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VDSL (Very high data 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 data 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 available bit rates range from about 26 Mbit/s symmetric for a loop of about 1500 m, up to 100 Mbit/s symmetric for a few hundred metres.
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.
A new VDSL standard is now available, named VDSL2; no current rollouts are known.
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 17 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.
- Germany
- VDSL currently unavailable; The technology is being used by former incumbent Deutsche Telekom who is planning to invest ca. € 3 billion to set up the requisite VDSL2 infrastructure in 50 cities until ca. 2007; despite a ruling by the European Commission in December 2004 that would force the company to make parts of this new infrastructure immediately available to competitors, deployment is ongoing. The extent and the terms of infrastructure access are still to be determined.
- Hong Kong
- VDSL is offered by HGC. A 10 Mbit/s up and down connection costs less than $15 USD/month with a 12 months contract. $20 USD/month without any contract. Both with unlimited bandwidth.
- 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).
- South Korea
- VDSL is offered in apartments by KT and other several providers, costing about $20-$40 USD/month.
- Spain
- VDSL Roll-out by Telefonica began in 2005 in selected places in Madrid. Commercial launch up is planned for 2007.
- Sweden
- Bredbandsbolaget AB supplies fiber-optic VDSL, but not officially.
- United States
- Qwest is offering both internet and television services over VDSL in Denver, Colorado, Omaha, Nebraska and Phoenix, Arizona.
External links
- The UNH-IOL DSL Knowledgebase (advanced tutorials)
- Telstra opposition
- NextLevel Communications (now part of Motorola Broadband)
- T-2 VDSL
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