The rate maximization problem in DSL with mixed spectrum and signal coordination

Theoretical research has demonstrated that the gains in data rate achievable with spectrum coordination or signal coordination techniques are substantial for digital subscriber line (DSL) networks. Work on these two fronts has progressed steadily and usually independently. In this paper, we combine the two types of coordination for a mixed DSL scenario, one in which some of the infrastructure required for full-fledged signal coordination is available, but not all. This kind of scenario, which is referred to as the DMT MIMO IC scenario, can be an important stepping stone for the development of DSL towards a fully signal coordinated architecture. Our solution has characteristics of both signal and spectrum coordination and delivers good performance. 1. INTRODUCTION Digital subscriber line (DSL) is today the most widespread technology for high speed data transmission. In the past ten years, theoretical research has shown that the improvements achievable with spectrum or signal coordination techniques (called dynamic spectrum management [DSM]) are significant. The main objective of these techniques is to avoid or cancel multi-user interference. i.e. crosstalk, the main source of performance degradation for DSL networks. Spectrum coordination (also known as DSM levels 1 and 2) aims to allocate power in the available spectrum so that crosstalk is avoided and minimized. Examples of well-known solutions are [1, 9, 11, 14, 15] Spectrum coordination algorithms do not deliver the same gains as signal coordination algorithms do, but they profit from simplified infrastructure requirements and smaller complexity.