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Re: [802.3_ISAAC] Question abut Schedl_etal_3dm_01_0926.pdf

Dear Ragnar,

 

Since I had prepared the figure you reference below, I’ll respond with the clarification. 

 

The use of RS-FEC(128-22) for the LS burst in the figure is a typo.  Some of us had considered using that one but decided that RS-FEC(130,124) was a better choice, and I forgot to update the draft figure.  If you look at subclause 192.3.2.2.16 in the chini_3dm_02a_D2d0_1G_comments-preview.pdf file on the web site for June 2 TF Ad Hoc, where the RS FEC codes are actually defined, you will see that the LS had indeed used RS-FEC(130,124) for the proposed 1G LS.  As is mentioned and apparent in that subclause, both of these RS-FEC codes use the same base polynomial (i.e., different shortening of the same base FEC).  Consequently, it is straightforward to use the same FEC engine for both. 

 

My apologies for the typo and resulting confusion!

 

Best regards,

 

Steve

 

From: Ragnar Jonsson <ragnar.jonsson@xxxxxxxxx>
Sent: Thursday, September 10, 2026 12:06 PM
To: STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx
Subject: [802.3_ISAAC] Question abut Schedl_etal_3dm_01_0926.pdf

 

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Dear Tony, Chao, Scott, and Mehmet,

 

I have a question regarding your proposed 1Gbps LS modulation in Schedl_etal_3dm_01_0926.pdf. On slide 8 it is stated that the changes are provided in chini_3dm_02a_D2d0_1G_comments-preview.pdf, but slides 9 through 11 propose a different RS-FEC for the 1Gbps link. Can you please clarify whether the intention is to update the RS-FEC, or keep the description in chini_3dm_02a_D2d0_1G_comments-preview.pdf?

 

The following is my understanding of the RS-FEC description in the two documents:

The Previous Description (Chini Document)
In chini_3dm_02a_D2d0_1G_comments-preview.pdf (Figure 192-hh), the 1 Gb/s LS path uses the RS-FEC(128,122) encoder—which is the FEC currently used for the HS path:

  • FEC: 6 × RS-FEC(128,122) superframes (with L=2 interleaving) = 12,288 PAM2 symbols
  • Padding: 32 Bytes = 256 PAM2 symbols
  • Total LS Burst: 12,544 PAM2 symbols

The New Description (Schedl, et al. Proposal)
In Schedl_etal_3dm_01_0926.pdf (Slides 8-11), the 1 Gb/s LS path is changed to use the RS-FEC(130,124) encoder—which is the FEC already used by the 100 Mb/s LS path:

  • FEC: 6 × RS-FEC(130,124) superframes (with L=2 interleaving) = 12,480 PAM2 symbols
  • Padding: 8 Bytes = 64 PAM2 symbols
  • Total LS Burst: 12,544 PAM2 symbols

 

Ragnar

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