Trading Off Rate and Power Consumption in DSL Systems

Abstract

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.

Modeling and optimization of the line-driver power consumption in xDSL systems

“…Furthermore, the presented LD power models have a qualitatively similar functional shape for transmit power values below 14.5dBm as they are all based on the elementary class-AB power relation in (2). In the following sections, we focus on the class-AB LD and analyze our hypothesis of Section 'Introduction' on the difference between LD power and TP optimization.…”

“…Depending on the used transmission profile (e.g., bandwidth) the LD power consumption can be somewhere between 30% and 60% of the modem's total power consumption [1][2][3]. The main focus for energy saving in DSL therefore lies on the LD power consumption [1,4].…”

“…An empirical model based on power measurements of a class-AB LD in ADSL2+ was presented in [2]. However, this model is not applicable to other DSL technologies or systems with different physical parameters.…”

“…The line-driver (LD) power consumption accounts for the largest part in the DSL power budget and scales with the transmit power (TP) [1][2][3]. With few exceptions [2,4,5], previous study has therefore focussed on minimizing the transmit sumpower [3,[6][7][8] through power spectral optimization, also known as dynamic spectrum management (DSM) [9].…”

“…For that purpose we propose two novel numerical approaches for LD power optimization which are based on successive geometric programming (GP) [14,15] and difference-ofconvex-functions programming (DCP) [16], respectively. These techniques help us to motivate the selected scenario for simulation of a DSL network with realistic parameters under the two DSM heuristics in [2,3], cf. the introduction in Section 'Empirical optimization study' for a more concise overview of our contributions.…”