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DSL systems have traditionally been tuned to maximize rate or margin, subject to constraints on transmitted power. Recently attention is focusing on reducing power consumption. We formulate a new DSL tuning framework in which the line driver power consumption is part of the objective function. The framework uses a model for line driver power consumption as a function of transmitted power, along with the traditional model for data rate as a function of transmitted power. Using this framework, we show that it is possible to achieve significant reductions in line driver power consumption while incurring modest reductions in data rate. To solve the resulting nonlinear problem efficiently, we propose a new heuristic algorithm based on the combination of linearization of the objective and subsequent linear programming techniques. Numerical studies illustrate the tradeoffs that are available in multi-line systems.

The ever growing demand for higher data rate is pushing existing electrical broadband communication systems, using coax or twisted pair cabling, to the limit. While optical access systems inherently have a much higher transmission capacity, upgrading the access network entirely to fiber remains a costly and time-consuming effort. Therefore, many operators deploy fiber gradually closer to the end user, while bridging the remaining distance through copper technologies such as VDSL2. In the next step of this evolutionary path, fiber is brought to distribution points that are in the range of no more than 200 m from the end user, with a copper access technology called G.fast delivering data rates of 500 Mb/s to 1 Gb/s over the remaining copper stretch. In this paper, we give an overview of the G.fast technology that is currently being standardized in ITU. We show the feasibility of its main technical requirements, namely i) powering of the access equipment through the customer premises modem, ii) high transmission efficiency for orthogonal frequency division multiplexing over short copper loops and iii) offering high net data rates to end users.