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Localization in wireless sensor networks is an important functionality that is required for tracking personnel and assets in industrial environments, especially for emergency response. Current commercial localization systems such as GPS suffer from the limitations of either high cost or low availability in many situations (e.g., indoor environments that exclude direct line-of-sight signal reception). The development of industrial wireless sensor networks such as WirelessHART provides an alternative. In this article, we present the design and implementation of ColLoc: a collaborative location and tracking system on WirelessHART as an industrially viable solution. This solution is built upon several technological advances. First, ColLoc adds the roaming functionality to WirelessHART and thus provides a means for keeping mobile WirelessHART devices connected to the network. Second, ColLoc employs a collaborative framework to integrate different types of distance measurements into the location estimation algorithm by weighing them according to their precision levels. ColLoc adopts several novel techniques to improve distance estimation accuracy and decreases the RSSI presurvey cost. These techniques include introducing distance error range constraints to the measurements, judiciously selecting the initial point in location estimation and online updating the signal propagationmodels in the anchor nodes, integrating Extended Kalman Filter (EKF) with trilateration to track moving objects. Our implementation of ColLoc can be applied to any WirelessHART-conforming network because no modification is needed on the WirelessHART field devices. We have implemented a complete ColLoc system to validate both the design and the effectiveness of our localization algorithm. Our experiments show that the mobile device never drops out of the WirelessHART network while moving around; with the help of even one dependable anchor, using RSSI can yield at least 75% of distance errors below 5 meters, which is quite acceptable for many typical industrial automation applications. [ABSTRACT FROM AUTHOR]

A complex real-time embedded system may consist of multiple application components each of which has its own timeliness requirements and is scheduled by a component-specific scheduler that is tailored to meet its requirements. In this paper, we propose Class-based Component Composition (CCC) for composing independent components in an open environment. CCC applies a workload classification scheme to guarantee that the supply of shared resource always meets the hard-real-time constraints for on-budget workloads. The CCC solution aims to achieve a balance over multiple design objectives in component composition including composition overhead, overload handling and accommodating the range of real-time applications. [ABSTRACT FROM AUTHOR]

Discusses the concepts of extremely and critically utilizing task set and an approach to find the utilization bound as a function of the information about the task set. Preemptive fixed-priority scheduling; Rate-monotonic priority assignment; Linear programming; Bound algorithms.

Presents a study which formalized the concept of similarity that has been used as an ad hoc basis by application engineers to provide more flexibility in concurrency control. Semantics of real-time transactions; Correctness criteria; Synchronization; Suggestions for future research.

A key index of the performance of a rule-based pro- gram used in real-time monitoring and control is its response time, defined by the longest program execution time before a fixed point of the program is reached from a start state. Previous work in computing the response-time bounds for rule-based programs effectively assumes that all rules take the same amount of firing time, It is also assumed that if two rules are enabled, then either one of them may be scheduled first for firing. These assumptions can result in loose bounds, especially in the case programmers choose to impose a priority structure on the set of rules. In this paper, we remove the uniform-firing-cost assumption and discuss how to get tighter bounds by taking rule-priority information into account. We show that the rule-suppression relation we previously introduced can be extended to incorporate rule-priority information. A bound-derivation algorithm for programs whose potential-trigger relations satisfy an acyclicity condition is presented, followed by its correctness proof and an analysis example. [ABSTRACT FROM AUTHOR]