Monday, October 7, 2024 9:59 AM
To: STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx
Subject: [EXTERNAL] [802.3_ISAAC] NEW Topic - PAM Levels

 

Hello everyone, A key topic to start looking at is the selection of PAM levels for various speeds in both FORWARD and REVERSE directions. Following is a brief overview of various existing solutions in this space. A quick observation from the

Hello everyone,

A key topic to start looking at is the selection of PAM levels for various speeds in both FORWARD and REVERSE directions.

Following is a brief overview of various existing solutions in this space.

A quick observation from the table below is that for rates in the range of 2.5G and 5G, PAM 2 is widely used and field proven.

Hence, PAM 2 would be a natural and excellent choice to start with.

[cid:image001.png@01DB189E.ECD47E90]

It should also be noted that that PAM 2 is by far the simplest modulation.

Regards

Kamal

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