Vectoring is a method of noise cancellation. It measures and monitors all of the lines in a cable bundle and for each line injects an equal and opposite signal to the predicted noise that will come from crosstalk from te other lines. Not perfect but if managed properly will improve the SNR.
For a very long line, will it help much? Comparing VDSL and VectorVDSL it is unlikely as the attenuation at the higher frequencies will not change and although a few more carriers might work the improvement will not be great if any. And with the band plan and positioning of upstream and downstream within it compared to ADSL, the result could be worse.
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