ITU-T - International Telecommunication Union/ITU Telcommunication Sector
适用范围
G.993.1 VDSL (Very high speed Digital Subscriber Line) permits the transmission of asymmetric and symmetric aggregate data rates up to tens of Mbit/s on twisted pairs. G.993.1 is an access technology that exploits the existing infrastructure of copper wires that were originally deployed for POTS services. While POTS uses approximately the lower 4 kHz and ADSL/HDSL use approximately 1 MHz of the copper wire spectrum@ G.993.1 uses up to 12 MHz of the spectrum. G.993.1 can be deployed from central offices or from Fibre-fed cabinets located near the customer premises. G.993.1 includes worldwide frequency plans that allow asymmetric and symmetric services in the same group of wire pairs (known as a binder). This is accomplished by designating frequency bands for the transmission of upstream and downstream signals. G.993.1 transceivers must overcome many types of ingress interference from radio and other transmission techniques that occur in the same frequencies of typical deployment scenarios. Similarly@ G.993.1 transmission power levels have been designed to minimize potential egress interference into other transmission systems. As with other Recommendations in the G.99x series@ G.993.1 uses G.994.1 to handshake and initiate the transceiver training sequence. It has been agreed in the ITU-T to develop a subsequent VDSL2 Recommendation that specifies only DMT modulation@ and that is based on this Recommendation (VDSL) and on ITU-T Rec. G.992.3 (ADSL2).