K-theory for Cuntz-Krieger algebras arising from real quadratic maps

We compute the $K$-groups for the Cuntz-Krieger algebras $\mathcal{O}_{A_{\mathcal{K}(f_{\mu})}}$, where $A_{\mathcal{K}(f_{\mu})}$ is the Markov transition matrix arising from the \textit{kneading sequence }$\mathcal{K} (f_{\mu})$ of the one-parameter family of real quadratic maps $f_{\mu}$.Comment: 8 page

On a test-bed application for the ART-WiSe framework

This report describes the development of a Test-bed Application for the ART-WiSe Framework with the aim of providing a means of access, validate and demonstrate that architecture. The chosen application is a kind of pursuit-evasion game where a remote controlled robot, navigating through an area covered by wireless sensor network (WSN), is detected and continuously tracked by the WSN. Then a centralized control station takes the appropriate actions for a pursuit robot to chase and “capture” the intruder one. This kind of application imposes stringent timing requirements to the underlying communication infrastructure. It also involves interesting research problems in WSNs like tracking, localization, cooperation between nodes, energy concerns and mobility. Additionally, it can be easily ported into a real-world application. Surveillance or search and rescue operations are two examples where this kind of functionality can be applied. This is still a first approach on the test-bed application and this development effort will be continuously pushed forward until all the envisaged objectives for the Art-WiSe architecture become accomplished

Security in hybrid ITS networks

Dissertação para obtenção do Grau de Mestre em Engenharia Informática e de ComputadoresSistemas de Transportes Inteligentes e Cooperativos (C-ITS) visam melhorar a segurança e a sustentabilidade dos transportes. No entanto, a comunicação dos sistemas Vehicleto-Everything é inerentemente aberta, levando a vulnerabilidades que atacantes podem explorar. Isto é uma ameaça a todos os utilizadores rodoviários, pois falhas de segurança podem levar a violações de privacidade ou a fatalidades. Além disso, elevadas taxas de mortalidade estão correlacionadas com utilizadores de mobilidade suave. Logo, no desenvolvimento de sistemas C-ITS, é crucial considerar, além dos veículos conectados, os utilizadores de mobilidade suave e os veículos sem a devida tecnologia. Este estudo apresenta uma nova abordagem desenvolvida no contexto emergente das redes híbridas, combinando tecnologias ITS-G5 e celulares. Dois protocolos, MFSPV e DLAPP, foram implementados e avaliados para introduzir garantias de segurança (como privacidade e integridade) nas comunicações dentro do ambiente híbrido C-ITS desenvolvido. Assim, este trabalho integra, com segurança, estações ITS conectadas por G5 e utilizadores de mobilidade suave, através de uma aplicação móvel via redes celulares. Para tal, utilizou-se equipamentos reais, incluindo on-board e roadside units. Tempos computacionais, de latência e de ponta-a-ponta (E2E) foram usados para avaliar o desempenho do sistema. O protocolo MFSPV supera o DLAPP em eficiência computacional, mas o DLAPP atinge uma latência de rede ligeiramente menor. No entanto, ambos introduzem apenas um atraso adicional de 11% nas comunicações híbridas E2E. A comunicação híbrida impõe, em média, 28.29ms extra de tempo E2E. A proposta mostra-se promissora, visto que atinge tempos de E2E abaixo dos requisitos de latência impostos na maioria dos casos de utilização do C-ITS.Cooperative Intelligent Transport Systems (C-ITS) continue to be developed to enhance transportation safety and sustainability. However, the communication of Vehicle-to-Everything systems is inherently open, leading to vulnerabilities that attackers can exploit.This represents a threat to all road users, as security failures can lead to privacy violations or even fatalities. Moreover, a high fatality rate is correlated with softmobility road users. So, in the development of C-ITS systems, it is crucial to broaden the perspective beyond connected vehicles to soft-mobility users and legacy vehicles. This study presents a novel approach developed in the context of emerging hybrid networks, combining ITS-G5 and cellular technologies. Two protocols, MFSPV and DLAPP, were implemented and evaluated to introduce security guarantees (such as privacy and integrity) in communications within the developed C-ITS hybrid environment. As a result, this work securely integrates G5-connected ITS stations and softmobility users through a smartphone application via cellular networks. Real equipment was utilised for this goal, including on-board and roadside units. Computational, latency and end-to-end times were used to assess the system performance.MFSPV outperforms DLAPP in computational efficiency, but DLAPP achieves a slightly lower network latency. Nevertheless, both only introduce an additional 11% delay in hybrid end-to-end communications. Hybrid communication imposes, on average, an extra 28.29ms of end-to-end time. The proposal shows promise as it reaches end-to-end times below the latency requirements imposed in most C-ITS use cases.N/

Two elementary cellular automata with a new kind of dynamic

Finite elementary cellular automata (ECAs) are studied, considering periodic and the four types of fixed boundary conditions. It is shown that two of these automata, rules 26 and 154, have particularly interesting dynamics. Both these rules are in Wolfram’s class 2 when subject to periodic boundary conditions but have chaotic dynamics, typical of Wolfram’s class 3, when we consider fixed boundary conditions a ℓ = 1 and a r = 0. The same rules, when fixed null boundary conditions a ℓ = 0 and a r = 0 are used, show complex dynamics with a mixture of order and disorder completely different from the one identified with Wolfram’s class 4: it grows in complexity in order to reach, in just a few time steps, an extremely simple, almost homogeneous configuration, from which the complexification starts again.info:eu-repo/semantics/publishedVersio

2D elementary cellular automata with four neighbors

This paper is concerned with the study of square boolean synchronous four-neighbor peripheral cellular automata. It is rst shown that, due to conjugation and plane re ection symmetry transformations, the number of dynamically nonequivalent such automata is equal to 4 856. The cellular automata for which the homogeneous nal states play a signi cant role are then identi ed. Finally, it is shown that, contrary to what happens in the case of one-dimensional boolean three-neighbor cellular automata, for some peripheral automata there is coexistence between a homogeneous nal state and other dynamics

Order and chaos: interactive computational activities for the classroom

It has long been believed that typical students learn better through contemporary approaches to questions originated by physics problems that allow experiments. This belief motivated us to develop interactive computational didactic materials about contemporaneous mathematics that can be used both in the classroom and in mathematics clubs in school. Dynamical Systems, the study of how physical systems evolve with time, inspired the activities developed. They share a key goal of understanding the order/chaos relationship in natural phenomena, human behaviour and social systems. Another goal to achieve is to give mathematics an experimental/laboratorial component, which rarely is present. In fact, all the interactive computational didactic materials developed include simulations and the capability to generate wonderful pictures, from which students can enjoy the beauty of mathematics.The first author was supported by the Centre of Research in Mathematics and Applications, University of Évora, through the FCT Pluriannual Funding Program. The second author was supported by FEDER Funds through "Programa Operacional Factores de Competitividade – COMPETE" and by Portuguese Funds through FCT -"Fundação para a Ciência e a Tecnologia", within the Project PEst-C/MAT/UI0013/2011

Dynamic cluster scheduling for cluster-tree WSNs

While Cluster-Tree network topologies look promising for WSN applications with timeliness and energy-efficiency requirements, we are yet to witness its adoption in commercial and academic solutions. One of the arguments that hinder the use of these topologies concerns the lack of flexibility in adapting to changes in the network, such as in traffic flows. This paper presents a solution to enable these networks with the ability to self-adapt their clusters’ duty-cycle and scheduling, to provide increased quality of service to multiple traffic flows. Importantly, our approach enables a network to change its cluster scheduling without requiring long inaccessibility times or the re-association of the nodes. We show how to apply our methodology to the case of IEEE 802.15.4/ZigBee cluster-tree WSNs without significant changes to the protocol. Finally, we analyze and demonstrate the validity of our methodology through a comprehensive simulation and experimental validation using commercially available technology on a Structural Health Monitoring application scenario

On the use of IEEE 802.15.4/Zigbee for time-sensitive wireless sensor network applications

Mestrado em Engenharia Electrotécnica e de ComputadoresRecent advancements in information and communication technologies are paving the way for new paradigms in embedded computing systems. This, allied with an increasing eagerness for monitoring and controlling everything, everywhere, is pushing forward the design of new Wireless Sensor Network (WSN) infrastructures that will tightly interact with the physical environment, in a ubiquitous and pervasive fashion. Such cyber-physical systems require a rethinking of the usual computing and networking concepts, and given that the computing entities closely interact with their environment, timeliness is of increasing importance. This Thesis addresses the use of standard protocols, particularly IEEE 802.15.4 and ZigBee, combined with commercial technologies as a baseline to enable WSN infrastructures capable of supporting the Quality of Service (QoS) requirements (specially timeliness and system lifetime) that future large-scale networked embedded systems will impose. With this purpose, in this Thesis we start by evaluating the network performance of the IEEE 802.15.4 Slotted CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) mechanism for different parameter settings, both through simulation and through an experimental testbed. In order to improve the performance of these networks (e.g. throughput, energyefficiency, message delay) against the hidden-terminal problem, a mechanism to mitigate it was implemented and experimentally validated. The effectiveness of this mechanism was also demonstrated in a real application scenario, featuring a target tracking application. A methodology for modelling cluster-tree WSNs and computing the worst-case endto-end delays, buffering and bandwidth requirements was tested and validated experimentally. This work is of paramount importance to understand the behaviour of WSNs under worst-case conditions and also to make the appropriate network settings. Our experimental work enabled us to identify a number of technological constrains, namely related to hardware/software and to the Open-ZB implementation in TinyOS. In this line, a new implementation effort was triggered to port the Open-ZB IEEE 802.15.4/ZigBee protocol stack to the ERIKA real-time operating system. This implementation was validated experimentally and its behaviour compared with the TinyOS–based implementation.Os últimos avanços nas tecnologias de informação e comunicação (ICTs) estão a abrir caminho para novos paradigmas de sistemas computacionais embebidos. Este facto, aliado à tendência crescente em monitorizar e controlar tudo, em qualquer lugar, está a alimentar o desenvolvimento de novas infra-estruturas de Redes de Sensores Sem Fios (WSNs), que irão interagir intimamente com o mundo físico de uma forma ubíqua. Este género de sistemas ciber-físicos de grande escala, requer uma reflexão sobre os conceitos de redes e de computação tradicionais, e tendo em conta a proximidade que estas entidades partilham com ambiente envolvente, o seu comportamento temporal é de acrescida importância. Esta Tese endereça a utilização de protocolos normalizados, em particular do IEEE 802.15.4 e ZigBee em conjunto com tecnologias comerciais, para desenvolver infraestruturas WSN capazes de responder aos requisitos de Qualidade de Serviço (QoS) (especialmente em termos de comportamento temporal e tempo de vida do sistema), que os futuros sistemas embebidos de grande escala deverão exigir. Com este propósito, nesta Tese começamos por analisar a performance do mecanismo de Slotted CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) do IEEE 802.15.4 para diferentes parâmetros, através de simulação e experimentalmente. De modo a melhorar a performance destas redes (ex. throughput, eficiência energética, atrasos) em cenários que contenham nós escondidos (hidden-nodes), foi implementado e validado experimentalmente um mecanismo para eliminar este problema. A eficácia deste mecanismo foi também demonstrada num cenário aplicacional real. Foi testada e validada uma metodologia para modelizar uma WSN em cluster-tree e calcular os piores atrasos das mensagens, necessidades de buffering e de largura de banda. Este trabalho foi de grande importância para compreender o comportamento deste tipo de redes para condições de utilização limite e para as configurar a priori. O nosso trabalho experimental permitiu identificar uma série de limitações tecnológicas, nomeadamente relacionadas com hardware/software e outras relacionadas com a implementação do Open-ZB em TinyOS. Isto desencadeou a migração da pilha protocolar IEEE 802.15.4/ZigBee Open-ZB para o ERIKA, um sistema operativo de tempo-real. Esta implementação foi validada experimentalmente e o seu comportamento comparado com o da implementação baseada em TinyOS

Towards Adaptive RF Fingerprint-based Authentication of IIoT devices

As IoT technologies mature, they are increasingly finding their way into more sensitive domains, such as Medical and Industrial IoT, in which safety and cyber-security are of great importance. While the number of deployed IoT devices continues to increase exponentially, they still present severe cyber-security vulnerabilities. Effective authentication is paramount to support trustworthy IIoT communications, however, current solutions focus on upper-layer identity verification or key-based cryptography which are often inadequate to the heterogeneous IIoT environment. In this work, we present a first step towards achieving powerful and flexible IIoT device authentication, by leveraging AI adaptive Radio Frequency Fingerprinting technique selection and tuning, at the PHY layer for highly accurate device authentication over challenging RF environments