Use of Coding to Combat Impulse Noise on Digital Subscriber Loops

The authors describe an approach to combatting impulse noise (IN) on digital subscriber loops using short-constraint length convolutional codes and Viterbi decoding operating in hard-decision-and-erasures mode. Attention is restricted to time-compression-multiplexing transmission schemes using bipolar, or alternate-mark inversion (AMI), line coding, and a rather idealized IN model, although the approach and general conclusions are more broadly applicable. They discuss the tradeoffs in choosing the channel encoding rate to yield an optimum compromise between error-control protection and the combined effects of intersymbol interference and crosstalk. Numerical results are demonstrated for selected typical line configurations.