Dynamics limited precoding, shaping, and blind equalization for fast digital transmission over twisted pair lines

A new combined precoding/shaping technique for fast digital transmission over twisted pair lines is proposed. Major advantages of this “dynamics shaping” are: dynamics of the signal at the input of the decision device are reduced by a great amount. Thereby, A/D-conversion, adaptive equalization, and symbol timing are rather facilitated. A trade-off between signal dynamics at the transmitter output, decision device input and SNR-gain by noise whitening is offered. For dynamics limitation relevant in practice, gains up to 6 dB are achieved. Additionally, the transmitter can be fixed to a typical application because, in contrast to Tomlinson-Harashima or other precoding techniques, blind adaptive equalization is practicable to remove residual intersymbol interference in the case of a mismatch of precoding and actual cable characteristics. The residual SNR-loss is negligible in most applications. SNR-gains due to noise prediction, channel coding and signal shaping simply can be combined using dynamics shaping. Nevertheless, system complexity is of the order of other precoding/shaping techniques. Although numerical results are only presented for a HDSL-application in the German Telekom subscriber network, the proposed transmission scheme may simplify all kinds of high-speed data communications via copper lines, such as LAN´s, ADSL, CDDI, etc