Distributed Real-time Embedded Systems Research Articles

CONTEXT-AWARE ONTOLOGY AND WEB SERVICES DISCOVERY FOR DISTRIBUTED EMBEDDED REAL-TIME SYSTEMS

Distributed Embedded Real-Time Systems (DERTS) consists of hundreds of interconnected devices, typically small and wirelessly-connected, which are designed to work for a long period of time. The massive interconnection of devices and the usage of heterogeneous languages, operating platforms and data standards make DERTS a competitive and complex system. In addition, the DERTS program is setting a trend of moving away from centralized, high-cost products towards lower cost and high volume products. In this regard, there is nothing more natural than considering the use of Service Oriented Architecture (SOA) to assist in the development of DERTS. This is because SOA enables different devices to exchange data regardless of issues of complexity. Moreover, context-awareness, which is widely studied for DERTS, also plays an important role for effective communication among devices. Thus, to build service-based DERTS while managing the complexity, context-aware ontologies are the best solution. In this paper, we developed a context-aware ontology for DERTS which is known as ConOntDERTS. To evaluate ConOntDERTS, we used two methods. In the first method, a criteria-based ontology evaluation was used; while in the second method, a survey was conducted to show that the results produced by ConOntDERTS were almost the same as human perception. Results of the evaluation show the consistency and feasibility of our ontology and the statistical test results show that ConOntDERTS ontology can produce consistent results with human perception.

Problems of instrumental support for the development of distributed embedded real-time systems

Distributed embedded real-time systems (DRTESs) are classified among objects that are complex in their development and crucial in their use. The problems of Instrumental Support and automation of development of DRTESs are still actual, even after more than 40 years of research. This paper refine the notion of DRTES. The shortcomings of traditional approaches to the design of DRTESs are considered and a model-oriented approach to the design is formulated. A concept of the instrumental environment supporting this approach has been proposed. Basic problems to be addressed when building such an environment are formulated. The current state of the art in solving these problems is described.

Development of reconfigurable distributed embedded systems with a model‐driven approach

SummaryIn this paper, we propose a model‐driven approach allowing to build reconfigurable distributed real‐time embedded (DRE) systems. The constant growth of the complexity and the required autonomy of embedded software systems management give the dynamic reconfiguration a big importance. New challenges to apply the dynamic reconfiguration at model level as well as runtime support level are required. In this direction, the development of reconfigurable DRE systems according to traditional processes is not applicable. New methods are required to build and to supply reconfigurable embedded software architectures. In this context, we propose an model‐driven engineering based approach that enables to design reconfigurable DRE systems with execution framework support. This approach leads the designer to specify step by step his/her system from a model to another one more refined until the targeted model is reached. This targeted model is related to a specific platform leading to the generation of the most part of the system implementation. We also develop a new middleware that supports reconfigurable DRE systems. Copyright © 2013 John Wiley & Sons, Ltd.

Service based meta-model for the development of distributed embedded real-time systems

The development complexity of Distributed Embedded Real-Time Systems (DERTS) can be reduced by the use of Service-Oriented Computing (SOC). However, the existing modeling methods allow modeling of either DERTS or SOC concepts and there is a lack of meta-model for Service-Oriented development of DERTS. This paper proposes a service-based meta-model for DERTS, along with the constraints of the elements of the meta-model. A Smart Home case study was designed to validate the meta-model. This meta-model could not only be beneficial for Service-Oriented development of DERTS, but can also be used at the Platform Independent Model (PIM) level of MDD.

Hierarchical CPU utilization control for real-time guarantees in power grid computing

Blackouts in our daily life can be disastrous with enormous economic loss. Blackouts usually occur when appropriate corrective actions are not effectively taken for an initial contingency. Therefore, it is critical to complete those tasks that are running power grid computing algorithms in the Energy Management System (EMS) in a timely manner to avoid blackouts. This problem can be formulated as guaranteeing end-to-end deadlines in a Distributed Real-time Embedded (DRE) system. However, existing feedback scheduling algorithms in DRE systems cannot be directly adopted to handle with significantly different timescales of power grid computing tasks. In this paper, we propose a hierarchical control solution to guarantee the deadlines of those tasks in EMS by grouping them based on their characteristics. Furthermore, we present an adaptive control scheme to achieve analytical assurance of control accuracy and system stability, in spite of significant system variation. Our solution is based on well-established control theory for guaranteed control accuracy and system stability and can adapt to changes in the system model without manual reconfiguration and profiling. Simulation results based on a realistic workload configuration demonstrate that our solution can guarantee timeliness for power grid computing and hence help to avoid blackouts.

Hierarchical server-based traffic scheduling in ethernet switches

Distributed Embedded Real-Time Systems (DERTS) are ever more complex, consisting of an increasing number of nodes with more functionality and handling more data. This scenario is pushing for paradigm changes in the methodologies to design complex DERTS. Namely, component-oriented design methodologies, exhibiting the composability property are considered an effective means to tackle the growing complexity of DERTS. Server-oriented architectures have proven to be an effective means to enable controlled resource sharing, providing composability among application components as well as between the application software and the hardware platform on which they execute.

Fine tuning of the multiplexing facilities of Java's Remote Method Invocation

AbstractThe proliferation of a new generation of distributed real‐time embedded systems (DRE) characterized by special restrictions on its storage capacities, its available computation time, and the messages they can send through the network suggests a comprehensive redesign of the current distribution infrastructure in order to tune its performance. In this changing panorama, the paper concerns one of the protocols, Java's Remote Method Protocol (JRMP), used nowadays to interconnect different nodes of a distributed Java system, and explores the cost of integrating an improved protocol‐level multiplexing strategy in the context of an end‐to‐end remote invocation. The new multiplexing strategy helps middleware manage more efficiently unscheduled invocations that appear at runtime generated from a certain client node, especially in cases where preallocation of resources or dimensioning for the worst‐case are techniques not plausible. To this end, the paper examines an alternative based on the definition of a new subprotocol, called ConnectionLess, which offers built‐in multiplexing facilities for distributed Java applications. The performance of the new subprotocol is compared against the three already defined by JRMP (namely SingleOp, Stream, and Multiplex), taking into consideration parameters such as memory consumed in the Java's virtual machine and end‐to‐end response times. Copyright © 2011 John Wiley & Sons, Ltd.

Evaluating Aspect- and Object-Oriented Concepts to Model Distributed Embedded Real-Time Systems Using RT-UML

The growing design complexity of today's embedded real-time systems requires new techniques aiming the raising of the abstraction level since earlier stages of design in order to deal with such complexity in a suitable way. This paper reports a case study, which provides an assessment of two well-know high-level paradigms, namely Aspect- (AO) and Object-Oriented (OO) Paradigms. Concepts of both paradigms were applied at modeling phase of a Distributed Embedded Real-Time System (DERTS). The handling of DERTS’ functional and non-functional requirements (at modeling level) using AO and OO concepts is discussed. Both paradigms are compared using of a set of software engineering metrics, which were adapted to be applied at modeling level. The presented results show the suitability of each paradigm for DERTS specification in terms of reusability quality of model elements.

Design and Performance Evaluation of an Adaptive Resource Management Framework for Distributed Real-Time and Embedded Systems

Achieving end-to-end quality of service (QoS) in distributed real-time embedded (DRE) systems require QoS support and enforcement from their underlying operating platforms that integrates many real-time capabilities, such as QoS-enabled network protocols, real-time operating system scheduling mechanisms and policies, and real-time middleware services. As standards-based quality of service (QoS) enabled component middleware automates integration and configuration activities, it is increasingly being used as a platform for developing open DRE systems that execute in environments where operational conditions, input workload, and resource availability cannot be characterized accurately a priori. Although QoS-enabled component middleware offers many desirable features, however, it historically lacked the ability to allocate resources efficiently and enable the system to adapt to fluctuations in input workload, resource availability, and operating conditions. This paper presents three contributions to research on adaptive resource management for component-based open DRE systems. First, we describe the structure and functionality of the resource allocation and control engine (RACE), which is an open-source adaptive resource management framework built atop standards-based QoS-enabled component middleware. Second, we demonstrate and evaluate the effectiveness of RACE in the context of a representative open DRE system: NASA's magnetospheric multiscale mission system. Third, we present an empirical evaluation of RACE's scalability as the number of nodes and applications in a DRE system grows. Our results show that RACE is a scalable adaptive resource management framework and yields a predictable and high-performance system, even in the face of changing operational conditions and input workload.

Distributed real-time embedded systems: Recent advances, future trends and their impact on manufacturing plant control

Real-time and embedded systems have historically been small scale. However, advances in microelectronics and software now allow embedded systems to be composed of a large set of processing elements, and the trend is towards significant enhanced functionality, complexity, and scalability, since those systems are increasingly being connected by wired and wireless networks to create large-scale distributed real-time embedded systems (DRES). Such embedded computing and information technologies have become at the same time an enabler for future manufacturing enterprises as well as a transformer of organizations and markets. This paper discusses opportunities for using recent advances in the DRES area in the deployment of intelligent, adaptive, and reconfigurable manufacturing plant control architectures.

Verifying distributed real-time properties of embedded systems via graph transformations and model checking

Component middleware provides dependable and efficient platforms that support key functional, and quality of service (QoS) needs of distributed real-time embedded (DRE) systems. Component middleware, however, also introduces challenges for DRE system developers, such as evaluating the predictability of DRE system behavior, and choosing the right design alternatives before committing to a specific platform or platform configuration. Model-based technologies help address these issues by enabling design-time analysis, and providing the means to automate the development, deployment, configuration, and integration of component-based DRE systems. To this end, this paper applies model checking techniques to DRE design models using model transformations to verify key QoS properties of component-based DRE systems developed using Real-time CORBA. We introduce a formal semantic domain for a general class of DRE systems that enables the verification of distributed non-preemptive real-time scheduling. Our results show that model-based techniques enable design-time analysis of timed properties and can be applied to effectively predict, simulate, and verify the event-driven behavior of component-based DRE systems.

DISTRIBUTED REAL-TIME EMBEDDED SYSTEMS: RECENT ADVANCES, FUTURE TRENDS AND THEIR IMPACT ON MANUFACTURING PLANT CONTROL

Real-time and embedded systems have historically been small scale. However, advances in microelectronics and software now allow embedded systems to be composed of a large set of processing elements, and the trend is toward significant enhanced functionality, complexity, and scalability, since those systems are increasingly being connected by wired and wireless networks to create large-scale distributed real-time embedded systems (DRES). Such embedded computing and information technologies have become at the same time an enabler for future manufacturing enterprises as well as a transformer of organizations and markets. This paper discusses opportunities for using recent advances in the DRES area in the deployment of intelligent, adaptive, and reconfigurable manufacturing plant control architectures.

Enhancing adaptivity via standard dynamic scheduling middleware

This paper makes three contributions to research on QoS-enabled middleware for open distributed real-time embedded (DRE) systems. First, it describes the design and implementation of a dynamic scheduling framework based on the OMG Real-Time CORBA 1.2 specification (RTC1.2) that provides capabilities for (1) propagating QoS parameters and a locus of execution across endsystems via a distributable thread abstraction and (2) enforcing the scheduling of multiple distributable threads dynamically using standard CORBA middleware. Second, it examines the results of empirical studies that show how adaptive dynamic scheduling and management of distributable threads can be enforced efficiently in standard middleware for open DRE systems. Third, it presents results from case studies of multiple adaptive middleware QoS management technologies to monitor and control the quality, timeliness, and criticality of key operations adaptively in a representative DRE avionics system.

Enhancing adaptivity via standard dynamic scheduling middleware

Abstract This paper makes three contributions to research on QoS-enabled middleware for open distributed real-time embedded (DRE) systems. First, it describes the design and implementation of a dynamic scheduling framework based on the OMG Real-Time CORBA 1.2 specification (RTC1.2) that provides capabilities for (1) propagating QoS parameters and a locus of execution across endsystems via a distributable thread abstraction and (2) enforcing the scheduling of multiple distributable threads dynamically using standard CORBA middleware. Second, it examines the results of empirical studies that show how adaptive dynamic scheduling and management of distributable threads can be enforced efficiently in standard middleware for open DRE systems. Third, it presents results from case studies of multiple adaptive middleware QoS management technologies to monitor and control the quality, timeliness, and criticality of key operations adaptively in a representative DRE avionics system.

Multiparadigm scheduling for distributed real-time embedded computing

Increasingly complex requirements, coupled with tighter economic and organizational constraints, are making it hard to build complex distributed real-time embedded (DRE) systems entirely from scratch. Therefore, the proportion of DRE systems made up of commercial-off-the-shelf (COTS) hardware and software is increasing significantly. There are relatively few systematic empirical studies, however, that illustrate how suitable COTS-based hardware and software have become for mission-critical DRE systems. This paper provides the following contributions to the study of real-time quality-of-service (QoS) assurance and performance in COTS-based DRE systems: it presents evidence that flexible configuration of COTS middleware mechanisms, and the operating system (OS) settings they use, allows DRE systems to meet critical QoS requirements over a wider range of load and jitter conditions than statically configured systems; it shows that in addition to making critical QoS assurances, noncritical QoS performance can be improved through flexible support for alternative scheduling strategies; and it presents an empirical study of three canonical scheduling strategies; specifically the conditions that predict success of a strategy for a production-quality DRE avionics mission computing system. Our results show that applying a flexible scheduling framework to COTS hardware, OSs, and middleware improves real-time QoS assurance and performance for mission-critical DRE systems.

Challenges for Building Complex Real-time Computing Systems

In the early years of computing, real-time systems consisted of single computers interfaced to a few sensors and effectors, and perhaps to a user control device as well. While such systems still exist, and have become almost ubiquitous in a myriad of everyday devices, the world of real-time computing has expanded in scope and complexity in ways comparable to the proliferation of computers for many other aspects of business, economic and social life. Perhaps the most recent evidence of this expansion is the employment of distributed processing to achieve the objectives of real-time system designers. With the expanded use of computers, particularly in distributed real-time embedded systems (DREs), issues of complexity have emerged that were not faced by early real-time system designers. Ccomplex aggregations of computers operating as a distributed system have assumed a distinctly different character from early real-time systems, exhibiting far more variation in form as well as in the underlying technology base. Dealing with this complexity has become a major driver for innovation in both system architecture and computing technology. The challenge designers face today is, how to design, build, deploy and maintain ever larger and more capable distributed real-time embedded systems to meet the demands of a changing world. Modern real-time systems are likely to be more than just systems; they are rapidly becoming large-scale systems of systems. Because of their long life and high cost, complex real-time systems cannot be recreated as new starts when new requirements emerge. They must evolve and undergo changes and upgrades in place. Furthermore, since the technology base on which DREs are built is changing rapidly, complex real-time systems must allow for the convenient insertion of new computing equipment and supporting software products. For these reasons, flexibility of design has become a paramount concern. This paper will present major challenges and promising solutions for the problem of building real-time open architectures. Based on our experience within the Navy shipboard computing systems domain, we will consider technical characteristics, change management, system flexibility and dynamic resource management.