A VDSL tutorial

This report is an introduction to very high-speed digital subscriber lines (VDSL). It gives an overview of the telephone access network and describes in more detail the characteristics of twisted-pair wire-line channel. We describe the different types of noise sources that exist, especially impulse noise, radio frequency interference (RFI), and crosstalk. We also describe some methods to deal with the different types of noise. The problem with radio frequency interference is two-fold and we address both the RFI-ingress and the RFI-egress problem. The different duplex methods and modulation methods proposed for VDSL are presented in this report, with the focus on discrete multitone modulation and the Zipper duplex method. The problem with very unequal levels of far-end crosstalk for different wire lengths is also addressed and we present some different power back-off methods to deal with that problem. Compatibility issues between VDSL and other types of systems are addressed in the last section. The report also contains an extensive bibliographyGodkänd; 2000; 20070912 (margjo)