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xDSL - allows mixing data, voice and video over conventional, copper phone lines.
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The service under development (since 1987).
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Competes with ISDN and cable modems
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xDSL family : ADSL, RADSL, IDSL, HDSL, SDSL, VDSL
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All xDSL technologies run on existing copper phone lines and use modulation to boost transmission rates.
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CAP - amplitude phase modulation
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DMT - discrete multi-tone modulation
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DWMT- discrete wavelet multi-tone modulation.
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The key in xDSL technology is modulation, a process in which one signal modifies a properties of another.
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Hardware: DSL requires modems and splitters for end-users; carriers use DSLAMs (digital subscriber line access multiplexers)
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Differences between xDSL technologies: speed, operating distance, applications, ratio between up and downstream
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Different approaches: ATM-based ADSL, ISDN DSL. The important thing is what is running over xDSL...
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