Broadband Related > Broadband Technology
Virtual noise?
burakkucat:
Using the Google search string "virtual noise dsl" the very first hit is to a Broadband Forum Technical Report, TR-197, titled "DQS: DSL Quality Management Techniques and Nomenclature" dating from August 2012.
Westie:
--- Quote from: Weaver on January 24, 2018, 07:13:05 AM ---...a reference to an ?IEEE paper that I could not access.
--- End quote ---
Is this the IEEE paper you are referring to?
Black Sheep:
Westie has provided a great link, and TBH I've never heard of virtual noise before today ??
But a quick search shows .... 'Compare with fixed noise margin for all the tones, The Virtual noise (VN) will improve the
downstream and upstream date rate , especially in short to medium loops. For the typical length in BT FTTC application, the VN does make sense.'
I'm sure Mr Cat or Kitz will be pouring over the Westie link, to gain a better idea of how it works !! ;) ;D
Weaver:
I was very confused by the language of TR-197 p 26
many thanks to the link to that paper from Universität Darmstadt - very good
Universität. It starts well
“The intuitive approach of assigning a higher SNR margin during initialization will lead to a tremendous loss in the overall data rate, since modems will use the same margin also when initialized during high noise times.”
Then I am immediately completely lost. But then I have just had a massive increase in pain medication, and everything is a bit of a blur.
Could anyone comment on that later paragraph?
Westie:
I was pretty lost before the end of the first page, and skimmed from page 2 onwards. :(
What I think the author was saying was that if the modem initialised using a higher SNR margin on a noisy line it would sync at a lower rate than by applying the same SNR margin to a theoretical (virtual) noise allowance, and when the noise abated the modem would be stuck on an artificially low rate.
But does this ignore DLM?
I look forward to hearing what the greater minds of B*kat & kitz make of it... ;D
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