Basic HTML version of Foils prepared 5 February 98

Foil 95 xDSL Digital Subscriber Line Technology

From Introduction to Networking Technologies CPS640 MultiMedia and Networking -- Spring Semester 1998. by Roman Markowski


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



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