DSL Advances

9.3. Next vs. Fext

If we compare the coupling coefficient for NEXT relative to that of FEXT, we see that the near-end crosstalk coupling is approximately six orders of magnitude greater than that for far-end crosstalk. On the other hand, notice that the coupling for NEXT increases at 15 dB per decade with increasing frequency, whereas the coupling for FEXT increases at 20 dB per decade with increasing frequency.

FEXT is an important consideration for ADSL crosstalk into other ADSLs. This is especially important for crosstalk from RT-fed ADSLs; this is a principal topic for work on the Issue 2 spectrum management standard.

A comprehensive study of loop plant cable characteristics, linear impairments, and crosstalk may be found in [1].

9.3.1. Channel ...