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Hi all, The presentation
https://www.ieee802.org/3/dm/public/0924/jonsson_razavi_3dm_01_09_15_24.pdf proposed to adopt the modulation scheme as defined in 802.3ch in the high data rate direction. Since PAM 2 is a special case of PAM 4, if a phy Tx can support 10G data rate with PAM 4, it definitely can support 2.5G and 5G data rates with PAM 2. In this case, the symbol rate of 5G will be the same as 10G and the symbol rate of 2.5G will be half of 10G. In the ACT modulation, one advantage of using PAM 2 in 2.5G and 5G is that it will reduce the echo effect to the camera receiver. Furthermore, in the both TDD and ACT, the complexity and power of PAM 2 receiver can be reduced by utilizing SerDes technology (https://www.ieee802.org/3/dm/public/0724/Chini_Tazebay_3dm_01a_0724.pdf). Regards, Frank From: Ragnar Jonsson <rjonsson@xxxxxxxxxxx>
Hi Kamal, Regarding your comment about “technical analysis
to show that PAM 2 is the right choice”: My analysis has been more focused on evaluating
what is the right choice, rather than to prove that a predetermined modulation is the right one. I think that it is very important that we evaluate everything with an open mind, rather than coming in with predetermined notion of what should be selected.
Regarding your point about “to reaffirm what I consider is an obvious choice”,
I think again that it is important to approach this with an open mind, and we should always be cognizant of the danger of confirmation biases.
Regarding your point about billions of ports using PAM2, I think that it is well established that PAM modulation works in real live. I hope we will not get to a point where this is disputed.
Ragnar From: Kamal Dalmia <kamal@xxxxxxxxxxxxxx>
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> Date: Monday, October 7, 2024 at 10:46 AM
To: Kamal Dalmia <kamal@xxxxxxxxxxxxxx>, STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx <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=hiHgBSUj2X0k3TORVxe0NCZAlJs6SEDHhwLDz5m9MbY&m=_aFdQPsawTUQSieR4pSI2FhasgjG2zMWE5A__tvcDM8_r5JvW-SkSZZfU67b8Sag&s=KrsYFlPaI8n2pGxjMvqMT2W1mwMSlpQUX2wwSQZCeYE&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> 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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