What’s VDSL?

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VDSL is a next-generation DSL technology with speeds of 52 Mbps downstream and 12 Mbps upstream. It uses QAM or DMT technology, with DMT being more commonly used. VDSL can provide HDTV, video-on-demand, and internet access, and can be bundled with HDTV packages. It creates 247 virtual channels within the available bandwidth. The end user’s speed depends on the distance from the local telephone company. VDSL is not readily available in the US, but a second-generation version known as VDSL2 boasts speeds of up to 100 Mbps.

Very high bit rate Digital Line Subscriber (VDSL) is next generation DSL at super accelerated speeds of 52 Mbps downstream and 12 Mbps upstream. Downstream data rates refer to download speed or how fast data travels on a computer, while upstream data speeds refer to upload speed or how fast data travels from a computer to the internet . The architecture is based on one of two technologies: QAM (quadrature amplitude modulation) or DMT (discrete multitone modulation). These two technologies are not compatible with each other and according to many manufacturers DMT is more commonly used.

VDSL is so resilient that it is capable of providing services such as HDTV and video-on-demand along with Internet access and can be bundled with HDTV packages as it establishes a presence in the market. It is the first high-speed technology capable of providing a whole home entertainment package, making it entirely unique. As demand increases, the price of the packages will likely decrease.

This technology can provide incredible bandwidth over standard telephone lines because voice communications over the telephone require only a fraction of the cable capacity. For a rough analogy, users might consider a multi-lane highway where only the slow lane is used for traffic traveling at very slow speeds. By opening the other lanes to faster hybrid traffic, the entire motorway or, in this case, the entire loop can be used. You can also use a telephone or fax machine simultaneously for Internet access or other VDSL services.

VDSL, based on discrete multitone modulation (DMT), creates 247 virtual channels within the available bandwidth. The integrity of each channel is monitored and data is transferred to an alternate channel as signals degrade. In this way, data is constantly moved to the best path for data transmission or reception, making DMT a robust, albeit complex, technology.

As with other broadband technologies, the end user’s speed will depend on how far the feed or loop is from the local telephone company or telecommunications office. Shorter distances allow for higher speeds, while longer loops reduce signal and speed. One disadvantage of this technology is that it requires a very short cycle of approximately 4,000 feet (1,219 meters) or three-quarters of a mile. Another complication can inadvertently create a solution to the distance problem: the complication of fiber optic lines.
Many telecommunications companies are installing fiber optic lines instead of copper lines. If a stretch of line between the customer and the telco is equipped with optical fiber, the VDSL signals are “lost in translation” by converting from analog (copper), to optical fiber (digital) and back to analog. A VDSL gateway device installed at the junction box will translate the signals into pulses of light that can pass through the fiber optic cable. Through this process, the distance barrier associated with copper wire and VDSL is “bridged” or bypassed. When the telco receives the light pulses, it sends the data to the junction box gateway, which converts the signal forward along the copper wires a short distance from the modem. In this scenario, distance is not a limiting factor.
VDSL is available worldwide in specific regions and growing, although it is not readily available in the United States. A second-generation version known as VDSL2 boasts speeds of up to 100 Mbps.




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