4,861 research outputs found
Integrated analysis of error detection and recovery
An integrated modeling and analysis of error detection and recovery is presented. When fault latency and/or error latency exist, the system may suffer from multiple faults or error propagations which seriously deteriorate the fault-tolerant capability. Several detection models that enable analysis of the effect of detection mechanisms on the subsequent error handling operations and the overall system reliability were developed. Following detection of the faulty unit and reconfiguration of the system, the contaminated processes or tasks have to be recovered. The strategies of error recovery employed depend on the detection mechanisms and the available redundancy. Several recovery methods including the rollback recovery are considered. The recovery overhead is evaluated as an index of the capabilities of the detection and reconfiguration mechanisms
The embedded operating system project
This progress report describes research towards the design and construction of embedded operating systems for real-time advanced aerospace applications. The applications concerned require reliable operating system support that must accommodate networks of computers. The report addresses the problems of constructing such operating systems, the communications media, reconfiguration, consistency and recovery in a distributed system, and the issues of realtime processing. A discussion is included on suitable theoretical foundations for the use of atomic actions to support fault tolerance and data consistency in real-time object-based systems. In particular, this report addresses: atomic actions, fault tolerance, operating system structure, program development, reliability and availability, and networking issues. This document reports the status of various experiments designed and conducted to investigate embedded operating system design issues
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A survey on online monitoring approaches of computer-based systems
This report surveys forms of online data collection that are in current use (as well as being the subject of research to adapt them to changing technology and demands), and can be used as inputs to assessment of dependability and resilience, although they are not primarily meant for this use
Division of Research and Economic Development Annual Report for FY2005
Annual report for the Division of Research and Economic Development of the University of Rhode Island for the year 2004-2005.
Includes statistics of project proposals, expenditures, URI Foundation Awards, previous annual report summaries and awards received by individual academic and administrative departments
Asynchronous epidemic algorithms for consistency in large-scale systems
Achieving and detecting a globally consistent state is essential to many services in the large
and extreme-scale distributed systems, especially when the desired consistent state is critical
for services operation. Centralised and deterministic approaches for synchronisation and
distributed consistency are not scalable and not fault-tolerant. Alternatively, epidemic-based
paradigms are decentralised computations based on randomised communications. They are
scalable, resilient, fault-tolerant, and converge to the desired target in logarithmic time with
respect to system size. Thus, many distributed services have adopted epidemic protocols
to achieve the consensus and the consistent state, mainly due to scalability concerns. The
convergence of epidemic protocols is stochastically guaranteed. However, the detection of
the convergence is probabilistic and non-explicit. In a real-world environment, systems are
unreliable, and epidemic protocols cannot converge to the desired state. Thus, achieving
convergence by itself does not ensure making a system-wide consistent state under dynamic
conditions.
The research work presented in this thesis introduces the Phase Transition Algorithm
(PTA) to achieve distributed consistent state based on the explicit detection of convergence.
Each phase in PTA is a decentralised decision-making process that implements epidemic data
aggregation, in which the detection of convergence implies achieving a global agreement. The
phases in PTA can be cascaded to achieve higher certainty as desired. Following the PTA,
two epidemic protocols, namely PTP and ECP, are proposed to acquire of consensus, i.e. for
the consistency in data dissemination and data aggregation. The protocols are examined
through simulations, and experimental results have validated the protocols ability to achieve
and explicitly detect the consensus among system nodes.
The research work has also studied the epidemic data aggregation under nodes churn and
network failures, in which the analysis has identified three phases of the aggregation process.
The investigations have shown a different impact of nodes churn on each phase. The phase
that is critical for the aggregation process has been studied further, which led to propose
new robust data aggregation protocols, REAP and REAP+. Each protocol has a different
decentralised replication method, and both implements distributed failure detection and
instantaneous mass restoration mechanisms. Simulations have validated the protocols, and
results have shown protocols ability to converge, detect convergence, and produce competitive
accuracy under various levels of nodes churn.
Furthermore, distributed consistency in continuous systems is addressed in the research.
The work has proposed a novel continuous epidemic protocol with the adaptive restart
mechanism. The protocol restarts either upon the detection of system convergence or upon
the detection of divergence. Also, the protocol introduces the seed selection method for
the peak data distribution in decentralised approaches, which was a challenge that requires
single-point initialisation and leader-election step. The simulations validated the performance
of the algorithm under static and dynamic conditions and approved that convergence and
divergence detection accuracy can be tuned as desired.
Finally, the research work shows that combining and integrating of the proposed protocols
enables extreme-scale distributed systems to achieve and detect global consistent states even
under realistic and dynamical conditions
Evolution of Communication Skills in Virtual Product Development Process: Experience From EGPR
More than a decade of continuous international collaboration of several European universities in teaching new product development in virtual environment gives unique opportunity to investigate evolution and development of communication techniques for NPD collaboration in virtual environment. This chapter provides theoretical and practical view on different aspects: technical evolution of ICT tools, development and fostering of communication flow, personal aspects of IT communication, with important emphasis on building of trust within virtual teams. The reader can extract from this chapter guidelines for work in collaborative virtual environment, to run effectively either small projects, meetings and lectures or even more complex projects, distributed among several dislocated teams. The chronological overview of the continuous virtual communication in the last 15 years gives also fair suggestions about future evolution for the next decade
User-Oriented QoS in Packet Video Delivery
We focus on packet video delivery, with an emphasis on the quality of service perceived by the end-user. A video signal passes through several subsystems, such as the source coder, the network and the decoder. Each of these can impair the information, either by data loss or by introducing delay. We describe how each of the subsystems can be tuned to optimize the quality of the delivered signal, for a given available bit rate in the network. The assessment of end-user quality is not trivial. We present recent research results, which rely on a model of the human visual system
Internet of Things-aided Smart Grid: Technologies, Architectures, Applications, Prototypes, and Future Research Directions
Traditional power grids are being transformed into Smart Grids (SGs) to
address the issues in existing power system due to uni-directional information
flow, energy wastage, growing energy demand, reliability and security. SGs
offer bi-directional energy flow between service providers and consumers,
involving power generation, transmission, distribution and utilization systems.
SGs employ various devices for the monitoring, analysis and control of the
grid, deployed at power plants, distribution centers and in consumers' premises
in a very large number. Hence, an SG requires connectivity, automation and the
tracking of such devices. This is achieved with the help of Internet of Things
(IoT). IoT helps SG systems to support various network functions throughout the
generation, transmission, distribution and consumption of energy by
incorporating IoT devices (such as sensors, actuators and smart meters), as
well as by providing the connectivity, automation and tracking for such
devices. In this paper, we provide a comprehensive survey on IoT-aided SG
systems, which includes the existing architectures, applications and prototypes
of IoT-aided SG systems. This survey also highlights the open issues,
challenges and future research directions for IoT-aided SG systems
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