Abstract—Contemporary telecommunication networks consume significant amounts of electricity. For this reason, energy-efficient systems have to be used for establishing such networks. Wired transmission and networking technologies form the basis of both, fixed and wireless networks. In wired access networks, among others, copper lines are exploited for high-performance data transfer using existing network infrastructure. The power demand and the energy efficiency of communication systems can be characterized by metrics such as transmit power or energy per bit, respectively. Often, transmission links are sought that show minimum power or energy demand at preset throughput and transmission quality. For the example of a linearly equalized pulse amplitude modulated transmission system operating via copper cable it is analyzed how constellation size and allocation of the equalization to transmitter and receiver can be utilized to minimize the necessary power or energy demand at constant bit rate and fixed error probability. First, the optimization of the constellation size leads to minima in the energy-related metrics depending on the combination of the given throughput and the band limitation imposed by the copper line. Second, the equalizer optimization shows that an equal segmentation of the equalizing characteristic is optimum, yielding minimum power or energy metrics for constant throughput and transmission quality. The results achieved reveal that an optimization of constellation size and equalizer segmentation yield clear energy savings with respect to conventional wired copper-cable communication systems operating in the baseband—supporting the energy efficient use of existing copper lines for highspeed data transmission in telecommunication networks.  
 
Keywords—digital baseband transmission, transmit power, energy efficiency, copper cable, constellation size, linear equalization, optimization