On Power Optimization in DSL Systems

Traditionally, dynamic spectrum management (DSM) deals with the rate maximization of digital subscriber lines subject to a per modem total transmit power constraint. Motivated by the desirability of reducing total power consumption, we reformulate the problem as one of minimizing the transmit power subject to minimum target rates. Both versions of the problem are special cases of a unified framework in which both rate maximization and power minimization are objectives. We also consider less complex formulation where a flat power backoff is applied relative to a fixed power profile. 1 I. INTRODUCTION Far-end crosstalk Crosstalk (FEXT) coupling is one of the main factors limiting the capacity of modern digital subscriber line (DSL) systems. The effects of crosstalk can be mitigated by dynamic spectrum management (DSM). Our focus here is on DSM level 2 (DSM2) (1), where the power spectral densities (PSDs) of the different users are coordinated to limit the impact of FEXT. More advanced coordination referred as vectoring, acts on the transmitted signals themselves in order to actively cancel crosstalk interference; a standard designed