Improving the Energy Efficiency of Broadband Copper Access Networks: Review and Performance Analysis

In this paper, we review the main techniques that can be applied to improve the energy efficiency of broadband copper access networks. Starting from a holistic view of the end-to-end copper access, we identify green opportunities in the different building blocks for different deployment practices. We shift the focus to the access telecommunication equipment and its supporting functions needed to operate the equipment in different environments depending on the access architecture. This system-level approach, guided by the power breakdown of the access nodes, reveals that some optimizations can result in more energy savings as opposed to others. In the second part, we narrow the scope and focus on the realistic energy saving in the telecommunication equipment when optimizing rate-power-stability tradeoffs at the physical layer through spectral optimization. For this purpose, we first review the main state of the art digital subscriber line (DSL) spectral optimization techniques. Then, we conduct (system level) power measurements of an operator-side DSL line board under various conditions of data rate, power spectral density, and stability. The experiments highlight practical opportunities and challenges for optimizing rate-power-stability tradeoffs in copper access systems with comparison to available simulation-based studies focusing on energy reduction through spectral optimization.