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End-to-End DSL Architectures by Wayne C. Vermillion

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Chapter 2

1: Which of the following impairments always prevents ADSL implementation?
  1. AM radio interference

  2. Impedance mismatch

  3. Load coils

  4. Bridged taps

A1: Answer: C. Load coils were designed specifically to block frequencies above the standard voice range, 0 to 4 kHz, which includes the range of DSL traffic. AM radio interference, impedance mismatches, and bridged taps are hindrances to DSL service but do not automatically prevent ADSL service.
2: Which of the following is not one of the three primary methods of forward error correction in ADSL?
  1. Trellis Coding

  2. DMT

  3. Interleaving

  4. Reed-Solomon Encoding

A2: Answer: B. Discrete multitone (DMT) is simply a type of modulation for DSL. Division into multiple tones does not correct any errors. Trellis Coding and Reed-Solomon ...

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