Dynamic spectrum management for energy-efficient transmission in DSL

Dynamic spectrum management (DSM) is an important technique for mitigating crosstalk noise in multi-user digital subscriber line (DSL) environments. Until now, most of the proposed algorithms for DSM have been designed solely for the purpose of bitrate maximization. These algorithms assume a fixed maximum total power and neglect the energy consumption in DSL modems. However, since recently there is a strong interest in the DSL field to reduce energy consumption as shown, e.g., by the European Commissions¿ code of conduct on energy consumption of broadband equipment. In contrast to traditional DSM, this paper will show how DSM can be used for minimizing the energy consumption. We will formulate a global optimization problem for energy minimization and discuss several of its peculiarities compared to the current DSM problems. Furthermore, we derive an iterative, dual-based and semi-distributed algorithm for its local solution, which we call energy-efficient spectrum balancing (EESB). The performance of the algorithm is evaluated through simulations, which show similar results to optimal schemes. In addition, EESB achieves substantial energy savings that can be exploited by adapting the transmit powers to users¿ bitrate demand.