Re: [802.3_ISAAC] NEW Topic - PAM Levels
Hi Alireza,
It appears that this is better suited for the older discussion thread related to delay/latency.
If you agree, please move this to that thread.
I would like to keep this thread with the subject line “NEW Topic - PAM Levels” focused on PAM 2 vs PAM 4 debate for 5G and 2.5G rates.
Thanks
Kamal
From: Alireza Razavi <arazavimajom@xxxxxxxxxxx>
Date: Monday, October 7, 2024 at 11:53 AM
To: STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx <STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_ISAAC] NEW Topic - PAM Levels
CAUTION: This email is from an external origin!
For 802.3dm, we are not designing in a vacuum; our goal is to replace existing efficient solutions. Through my analysis of legacy products, I've observed that these solutions made deliberate choices to achieve low latency.
For example, The GPIO delay for FPD-Link III are
[cid:image001.png@01DB18AD.BFC94890]
In comparison, GMSLII has made significant efforts to maintain a low-latency design
[cid:image002.png@01DB18AD.BFC94890]
I believe it's misguided to dismiss these performance metrics. Our objective should be to create a standard that results in a superior solution rather than compromise on performance.
For further details, please refer to the two presentations from the 802.3dm ad-hoc meeting.
https://www.ieee802.org/3/dm/public/adhoc/082224/razavi_dm_08222024_v2.pdf
https://www.ieee802.org/3/dm/public/adhoc/082224/razavi_dm_08222024_v2.pdf
alireza
From: Kamal Dalmia <kamal@xxxxxxxxxxxxxx>
Sent: Monday, October 7, 2024 10:58 AM
To: STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx
Subject: [EXTERNAL] Re: [802.3_ISAAC] NEW Topic - PAM Levels
As I have shown via comprehensive table, PAM 2 is the known and field proven technology for the rates in the range of 2. 5G and 5G. Cumulative shipments using PAM 2 are likely exceed 1 BILLION ports. That being said, I have kicked off the discussion
As I have shown via comprehensive table, PAM 2 is the known and field proven technology for the rates in the range of 2.5G and 5G. Cumulative shipments using PAM 2 are likely exceed 1 BILLION ports.
That being said, I have kicked off the discussion so that proper analysis can be done to reaffirm what I consider is an obvious choice. I am personally aware that there are many experts working on technical analysis to show that PAM 2 is the right choice for the cases I am starting with.
Looking forward to the technically focused and healthy discussions.
Cheers,
Kamal
From: Ragnar Jonsson <rjonsson@xxxxxxxxxxx<mailto:rjonsson@xxxxxxxxxxx>>
Date: Monday, October 7, 2024 at 10:46 AM
To: Kamal Dalmia <kamal@xxxxxxxxxxxxxx<mailto:kamal@xxxxxxxxxxxxxx>>, STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx> <STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx>>
Subject: RE: NEW Topic - PAM Levels
CAUTION: This email is from an external origin!
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://urldefense.proofpoint.com/v2/url?u=https-3A__www.ieee802.org_3_dm_public_0924_jonsson-5Frazavi-5F3dm-5F01-5F09-5F15-5F24.pdf&d=DwIFAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=tb0FdR2suKYfJsnso0Nf459NsduEeOTKOS6qw2jIj90&m=zYLyhib5vk1Cq7Mq0e523mEav57kHa-axQ2CWG6TrzDKUC2mfTltnq-JgHRqJ_CD&s=anS_hXeHtSIxNEqY_yGWGlY0_PBwZmgCqN5ZyySnpbI&e=
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<mailto:kamal@xxxxxxxxxxxxxx>>
Sent: Monday, October 7, 2024 9:59 AM
To: STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx<mailto: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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