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Re: [STDS-802-3-400G] IEEE P802.3bs TDECQ optimizing eye time centre of eye

If you are able to make the stressed eye exactly per the recipe it won’t increase the stress in the stressed receiver conformance test signal because with the BT filter closing the eye in the TX and the software BT filter in the RX as the only data dependent degradations the optimum eye sampling and the central eye are in the same place.     In the likely event that a real stressed receiver test system isn’t that perfect the stress applied to an Rx that can adapt its timing won’t be any greater than with this perfect test equipment.   Obviously if the Rx isn’t adapting its timing then there is a problem with the Rx, as this change assumes all Rx’s can adapt.


From: Hayakawa, Akinori [mailto:hayakawa_aki@xxxxxxxxxxxxxx]
Sent: Thursday, August 31, 2017 11:25 PM
To: STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-3-400G] IEEE P802.3bs TDECQ optimizing eye time centre of eye



Hi, Jonathan,


Do you suggest to apply this change to not only TDECQ measurement but also SECQ measurement? If so, I think this change will give higher stress to the stressed receiver conformance test signal. Is my understanding correct?


Best regards,



Akinori Hayakawa


Network System Laboratory

Network Component Project

10-1, Morinosato-Wakamiya, Atsugi 243-0197, Japan

TEL : +81-46-250-8251

FAX : +81-46-250-8274

E-mail : hayakawa_aki@xxxxxxxxxxxxxx



From: Jonathan King [mailto:jonathan.king@xxxxxxxxxxx]
Sent: Friday, September 01, 2017 3:17 AM
To: STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: [STDS-802-3-400G] IEEE P802.3bs TDECQ optimizing eye time centre of eye


Dear colleagues,

Please find attached a short presentation which I hope to review in the 802.3bs face to face meeting in Charlotte, and which describes a proposed change to the TDECQ method which will allow TDECQ to be calculated at the optimum eye timing point, by allowing the histogram time positions to be adjusted for optimum TDECQ.  This change would reflect the capabilities of real world  implementations of receivers with T spaced and T /2 spaced equalizers.


Without this change, the TDECQ definition in the current draft (802.3 D3.3) means that transmitters with equalized eyes which are offset from the time centre of the eye are penalized with higher TDECQ, which would contribute to the decorrelation of Tx TDECQ and measured link performance.


I believe the change is absolutely necessary to prevent unnecessary transmitter TDECQ failures. 


If you are willing to be a supporter of this proposed change please send me an e-mail to let me know your name and affiliation.

Feel free to ask questions of course!


Best wishes

Jonathan King