DYNAMICS LIMITED PRECEDING, SHAPING, AND BLIND EQUALIZATION FOR FAST DIGITAL TRANSMISSION OVER TWISTED PAIR LINES

A new combined preceding/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 preceding techniques, blind adaptive equalization is practicable to remove residual intersymbol interference in the case of a mismatch of preceding 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 preceding/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 as LAN's, ADSL, CDDI, etc.