Browsing by Author "Melo, Paulo"
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- Application protocols and wireless communication for IoT: a simulation case study proposalPublication . Novelli, Lucas; Jorge, Luisa; Melo, Paulo; Koscianski, AndreThe current Internet of Things (IoT) solutions require support at different network layers, from higher level applications to lower level media-based support. This paper presents some of the main application requirements for IoT, characterizing architecture, Quality of Service (QoS) features, security mechanisms, discovery service resources and web integration options and the protocols that can be used to provide them (e.g. CoAP, XMPP, DDS, MQTT-SN, AMQP). As examples of lower-level requirements and protocols, several wireless network characteristics (e.g. ZigBee, Z-Wave, BLE, LoRaWAN, SigFox, IEEE 802.11af, NB-IoT) are presented. The variety of possible applications scenarios and the heterogeneity of enabling technologies combined with a large number of sensors and devices, suggests the need for simulation and modeling tactics to describe how the previous requirements can be met. As a potential solution, the creation of simulation models and the usage of the OMNET++ simulation tool to enable meaningful IoT simulation is discussed. The analysis of the behavior of IoT applications is proposed for two use cases: Wireless Sensor Networks (WSN) for home and industrial automation, and Low Power Wide Area (LPWA) networks for smart meters, smart buildings, and smart cities.
- Building a test bed for simulation analysis for the internet of thingsPublication . Novelli, Lucas; Jorge, Luisa; Melo, Paulo; Koscianski, AndreThe current Internet of Things (IoT) solutions require support at different network layers, from higher level applications to lower level media-based support. The dissertation presents some of the main application requirements for IoT, characterizing architecture, Quality of Service (QoS) features, security mechanisms, discovery service resources and web integration options and the protocols that can be used to provide them (e.g. CoAP, XMPP, DDS, MQTT-SN, AMQP). As examples of lower-level requirements and protocols, several wireless network characteristics (e.g. ZigBee, Z-Wave, BLE, LoRaWAN, SigFox, IEEE 802.11af, NB-IoT) are presented. The variety of possible applications scenarios and the heterogeneity of enabling technologies combined with a large number of sensors and devices, suggests the need for simulation and modeling tactics to describe how the previous requirements can be met. As a potential solution, the creation of simulation models and the usage of the OMNET++ simulation tool to enable meaningful IoT simulation is discussed. The analysis of the behavior of IoT applications is proposed for two use cases: Wireless Sensor Networks (WSN) for home and industrial automation, and Low Power Wide Area (LPWA) networks for smart meters, smart buildings, and smart cities.
- Calculating a maximally node and SRLG-disjoint path pair of min-sum cost in GMPLS networksPublication . Gomes, Teresa; Jorge, Luísa; Melo, Paulo; Girão-Silva, Rita; Mendes, SérgioIn end-to-end connections it is sometimes not possible to find a totally disjoint path pair. In this context it may be reasonable to accept a path pair which is as disjoint as possible, and thus provide the best (in a certain sense) level of the single fault protection that can be ensured. A Shared Risk Link Group (SRLG) is a group of links which have a common risk of failure (which may result from the sharing of common resources at a lower layer). The concept of SRLG allows an upper layer to be capable of implementing diverse routing, taking into account the existence of common risks of failure. Two heuristics for solving the min-sum maximally node and SRLG-disjoint path pair, formulated as a multi-objective optimization problem, are presented. The relative performance of the heuristics is evaluated using three different networks. The envisaged application scenario of these path calculation algorithms is Generalized Multiprotocol Label Switching (GMPLS) networks.
- Conflicts and resolutions in managing water allocation at the watershed scalePublication . Srdjevic, Zorica; Srdjevic, Bojan; Melo, Paulo; Jorge, LuísaMultiple runs of a river basin model produced information about water allocation under different users’ priorities, creating a set of allocation scenarios as possible decision alternatives. To identify the most desired scenario that will, expectedly, be more readily accepted and implemented, involvement of stakeholders and reaching the consensus among them in evaluating scenarios are essential. This article describes methodology for integrating multi-criteria optimization as an efficient tool for the evaluation of scenarios in a group context, with river basin simulation-optimization models. Methodology was developed within the scope of the bilateral project Serbia–Portugal, and it consisted of five phases: defining the preference schemes of allocation, running the ACQUANET model, evaluating the criteria and strategies with analytic hierarchy process, aggregation and initial search for consensus in subgroups, and obtaining the final consensus converged result (best management strategy). The approach was tested on the water allocation problem in the Nadela watershed in Vojvodina Province in Serbia, with participation of 23 stakeholders. Promising results recommended the approach for the testing in different conditions in the area near Bragança in northeast Portugal (Sabor watershed).
- Determinação de k caminhos disjuntos nos SRLGPublication . Gomes, Teresa; Soares, Miguel; Craveirinha, José; Jorge, Luísa; Melo, PauloA determinação de um conjunto de caminhos disjuntos nos SRLG é um problema NP-Completo, de grande interesse no desenvolvimento de métodos de encaminhamento resiliente. Existem poucas heurísticas para a determinação de k de caminhos disjuntos nos SRLG, e tanto quanto nos foi possível averiguar, não existe nenhuma heurística que tente minimizar o custo total do conjunto de caminhos a determinar. São aqui propostas duas heurísticas que procuram determinar um conjunto de k caminhos disjuntos nos nós e nos SRLG, de custo aditivo mínimo.
- Failure simulation in software-defined networks with differential link availabilityPublication . Melo, Paulo; Jorge, Luisa; Gomes, TeresaIn Software-Defined Networks (SDN) the placement of controllers is an important factor for overall network reliability. Whereas most studies assume that all links have similar link failure rates/availability, placing controllers taking into account differences in link availability can yield advantages. This is even more relevant if the network is designed with a particular subset of high availability links (a spine). After presenting integer linear programming formulations to support controller placement considering differential link availability, we propose a simulation approach to verify the reliability change due to that placement. From a simulational study using 2 networks, 30 different link availability configurations we found a definite advantage in overall reliability in using the knowledge of high availability links to place the controllers. However, while there were also advantages to using certain spines for individual networks, these advantages were not uniform, and varied according to networks, the number of controllers placed and link availability ratio. Further work is suggested to check whether fault patterns may influence the reliability advantage of individual spines.
- Maximally node and SRLG-disjoint path pair of min-sum cost in GMPLS networks: a lexicographic approachPublication . Gomes, Teresa; Jorge, Luísa; Melo, Paulo; Girão-Silva, RitaPath protection is a fast and capacity-efficient approach for increasing the availability of end-to-end connections. However, sometimes it is not possible to obtain a fully disjoint path pair. In this case, it may be admissible to consider a path pair which is as disjoint as possible, and thus provide the best (in a certain sense) level of the single-fault protection that can be ensured using this type of approach. A shared risk link group (SRLG) is a group of links which have a common risk of failure. Two new heuristics for solving the min-sum maximally node and SRLG-disjoint path pair are presented. The relative performance of the new heuristics and also of two other previously proposed heuristics is evaluated using four different networks. Results, regarding accuracy and execution time of the studied heuristics, show that one of the new proposed algorithms can be a good compromise for use in the Generalized Multi-protocol Label Switching control plane.
- Multiclass data plane recovery using different recovery schemes in SDN: a simulation analysisPublication . Jorge, Luisa; Melo, Paulo; Gomes, TeresaTo provide dependable services SDN networks need to be resilient to link or switching node failures. This entails, when faults occur, ensuring differentiated types of recovery, according to carried traffic, to routing paths. However, the choice of the recovery scheme best suited to each traffic class is not direct, nor is obvious the impact of the combination of various recovery schemes, according to traffic classes. We explore the usage of different recovery schemes for traffic with distinct requirements Simulation analysis confirms that using different recovery schemes for distinct types of traffic does create differentiated effects in terms of traffic carried and bandwidth usage.
- Proteção em redes GMPLS considerando informação acerca dos SRLGPublication . Gomes, Teresa; Soares, Miguel; Craveirinha, José; Melo, Paulo; Jorge, Luísa; Mirones, Vítor; Brizído, AndréGarantir a resiliência das redes de telecomunicações é uma preocupação permanente dos operadores de telecomunicações. Numa rede Generalized Multiprotocol Label Switching (GMPLS) pode ser distribuída informação acerca de conjuntos de arcos que partilham riscos de falha, designados por Shared Risk Link Group (SRLG). Esta informação permite aos Path Computation Elements (PCE) determinar rotas protegidas, ou seja calcular um par de caminhos disjuntos nos SRLG. Um PCE deve responder de forma rápida às solicitações sem necessitar de demasiados recursos. Desta restrição advém a importância de desenvolver algoritmos eficientes para a determinação de caminhos disjuntos nos SRLG. É descrita uma nova versão da heurística CoSE-MS que procura determinar um par de caminhos disjuntos nos SRLG de custo aditivo mínimo. Resultados experimentais num sistema embebido comprovaram que a nova versão é computacionalmente mais eficiente que a anterior, sem comprometer a sua precisão.
- Quantitative support for UX methods identification: how can multiple criteria decision making help?Publication . Melo, Paulo; Jorge, LuísaThis paper presents views on how quantitative multiple criteria decision-making (MCDM) approaches may be applied to certain aspects of user experience design and evaluation (D&E) methods identification, emphasizing its strengths and weaknesses for this task. Often D&E methods need to be applied in contexts different of those they had been applied before and as such must be transferred to those new contexts. This work presents a model for the quantitative method matching step of the transfer process, describes how different MCDM methods can be applied to this task, and discusses the results of an experience that tried to apply a couple of MCDM procedures to method selection.