Probe-based end-to-end overload control for networks of SIP servers

The Session Initiation Protocol (SIP) has been adopted by the IETF as the control protocol for creating, modifying and terminating multimedia sessions. Overload occurs in SIP networks when SIP servers have insufficient resources to handle received messages. Under overload, SIP networks may suffer from congestion collapse due to current ineffective SIP overload control mechanisms. This paper introduces a probe-based end-to-end overload control (PEOC) mechanism, which is deployed at the edge servers of SIP networks and is easy to implement. By probing the SIP network with SIP messages, PEOC estimates the network load and controls the traffic admitted to the network according to the estimated load. Theoretic analysis and extensive simulations verify that PEOC can keep high throughput for SIP networks even when the offered load exceeds the capacity of the network. Besides, it can respond quickly to the sudden variations of the offered load and achieve good fairness.

The relationship between young people's transit use and their perceptions of equity concepts in transit service provision

This study investigates the effect of price and travel mode fairness and spatial equity in transit provision on the perceived transit service quality, willingness to pay, and habitual frequency of use. Based on the theory of planned behavior, we developed a web-based questionnaire for revealed preferences data collection. The survey was administered among young people in Copenhagen and Lisbon to explore the transit perceptions and use under different economic and transit provision conditions. The survey yielded 499 questionnaires, analyzed by means of structural equation models. Results show that higher perceived fairness relates positively to higher perceived quality of transit service and higher perceived ease of paying for transit use. Higher perceived spatial equity in service provision is associated with higher perceived service quality. Higher perceived service quality relates to higher perceived ease of payment, which links to higher frequency of transit use.

Transit Use by Young People in Times of Financial Austerity: A Cause of Equity Concern?

This study investigates the effect of price and travel time fairness and spatial equity in transit provision on the perceived transit service quality, willingness to pay, and habitual frequency of use. Based on the theory of planned behavior, we developed a web-based questionnaire for revealed preferences data collection. The survey was administered among young people in Copenhagen and Lisbon to explore the transit perceptions and use under different economic and transit provision conditions. The survey yielded 499 questionnaires, analyzed by means of structural equation models. Results show that higher perceived fairness relates positively to higher perceived quality of transit service and higher perceived ease of paying for transit use. Higher perceived spatial equity in service provision is associated with higher perceived service quality. Higher perceived service quality relates to higher perceived ease of payment, which links to higher frequency of transit use.

A control theoretic approach to solve a constrained uplink power dynamic game

This paper addresses an uplink power control dynamic game where we assume that each user battery represents the system state that changes with time following a discrete-time version of a differential game. To overcome the complexity of the analysis of a dynamic game approach we focus on the concept of Dynamic Potential Games showing that the game can be solved as an equivalent Multivariate Optimum Control Problem. The solution of this problem is quite interesting because different users split the activity in time, avoiding higher interferences and providing a long term fairness.

Contribution to the improvement of communication services in nanosatellite constellations using delay and disruption tolerant networking based architectures

Esta tesis se desarrolla dentro del marco de las comunicaciones satelitales en el innovador campo de los pequeños satélites también llamados nanosatélites o cubesats, llamados así por su forma cubica. Estos nanosatélites se caracterizan por su bajo costo debido a que usan componentes comerciales llamados COTS (commercial off-the-shelf) y su pequeño tamaño como los Cubesats 1U (10cm*10 cm*10 cm) con masa aproximada a 1 kg. Este trabajo de tesis tiene como base una iniciativa propuesta por el autor de la tesis para poner en órbita el primer satélite peruano en mi país llamado chasqui I, actualmente puesto en órbita desde la Estación Espacial Internacional. La experiencia de este trabajo de investigación me llevo a proponer una constelación de pequeños satélites llamada Waposat para dar servicio de monitoreo de sensores de calidad de agua a nivel global, escenario que es usado en esta tesis. Es ente entorno y dadas las características limitadas de los pequeños satélites, tanto en potencia como en velocidad de datos, es que propongo investigar una nueva arquitectura de comunicaciones que permita resolver en forma óptima la problemática planteada por los nanosatélites en órbita LEO debido a su carácter disruptivo en sus comunicaciones poniendo énfasis en las capas de enlace y aplicación. Esta tesis presenta y evalúa una nueva arquitectura de comunicaciones para proveer servicio a una red de sensores terrestres usando una solución basada en DTN (Delay/Disruption Tolerant Networking) para comunicaciones espaciales. Adicionalmente, propongo un nuevo protocolo de acceso múltiple que usa una extensión del protocolo ALOHA no ranurado, el cual toma en cuenta la prioridad del trafico del Gateway (ALOHAGP) con un mecanismo de contienda adaptativo. Utiliza la realimentación del satélite para implementar el control de la congestión y adapta dinámicamente el rendimiento efectivo del canal de una manera óptima. Asumimos un modelo de población de sensores finito y una condición de tráfico saturado en el que cada sensor tiene siempre tramas que transmitir. El desempeño de la red se evaluó en términos de rendimiento efectivo, retardo y la equidad del sistema. Además, se ha definido una capa de convergencia DTN (ALOHAGP-CL) como un subconjunto del estándar TCP-CL (Transmission Control Protocol-Convergency Layer). Esta tesis muestra que ALOHAGP/CL soporta adecuadamente el escenario DTN propuesto, sobre todo cuando se utiliza la fragmentación reactiva. Finalmente, esta tesis investiga una transferencia óptima de mensajes DTN (Bundles) utilizando estrategias de fragmentación proactivas para dar servicio a una red de sensores terrestres utilizando un enlace de comunicaciones satelitales que utiliza el mecanismo de acceso múltiple con prioridad en el tráfico de enlace descendente (ALOHAGP). El rendimiento efectivo ha sido optimizado mediante la adaptación de los parámetros del protocolo como una función del número actual de los sensores activos recibidos desde el satélite. También, actualmente no existe un método para advertir o negociar el tamaño máximo de un “bundle” que puede ser aceptado por un agente DTN “bundle” en las comunicaciones por satélite tanto para el almacenamiento y la entrega, por lo que los “bundles” que son demasiado grandes son eliminados o demasiado pequeños son ineficientes. He caracterizado este tipo de escenario obteniendo una distribución de probabilidad de la llegada de tramas al nanosatélite así como una distribución de probabilidad del tiempo de visibilidad del nanosatélite, los cuales proveen una fragmentación proactiva óptima de los DTN “bundles”. He encontrado que el rendimiento efectivo (goodput) de la fragmentación proactiva alcanza un valor ligeramente inferior al de la fragmentación reactiva. Esta contribución permite utilizar la fragmentación activa de forma óptima con todas sus ventajas tales como permitir implantar el modelo de seguridad de DTN y la simplicidad al implementarlo en equipos con muchas limitaciones de CPU y memoria. La implementación de estas contribuciones se han contemplado inicialmente como parte de la carga útil del nanosatélite QBito, que forma parte de la constelación de 50 nanosatélites que se está llevando a cabo dentro del proyecto QB50. ABSTRACT This thesis is developed within the framework of satellite communications in the innovative field of small satellites also known as nanosatellites (<10 kg) or CubeSats, so called from their cubic form. These nanosatellites are characterized by their low cost because they use commercial components called COTS (commercial off-the-shelf), and their small size and mass, such as 1U Cubesats (10cm * 10cm * 10cm) with approximately 1 kg mass. This thesis is based on a proposal made by the author of the thesis to put into orbit the first Peruvian satellite in his country called Chasqui I, which was successfully launched into orbit from the International Space Station in 2014. The experience of this research work led me to propose a constellation of small satellites named Waposat to provide water quality monitoring sensors worldwide, scenario that is used in this thesis. In this scenario and given the limited features of nanosatellites, both power and data rate, I propose to investigate a new communications architecture that allows solving in an optimal manner the problems of nanosatellites in orbit LEO due to the disruptive nature of their communications by putting emphasis on the link and application layers. This thesis presents and evaluates a new communications architecture to provide services to terrestrial sensor networks using a space Delay/Disruption Tolerant Networking (DTN) based solution. In addition, I propose a new multiple access mechanism protocol based on extended unslotted ALOHA that takes into account the priority of gateway traffic, which we call ALOHA multiple access with gateway priority (ALOHAGP) with an adaptive contention mechanism. It uses satellite feedback to implement the congestion control, and to dynamically adapt the channel effective throughput in an optimal way. We assume a finite sensor population model and a saturated traffic condition where every sensor always has frames to transmit. The performance was evaluated in terms of effective throughput, delay and system fairness. In addition, a DTN convergence layer (ALOHAGP-CL) has been defined as a subset of the standard TCP-CL (Transmission Control Protocol-Convergence Layer). This thesis reveals that ALOHAGP/CL adequately supports the proposed DTN scenario, mainly when reactive fragmentation is used. Finally, this thesis investigates an optimal DTN message (bundles) transfer using proactive fragmentation strategies to give service to a ground sensor network using a nanosatellite communications link which uses a multi-access mechanism with priority in downlink traffic (ALOHAGP). The effective throughput has been optimized by adapting the protocol parameters as a function of the current number of active sensors received from satellite. Also, there is currently no method for advertising or negotiating the maximum size of a bundle which can be accepted by a bundle agent in satellite communications for storage and delivery, so that bundles which are too large can be dropped or which are too small are inefficient. We have characterized this kind of scenario obtaining a probability distribution for frame arrivals to nanosatellite and visibility time distribution that provide an optimal proactive fragmentation of DTN bundles. We have found that the proactive effective throughput (goodput) reaches a value slightly lower than reactive fragmentation approach. This contribution allows to use the proactive fragmentation optimally with all its advantages such as the incorporation of the security model of DTN and simplicity in protocol implementation for computers with many CPU and memory limitations. The implementation of these contributions was initially contemplated as part of the payload of the nanosatellite QBito, which is part of the constellation of 50 nanosatellites envisaged under the QB50 project.

DISCURSOS E PRÁTICAS COMUNICACIONAIS: SAÚDE NA WEB

Esta dissertação aborda aspectos das práticas comunicacionais no contexto da comunicação de saúde. Como foco, os discursos instaurados nos Portais Nacionais das Sociedades Científicas Cardiol e Diabetes . O recorte temporal centrou-se no período de 1º de setembro a 1º de dezembro de 2008. A metodologia empregada é a qualitativa e deve-se, preferencialmente, ater ao texto, ao conteúdo latente (insinuado) e à linguagem manifesta. Verifica-se, também, a apresentação do layout e alguns tópicos de avaliação da usabilidade das páginas. O estudo é fundamentado na perspectiva da Análise de Discurso francesa (AD). Outras abordagens teóricas interdisciplinares também compõem as reflexões. Observa-se que a proposta de inserção de um discurso de prevenção de doenças e promoção de saúde, em seu sentido mais amplo, e nas atuais discussões, parece promissora para a descrição dessas representações nos diversos estágios de desenvolvimento humano e sociocultural. Há indícios de que a promoção da saúde amplia seu escopo e passa a relacionar vida, saúde, solidariedade, equidade, democracia, cidadania, desenvolvimento, participação e intenção de parceria com todos os indivíduos e segmentos. Os exemplares analisados indicam que nos enunciados, compreendidos como unidades reais da comunicação discursiva, os editores falam pelo especialista caracterizando, assim, também, como gênero científico.(AU)

DISCURSOS E PRÁTICAS COMUNICACIONAIS: SAÚDE NA WEB

Esta dissertação aborda aspectos das práticas comunicacionais no contexto da comunicação de saúde. Como foco, os discursos instaurados nos Portais Nacionais das Sociedades Científicas Cardiol e Diabetes . O recorte temporal centrou-se no período de 1º de setembro a 1º de dezembro de 2008. A metodologia empregada é a qualitativa e deve-se, preferencialmente, ater ao texto, ao conteúdo latente (insinuado) e à linguagem manifesta. Verifica-se, também, a apresentação do layout e alguns tópicos de avaliação da usabilidade das páginas. O estudo é fundamentado na perspectiva da Análise de Discurso francesa (AD). Outras abordagens teóricas interdisciplinares também compõem as reflexões. Observa-se que a proposta de inserção de um discurso de prevenção de doenças e promoção de saúde, em seu sentido mais amplo, e nas atuais discussões, parece promissora para a descrição dessas representações nos diversos estágios de desenvolvimento humano e sociocultural. Há indícios de que a promoção da saúde amplia seu escopo e passa a relacionar vida, saúde, solidariedade, equidade, democracia, cidadania, desenvolvimento, participação e intenção de parceria com todos os indivíduos e segmentos. Os exemplares analisados indicam que nos enunciados, compreendidos como unidades reais da comunicação discursiva, os editores falam pelo especialista caracterizando, assim, também, como gênero científico.(AU)

Estudo de associação entre déficits de reconhecimento de emoções em faces, flexibilidade mental e adequação social, em pacientes com transtorno bipolar do tipo I eutímicos, comparados com controles normais

Introdução: O objetivo do estudo foi investigar se há associação entre déficits na capacidade de reconhecimento de emoções faciais e déficits na flexibilidade mental e na adequação social em pacientes com Transtorno Bipolar do tipo I eutímicos quando comparados a sujeitos controles sem transtorno mental. Métodos: 65 pacientes com Transtorno Bipolar do tipo I eutímicos e 95 controles sem transtorno mental, foram avaliados no reconhecimento de emoções faciais, na flexibilidade mental e na adequação social através de avaliações clínicas e neuropsicológicas. Os sintomas afetivos foram avaliados através da Escala de Depressão de Hamilton e da Escala de Mania de Young, o reconhecimento de emoções faciais através da Facial Expressions of Emotion: Stimuli and Tests, a flexibilidade mental avaliada através do Wisconsin Card Sorting Test e a adequação social através da Escala de Auto- Avaliação de Adequação Social. Resultados: Pacientes com Transtorno Bipolar do tipo I eutímicos apresentam uma associação de maior intensidade comparativamente aos controles entre o reconhecimento de emoções faciais e a flexibilidade mental, indicando que quanto mais preservada a flexibilidade mental, melhor será a habilidade para reconhecer emoções faciais Neste grupo às correlações de todas as emoções são positivas com o total de acertos e as categorias e são negativas com as respostas perseverativas, total de erros, erros perseverativos e erros não perseverativos. Não houve uma correlação entre o reconhecimento de emoções faciais e a adequação social, apesar dos pacientes com Transtorno Bipolar do tipo I eutímicos apresentar uma pior adequação social, sinalizando que a pior adequação social não parece ser devida a uma dificuldade em reconhecer e interpretar adequadamente as expressões faciais. Os pacientes com Transtorno Bipolar do tipo I eutímicos não apresentam diferenças significativas no reconhecimento de emoções faciais em relação aos controles, entretanto no subteste surpresa (p=0,080) as diferenças estão no limite da significância estatística, indicando que portadores de transtorno bipolar do tipo I eutímicos tendem a apresentar um pior desempenho no reconhecimento da emoção surpresa em relação aos controles. Conclusão: Nossos resultados reforçam a hipótese de que existe uma associação entre o reconhecimento de emoções faciais e a preservação do funcionamento executivo, mais precisamente a flexibilidade mental, indicando que quanto maior a flexibilidade mental, melhor será a habilidade para reconhecer emoções faciais e melhorar o desempenho funcional do paciente. Pacientes bipolares do tipo I eutímicos apresentam uma pior adequação social quando comparados aos controles, o que pode ser uma consequência do Transtorno Bipolar que ratifica a necessidade de uma intervenção terapêutica rápida e eficaz nestes pacientes

Priority realloc: um mecanismo para alocação de rotas e recursos em redes EON.

Backbone networks are responsible for long-haul data transport serving many clients with a large volume of data. Since long-haul data transport service must rely on a robust high capacity network the current technology broadly adopted by the industry is Wavelength Division Multiplexing (WDM). WDM networks enable one single ber to operate with multiple high capacity channels, drastically increasing the ber capacity. In WDM networks each channel is associated with an individual wavelength. Therefore a whole wavelength capacity is assigned to a connection, causing waste of bandwidth in case the connection bandwidth requirement is less than the channel total capacity. In the last half decade, Elastic Optical Networks (EON) have been proposed and developed based on the fexible use of the optical spectrum known as the exigrid. EONs are adaptable to clients requirements and may enhance optical networks performance. For these reasons, research community and data transport providers have been demonstrating increasingly high interest in EONs which are likely to replace WDM as the universally adopted technology in backbone networks in the near future. EONs have two characteristics that may limit its ecient resources use. The spectrum fragmentation, inherent to the dynamic EON operation, decrease the network capacity to assign resources to connection requests increasing network blocking probability. The spectrum fragmentation also intensifides the denial of service to higher rate request inducing service unfairness. Due to the fact EONs were just recently developed and proposed, the aforementioned issues were not yet extensively studied and solutions are still being proposed. Furthermore, EONs do not yet provide specific features as differentiated service mechanisms. Differentiated service strategies are important in backbone networks to guarantee client\'s diverse requirements in case of a network failure or the natural congestion and resources contention that may occur at some periods of time in a network. Impelled by the foregoing facts, this thesis objective is three-fold. By means of developing and proposing a mechanism for routing and resources assignment in EONs, we intend to provide differentiated service while decreasing fragmentation level and increasing service fairness. The mechanism proposed and explained in this thesis was tested in a EON simulation environment and performance results indicated that it promotes beneficial performance enhancements when compared to benchmark algorithms.

O "due process" redescoberto à sombra do verde

Tese de doutoramento, Direito (Ciências Jurídico-Políticas), Universidade de Lisboa, Faculdade de Direito, 2016

Social cohesion in Europe after the crisis

In the last few years, Europe has been forced to re-think its socio-economic model. Social indicators speak for themselves. Real household income declined significantly between 2008 and 2012, employment rates are lower and the number of people in poverty saw a steady rise with a growing divergence between EU countries. In the eurozone, cuts in public spending and internal devaluation have been the main tools to aim at a correction of unsustainable fiscal positions and a strengthening of competitiveness. It has carried a heavy social price tag. Outside of the eurozone, austerity has also been the prevailing policy, seen as inevitable to avoid economic instability. The crisis has not hit everyone equally. The general losses have been high, but there have also been some quite important redistributive effects. With all the difficulties of defining and measuring 'fairness', it is clear that the adjustment has not been equitable. Apart from issues of market failure, there have been direct increases of inequality within each of the member states. Higher poverty rates have been observed, rises in inequalities between higher and lower income earners as well as intergenerational inequalities between age groups. Long-term consequences are only beginning to surface in the public debate as the most immediate pressures of the crisis are slowly overcome. In this report, the authors first of all look at the results of the survey we have carried out in seven European countries and review perceptions of the socio-economic model. Subsequently, they assess the importance of the social dimension in the broader context of the European growth model. The authors discuss the impact of the structural challenges of globalisation, demography and technological change. They then review the EU’s performance in the crisis. Finally, the authors make a number of recommendations on how to bridge the gap between Europeans‘ expectations and reality.

Europe's economic challenges and the importance of ideas and innovation. CHALLENGE EUROPE Issue 22 - Challenges and new beginnings: Priorities for the EU's new leadership, September 2014.

How will we Europeans earn our living in 20 or 30 years' time? And how can it be done, while remaining true to our values of fairness, freedom and solidarity? These fundamental questions predate the financial crisis and will still be with us once we have fully overcome it. Of all the groups in society, business leaders are probably most keenly aware of the challenge posed by globalisation. They have their finger on the pulse of global economic activity and keep alerting me that Europe is losing out. The trade unions, generally more focused on the economy's demand side, regularly call for more (public) investment. Their leadership remains highly committed to Europe but they can sense a rise of Euro-scepticism among their members. We must, and can bring these two narratives together. Yes, global change is relentless and our societies must adapt, but we can also preserve what makes Europe such a special place: a unique combination of relative prosperity, solidarity, individual freedoms, and security. This challenge was always on my mind.

The growing intergenerational divide in Europe. Bruegel Policy Contribution Issue 2015/17, November 2015

During the economic and financial crisis, the divide between young and old in the European Union increased in terms of economic well-being and allocation of resources by governments. As youth unemployment and youth poverty rates increased, government spending shifted away from education, families and children towards pensioners. To address the sustainability of pension systems, some countries implemented pension reforms. We analysed changes to benefit ratios, meaning the ratio of the income of pensioners to the income of the active working population, and found that reforms often favoured current over future pensioners, increasing the intergenerational divide. We recommend reforms in three areas to address the intergenerational divide: improving European macroeconomic management, restoring fairness in government spending so the young are not disadvantaged, and pension reforms that share the burden fairly between generations.

Institutions and Growth in Europe. CEPS Working Document No. 421, April 2016

This paper provides empirical evidence in support of the view that the quality of institutions is an important determinant of long-term growth of European countries. When also taking into account the initial level of GDP per capita and government debt, cross-country institutional differences can explain to a great extent the relative long-term GDP performance of European countries. It also shows that an initial government debt level above a threshold (e.g. 60-70%) coupled with institutional quality below the EU average tends to be associated with particularly poor long-term real growth performance. Interestingly, the detrimental effect of high debt levels on long-term growth seems cushioned by the presence of very sound institutions. This might be because good institutions help to alleviate the debt problem in various ways, e.g. by ensuring sufficient fiscal consolidation in the longer-run, allowing for better use of government expenditures and promoting sustainable growth, social fairness and more efficient tax administration. The quality of national institutions seems to enhance the long-term GDP performance across a large sample of countries, also including OECD countries outside Europe. The paper offers some evidence that, in the presence of good institutions, conditions for catching-up seem generally good also for euro-area and fixed exchange rate countries. Looking at sub-groupings, it seems that sound institutions may be particularly important for long-term growth in the countries where the exchange rate tool is no longer available (and where also sovereign debt is high), and less so in the countries with flexible exchange rate regimes. However, this result is preliminary and requires further research. The empirical findings on the importance of institutions are robust to various measures of output growth, different measures of institutional indicators, different sample sizes, different country groupings and to the inclusion of additional control variables. Overall, the results tend to support the call for structural reforms in general and reforms enhancing the efficiency of public administration and regulation, the rule of law and the fight against rent-seeking and corruption in particular.

Avaliação de Desempenho: será um processo considerado como justo?

O presente estudo procura estabelecer a relação entre a Percepção de Justiça e Satisfação com o Sistema de Avaliação de Desempenho. A metodologia utilizada foi a quantitativa, pois permite validar a revisão da literatura efetuada, onde se procura analisar a relação entre a Percepção de Justiça e a Satisfação com o Sistema de Avaliação de Desempenho através de um conjunto de hipóteses que posteriormente serão testadas. Para se testar as hipóteses recolheu-se os dados através da adaptação de um questionário já aplicado em Portugal (Porfírio, 2006). O mesmo foi aplicado a 89 funcionários de uma empresa do ramo Transitário. Para o tratamento dos dados recolhidos vai ser utilizado o programa IBM SPSS Statistics 20. De acordo com os resultados obtidos verificou-se que existe uma relação positiva e significativa entre a Percepção de Justiça na dimensão Distributiva e a Satisfação com o Sistema de Avaliação de Desempenho. Não se tendo verificado o mesmo para a dimensão Procedimental. Em relação ao Big Five podemos constatar que é significativo e que exerce controlo entre a Percepção de Justiça Distributiva e a Satisfação com o Sistema de Avaliação de Desempenho, não se tendo comprovado o mesmo para a Percepção de Justiça Procedimental.