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Re: [802.3_50G] Question on precoder optionality


As far as I am aware there is no proposal to use pre-coding in 802.3bs for 200GbE or 400GbE. At these rates  the issue of burst errors on the electrical interface was addressed by using codeword interleaving in the FEC. 

In 802.3cd  we changed  to using pre-coding  to address the impact of burst errors for 50GbE and NG 100GbE, because people were concerned about the latency impact of using codeword interleaving at these lower rates.


From: "Matt Traverso (mattrave)" <mattrave@xxxxxxxxx>
Reply-To: "Matt Traverso (mattrave)" <mattrave@xxxxxxxxx>
Date: Wednesday, August 31, 2016 at 10:54 AM
To: "STDS-802-3-50G@xxxxxxxxxxxxxxxxx" <STDS-802-3-50G@xxxxxxxxxxxxxxxxx>
Subject: [802.3_50G] Question on precoder optionality



In the July meeting we adopted the PMA baseline which included PAM4 precoding (detailed in hegde_3cd_01_0716). The adopted baseline presentation (nicholl_3cd_01a_0716) states “Mandatory to implement for Tx on PMAs driving backplane, copper and C2C.” & “Optional to enable (on links with dominant first DFE tap)”.


Is the intention that the precoding is “global” across all 8 physical lanes in 200/400GAUI-8?  Or can it be optional on a single physical lane on the AUI?


Or perhaps this is for further discussion…