VDSL (Very-high-speed
Digital Subscriber Line)
technology is a
broadband transport technology that
exploits existing
copper telephone lines to provide high-
bandwidth transport services. With VDSL
modems, ordinary telephone lines are used to deliver simultaneously faster
Internet access,
interactive video, and high-speed
data communications services. VDSL allows transfer rates of up to 58
Mbps.
VDSL is currently going through a standards issue, so it isn't widely deployed yet. The VDSL alliance favors a line coding scheme based on Discrete Multitone (DMT), a multi-carrier system that is more compatible with existing ADSL technology. The VDSL coalition favors a line coding scheme based on Quadature Amplitude Modulation (QAM), a single-carrier system that is less expensive and consumes less power.