www.ee.kth.se Deadline-constrained transmission scheduling and data evacuation in wirelessHART networks

The process automation industry is adopting wireless technologies, but in such harsh environments technologies like Bluetooth and ZigBee are not reliable enough. An alternative to Bluetooth and ZigBee is WirelessHART that can cope with the noisy environment but instead imposes very high demands

, it is important to develop a wireless transmission scheduling and control co-design approach to optimize the control performance subject to network resource constraints. This work addresses the co-design problem of determining the optimal sampling rates of multiple feedback control loops sharing a WirelessHART

Abstract: WirelessHART networks are gaining ground as a real-time communication infrastructure in industrial wireless control systems. Because wireless communication is often susceptible to transmission failures in industrial environments, it is essential to account for failures in the delay

-channel TDMA transmission, redundant routes, and avoidance of spatial reuse of channels for enhanced reliability and real-time performance. This paper makes several key contributions to real-time transmission scheduling in WirelessHART networks: (1) formulation of the end-to-end real-time transmission

, reliability, feedback latency, battery longevity, etc. In this paper we report some experience with implementing control over wireless. The platform we use is the WirelessHART mesh network, the first international industrial wireless control standard. We describe a full implementation of the standard

Migrating operating system instances across distinct physical hosts is a useful tool for administrators of data centers and clusters: It allows a clean separation between hardware and software, and facilitates fault management, load balancing, and low-level system maintenance. By carrying out

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The difficulty of developing reliable distributed softwme is an impediment to applying distributed computing technology in many settings. Expeti _ with the Isis system suggests that a structured approach based on virtually synchronous _ groups yields systems that are substantially easier to develop, exploit sophisticated forms of cooperative computation, and achieve high reliability. This paper reviews six years of resemr,.hon Isis, describing the model, its impl_nentation challenges, and the types of applicatiom to which Isis has been appfied. 1 In oducfion One might expect the reliability of a distributed system to follow directly from the reliability of its con-stituents, but this is not always the case. The mechanisms used to structure a distributed system and to implement cooperation between components play a vital role in determining how reliable the system will be. Many contemporary distributed operating systems have placed emphasis on communication performance, overlooking the need for tools to integrate components into a reliable whole. The communication primitives supported give generally reliable behavior, but exhibit problematic semantics when transient failures or system configuration changes occur. The resulting building blocks are, therefore, unsuitable for facilitating the construction of systems where reliability is impo/tant. This paper reviews six years of research on Isis, a syg_,,m that provides tools _ support the construction of reliable distributed software. The thesis underlying l._lS is that development of reliable distributed software can be simplified using process groups and group programming too/_. This paper motivates the approach taken, surveys the system, and discusses our experience with real applications.

"Grid" computing has emerged as an important new field, distinguished from conventional distributed computing by its focus on large-scale resource sharing, innovative applications, and, in some cases, high-performance orientation. In this article, we define this new field. First, we review the "Grid problem," which we define as flexible, secure, coordinated resource sharing among dynamic collections of individuals, institutions, and resources---what we refer to as virtual organizations. In such settings, we encounter unique authentication, authorization, resource access, resource discovery, and other challenges. It is this class of problem that is addressed by Grid technologies. Next, we present an extensible and open Grid architecture,inwhich protocols, services, application programming interfaces, and software development kits are categorized according to their roles in enabling resource sharing. We describe requirements that we believe any such mechanisms must satisfy and we discuss the importance of defining a compact set of intergrid protocols to enable interoperability among different Grid systems. Finally, we discuss how Grid technologies relate to other contemporary technologies, including enterprise integration, application service provider, storage service provider, and peer-to-peer computing. We maintain that Grid concepts and technologies complement and have much to contribute to these other approaches.