Very High Speed Digital Subscriber Line
VDSL or VHDSL (Very High Speed DSL) is a DSL technology providing faster data transmission over a single twisted pair of copper wires. These fast speeds mean that VDSL is capable of supporting new high bandwidth applications such as HDTV, as well as telephone services (Voice over IP) and general Internet access, over a single connection. VDSL is deployed over existing wiring used for POTS (Plain Old Telephone System) and lower-speed DSL connections.
Second-generation VDSL2 systems (ITU-T G.993.2) utilize bandwidth of up to 30 MHz to provide data rates exceeding 100 Mbit/s simultaneously in both the upstream and downstream directions. The maximum available bit rate is achieved at a range of about 300 meters; performance degrades as the loop attenuation increases.
Currently, the standard VDSL uses up to 7 different frequency bands, which enables customization of data rate between upstream and downstream depending on the service offering and spectrum regulations. First generation VDSL standard specified both QAM (Quadrature amplitude modulation) and DMT (Discrete Multi-Tone modulation.) In 2006, ITU-T standardized VDSL in recommendation G.993.2 which specified only DMT modulation for VDSL2.