Coding, equalization and feedback of digital cable pair signals

The performance with near-end crosstalk noise of zero-forcing optimum mean-squared-noise equalizer repeaters is studied. For 48-channel systems, duobinary is 5.6 dB superior to binary, and coding to reduce low frequency energy causes a 4 to 6 dB performance degradation. Multi-tap decision feedback gives an additional 7.7 dB improvement over duobinary; a single tap gives only 1 to 2 dB improvement. Performance equivalent to present 24-channel repeaters but with 48-channel capacity using simple coding schemes appears feasible.