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DSL (Digital subscriber line)
DSL or xDSL, is a family of technologies that provides digital data transmission over the wires of a local telephone network. DSL originally stood for digital subscriber loop, although in recent years, the term digital subscriber line has been widely adopted as a more marketing-friendly term for ADSL, which is the most popular version of consumer-ready DSL. DSL can be used at the same time and on the same telephone line with regular telephone, as it uses high frequency, while regular telephone uses low frequency.
Typically, the download speed of consumer DSL services ranges from 256 kilobits per second (kbit/s) to 24,000 kbit/s, depending on DSL technology, line conditions and service level implemented. Typically, upload speed is lower than download
DSL (VDSL) typically works by dividing the frequencies used in a single phone line into two primary "bands". The ISP data is carried over the high-frequency band (25 kHz and above) whereas the voice is carried over the lower-frequency band (4 kHz and below).The user typically installs a DSL filter on each phone. This filters out the high frequencies from the phone line, so that the phone only sends or receives the lower frequencies (the human voice). The DSL modem and the normal telephone equipment can be used simultaneously on the line without interference from each other.
DSL technologies
The line length limitations from telephone exchange to subscriber are more restrictive for higher data transmission rates. Technologies such as VDSL provide very high speed, short-range links as a method of delivering "triple play" services (typically implemented in fiber to the curb network architectures). Technologies likes GDSL can further increase the data rate of DSL. Fiber Optic technologies exist today that allow the conversion of copper based IDSN, ADSL and DSL over fiber optics.
Example DSL technologies (sometimes called xDSL) include:
ISDN Digital Subscriber Line (IDSL), uses ISDN based technology to provide data flow that is slightly higher than dual channel ISDN.
High Data Rate Digital Subscriber Line (HDSL / HDSL2), was the first DSL technology that uses a higher frequency spectrum of copper, twisted pair cables.
Symmetric Digital Subscriber Line (SDSL / SHDSL), the volume of data flow is equal in both directions.
Symmetric High-speed Digital Subscriber Line (G.SHDSL), a standardised replacement for early proprietary SDSL.
Asymmetric Digital Subscriber Line (ADSL), the volume of data flow is greater in one direction than the other.
Asymmetric Digital Subscriber Line 2 (ADSL2), an improved version of ADSL
Asymmetric Digital Subscriber Line 2 Plus (ADSL2+), A version of ADSL2 that doubles the data rates by using twice the spectrum.
Asymmetric Digital Subscriber Line Plus Plus (ADSL++), technology developed by Centillium Communications for Japan market that extends downstream rates to 50 Mbit/s by using spectrum up to 3.75 MHz.
Rate-Adaptive Digital Subscriber Line (RADSL)
Very High Speed Digital Subscriber Line (VDSL)
Very High Speed Digital Subscriber Line 2 (VDSL2), an improved version of VDSL
Etherloop Ethernet Local Loop
Uni Digital Subscriber Line (UDSL), technology developed by Texas Instruments, backwards compatible with all DMT standards
Gigabit Digital Subscriber Line (GDSL), based on binder MIMO technologies[7].
(UHDSL) Universal Digital Subscriber Line using fiber optics. Developed in 2005 by RLH Industries, Inc. Converts HDSL-1, 2 or 4 copper service into fiber optic HDSL service.
Typically, the download speed of consumer DSL services ranges from 256 kilobits per second (kbit/s) to 24,000 kbit/s, depending on DSL technology, line conditions and service level implemented. Typically, upload speed is lower than download
DSL (VDSL) typically works by dividing the frequencies used in a single phone line into two primary "bands". The ISP data is carried over the high-frequency band (25 kHz and above) whereas the voice is carried over the lower-frequency band (4 kHz and below).The user typically installs a DSL filter on each phone. This filters out the high frequencies from the phone line, so that the phone only sends or receives the lower frequencies (the human voice). The DSL modem and the normal telephone equipment can be used simultaneously on the line without interference from each other.
DSL technologies
The line length limitations from telephone exchange to subscriber are more restrictive for higher data transmission rates. Technologies such as VDSL provide very high speed, short-range links as a method of delivering "triple play" services (typically implemented in fiber to the curb network architectures). Technologies likes GDSL can further increase the data rate of DSL. Fiber Optic technologies exist today that allow the conversion of copper based IDSN, ADSL and DSL over fiber optics.
Example DSL technologies (sometimes called xDSL) include:
ISDN Digital Subscriber Line (IDSL), uses ISDN based technology to provide data flow that is slightly higher than dual channel ISDN.
High Data Rate Digital Subscriber Line (HDSL / HDSL2), was the first DSL technology that uses a higher frequency spectrum of copper, twisted pair cables.
Symmetric Digital Subscriber Line (SDSL / SHDSL), the volume of data flow is equal in both directions.
Symmetric High-speed Digital Subscriber Line (G.SHDSL), a standardised replacement for early proprietary SDSL.
Asymmetric Digital Subscriber Line (ADSL), the volume of data flow is greater in one direction than the other.
Asymmetric Digital Subscriber Line 2 (ADSL2), an improved version of ADSL
Asymmetric Digital Subscriber Line 2 Plus (ADSL2+), A version of ADSL2 that doubles the data rates by using twice the spectrum.
Asymmetric Digital Subscriber Line Plus Plus (ADSL++), technology developed by Centillium Communications for Japan market that extends downstream rates to 50 Mbit/s by using spectrum up to 3.75 MHz.
Rate-Adaptive Digital Subscriber Line (RADSL)
Very High Speed Digital Subscriber Line (VDSL)
Very High Speed Digital Subscriber Line 2 (VDSL2), an improved version of VDSL
Etherloop Ethernet Local Loop
Uni Digital Subscriber Line (UDSL), technology developed by Texas Instruments, backwards compatible with all DMT standards
Gigabit Digital Subscriber Line (GDSL), based on binder MIMO technologies[7].
(UHDSL) Universal Digital Subscriber Line using fiber optics. Developed in 2005 by RLH Industries, Inc. Converts HDSL-1, 2 or 4 copper service into fiber optic HDSL service.
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