Distributed Real-time Embedded Research Articles

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.

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.

A tool for component-based schedulability analysis of distributed real-time pipelines

In many scenarios, such as in the automotive context [1], [2], the complexity of developing a distributed real-time embedded (DRE) system is reduced by dividing the system into separate components, possibly developed by a different teams or third-party companies. The component-based approach does simplify both the analysis and the integration, although it introduce some waste of resource.

Analyzing Schedulability of Energy-oriented Distributed Real-time Embedded Software

As computer systems become increasingly inter-networked, most of critical systems are distributed real-time embedded ( DRE ) system. A challenging problem faced by researchers and developers of DRE system is devising and implementing an effective method that can analyze requirements in varying operational conditions. In this paper, we analyze the requirements of DRE software and construct the corresponding energy consumption model, which is divided into fork module and leaf module based on its characteristics, and an energy consumption schema with time constrains is proposed for DRE software. The concept of critical task is presented according to the different position of task in the module, then constructing divide task set for module based on the characteristics of module and its critical task's position, the idle time allocation strategy and DVS adjustment method of sub task set are also advanced. Finally, a specific example is given to simulate the analysis process, the results show that the method can be a good solution to analyze DRE software.

An Approach to Formally Modeling and Verifying Distributed Real-time Embedded Software

As computer systems become increasingly inter-networked, Distributed Real-time Embedded (DRE) systems has became increasingly common and important, a challenging problem faced by researchers and developers of DRE software is devising and implementing an method that can effectively analyze requirements in varying operational conditions. In this paper, a Hierarchical Distributed Real-time Embedded net (HDRE-net) is proposed as software analysis tool. The basic task, function module and communication process are modeled by using HDRE-net, thus forming the whole application through the synthesis operation of Petri net. Time Reachability Graph is adopted to analyze the correctness of HDRE-net, the basic properties of DRE software are also considered. Finally, a specific example is given to simulate the analysis process, and the results show that the method can be a good solution to analyze DRE software.

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.

Quality measures for embedded systems and their application to control and certification

Distributed, real-time embedded (DRE) systems, such as that being developed under the DARPA Adaptive Reflective Middleware System (ARMS) program, require predictable, controlled real-time behavior. It is a challenge to develop ways to measure and evaluate the quality, or utility, of DRE system performance in the context of the dynamic, unpredictable environments in which they operate. This difficulty runs hand-in-hand with the challenge of providing adequate control of the system to effect behavior in the system that will allow the controlled system to be certified as exhibiting correct behavior. As part of the ARMS program, we have been developing utility-based measures of system quality for assessing correct behavior of a system and for driving feedback control at runtime. This paper describes the real-time utility measures we have developed for ARMS and their use as feedback signals to a control system that manages the dynamic allocation of resources to applications in the system. We then explore the issues associated with using utility-based assessment as part of an evidence-based certification process for dynamic real-time systems.

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.

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.