BT Technology Journal - Archive

Commemorating 25 years of publication

A long reach digital subscriber loop transceiver

P F Adams, S A Cox, R B P Carpenter and N G Cole

An echo-cancelling duplex transmission system is described for the digital subscriber loop which uses a 4-level zero redundancy line code (2B1Q) to give very long reach in the presence of crosstalk. Novel digital signal processing algorithms are used to simplify the analogue line interface circuitry. All the digital signal processing, along with sophisticated maintenance and interfacing circuitry, can be contained on a single LSI circuit. Measured performance results are presented.

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