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xDSL technologies

xDSL is a general term for all DSL variants that use the telephone cables in the connection area on a broadband basis. The "x" stands for one or two letters that characterize the corresponding DSL method. If the "x" is replaced by an "A", this indicates asymmetrical transmission, which works with different data rates in the upstream and downstream

, "

S" stands for symmetrical data rates, "I" for ISDN, " RA


for rate adaptive or speed adaptive, etc.

All xDSL processes have in common that the transmission between the subscriber and the exchange takes place via copper twisted pairs. The different xDSL variants use different frequency ranges, bridge different distances and have different data rates. Since xDSL uses different frequency ranges than trunk voice

, the latter can be transmitted in parallel with the xDSL signal

DSL variants

DSL variants

The different DSL methods

In concept, the high-speed connections are routed from the core network to theDigital Subscriber Line Access Multiplexer (DSLAM), which demodulates them and multiplexes them onto the subscriber lines

(local loops). Thesubscriber-side DSL modem is thus directly connected to the DSLAM in the local exchange

via thesubscriber line.

Under xDSL, there are various procedures and variants that differ in data rates, modulation procedures and data rates: ADSL (Asymmetric DSL), ADSL2, ADSL2+, IDSL (ISDN DSL), RADSL (Rate Adaptive DSL), SDSL (Symmetrical DSL), HDSL (High Bit Rate DSL), VDSL (Very High Speed DSL), VDSL2, CDSL (Consumer DSL) and SHDSL (Single Pair High Bit Rate


Multiplexing function of the DSLAM from 155 Mbit/s to several hundred DSL lines

Multiplexing function of the DSLAM from 155 Mbit/s to several hundred DSL lines

The limitations of DSL methods lie in the subscriber lines, which are often old copper twisted pairs with limited transmission characteristics in terms of their line quality, bandwidth, distance and crosstalk. In order to be able to use these copper lines nevertheless for high data transmission rates, Alcatel-Lucent has developed various procedures for Dynamic Spectrum Management (DSM), which are standardized by the International Telecommunication Union (ITU-T). The procedures include vectoring, line bonding and phantom operation.

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Englisch: xDSL technologies
Updated at: 22.09.2018
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