Spectrum optimization in multi-user multi-carrier systems with iterative convex and nonconvex approximation methods

Several practical multi-user multi-carrier communication systems are characterized by a multi-carrier interference channel system model where the interference is treated as noise. For these systems, spectrum optimization is a promising means to mitigate interference. This however corresponds to a challenging nonconvex optimization problem. Existing iterative convex approximation (ICA) methods consist in solving a series of improving convex approximations and are typically implemented in a per-user iterative approach. However they do not take this typical iterative implementation into account in their design. This paper proposes a novel class of iterative approximation methods that focuses explicitly on the per-user iterative implementation, which allows to relax the problem significantly, dropping joint convexity and even convexity requirements for the approximations. A systematic design framework is proposed to construct instances of this novel class, where several new iterative approximation methods are developed with improved per-user convex and nonconvex approximations that are both tighter and simpler to solve (in closed-form). As a result, these novel methods display a much faster convergence speed and require a significantly lower computational cost. Furthermore, a majority of the proposed methods can tackle the issue of getting stuck in bad locally optimal solutions, and hence improve solution quality compared to existing ICA methods.Comment: 33 pages, 7 figures. This work has been submitted for possible publicatio

Computational intelligence in performance evaluation and fault prognosis in telecommunication access networks

Telecommunication connections are highly reliable and manageable, however, the handling of several parts of the networks is problematic. One of these parts is the access network. The variegation of the applied technologies and the individual connections to the customers in access networks makes the preliminary estimation of the performance of the telecommunications services and troubleshooting difficult. There are existing methods which can handle such problems, but the telecommunications companies (TELCO) are continuously looking for newer and more efficient methods. In this paper some existing methods for performance evaluation and the prediction of the probable failures of the wire pairs of telecommunications access networks are reviewed and novel methods that are based on the measurements of the wire pairs and use computational intelligence, fuzzy inference methods and evolutionary models are introduced