Signal Shaping for PeakPower and Dynamics Reduction in Transmission Schemes Employing Prec.pdf

IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 50, NO. 5, MAY 2002 735 Signal Shaping for Peak-Power and Dynamics Reduction in Transmission Schemes Employing Precoding Robert F. H. Fischer, Member, IEEE, Roman Tzschoppe, and Johannes B. Huber, Senior Member, IEEE Abstract— Precoding, i.e., nonlinear pre-equalization, at the as the range of linear operation can be narrowed. This moreover transmitter side has been proved to be a very efficient strategy reduces the power loss of the line driver, as it is directly related for channel equalization in single-carrier digital transmission to the peak-to-average power ratio of the transmitted signal. As schemes. It enables the application of coded modulation in a seamless fashion. A drawback of precoding is that the signal at the an example, we study the application to single-pair digital sub- input of the decision device exhibits a huge dynamic range. Based scriber lines (SDSLs), a member of the so-called xDSL family, on dynamics shaping, a combined precoding/shaping technique which has been developed and standardized over the last several introduced in the paper by Fischer et al. in 1995, a new shaping years. Applying these techniques, the “last mile” from the cen- strategy is developed in this paper. This technique enables a flex- tral office to the customer can be bridged, and new digital ser- ible tradeoff among: 1) reduction of the average transmit power; 2) avoidance of peaks in the transmit signal in order to facilitate vices can be provided cost-effectively to a wide range of users. line driver implementation; and 3) restriction of the maximum After introducing the system model of transmission sc