Optimal Power Allocation under Per-Modem Total Power and Spectral Mask Constraints in XDSL Vector Channels with Alien Crosstalk

In xDSL systems, in-domain crosstalk is easily dealt with based on zero-forcing receiver or precoding while out of domain or alien crosstalk requires a more advanced processing. In vector channels, multiple input multiple output (MIMO) signal processing mitigates both types of crosstalk, usually by means of a pre-whitening filter, singular value decomposition (SVD) based transmission and waterfilling based power allocation. In this paper, we investigate the problem of power allocation in xDSL vector channels under in-domain and alien crosstalk. We propose a new power allocation algorithm to maximize the MIMO capacity under per-modem total power constraints and spectral mask constraints, leading to a generalized SVD-based transmission.