Joint multiuser detection and optimal spectrum balancing for digital subscriber lines

This paper presents a joint multiuser detection and optimal spectrum balancing algorithm for heavily unbalanced crosstalk channels in digital subscriber line systems. To ensure detection of strong crosstalk only, the set of tones subject to multiuser detection must be chosen carefully. The problem of tone selection is highly coupled with the transmit power spectra and thus the optimal solution requires the two problems to be solved jointly. This paper makes use of the idea of dual decomposition to solve the above problem. By minimizing the Lagrangian dual of the primal problem, the joint tone selection and optimal spectral balancing problem can be solved globally and efficiently. Simulations show considerable bit rate increase when multiuser detection is performed with optimal spectrum balancing.