Very-high-bit-rate Digital Subscriber Line

From Free net encyclopedia

VDSL (very high bit-rate DSL) is an xDSL technology providing data transmission up to a theoretical limit of 52 Mbit/s downstream and 12 Mbit/s upstream over a single twisted pair of wires. Compare HDSL (High bit-rate Digital Subscriber Line).

Currently, the standard VDSL uses up to 4 different frequency bands, two for upstream (from the client to the telco) and two for downstream. The standard modulation technique is either QAM (Quadrature amplitude modulation) or DMT (Discrete multitone modulation) which are not compatible, but have similar performance. The current mostly used technology is DMT (the same technology used in cable modems).

The available bit rates ranges from about 26 Mbit/s symmetric for a loop of about 1500 m, up to 100 Mbit/s symmetric for a few hundred metres.

VDSL is capable of supporting high bandwidth applications such as HDTV. Qwest is currently prototyping the service and may offer a HDTV package as early as 1Q 05.

A new VDSL standard is now available, named VDSL2; no current rollouts are known.

[edit]

Supply

As of 2006, the market is still small, except in Japan and South Korea, where VDSL is predominant.

Australia
- The sole VDSL supplier is TransACT, who use VDSL for Digital TV, Internet and WAN applications over their Fibre-To-The-Curb network. (VDSL is not ratified for use on Telstra supplied copper lines in Australia yet, and Telstra has publicly voiced opposition to VDSL).

Belgium
- Belgacom is providing VDSL in parts of the country (about 6% coverage), but limited to 9 Mbit/s down, 400 kbit/s up and with a monthly download limit of 30 GiB.

Canada
- VDSL is offered in urban areas by SaskTel in Saskatchewan, MTS in Manitoba, and Bell ExpressVu in Ontario and Quebec.

Finland
- Provided in Oulu by OPOY and in Turku by Auria. The services provided in Turku and Oulu are actually based on Cisco's LRE. A few universities also provide fiber-optic VDSLs to their students.

France
- Erenis is offering both internet and telephone over VDSL in Paris. The broadband is 60 Mbit/s down and 6 Mbit/s up [1]

Germany
- VDSL currently unavailable; the technology was being championed by market leader Deutsche Telekom who originally planned to invest ca. € 3 billion to set up the requisite infrastructure in 50 cities until ca. 2007; however, in the wake of a ruling by the European Commission in December 2004 that would force the company to make this new infrastructure immediately available to competitors, a strategic switch to the cheaper ADSL2+ may be imminent.

Hong Kong
- VDSL is offered by HGC.

Japan
- VDSL is indirectly offered in many areas by NTT, Japan's largest telco in conjunction with FTTH service. It is used as a mechanism to wire apartments and other existing construction as a lower cost alternative to pulling optical fiber to each unit.

Netherlands
- VDSL Roll-out is tested by the company KPN and is expected in Q2 2006 to be used. ADSL2+ is already being used on large parts of the network.

Slovenia
- VDSL appeared on 1 October, 2005. It is provided by T-2.net, offering triple play services with internet speeds ranging from 1 Mbit/s/256 kbit/s to 40 Mbit/s/15 Mbit/s at more than 120 locations across the country. A 10 Mbit/s/10 Mbit/s connection costs around US$65 per month. There is no fair-use policy (uncapped downloads).