G.SHDSL, VDSL, and VDSL2
To provide more bandwidth to customers, telco providers kept pace by offering ever-faster xDSL variations (ADSL, HDSL, SDSL etc.). Suppliers have kept pace likewise, with technologies to give network managers higher-speed ways to link networks over POTS lines.
But as bandwidth-intensive requirements have increased, so has the need for technologies that support broadband wireline links for point-to-point Ethernet connectivity and at longer distances.
G.SHDSL — Ratified as a standard in 2001, G.SHDSL (also known as SHDSL) combines ADSL and SDSL features for communications over two or four (multiplexed) copper wires. As a departure from older DSL services designed to provide higher downstream speeds, G.SHDSL specified higher upstream rates, too. For higher-bandwidth symmetric links, newer G.SHDSL devices for 4-wire applications support 10-Mbps rates at distances up to
1.3 miles (2 km). Equipment for 2-wire deployments can transmit up to 5.7 Mbps the same distance.
Also approved in 2001, VDSL (Very High Bitrate DSL) as a DSL service allows for downstream/upstream rates up to 52 Mbps/16 Mbps. Extenders for local networks boast 100-Mbps/
60-Mbps speeds when communicating at distances up to 500 feet (152.4 m) over a single voice-grade twisted pair.
As a broadband solution, VDSL enables the simultaneous transmission of voice, data, and video, including HDTV, video on demand, and high- quality videoconferencing. Depending on the application, you can set VDSL to run symmetrically or asymmetrically.
VDSL2 (Very High Bitrate DSL 2), standardized in 2006, provides a higher bandwidth (up to 30 MHz) and higher symmetrical speeds than VDSL, enabling its use for Triple Play services (data, video, voice) at longer distances. While VDSL2 supports upstream/downstream rates similar to VDSL, at longer distances, the speeds don’t fall off as much as those transmitted with ordinary VDSL equipment.