The Bandwidth minimization problem

Mestrado em Métodos Quantitativos para a Decisão Económica e EmpresarialEsta dissertação tem como objetivo comparar o desempenho de duas heurísticas com a resolução de um modelo exato de programação linear inteira na determinação de soluções admissíveis do problema de minimização da largura de banda para matrizes esparsas simétricas. As heurísticas consideradas foram o algoritmo de Cuthill e McKee e o algoritmo Node Centroid com Hill Climbing. As duas heurísticas foram implementadas em VBA e foram avaliadas tendo por base o tempo de execução e a proximidade do valor das soluções admissíveis obtidas ao valor da solução ótima ou minorante. As soluções ótimas e os minorantes para as diversas instâncias consideradas foram obtidos através da execução do código para múltiplas instâncias e através da resolução do problema de Programação Linear Inteira com recurso ao Excel OpenSolver e ao software de otimização CPLEX. Como inputs das heurísticas foram utilizadas matrizes com dimensão entre 4×4 e 5580×5580, diferentes dispersões de elementos não nulos e diferentes pontos de partida.This dissertation intends to compare the performance of two heuristics with the resolution on the exact linear integer program model on the search for admissible solutions of the bandwidth minimization problem for sparse symmetric matrices. The chosen heuristics were the Cuthill and McKee algorithm and the Node Centroid with Hill Climbing algorithm. Both heuristics were implemented in VBA and they were rated taking into consideration the execution time in seconds, the relative proximity of the value obtained to the value of the optimal solution or lower bound. Optimal solutions and lower bounds were obtained through the execution of the code for several instances and trough the resolution of the integer linear problem using the Excel Add-In OpenSolver and the optimization software CPLEX. The inputs for the heuristics were matrices of dimension between 4×4 and 5580×5580, different dispersion of non-null elements and different initialization parameters.info:eu-repo/semantics/publishedVersio

Memetic Multi-Objective Particle Swarm Optimization-Based Energy-Aware Virtual Network Embedding

In cloud infrastructure, accommodating multiple virtual networks on a single physical network reduces power consumed by physical resources and minimizes cost of operating cloud data centers. However, mapping multiple virtual network resources to physical network components, called virtual network embedding (VNE), is known to be NP-hard. With considering energy efficiency, the problem becomes more complicated. In this paper, we model energy-aware virtual network embedding, devise metrics for evaluating performance of energy aware virtual network-embedding algorithms, and propose an energy aware virtual network-embedding algorithm based on multi-objective particle swarm optimization augmented with local search to speed up convergence of the proposed algorithm and improve solutions quality. Performance of the proposed algorithm is evaluated and compared with existing algorithms using extensive simulations, which show that the proposed algorithm improves virtual network embedding by increasing revenue and decreasing energy consumption.Comment: arXiv admin note: text overlap with arXiv:1504.0684

Telecommunications Network Planning and Maintenance

Telecommunications network operators are on a constant challenge to provide new services which require ubiquitous broadband access. In an attempt to do so, they are faced with many problems such as the network coverage or providing the guaranteed Quality of Service (QoS). Network planning is a multi-objective optimization problem which involves clustering the area of interest by minimizing a cost function which includes relevant parameters, such as installation cost, distance between user and base station, supported traffic, quality of received signal, etc. On the other hand, service assurance deals with the disorders that occur in hardware or software of the managed network. This paper presents a large number of multicriteria techniques that have been developed to deal with different kinds of problems regarding network planning and service assurance. The state of the art presented will help the reader to develop a broader understanding of the problems in the domain