Design of algorithms for Dynamic Spectrum Management (DSM) level-3 in xDSL: Comparison and application to phantom mode signals

In xDSL, the information is carried differentially through two copper wires. This transmission mode is called Differential-Mode (DM). While Common-Mode reception can mitigate part of the colored noise, the major drawback of CM transmission is the egress caused to other lines. The use of Multiple Input Multiple Output (MIMO) binder allows to further use a differential signal between two common modes referred to as Phantom Mode (PM) tranmission causing no significant egress to other lines. PM transmission increases the capacity by a factor (2N-1)/N (N the number of differential lines). In this paper we study three types of algorithms for optimal power allocation in MIMO systems with colored noise using PM transmission under practical implementation (per-modem total power constraints and non-zero SNR gap). First, the two-sided coordination case is studied leading to a SVD-based algorithm. Then, one-sided algorithms for Multiple Access Channels (MAC) and Broadcast Channels (BC) are investigated. Finally, we compare these Dynamic Spectrum Management (DSM) level-3 algorithm with a DSM level-2 algorithm for Interference Channels (IC). The three types of algorithms are compared in the simulation results applying a VDSL2 scenario.