2003.bib

@phdthesis{PEDREIRAS_SFRTCDS_2003,
  author = {Pedreiras, P.},
  title = {Supporting Flexible Real-Time Communication on Distributed Systems},
  school = {University of Aveiro},
  year = {2003},
  type = {},
  address = {Aveiro, Portugal},
  month = {June},
  note = {},
  key = {},
  abstract = {Distributed computer-control systems (DCCS) are widely disseminated, appearing in applications ranging from automated process and manufacturing control to automotive, avionics and robotics. Many of these applications comprise real-time activities, that is, activities that must be performed within strict time bounds. Due to its distributed nature, these systems comprise multiple autonomous processing units that, despite being autonomous, need to exchange data in order to achieve control over the environment. For this reason the data exchange among different nodes is also subject to real-time constraints, and thus the communication subsystem must be able to deliver data within specific time bounds.

Many DCCS applications are complex and heterogeneous, comprising different sets of activities with different properties and requirements. For instance, they commonly include periodic activities, e.g. resulting from closed loop control, and sporadic activities resulting from events that occur at unpredictable instants in time in the environment under control. These types of activities can have distinct levels of criticalness and timeliness requirements, independently of their activation nature. On the other hand, flexibility is becoming increasingly important in DCCS, due both to the need of reducing the costs of set-up, configuration changes and maintenance, and also to the recent use of DCCS in new types of applications, such as agile manufacturing, real-time databases with variable number of clients, automotive, mobile robotics in unstructured environments and automatic traffic control systems, that must deal with environments that are inherently dynamic.

To cope with such high degree of complexity and dynamism, distributed real-time systems must support both time and event-triggered communication services under timing constraints and, at the same time, they must be operationally flexible, supporting on-the-fly changes to the computational activities they execute. Concerning specifically the communication subsystem, existing real-time protocols do not generally fulfill these requirements. In systems eminently time-triggered, event-triggered services are either non-existing or handled inefficiently, while in systems eminently event-triggered, interesting properties of time-triggered services are normally lost. On the other hand, flexibility and timeliness are often considered as conflicting: systems that provide timeliness guarantees are based on a static configuration of the communication activities while systems that support dynamic changes to the communication activities do not provide timeliness guarantees}
}

@article{FERREIRA_SICICA_2003,
  author = {Ferreira, J. and Almeida, L. and Martins, L. and Pedreiras, P.},
  title = {Components to enforce fail-silent behaviour in dynamic master-slave systems},
  journal = {5th IFAC International Symposium on Intelligent Components and Instruments for Control Applications (SICICA'2003)},
  year = {2003},
  volume = {},
  number = {},
  pages = {143--150},
  month = {July},
  doi = {},
  issn = {},
  isbn = {},
  keywords = {CAN, FTT-CAN, field buses},
  note = {},
  key = {},
  abstract = {This paper considers the case in which master-slave fieldbus networks are used in safety-critical embedded applications, such as transportation systems. Traditional approaches to system design, due to fault-tolerance reasons, have considered static cyclic table-based traffic scheduling, only. However, there is a growing demand for flexibility and integration, mainly to improve efficiency in the use of system resources, with the network playing a central role to support such properties. This calls for dynamic on-line traffic scheduling techniques so that dynamic communication requirements are adequately supported. This paper considers such dynamic master-slave architectures and addresses the problem of enforcing fail silent behavior both in the master and in the slave nodes. Two different mechanisms are proposed, one based on dynamic bus guardians for the slave nodes only, to impose fail silent behavior in the time domain, and other based on internal replication and temporized agreement, to impose fail silence both in the temporal and value domains. Despite being potentially applicable to a set of master-slave networks, this paper discusses the specific implementation of the proposed mechanisms on top of the FTT-CAN protocol}
}

@inproceedings{FERREIRA_SRDS_2003,
  author = {Ferreira, J. and Almeida, L. and Fonseca, J. A. and Rodriguez-Navas, G.},
  title = {Enforcing Consistency of Communication Requirements Updates in FTT-CAN},
  booktitle = {Workshop on Dependable Embedded Systems (SRDS'2003) Proceedings of the 22nd Symposium on Reliable Distributed Systems (DES'2003)},
  year = {2003},
  editor = {},
  volume = {},
  series = {},
  pages = {},
  address = {Florence, Italy},
  month = {October},
  organization = {},
  publisher = {},
  doi = {},
  issn = {},
  isbn = {},
  keywords = {CAN, FTT-CAN, Protocols},
  note = {},
  key = {},
  abstract = {Traditional design approaches to safety-critical distributed systems, due to fault-tolerance reasons, have typically considered static cyclic table-based traffic scheduling. However, there is a growing demand for flexibility and integration, mainly to improve efficiency in the use of system resources, with the network playing a central role to support such properties. This calls for dynamic on-line traffic scheduling techniques so that dynamic communication requirements are adequately supported. The FTT-CAN protocol (Flexible Time-Triggered communication over Controller Area Network) has been developed specifically to deliver that kind of support with timeliness guarantees. It uses a master-slave approach with one or more master replicas for faulttolerance reasons. The communication requirements are held in a table, that is replicated in all masters. This paper considers the problem of updating the communication requirements while maintaining coherency and synchronization between the master and all its replicas. The paper also discusses the generalization of the proposed mechanism which can easily be adapted to other dynamic master-slave protocols}
}

@inproceedings{PEDREIRAS_IPDPS_2003,
  author = {Pedreiras, P. and Almeida, L.},
  title = {The flexible time-triggered (FTT) paradigm: an approach to QoS management in distributed real-time systems},
  booktitle = {17th International Symposium on Parallel and Distributed Processing (IPDPS'2003)},
  year = {2003},
  editor = {},
  volume = {},
  series = {},
  pages = {},
  address = {Nice, France},
  month = {April},
  organization = {},
  publisher = {},
  doi = {10.1109/IPDPS.2003.1213243},
  issn = {1530-2075},
  isbn = {},
  keywords = {Ethernet, FTT-Ethernet, message passing, protocols, quality management, quality of service, real-time systems},
  note = {},
  key = {},
  abstract = {Real-time distributed systems are becoming pervasive, supporting a broad range of applications such as avionics, automotive, adaptive control, robotics, computer vision and multimedia. In such systems, several activities are executed on different nodes and cooperate via message passing. One increasingly important concept is that of quality-of-service (QoS), i.e. a system performance metric from the application point-of-view. Concerning the communication system, the QoS delivered to the application is a function of communication parameters such as the rates of message streams. In previous work, the authors have developed two network protocols, FTT-CAN and FTT-Ethernet, which allow online changes to the set of message streams under guaranteed timeliness. The specific network protocols are abstracted away leading to a generic communication paradigm named Flexible Time-Triggered (FTT), which supports online QoS management, with arbitrary policies, in distributed real-time systems. Two possible QoS management policies are referred, priority-based and another one based on the elastic task model, and their use is illustrated with a case study}
}

@inproceedings{PEDREIRAS_RTLIA_2003,
  author = {Pedreiras, P. and Leite, R. and Almeida, L.},
  title = {Characterizing the Real-Time Behavior of Prioritized Switched-Ethernet},
  booktitle = {2nd International Workshop on Real-Time LANs in the Internet Age (RTLIA'2003) Proceedings},
  year = {2003},
  editor = {},
  volume = {},
  series = {},
  pages = {},
  address = {Oporto, Portugal},
  month = {July},
  organization = {},
  publisher = {},
  doi = {},
  issn = {},
  isbn = {},
  keywords = {Ethernet},
  note = {},
  key = {},
  abstract = {Ethernet is, today, the de facto standard in the Local Area Networks general domain. Despite having been designed for the office environment, it has been appropriately modified or adapted in order to fulfill the requirements of many other fields, including large distributed embedded systems and industrial automation. One typical requirement in such application fields is the need to deliver time-constrained communication services, which cannot be efficiently met using the original CSMA/CD medium access control. Among many possible solutions, either software or hardware-based, the one that became more popular, recently, is the use of switches. However, this does not enforce timeliness per se. In this paper we show a set of practical experiments that reveal the weaknesses of switched Ethernet in what concerns real-time behavior. The results point to the need for further traffic control, at the data sources, if a predictable behavior of the switch is desired}
}