Conhecimento da mobilidade do consumidor em redes centradas em informação

Mobile data traffic is expanding significantly since the surge and evolution of wireless communication technologies, leading to the design and implementation of different types of mobile networks. Information Centric Network paradigms have been pointed as an alternative to bypass the restrictions imposed by the traditional IP Networks, such as the one imposed by the mobility of its users. Despite their potential advantages regarding mobile wireless environments, several significant research challenges remain to be addressed, more specifically the communication damage due to handover, causing loss of packets. The scope of this dissertation is the development of NDN-based mechanisms with support for Consumer mobility in two different communication approaches: single content request and publish-subscribe. The proposed schemes address a remote mobility predictor entity, whose purpose is to monitor and anticipate trajectories, while compelling the infrastructure to adjust to the new paths, resulting in an efficient way to manage the consumers’ mobility with the purpose of attaining a better quality of service to users. The implementation and evaluation of the proposed schemes were performed using ndnSIM, through functional and non-functional scenarios. The latter uses real traces of urban mobility and connectivity. The obtained results show that the proposed solution far surpasses the native NDN workflow and the traditional publish-subscribe solutions with respect to content delivery ratio and network overhead.O tráfego de dados móveis tem vindo a crescer significativamente, sobretudo devido à evolução das tecnologias de comunicação sem fios, o que tem vindo a implicar o desenho e implementação de novos e diferentes tipos de redes móveis. Os paradigmas de redes centradas em informação têm sido apontados como uma alternativa para contornar as restrições impostas pelas redes tradicionais IP, nomeadamente a mobilidade dos seus utilizadores. Apesar das potenciais vantagens em relação aos ambientes móveis sem fios, vários desafios de investigação ainda necessitam de ser resolvidos, mais especificamente aqueles relacionados com o processo de handover dos seus utilizadores móveis, levando por vezes à perda de informação. Esta dissertação tem como objetivo o desenvolvimento de mecanismos de suporte à mobilidade do Consumidor para redes ICN, utilizando duas abordagens distintas de comunicação: solicitação única de conteúdo e o modelo publish − subscribe. Os esquemas propostos exploram uma entidade remota de previsão de mobilidade, cujo objetivo é monitorizar e antecipar eventuais trajetórias de posição dos utilizadores móveis, obrigando a infraestrutura a ajustar-se aos novos caminhos do consumidor, resultando numa forma eficiente de gestão de mobilidade dos utilizadores com o objetivo de garantir uma melhor qualidade de serviço. A implementação e avaliação dos esquemas propostos foi realizada utilizando o ndnSIM, em cenários funcionais e não funcionais. Estes últimos utilizam registos reais de mobilidade e conetividade urbana. Os resultados obtidos mostram que a solução proposta ultrapassa significativamenta a versão nativa do NDN e as soluções tradicionais de publish − subscribe, considerando a taxa de entrega de conteúdos e sobrecarga da rede.Mestrado em Engenharia de Computadores e Telemátic

Investigations and Analysis of Dynamical and Steady State Properties of Chemical Reaction Systems

In this paper, we investigate results from chemical reaction network theory and a list of techniques to test for the reaction-coordinates dynamical system to have a partial order induced by a positive orthant cone. A successful result from one of these tests guarantees mono-stationarity (and indeed convergence). We also investigate a recently published algorithmic and computational approach to determine whether a reaction network establishes mono- or multi-stationarity. We test new reactions that have not been previously introduced in the literature for mono- or multi-stationarity using this approach. This includes the two-site phosphorylation reaction network and a modified double phosphorylation reaction network that more accurately models the action of the enzymes of two distinct sites. We also use the enzymatic futile cycle as a running example to illustrate these results. We conclude the two-site phosphorylation reaction network is multi-stationary; while the original double phosphorylation reaction network is also multi-stationary, our modified version is mono-stationary

Factors influencing price volatility on soybeans futures prices

Recent unexpected changes (mid-2007- Aug 2011) in agricultural commodity markets have led stakeholders to ask if the volatility of futures prices currently observed are still the result of traditional fundamentals. Consequently, the purpose of this research was to identify those factors that affect monthly soybeans futures price volatility. To accomplish this study, four relevant factors are explored. First, the integration between energy and agricultural markets is accounted for via oil spot prices, as well as a dummy variable to account for the shift in the U.S renewable fuel policy since 2007. Second, the increasing consumption of commodities from China is analyzed by measuring their imports of soybeans from Argentina, Brazil, and the U.S. Third, U.S monetary policy is examined by including a U.S dollar index compared to currencies from China (Yuan), Brazil (Real), and Argentina (Peso), which are the main producers, consumers and traders of soybeans. Finally, financial speculation is analyzed by the number of speculative funds (mutual and index funds) available for public investors. Evidence was found that the variability of oil spot prices, soybean imports to China, and the number of index funds are able to explain monthly soybeans future price volatility, from September 2006 to August 2011. Although U.S renewable fuel policy is included in the analysis, there is no statistical evidence of its influence on monthly soybeans futures prices. Similarly, there is no evidence that the U.S dollar index and the number of mutual funds are able to explain past values of soybeans futures price volatility. Excessive volatility in futures price may cause problems for those utilizing futures markets in their business operation, as well as for consumers. While the increasing risk has led to inefficient resource allocation for producers, merchandisers, and speculators, high prices have influenced the food security of developing countries with lower incomes, i.e. affecting the ability of lower income households to get access to soy products used for human consumption

Development of a drone-based miniaturized payload for LoRa communications experiment proof-of-concept

The remote sensing and interference detector with RadIometry and vegeTation Analysis (RITA), is a payload of 1U that will fly onboard Alainsat-1 a 3U CubeSat. Among other tests and experiments, it will perform a proof of concept of a LoRa custom module for space-to-Earth communications between the satellite and a terrestrial network of Internet of Things sensors. The LoRa communications experiment proof-of-concept has been performed using several ground IoT nodes and a miniaturized drone-based payload. The communications have been performed using two MAC protocols which are compatible with an IoT scenario: pure ALOHA and CSMA/CA with RTS/CTS. In both protocols, the useful information to be sent is the data contained in the Data Packet. In this packet, the data obtained by the capacitive soil moisture sensor and the temperature sensor are stored. In order to perform LoRa communications experiment proof-of-concept, two measurement campaigns have been realized. In the first measurement campaign, the correct functioning of the LoRa modules and sensors has been tested. In the second measurement campaign, several experiments have been performed in which pure ALOHA and CSMA/CA protocols have been tested. In order to test different experiments with different configurations of the protocols, a general code structure has been designed where both the ground nodes and the drone payload are controlled by a command sent by the user. Therefore, the choice of the protocol to be used as well as the configurable parameters of each protocol are sent through a remote command. Finally, the results obtained in both protocols are analyzed and it is concluded which of the two has better performance against an IoT communications scenario

Cognitive radio for TVWS usage

Spectrum scarcity is an emerging issue in wireless communication systems due to the increasing demand of broadband services like mobile communications, wireless internet access, IoT applications, among others. The migration of analog TV to digital systems (a.k.a. digital TV switchover) has led to the release of a significant spectrum share that can be used to support said additional services. Likewise, TV white spaces emerge as spectral opportunities that can also be explored. Hence, cognitive radio (CR) presents itself as a feasible approach to efficiently use resources and exploit gaps within the spectrum. The goal of this paper is to unveil the state of the art revolving around the usage of TV white spaces, including some of the most important methods developed to exploit such spaces, upcoming opportunities, challenges for future research projects, and suggestions to improve current models