1. Technical Field
This invention relates generally to methods, systems and apparatus for managing digital communications systems.
2. Description of Related Art
Digital subscriber line (DSL) technologies provide potentially large bandwidth for digital communication over existing telephone subscriber lines (referred to as loops and/or the copper plant). In particular, DSL systems can adjust to line characteristics by using a discrete multitone (DMT) line code that assigns bits to tones (sub-carriers), which can be adjusted to channel conditions determined during modem training/initialization (e.g., transceivers that function as both transmitters and receivers) at each end of the line.
In DSL systems, crosstalk among the twisted pairs typically reduces and/or limits performance. Significant problems arise already-operating DSL lines when one or more previously unused twisted pairs first activate for DSL operation (or for DSL service upgrade). Such activation can disrupt the already-operating DSL systems when they receive crosstalk caused by the new service(s). In vectored DSL systems, activation of one or more new lines can interfere with the vectored system operation which, prior to new line activation, has been configured to operate in a certain way. Vectored system re-configuration may thus be needed to avoid disrupting strong crosstalk.
Systems, apparatus, methods and techniques that provide improvements for training DSL systems when adding new lines would represent a significant advancement in the art. More specifically, systems, apparatus, methods and techniques for implementing such training for vectored DSL systems likewise would represent a significant advancement in the art.