Distributed spectrum coordination for DSL broadband access networks

Abstract

Digital subscriber line (DSL) technology is the dominating
broadband internet access technology with a market share of over
66 percent of all broadband subscribers worldwide. The main performance
bottleneck of modern DSL networks is the crosstalk interference
generated among different lines (i.e. twisted pair cables) inside
the same cable bundle. Multi-user spectrum coordination is
recognized as a key technology to tackle this crosstalk problem. It
consists of optimizing the users' transmit spectra so as to
mitigate the destructive impact of crosstalk, leading to spectacular
data rate performance gains as well as power savings. The
corresponding optimization problems are however large-scale
nonconvex problems. In this paper we provide a survey of recent
developments on spectrum coordination techniques where the main
focus is on distributed spectrum coordination. Here, individual
users optimize their transmit spectra based on local measures while
they are steered by a centralized controller (spectrum management
center)
so as to obtain a good global network performance. It is shown how
state-of-the-art techniques from mathematical programming are used
to obtain distributed algorithms with very low complexity and
yet good performance. Finally simulation results are shown that
demonstrate the impact of spectrum coordination for DSL broadband
access.