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- A game-based algorithm for fair bandwidth allocation in fibre-wireless access networksPublication . Coimbra, José; Schutz, G.; Correia, NoéliaFibre-Wireless (FiWi) access networks have been proposed as flexible and cost-effective solutions for future access networks. At the wireless mesh section, wireless routers have to forward both local traffic from directly connected users and foreign traffic from neighbour wireless routers. How to allocate resources to local and foreign traffic at each router in a balanced way, while avoiding starvation of routers requiring less resources, is a fundamental issue that must be solved so that new services emerge. Here, we develop a repeated game framework for bandwidth allocation and propose an algorithm that allocates bandwidth in a fair manner. The algorithm is able to detect over claiming routers and avoid possible denial of service that these may cause to others. Moreover, unfruitful use of resource is prevented, avoiding the forwarding of packets that would be dropped at some point later in the path, and queueing delay conditions are kept similar among local and foreign traffic. These fair network conditions open way for QoS support since it is easier to ensure the operationality of services.
- Disclosing proteins in the leaves of cork oak plants associated with the immune response to Phytophthora cinnamomi inoculation in the roots: a long-term proteomics approachPublication . Coelho, Ana Cristina; Pires, Rosa; Schütz, Gabriela; Santa, Cátia; Manadas, Bruno; Pinto, Patricia ISThe pathological interaction between oak trees and Phytophthora cinnamomi has implications in the cork oak decline observed over the last decades in the Iberian Peninsula. During host colonization, the phytopathogen secretes effector molecules like elicitins to increase disease effectiveness. The objective of this study was to unravel the proteome changes associated with the cork oak immune response triggered by P. cinnamomi inoculation in a long-term assay, through SWATH-MS quantitative proteomics performed in the oak leaves. Using the Arabidopis proteome database as a reference, 424 proteins were confidently quantified in cork oak leaves, of which 80 proteins showed a p-value below 0.05 or a fold-change greater than 2 or less than 0.5 in their levels between inoculated and control samples being considered as altered. The inoculation of cork oak roots with P. cinnamomi increased the levels of proteins associated with protein-DNA complex assembly, lipid oxidation, response to endoplasmic reticulum stress, and pyridine-containing compound metabolic process in the leaves. In opposition, several proteins associated with cellular metabolic compound salvage and monosaccharide catabolic process had significantly decreased abundances. The most significant abundance variations were observed for the Ribulose 1,5-Bisphosphate Carboxylase small subunit (RBCS1A), Heat Shock protein 90-1 (Hsp90-1), Lipoxygenase 2 (LOX2) and Histone superfamily protein H3.3 (A8MRLO/At4G40030) revealing a pertinent role for these proteins in the host-pathogen interaction mechanism. This work represents the first SWATH-MS analysis performed in cork oak plants inoculated with P. cinnamomi and highlights host proteins that have a relevant action in the homeostatic states that emerge from the interaction between the oomycete and the host in the long term and in a distal organ.
- A solution for a real-time stochastic capacitated vehicle routing problem with time windowsPublication . Cardoso, Pedro J. S.; Schütz, Gabriela; Mazayev, Andriy; Ey, Emanuel; Corrêa, TiagoReal-time distribution planning presents major difficulties when applied to large problems. Commonly, this planning is associated to the capacitated vehicle routing problem with time windows (CVRPTW), deeply studied in the literature. In this paper we propose an optimization system developed to be integrated with an existing Enterprise Resource Planning (ERP) without causing major disruption to the current distribution process of a company. The proposed system includes: a route optimization module, a module implementing the communications within and to the outside of the system, a non-relational database to provide local storage of information relevant to the optimization procedure, and a cartographic subsystem. The proposed architecture is able to deal with dynamic problems included in the specification of the project, namely: arrival of new orders while already optimizing as well as locking and closing of routes by the system administrator. A back-office graphical interface was also implemented and some results are presented.
- GACN: Self-clustering genetic algorithm for constrained networksPublication . A. Martins, J.; Mazayev, Andriy; Correia, Noélia; Schutz, G.; Barradas, A.Extending the lifespan of a wireless sensor network is a complex problem that involves several factors, ranging from device hardware capacity (batteries, processing capabilities, and radio efficiency) to the chosen software stack, which is often unaccounted for by the previous approaches. This letter proposes a genetic algorithm-based clustering optimization method for constrained networks that significantly improves the previous state-of-the-art results, while accounting for the specificities of the Internet engineering task force, Constrained RESTful Environment (CoRE), standards for data transmission and specifically relying on CoRE interfaces, which fit this purpose very well.
- Network game based routing for energy efficient fibre-wireless access networksPublication . Coimbra, José; Schutz, G.; Correia, NoéliaThe currently growing demand for information and communication technologies (ICTs), and multimedia services, is generating a fast expansion of digital traffic. To fulfill such demands, new generation access architectures have been pro-posed that try to integrate and optimize available technologies. Besides allowing new services to emerge, such architectures also offer a great opportunity to develop new methods that try to increase energy efficiency by proper equipment management and sharing of resources. Here we focus on energy saving in Fibre-Wireless (FiWi) access networks, which provide high bandwidth and ubiquity to future multimedia services and applications. The goal is to exploit the path diversity of mesh FiWi networks to improve energy efficiency. A model based on network formation game theory is developed, creating ground for energy efficient routing algorithms. To obtain stable and efficient networks, the use of a new stability concept, which avoids unconnected nodes, is proposed and a dynamic network formation process is presented and applied to the model. Our results show that significant energy efficiency gains can be obtained. It is also shown that gateway placement can have a strong impact on energy efficiency.
- Dynamic aggregation and scheduling in CoAP/Observe-based wireless sensor networksPublication . Correia, Noélia; Sacramento, David; Schutz, G.Wireless sensor networks (WSNs) are starting to have a high impact on our societies and, for next generation WSNs to become more integrated with the Internet, researchers recently proposed to embed IPv6 into such very constrained networks. Also, constraint application protocol (CoAP) and Observe have been proposed for RESTful services to be provided. CoAP/Observe supports the use of caches/proxies and, for this reason, an observation request may resort to multiple client/server registration steps in order to get notifications. Here, we propose to plan the multiple registration steps, at proxies, of multiple observation requests in order to make proper aggregation/scheduling of notifications for transmission. This leads to less energy consumption and to an effective use of bandwidth, avoiding energy depletion of nodes, and increasing the network lifetime. Besides, mathematically formalizing the problem, a heuristic approach is developed and a discussion on how to incorporate algorithm's decision into the network is done. The proposed framework can be applied to multiple application domains (e.g., monitoring, machine to machine).
- A computational study of a parallel Branch and Bound algorithm for the quadratic 0-1 programming problem on transputersPublication . Schutz, G.; Pires, F. M.; Ruano, AntonioDiscrete optimization problems are very difficult to solve, even if the dimantion is small. For most of them the problem of finding an ε-approximate solution is already NP-hard.
- A heuristic for fault-tolerance provisioning in multi-radio hybrid wireless-optical broadband access networkPublication . Schutz, G.; Correia, NoéliaThe wireless-optical broadband-access network (WOBAN) architecture has been proposed as a flexible and cost-effective solution for future access networks. However, for WOBANs to provide geographically continuous wireless coverage it is necessary to integrate fault-tolerance in the design of such networks. In this paper we develop a heuristic algorithm to solve the problem of planning a wireless and optical fault-tolerant multi-radio WOBAN, considering any fault-tolerance scenario (e.g. some nodes/links/region only), while making an efficient reuse of spectrum.
- Resolução de problemas de optimização combinatória em máquinas paralelasPublication . Schütz, Gabriela; Ruano, António; Pires, Fernanda MaríliaEm muitas e variadas áreas, tais como, transportes, logística, telecomunicações, informática, gestão e planeamento, etc., depara-se com problemas em que se tem como objectivo encontrar a melhor solução entre um número finito ou infinito numerável de alternativas discretas. São os chamados Problemas de Optimização Combinatória. A enorme quantidade de aplicações concretas com que se defrontam a generalidade das empresas e instituições levou, nas últimas décadas, a uma intensa actividade no sentido de desenvolver teorias e técnicas eficientes para a resolução destes problemas de Matemática Discreta.
- Estudo computacional de um algoritmo genético para o problema de optimização de rotas de veículosPublication . Schutz, G.; Pires, F. M.; Ruano, AntonioO problema básico da distribuição e/ou recolha de produtos é um problema de Optimização Combinatória que consiste em determinar o conjunto de rotas que partem de um depósito central, cuja localização é conhecida, servem um conjunto de clientes com procuras e localizações pré - definidas, minimizando a distância total percorrida. Este é um problema NP-difícil, para o qual poucos métodos exactos foram desenvolvidos, sendo demasiado demorados e não sendo sequer exequíveis para a generalidade dos problemas de dimensão média. Assim, as abordagens mais comuns e eficientes baseiam-se em métodos heurísticos. Numa classificação superficial podem-se considerar duas classes de métodos heurísticos: os “clássicos” e os “modernos”. Os primeiros incluem, entre outros, os métodos construtivos de rota, os métodos de duas fases e os de melhoramento de rotas. Estes métodos foram basicamente desenvolvidos nos anos 60 e 70, embora continuem a ser utilizados e melhorados. Por outro lado, os métodos “modernos” têm como característica comum o recurso à pesquisa local utilizando técnicas de intensificação e diversificação dessa pesquisa. Entre outras, têm aparecido recentemente heurísticas baseadas em: Simulação de Têmpera; algoritmos Genéticos; Pesquisa Tabu; Algoritmos Difusos e Redes Neuronais. Combinações destas técnicas têm conduzido a algoritmos híbridos e a meta-heurísticas. Neste trabalho é feita a apresentação de um Algoritmo Genético para o Problema de Optimização de Rotas de Veículos. Apresenta-se a sua implementação e um estudo computacional comparativo com duas heurísticas “clássicas” num conjunto de problemas - teste conhecidos da literatura.