DSL Advances

3.1. Basic Performance Enhancement

A key issue that has limited deployment speeds, especially in the United States where labor is very expensive, is the need in the earliest ADSL systems to send trained field personnel to the customer premises to eliminate a problem that prevents or degrades service. Problems with service may often not be the physical layer and can be related to computer software incompatibilities, external-to-ADSL equipment-interface problems, and so forth. However, as those nonphysical-layer problems have diminished, the issue of unusual noise disturbances or line effects that limit the range become more important. Replacement of the line, or “pair-selection” as it is often called, requires labor and thus increases the cost ...