Toward green copper broadband access networks

This article gives an overview on the state of the art of the different options to save energy in copper-based broadband access nodes while maintaining performance and QoS. The main focus is on the potential energy saving in the physical layer and the access network architecture. We show that today the physical layer, when not optimized properly, is one of the main sources of energy consumption in copper-based access networks. On one hand this is due to the intrinsic high attenuation of the copper lines, and on the other hand to the different noise sources like electromagnetic coupling between lines in the same cable. The redesign of the access network by moving from a centralized network architecture to a more distributed network architecture, although initially driven by capacity increase needs, can be positioned as an energy efficiency enabler in the access nodes. It can be shown that under reasonable assumptions between 30 and 200 GWh per year can be saved globally. Some discussion and comparison of copper and fiber-based access networks from the "green angle" revealed that although FTTH can offer higher bandwidth at lower power, using the proper copper-based access network architecture is still able to come close on both aspects.