Algoritmos de alocação dinâmica de recursos rádio para sistemas 4G baseados em MC-CDMA

Este trabalho considera o processo de scheduling de pacotes para sistemas rádio móvel da 4ª geração baseados em MC-CDMA. É proposto um algoritmo que se baseia na prioritização de pacotes usando uma métrica que combina requisitos de serviço com a qualidade da ligação, i.e., usa informação proveniente da camada física e camadas superiores para decidir quais os pacotes que devem ser transmitidos. O algoritmo proposto é comparado em termos de desempenho com o algoritmo que maximiza o throughput da célula, e que se baseia exclusivamente na qualidade da ligação física. Para permitir um enquadramento adequado do contexto onde se insere o problema tratado, inclui-se neste trabalho uma análise da evolução das comunicações móveis e dos requisitos e expectativas previsíveis para a componente de banda larga de 4ª geração, bem como uma descrição dos principais estudos e parâmetros definidos pelo projecto europeu MATRICE, onde este trabalho se insere. Tendo em conta que a análise de esquemas de alocação dinâmica de recursos rádio é feita normalmente com recurso a simulações, apresenta-se igualmente o modelo de simulação utilizado neste trabalho. O modelo de simulação a nível de sistema inclui interfaces simplificadas à camada física e rede IP, com o objectivo de não sobrecarregar as simulações, tratando-se os cálculos ao essencial das da parte de sistema. Relativamente às interfaces com a camada física, duas interfaces foram implementadas, interface de valor médio para simulação de aplicações tempo-real em que tempo de sessão é normalmente superior ao tempo de coerência do canal e interface de valor actual para aplicações do tipo comutação de pacotes em que o tempo de sessão é pequeno comparado com tempo de coerência do canal. A avaliação do desempenho dos algoritmos de scheduling propostos é feita utilizando um sistema gestão de recursos semelhante ao proposto pela 3GPP para o HSDPA que inclui modulação e codificação adaptativa, ARQ Híbrido com o Chase combining. Os resultados obtidos mostram que o algoritmo proposto em comparação com o que maximiza o throughput revela-se num mecanismo mais adequado para scheduling de pacotes quando os requisitos de serviços devem ser levados em conta e que o aumento da satisfação de utilizadores, medido pelo número de utilizadores satisfeitos, é feito com base na diminuição do throughput da célula. Os resultados mostram ainda que a escolha de diferentes parâmetros permitem a afinação do algoritmo a diferentes comportamentos, optimizando o desempenho dependente do tipo de serviço e quantidade tráfego esperados no sistema. ABSTRACT: This work deals with packet scheduling algorithms for the broadband component of 4G systems. A scheduling algorithm that combines QoS requirements with information from the physical layer is proposed and its performance assessed against the scheduling algorithm used in HSDPA that aims to maximize the throughput. To provide the appropriate framework for the issues tackled in this dissertation, a description of the evolution of mobile communications along with the main requirements and alternatives envisioned for 4G systems is provided, where the main technological are taken from the European IST project MATRICE where the current work fits. Since system level studies are performed resorting to simulations, a thorough description of the requirements and options used in the system level modelling is provided. The system level simulation model includes simplified interfaces models to the physical layer and to the IP layer, to avoid complex and heavy simulations. Physical layer interface included average value interface to be used in simulations of real-time applications, where session duration is longer than coherence time of the fading radio channel. Actual value interface is used for packet based applications where the session duration is short when compared to the coherence time of the fading radio channel. The evaluation of the proposed scheduling algorithm is performed using a resource management system based on the 3GPP HSDPA which includes adaptive modulation and coding, Hybrid ARQ with Chase combining. The results shown that when compared against the maximum throughput algorithm, the proposed algorithm is the most suitable for packet scheduling when both quality of service requirements and user satisfaction must be considered. Furthermore since the performance results represent a trade-off between the number of satisfied user and the cell throughput, it is possible through the appropriate parameterization to adjust the proposed algorithm to different behaviours according to the type and load of the traffic in the system

Energy-efficient cooperative resource allocation for OFDMA

Energy is increasingly becoming an exclusive commodity in next generation wireless communication systems, where even in legacy systems, the mobile operators operational expenditure is largely attributed to the energy bill. However, as the amount of mobile traffic is expected to double over the next decade as we enter the Next Generation communications era, the need to address energy efficient protocols will be a priority. Therefore, we will need to revisit the design of the mobile network in order to adopt a proactive stance towards reducing the energy consumption of the network. Future emerging communication paradigms will evolve towards Next Generation mobile networks, that will not only consider a new air interface for high broadband connectivity, but will also integrate legacy communications (LTE/LTE-A, IEEE 802.11x, among others) networks to provide a ubiquitous communication platform, and one that can host a multitude of rich services and applications. In this context, one can say that the radio access network will predominantly be OFDMA based, providing the impetus for further research studies on how this technology can be further optimized towards energy efficiency. In fact, advanced approaches towards both energy and spectral efficient design will still dominate the research agenda. Taking a step towards this direction, LTE/LTE-A (Long Term Evolution-Advanced) have already investigated cooperative paradigms such as SON (self-Organizing Networks), Network Sharing, and CoMP (Coordinated Multipoint) transmission. Although these technologies have provided promising results, some are still in their infancy and lack an interdisciplinary design approach limiting their potential gain. In this thesis, we aim to advance these future emerging paradigms from a resource allocation perspective on two accounts. In the first scenario, we address the challenge of load balancing (LB) in OFDMA networks, that is employed to redistribute the traffic load in the network to effectively use spectral resources throughout the day. We aim to reengineer the load-balancing (LB) approach through interdisciplinary design to develop an integrated energy efficient solution based on SON and network sharing, what we refer to as SO-LB (Self-Organizing Load balancing). Obtained simulation results show that by employing SO-LB algorithm in a shared network, it is possible to achieve up to 15-20% savings in energy consumption when compared to LTE-A non-shared networks. The second approach considers CoMP transmission, that is currently used to enhance cell coverage and capacity at cell edge. Legacy approaches mainly consider fundamental scheduling policies towards assigning users for CoMP transmission. We build on these scheduling approaches towards a cross-layer design that provide enhanced resource utilization, fairness, and energy saving whilst maintaining low complexity, in particular for broadband applications

Veterinary Antibiotics in the Environment

In recent years, pharmaceutical pollution in the environment has been a great concern due to the potential effects on the human and animal health. Some of the most used classes such as antibiotics, which are used to prevent and treat bacterial infections and promote the growth of livestock, deserve to be highlighted since their intensive use has contaminated environmental matrices such as soil, water, sediment, plants, and animals with effects on the biota. To better understand the potential ecological risk of antibiotics in environments and to develop management strategies for these substances searching to reach the reduction of these compounds in aquatic systems, one of the most important steps is to determine the environmental concentrations of these compounds in the environments through analytical methods and evaluate their effects on the biota. The goal of this chapter is contribute with information about the effects of these compounds on the biota as well as its environmental behavior and bacterial resistance in additional to the main techniques for samples preparation and quantitative and confirmatory methods for its determination in the environment

Analysis of a Homomorphic MAC-based scheme against tag pollution in RLNC-enabled wireless networks

Network Coding-enabled wireless networks are vulnerable to data pollution attacks where adversary nodes inject into the network polluted (i.e. corrupted) packets that prevent the destination nodes from decoding correctly. Even a small proportion of pollution can quickly propagate into other packets via re-coding, occurred at the intermediate nodes, and lead to resource waste. Therefore, during the past few years, several solutions have been proposed to provide resistance against data pollution attacks. One of the most well-known solutions is Homomorphic Message Authentication Code (HMAC). However, HMAC is susceptible to a new type of pollution attacks, called tag pollution attacks, in which a malicious node randomly modifies MAC tags appended at the end of the transmitted packets. To address this issue, we have recently proposed an HMAC-based scheme making use of two types of MAC tags to provide resistance against both data pollution attacks and tag pollution attacks. In this paper, we steer our focus on improving the resistance of our proposed scheme against tag pollution attacks by decreasing the number of MACs. Finally, we analyze the impact of the total number of MACs on the bandwidth overhead of the proposed scheme

A CENTRALIDADE DA EDUCAÇÃO NO COMBATE À POBREZA: a visão de profissionais que atuam com populações empobrecidas

O artigo apresenta uma análise das concepções de educação e de pobreza de profissionais da educação e de outros envolvidos com populações empobrecidas, matriculados nos Cursos de Especialização e Aperfeiçoamento em Educação, Pobreza e Desigualdade Social, desenvolvidos, respectivamente, pela Universidade Federal de Santa Catarina e pela Universidade de Brasília, objetivando discutir a centralidade atribuída à educação no enfrentamento da pobreza. É parte de uma pesquisa mais ampla pautada numa perspectiva quantitativa e qualitativa quanto à abordagem, básica quanto à natureza, exploratória e descritiva quanto aos objetivos e bibliográfica e documental quanto aos procedimentos. Conclui que pode estar ocorrendo uma relativização do papel da educação no combate à pobreza.Palavras-chave: Educação. Pobreza. Profissionais nas políticas sociais.THE CENTRALITY OF EDUCATION IN THE FIGHT AGAINST POVERTY: the view of professionals working with impoverished populationsAbstractThis article presents an analysis of the conceptions of education and poverty by professionals in education and others involved with impoverished populations enrolled in the Cursos de Especialização e Aperfeiçoamento em Educação, Pobreza e Desigualdade Social (Specialization Courses in Education, Poverty and Social Inequality), offered by the Federal University of Santa Catarina and by the University of Brasília, which aimed to discuss the centrality attributed to education in the fight against poverty. It is part of a broader research based on a quantitative and qualitative perspective regarding the approach, basic regarding the nature, exploratory and descriptive regarding the objectives, and bibliographic and documentary regarding the procedures. It concludes that there may be a diminishing role of education in the fight againstpoverty.Keywords: Education. Poverty. Professionals in social policies

Screening of worldwide cowpea collection to drought tolerant at a germination stage

Supplementary material related to this article can be found, in the online version, at doi: https://doi.org/10.1016/j.scienta.2018.11.082.Global warming has an increasing impact on the availability of water for agriculture. Crops tolerant to high temperatures and drought, such as cowpea (Vigna unguiculata L. Walp.), have an added value in the near future. The main objective of this study was to evaluate the effect of drought on seed germination and seedling emergence of cowpea genotypes, in order to screen the most tolerant genotypes. Seeds from 58 cowpea genotypes all over the world were submitted to two stress conditions, induced by PEG-6000 (corresponding to osmotic potentials of -0.75 bars and -1.5 bars). Germination and seedling growth parameters, vigor index and proline content were determined to assess drought tolerance. The results revealed significant differences of all parameters among genotypes after treatments and interaction of both. Water stress caused a general decrease in germination and seedling growth, while an increase in proline content was observed. A high variation of drought responses were detected among genotypes, being possible to select seven genotypes (C11, C18, C44, C46, C47, C50 and C54) as tolerant to drought at germination stage. These results will be useful to select the best suitable parents for insertion in future breeding programs.This study was supported by EUROLEGUME project. This project has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 613781. European Investment Funds by FEDER/COMPETE/POCI - Operational Competitiveness and Internationalization Programme, under Project POCI-01-0145-FEDER-006958 and National Funds by FCT - Portuguese Foundation for Science and Technology, under the projects UID/AGR/04033/2013 and UID/AGR/04046/2013

Experiência de uma abordagem prática no ensino de Botânica

Fazer com que o aluno saia da sala de aula e explore outros objetos de estudo é um desafio para qualquer docente, e esta prática permite que os alunos possam reconhecer e diferenciar conhecimentos teóricos de práticos; pensando nisto, o presente estudo abordará uma experiência prática desenvolvida no Horto Florestal localizado em Rio Branco, no Acre. Através desta, os alunos do curso de Ciências Biológicas do IFAC participantes desta prática puderam visualizar e distinguir os diversos grupos de plantas e organismos estudados dentro do ensino de Botânica. Para a realização deste trabalho, adotou-se uma metodologia de pesquisa de campo e em seguida uma análise qualitativa, utilizando-se de questionários semiestruturados, com a finalidade de compreender como a saída do ambiente de aula formal é relevante para o aprendizado dos alunos, ou, pelo contrário, se simplesmente a aula prática não altera a maneira do aprendizado do discente em relação ao ensino de Botânica. Os questionários utilizados nesta pesquisa continham três eixos de interesse distintos, como: Eixo 1. O conhecimento prévio dos alunos em relação ao ensino de Botânica; Eixo 2. A existência de dificuldades no processo de aprendizagem de Botânica; Eixo 3. A preferência da sala de aula ou de outro ambiente de aprendizagem. Após a escolha aleatória e posteriormente análise do questionário de 5 alunos em um espaço amostral de 22, o presente estudo obteve como resultado a inferência de que, para que o processo de ensino e aprendizagem do aluno seja efetivado, o docente deve sempre ter em seus planos de aula atividades que sejam práticas, tendo em vista que a prática faz com que o aluno possa entender o conteúdo abordado, e, por conseguinte, venha a ser o autor da sua busca pelo conhecimento. Outrossim, vários trabalhos científicos abordam acerca da necessidade de levar o aluno para ambientes não formais, o que corrobora a tentativa deste estudo de apresentar o quanto a prática é importante para o aluno