Actes de l'Ecole d'Eté Temps Réel 2005 - ETR'2005

Pdf des actes disponible à l'URL http://etr05.loria.fr/Le programme de l'Ecole d'été Temps Réel 2005 est construit autour d'exposés de synthèse donnés par des spécialistes du monde industriel et universitaire qui permettront aux participants de l'ETR, et notamment aux doctorants, de se forger une culture scientifique dans le domaine. Cette quatrième édition est centrée autour des grands thèmes d'importance dans la conception des systèmes temps réel : Langages et techniques de description d'architectures, Validation, test et preuve par des approches déterministes et stochastiques, Ordonnancement et systèmes d'exploitation temps réel, Répartition, réseaux temps réel et qualité de service

Mobile Ad-Hoc Networks

Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of-the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: quality-of-service and video communication, routing protocol and cross-layer design. A few interesting problems about security and delay-tolerant networks are also discussed. This book is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks

Tolerância a falhas em sistemas de comunicação de tempo-real flexíveis

Nas últimas décadas, os sistemas embutidos distribuídos, têm sido usados em variados domínios de aplicação, desde o controlo de processos industriais até ao controlo de aviões e automóveis, sendo expectável que esta tendência se mantenha e até se intensifique durante os próximos anos. Os requisitos de confiabilidade de algumas destas aplicações são extremamente importantes, visto que o não cumprimento de serviços de uma forma previsível e pontual pode causar graves danos económicos ou até pôr em risco vidas humanas. A adopção das melhores práticas de projecto no desenvolvimento destes sistemas não elimina, por si só, a ocorrência de falhas causadas pelo comportamento não determinístico do ambiente onde o sistema embutido distribuído operará. Desta forma, é necessário incluir mecanismos de tolerância a falhas que impeçam que eventuais falhas possam comprometer todo o sistema. Contudo, para serem eficazes, os mecanismos de tolerância a falhas necessitam ter conhecimento a priori do comportamento correcto do sistema de modo a poderem ser capazes de distinguir os modos correctos de funcionamento dos incorrectos. Tradicionalmente, quando se projectam mecanismos de tolerância a falhas, o conhecimento a priori significa que todos os possíveis modos de funcionamento são conhecidos na fase de projecto, não os podendo adaptar nem fazer evoluir durante a operação do sistema. Como consequência, os sistemas projectados de acordo com este princípio ou são completamente estáticos ou permitem apenas um pequeno número de modos de operação. Contudo, é desejável que os sistemas disponham de alguma flexibilidade de modo a suportarem a evolução dos requisitos durante a fase de operação, simplificar a manutenção e reparação, bem como melhorar a eficiência usando apenas os recursos do sistema que são efectivamente necessários em cada instante. Além disto, esta eficiência pode ter um impacto positivo no custo do sistema, em virtude deste poder disponibilizar mais funcionalidades com o mesmo custo ou a mesma funcionalidade a um menor custo. Porém, flexibilidade e confiabilidade têm sido encarados como conceitos conflituais. Isto deve-se ao facto de flexibilidade implicar a capacidade de permitir a evolução dos requisitos que, por sua vez, podem levar a cenários de operação imprevisíveis e possivelmente inseguros. Desta fora, é comummente aceite que apenas um sistema completamente estático pode ser tornado confiável, o que significa que todos os aspectos operacionais têm de ser completamente definidos durante a fase de projecto. Num sentido lato, esta constatação é verdadeira. Contudo, se os modos como o sistema se adapta a requisitos evolutivos puderem ser restringidos e controlados, então talvez seja possível garantir a confiabilidade permanente apesar das alterações aos requisitos durante a fase de operação. A tese suportada por esta dissertação defende que é possível flexibilizar um sistema, dentro de limites bem definidos, sem comprometer a sua confiabilidade e propõe alguns mecanismos que permitem a construção de sistemas de segurança crítica baseados no protocolo Controller Area Network (CAN). Mais concretamente, o foco principal deste trabalho incide sobre o protocolo Flexible Time-Triggered CAN (FTT-CAN), que foi especialmente desenvolvido para disponibilizar um grande nível de flexibilidade operacional combinando, não só as vantagens dos paradigmas de transmissão de mensagens baseados em eventos e em tempo, mas também a flexibilidade associada ao escalonamento dinâmico do tráfego cuja transmissão é despoletada apenas pela evolução do tempo. Este facto condiciona e torna mais complexo o desenvolvimento de mecanismos de tolerância a falhas para FTT-CAN do que para outros protocolos como por exemplo, TTCAN ou FlexRay, nos quais existe um conhecimento estático, antecipado e comum a todos os nodos, do escalonamento de mensagens cuja transmissão é despoletada pela evolução do tempo. Contudo, e apesar desta complexidade adicional, este trabalho demonstra que é possível construir mecanismos de tolerância a falhas para FTT-CAN preservando a sua flexibilidade operacional. É também defendido nesta dissertação que um sistema baseado no protocolo FTT-CAN e equipado com os mecanismos de tolerância a falhas propostos é passível de ser usado em aplicações de segurança crítica. Esta afirmação é suportada, no âmbito do protocolo FTT-CAN, através da definição de uma arquitectura tolerante a falhas integrando nodos com modos de falha tipo falha-silêncio e nodos mestre replicados. Os vários problemas resultantes da replicação dos nodos mestre são, também eles, analisados e várias soluções são propostas para os obviar. Concretamente, é proposto um protocolo que garante a consistência das estruturas de dados replicadas a quando da sua actualização e um outro protocolo que permite a transferência dessas estruturas de dados para um nodo mestre que se encontre não sincronizado com os restantes depois de inicializado ou reinicializado de modo assíncrono. Além disto, esta dissertação também discute o projecto de nodos FTT-CAN que exibam um modo de falha do tipo falha-silêncio e propõe duas soluções baseadas em componentes de hardware localizados no interface de rede de cada nodo, para resolver este problema. Uma das soluções propostas baseiase em bus guardians que permitem a imposição de comportamento falhasilêncio nos nodos escravos e suportam o escalonamento dinâmico de tráfego na rede. A outra solução baseia-se num interface de rede que arbitra o acesso de dois microprocessadores ao barramento. Este interface permite que a replicação interna de um nodo seja efectuada de forma transparente e assegura um comportamento falha-silêncio quer no domínio temporal quer no domínio do valor ao permitir transmissões do nodo apenas quando ambas as réplicas coincidam no conteúdo das mensagens e nos instantes de transmissão. Esta última solução está mais adaptada para ser usada nos nodos mestre, contudo também poderá ser usada nos nodos escravo, sempre que tal se revele fundamental.Distributed embedded systems (DES) have been widely used in the last few decades in several application fields, ranging from industrial process control to avionics and automotive systems. In fact, it is expectable that this trend will continue over the years to come. In some of these application domains the dependability requirements are of utmost importance since failing to provide services in a timely and predictable manner may cause important economic losses or even put human life in risk. The adoption of the best practices in the design of distributed embedded systems does not fully avoid the occurrence of faults, arising from the nondeterministic behavior of the environment where each particular DES operates. Thus, fault-tolerance mechanisms need to be included in the DES to prevent possible faults leading to system failure. To be effective, fault-tolerance mechanisms require an a priori knowledge of the correct system behavior to be capable of distinguishing them from the erroneous ones. Traditionally, when designing fault-tolerance mechanisms, the a priori knowledge means that all possible operational modes are known at system design time and cannot adapt nor evolve during runtime. As a consequence, systems designed according to this principle are either fully static or allow a small number of operational modes only. Flexibility, however, is a desired property in a system in order to support evolving requirements, simplify maintenance and repair, and improve the efficiency in using system resources by using only the resources that are effectively required at each instant. This efficiency might impact positively on the system cost because with the same resources one can add more functionality or one can offer the same functionality with fewer resources. However, flexibility and dependability are often regarded as conflicting concepts. This is so because flexibility implies the ability to deal with evolving requirements that, in turn, can lead to unpredictable and possibly unsafe operating scenarios. Therefore, it is commonly accepted that only a fully static system can be made dependable, meaning that all operating conditions are completely defined at pre-runtime. In the broad sense and assuming unbounded flexibility this assessment is true, but if one restricts and controls the ways the system could adapt to evolving requirements, then it might be possible to enforce continuous dependability. This thesis claims that it is possible to provide a bounded degree of flexibility without compromising dependability and proposes some mechanisms to build safety-critical systems based on the Controller Area Network (CAN). In particular, the main focus of this work is the Flexible Time-Triggered CAN protocol (FTT-CAN), which was specifically developed to provide such high level of operational flexibility, not only combining the advantages of time- and event-triggered paradigms but also providing flexibility to the time-triggered traffic. This fact makes the development of fault-tolerant mechanisms more complex in FTT-CAN than in other protocols, such as TTCAN or FlexRay, in which there is a priori static common knowledge of the time-triggered message schedule shared by all nodes. Nevertheless, as it is demonstrated in this work, it is possible to build fault-tolerant mechanisms for FTT-CAN that preserve its high level of operational flexibility, particularly concerning the time-triggered traffic. With such mechanisms it is argued that FTT-CAN is suitable for safetycritical applications, too. This claim was validated in the scope of the FTT-CAN protocol by presenting a fault-tolerant system architecture with replicated masters and fail-silent nodes. The specific problems and mechanisms related with master replication, particularly a protocol to enforce consistency during updates of replicated data structures and another protocol to transfer these data structures to an unsynchronized node upon asynchronous startup or restart, are also addressed. Moreover, this thesis also discusses the implementations of fail-silence in FTTCAN nodes and proposes two solutions, both based on hardware components that are attached to the node network interface. One solution relies on bus guardians that allow enforcing fail-silence in the time domain. These bus guardians are adapted to support dynamic traffic scheduling and are fit for use in FTT-CAN slave nodes, only. The other solution relies on a special network interface, with duplicated microprocessor interface, that supports internal replication of the node, transparently. In this case, fail-silence can be assured both in the time and value domain since transmissions are carried out only if both internal nodes agree on the transmission instant and message contents. This solution is well adapted for use in the masters but it can also be used, if desired, in slave nodes

Real-time wireless networks for industrial control systems

The next generation of industrial systems (Industry 4.0) will dramatically transform manyproductive sectors, integrating emerging concepts such as Internet of Things, artificialintelligence, big data, cloud robotics and virtual reality, to name a few. Most of thesetechnologies heavily rely on the availability of communication networks able to offernearly–istantaneous, secure and reliable data transfer. In the industrial sector, these tasks are nowadays mainly accomplished by wired networks, that combine the speed ofoptical fiber media with collision–free switching technology. However, driven by the pervasive deployment of mobile devices for personal com-munications in the last years, more and more industrial applications require wireless connectivity, which can bring enormous advantages in terms of cost reduction and flex-ibility. Designing timely, reliable and deterministic industrial wireless networks is a complicated task, due to the nature of the wireless channel, intrinsically error–prone andshared among all the devices transmitting on the same frequency band. In this thesis, several solutions to enhance the performance of wireless networks employed in industrial control applications are proposed. The presented approaches differ in terms of achieved performance and target applications, but they are all characterized by an improvement over existing industrial wireless solutions in terms of timeliness, reliability and determinism. When possible, an experimental validation of the designed solutions is provided. The obtained results prove that significant performance improvements are already possible, often using commercially available devices and preserving compliance to existing standards. Future research efforts, combined with the availability of new chipsets and standards, could lead to a world where wireless links effectively replace most of the existing cables in industrial environments, as it is already the case in the consumer market

Aerial Vehicles

This book contains 35 chapters written by experts in developing techniques for making aerial vehicles more intelligent, more reliable, more flexible in use, and safer in operation.It will also serve as an inspiration for further improvement of the design and application of aeral vehicles. The advanced techniques and research described here may also be applicable to other high-tech areas such as robotics, avionics, vetronics, and space

Mobility-based Routing Overhead Management in Reconfigurable Wireless Ad hoc Networks

Mobility-Based Routing Overhead Management in Reconfigurable Wireless Ad Hoc Networks Routing Overheads are the non-data message packets whose roles are establishment and maintenance of routes for data packets as well as neighbourhood discovery and maintenance. They have to be broadcasted in the network either through flooding or other techniques that can ensure that a path exists before data packets can be sent to various destinations. They can be sent reactively or periodically to neighbours so as to keep nodes updated on their neighbourhoods. While we cannot do without these overhead packets, they occupy much of the limited wireless bandwidth available in wireless networks. In a reconfigurable wireless ad hoc network scenario, these packets have more negative effects, as links need to be confirmed more frequently than in traditional networks mainly because of the unpredictable behaviour of the ad hoc networks. We therefore need suitable algorithms that will manage these overheads so as to allow data packet to have more access to the wireless medium, save node energy for longer life of the network, increased efficiency, and scalability. Various protocols have been suggested in the research area. They mostly address routing overheads for suitability of particular protocols leading to lack of standardisation and inapplicability to other protocol classes. In this dissertation ways of ensuring that the routing overheads are kept low are investigated. The issue is addressed both at node and network levels with a common goal of improving efficiency and performance of ad hoc networks without dedicating ourselves to a particular class of routing protocol. At node level, a method hereby referred to as "link availability forecast", that minimises routing overheads used for maintenance of neighbourhood, is derived. The targeted packets are packets that are broadcasted periodically (e.g. hello messages). The basic idea in this method is collection of mobility parameters from the neighbours and predictions or forecasts of these parameters in future. Using these parameters in simple calculations helps in identifying link availabilities between nodes participating in maintenance of networks backbone. At the network level, various approaches have been suggested. The first approach is the cone flooding method that broadcasts route request messages through a predetermined cone shaped region. This region is determined through computation using last known mobility parameters of the destination. Another approach is what is hereby referred as "destination search reverse zone method". In this method, a node will keep routes to destinations for a long time and use these routes for tracing the destination. The destination will then initiate route search in a reverse manner, whereby the source selects the best route for next delivery. A modification to this method is for the source node to determine the zone of route search and define the boundaries within which the packet should be broadcasted. The later method has been used for simulation purposes. The protocol used for verification of the improvements offered by the schemes was the AODV. The link availability forecast scheme was implemented on the AODV and labelled AODV_LA while the network level implementation was labelled AODV_RO. A combination of the two schemes was labelled AODV_LARO

Telemedicine

Telemedicine is a rapidly evolving field as new technologies are implemented for example for the development of wireless sensors, quality data transmission. Using the Internet applications such as counseling, clinical consultation support and home care monitoring and management are more and more realized, which improves access to high level medical care in underserved areas. The 23 chapters of this book present manifold examples of telemedicine treating both theoretical and practical foundations and application scenarios

Anales del XIII Congreso Argentino de Ciencias de la Computación (CACIC)

Contenido: Arquitecturas de computadoras Sistemas embebidos Arquitecturas orientadas a servicios (SOA) Redes de comunicaciones Redes heterogéneas Redes de Avanzada Redes inalámbricas Redes móviles Redes activas Administración y monitoreo de redes y servicios Calidad de Servicio (QoS, SLAs) Seguridad informática y autenticación, privacidad Infraestructura para firma digital y certificados digitales Análisis y detección de vulnerabilidades Sistemas operativos Sistemas P2P Middleware Infraestructura para grid Servicios de integración (Web Services o .Net)Red de Universidades con Carreras en Informática (RedUNCI

Anales del XIII Congreso Argentino de Ciencias de la Computación (CACIC)

Contenido: Arquitecturas de computadoras Sistemas embebidos Arquitecturas orientadas a servicios (SOA) Redes de comunicaciones Redes heterogéneas Redes de Avanzada Redes inalámbricas Redes móviles Redes activas Administración y monitoreo de redes y servicios Calidad de Servicio (QoS, SLAs) Seguridad informática y autenticación, privacidad Infraestructura para firma digital y certificados digitales Análisis y detección de vulnerabilidades Sistemas operativos Sistemas P2P Middleware Infraestructura para grid Servicios de integración (Web Services o .Net)Red de Universidades con Carreras en Informática (RedUNCI