A nonlinear complementarity approach to multiuser power control for digital subscriber lines

In this paper we formulate the problem of multiuser power control for digital subscriber lines (DSL) as a nonlinear complementarity problem (NCP). We study conditions under which the resulting NCP belongs to the class P0 and its solution is B-regular. The NCP formulation makes it possible to use the Newton type smoothing methods to efficiently compute a Nash equilibrium solution. In our computer simulations, the smoothing method appears much more robust to the presence of strong interference than the existing Synchronous Water-filling method. We also present an extension of the NCP formulation which can lead to substantial increase in the rate sum performance of the DSL system.