[802.3_ISAAC] Comments on "Echo in Asymmetric Frequency-Multiplexed Systems"

[Frank Wang (王順生) <frank.wang@xxxxxxxxxxx>]

Dear Hossein,

 

Thank you for your contribution last week. (https://www.ieee802.org/3/dm/public/0724/sedarat_3dm_202407.pdf)

 

In the summary, you wrote that there is no need for echo cancellation in the FDD upstream receiver.

I have two comments for it:

1.      To better evaluate whether the echo cancellation is required in the FDD upstream receiver by using the analysis method during slide 5 to slide 10, I think the down-stream rate = 2.5Gbps is a better choice, because it results more echo component in the received signal as compare to down-stream rate = 10Gbps.

2.      Do you assume not only perfect LPF but also perfect hybrid circuit in the AFE block of slide 8? In my option, the residual echo (especially the near-end echo) due to a non-ideal hybrid circuit won’t be small enough to be ignored. You either use an echo canceller to deal with it or suffer the SNR degradation. Can you comment on the SNR margin when the hybrid circuit is non-ideal?

 

Regards,

Frank

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