IEEE Industrial Electronics Society
IEEE Industrial Electronics Society
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Introducing Associate Editor – Jean-Marie Proth
Guest Editorial: Special Section on Real Time Networked Embedded Systems
Thomas Nolte and Roberto Passerone
Real-Time Embedded Systems
1. Resource-sharing servers for Open Environments
Bertogna, Marko; Fisher, Nathan; Baruah, Sanjoy
Abstract: We study the problem of executing a collection of independently designed and validated task systems upon a common platform comprised of a preemptive processor and additional shared resources. We present an abstract formulation of the problem and identify the major issues that must be addressed in order to solve this problem. We present (and prove the correctness of) algorithms that address these issues, and thereby obtain a design for an open real-time environment.
2. Legacy Real-Time Applications in a Reservation-Based System
Abeni, Luca and Palopoli, Luigi
Abstract: A remarkable research activity has been carried out in the past few years to support real-time applications by means of appropriate scheduling solutions. Unfortunately, most of such techniques can be used only if real-time applications are developed according to a specialised API, and if some important information (such as the Worst Case Execution Time) are known a-priori. In this paper, we present a novel technique, called Legacy Feedback Scheduling (LFS), for scheduling a class of legacy applications that need the support of a real-time scheduler but are not written using a specialised API and have unknown or varying execution requirements. The approach is based on the combination of a resource reservation scheduler and a feedback based adaptation mechanism for identifying the correct scheduling parameters.
3. Improving the size of communication buffers in synchronous models with time constraints
Di Natale, Marco (contact); Wang, Guoqiang; Sangiovanni-Vincentelli, Alberto
Abstract: Model-based development of embedded applications is a major trend in the industry because of the possibility of early validation and verification of properties by simulation or formal methods. The productivity advantage of model-based development is fully leveraged if the model is automatically translated into code by generator programs. The validity of the simulation and/or verification results on the model is retained only if the generated code is guaranteed to preserve the model semantics. At the same time, the implementation must make efficient use of the execution platform resources. The implementation of communication between functional blocks in a synchronous reactive model requires buffering schemes and access procedures at the kernel level. We demonstrate how it is possible to leverage task timing information to obtain tighter bounds on the communication buffers. The approach is applied to an automotive case study, showing the improvements with respect to previous methods.
4. Cross-abstraction Functional Verification and Performance Analysis of Chip Multiprocessor Designs
Madl, Gabor; Pasricha, Sudeep; Dutt, Nikil; Abdelwahed, Sherif
Abstract: This paper introduces the Cross-abstraction Real-time Analysis (CARTA) framework for the model-based functional verification and performance estimation of chip multiprocessors (CMP) utilizing bus matrix (or crossbar switch) interconnection networks. We argue that the inherent complexity in CMP designs requires the synergistic use of various models of computation to efficiently manage the trade-offs between accuracy and complexity. Our approach builds on domain-specific modeling languages (DSMLs) to describe an open-source tool-chain that provides a cross-abstraction bridge between the finite state machine (FSM), discrete event (DE) and timed automata (TA) models of computation, and utilizes multiple model checkers to analyze formal properties at the cycle-accurate and transaction-level abstractions. The cross-abstraction analysis exploits accuracy for functional verification, and achieves significant speedups for performance estimation with marginal accuracy loss. We demonstrate results on an industrial strength networking CMP design utilizing a bus matrix interconnection network. To the best of our knowledge, the CARTA framework is the first model-based tool-chain that utilizes multiple abstractions and model checkers for the comprehensive and formal functional verification, performance estimation, and real-time verification of bus matrix based CMP designs.
5. Pinpointing Interrupts in Embedded Real-Time Systems using Hashed Execution Contexts
Sundmark, Daniel; Ermedahl, Andreas; Stärner, Johan
Abstract: Cyclic debugging is the process of iteratively re-executing a failed execution in order to determine the cause of the failure, \ie the bug. In this process, being able to correctly reproduce the faulty execution is an absolute necessity. In sequential, deterministic, non-real-time software, this reproducibility is inherent. However, when the execution is preempted by interrupts, this has severe effects on program reproducibility, since, during the reproduction, it is required for interrupts to occur at the exact same instructions. Previously, this problem has been solved using instruction counters, that induce large execution time perturbations, or by special hardware solutions which impose a risk of inexact results. In this paper, we propose an alternative method for pinpointing interrupts using hashed values of selected parts of the program execution context. Although our method in some cases can be ambiguous, we show that it serves as a pragmatic method for pinpointing and reproducing interrupts in embedded real-time systems. Moreover, our method does not rely on special hardware or compilers, is simple to implement and use, and requires little execution time and memory.
Distributed Real-Time Systems
6. A Real-time Service-Oriented Architecture for Industrial Automation
Cucinotta, Tommaso (contact); Mancina, Antonio; Anastasi, Gaetano; Lipari, Giuseppe; Mangeruca, Leonardo; Checcozzo, Roberto; Rusina, Fulvio
Abstract: Industrial automation platforms are experiencing a paradigm shift. New technologies are making their way in the area, including embedded real-time systems, standard local area networks like Ethernet, Wi-Fi and ZigBee, standard IP-based communication protocols, standard Service Oriented Architectures (SOA) and Web Services. An automation system will be composed of flexible autonomous components with Plug & Play functionality, self configuration and diagnostic, and autonomic local control that communicate through standard networking technologies. However, the introduction of these new technologies raises many important problems that need to be properly solved, one of these being the need to support real-time and Quality of Service (QoS) for hard and soft real-time applications. This paper describes a Service-Oriented Architecture enhanced with real-time capabilities for Industrial Automation. The proposed architecture allows for negotiation of the QoS requested by clients to web services, and provides temporal encapsulation of individual activities. This way, it is possible to perform an a-priori analysis of the temporal behavior of each service, and to avoid unwanted interferences among components. After describing the architecture, experimental results gathered on a real implementation of the framework (which leverages AQuoSA, a soft real-time scheduler for the Linux kernel) are presented, showing the effectiveness of the proposed solution. The experiments were performed on simple case studies designed in the context of industrial automation applications.
7. QoS-aware Real-Time Composition Algorithms for Service-Based Applications
Estevez-Ayres, Iria (contact); Basanta-Val, Pablo; García-Valls, Marisol; A. Fisteus, Jesús; Almeida, Luis
Abstract: This paper presents a model for QoS-aware service composition in distributed systems with real-time and fault-tolerance requirements. This model can be applied in application domains like, for example, remote monitoring, control and surveillance. Classic approaches to real-time systems do not provide the flexibility and fault-tolerance required in new emerging environments that need to combine a high degree of dynamism with temporal predictability. Our approach addresses these new challenges by combining concepts from the service oriented paradigm and distributed real-time systems. We propose a concrete system model based on a holistic time-triggered-based approach for design and configuration. Based on this model, we propose two algorithms for the composition of QoS-aware service-based applications with temporal requirements: an exhaustive algorithm that computes the optimal service combination in terms of a figure of merit, suitable for off-line composition; and an improved algorithm based on heuristics and partial figures of merit, suitable for on-line composition. Experimental results show that the latter reduces dramatically the number of combinations explored with a minimal degradation in the quality of the solution, making it feasible for on-line execution in dynamic environments.
8. Simple asynchronous remote invocations for distributed real-time Java
Basanta-Val, Pablo (contact); García-Valls, Marisol; Estevez-Ayres, Iria
Abstract: More and more the use of real-time distribution middlewares programmed with high-level languages like Java is becoming of interest for industrial systems because this type of infrastructures reduce development efforts required to both design and maintain complex networked applications. In that way towards having better development tools, this article deals with the very specific issue of the asynchronism, from the particular perspective of Java's distributed technologies. It proposes and evaluates an extension to the Java's remote method invocation (RMI) with additional support for asynchronous remote invocations. Such a mechanism makes transmission of some kind of messages, typically those that do not require from any confirmation from the server, much more efficiently than synchronous communications, and consequently optimize and speed up the performance of many industrial networked applications. More in detail, this paper concerns with the model, itself, and the set of changes it requires within their middleware programming interfaces and inside communication protocols to accommodate the proposed model. The proposal is supported by empirical evidences of a prototype developed as partial proof-of-concept.
Real-Time Networks
9. Improving Quality-of-Service in Wireless Sensor Networks by mitigating hidden-node collisions
Kouba, Anis; Severino, Ricardo; Alves, Mario; Tovar, Eduardo
Abstract: This paper proposes H-NAMe, a very simple yet extremely efficient Hidden-Node Avoidance Mechanism for WSNs. H-NAMe relies on a grouping strategy that splits each cluster of a WSN into disjoint groups of non-hidden nodes that scales to multiple clusters via a cluster grouping strategy that guarantees no interference between overlapping clusters. Importantly, H-NAMe is instantiated in IEEE 802.15.4/ZigBee, which currently are the most widespread communication technologies for WSNs, with only minor add-ons and ensuring backward compatibility with their protocols standards. H-NAMe was implemented and exhaustively tested using an experimental test-bed based on “off-the-shelf” technology, showing that it increases network throughput and transmission success probability up to twice the values obtained without H-NAMe. H-NAMe effectiveness was also demonstrated in a target tracking application with mobile robots over a WSN deployment.
10. An Adaptive Approach for Topology Management in Large and Dense Real-Time Wireless Sensor Networks
Toscano, Emanuele and Lo Bello, Lucia
Abstract: Topology management protocols play an important role in WSNs, managing the sleep transitions of the nodes to make data transmissions occur in an energy-efficient way, thus prolonging network lifetime. However, classical topology management protocols are not suitable for real-time WSNs, as they may introduce unbounded delays. Previous work presented a static topology management protocol specifically designed for real-time WSNs which is able to provide bounded delay and routing fidelity. This paper extends such work, presenting a dynamic topology management protocol that surpasses the static approach introducing support for event-driven data transmissions and node joining at run-time and providing a novel adaptive technique for energy balancing among nodes to further increase network lifetime. The paper provides a detailed description of the dynamic protocol and simulation results on network lifetime and routing performance with comparative assessments.
11. Hardware Acceleration for Programmable Real-Time Ethernet Fischmeister, Sebastian; Trausmuth, Robert; Lee, Insup
Abstract: Distributed real-time applications implement distributed
applications with timeliness requirements. Such systems require a
deterministic communication medium with bounded communication delays.
Ethernet is a widely used commodity network with many appliances and
network components and represents a natural fit for real-time
application; unfortunately, standard Ethernet provides no bounded communication delays. Conditional state-based communication schedules
provide expressive means for specifying and executing with choice points
while staying verifiable. Such schedules implement an arbitration scheme
and provide the developer with means to fit the arbitration scheme to
the application demands instead of requiring the developer to tweak the
application to fit a predefined scheme. An evaluation of this approach
as software prototypes showed that jitter and execution overhead may
diminish the gains. This work successfully addresses this problem with a
synthesized soft processor. We present results around the development of
the soft processor, the design choices, and the measurements on throughput and robustness..
12. Memory-efficient segment-based packet-combining schemes in face of deadlines
Andreas Willig
Abstract: In this paper we consider segment-based hard-decision packet-combining schemes. The schemes presented here are memory-efficient and easy to implement, and some of them appproach the performance of majority-voting schemes without having the same memory requirements. One particularly interesting scheme combines segment-based transmission with Luby-type erasure codes.
13. Extending the Lifetime of Wireless Sensor Networks through Adaptive Sleep
Anastasi, Giuseppe; Conti, Marco; Di Francesco, Mario
Abstract: In recent years, the use of wireless sensor networks for industrial applications has rapidly increased. However, energy consumption still remains one of the main limitations of this technology. As communication typically accounts for the major power consumption, the activity of the transceiver should be minimized, in order to prolong the network lifetime. To this end, this paper proposes an Adaptive Staggered sLEEp Protocol (ASLEEP) for efficient power management in wireless sensor networks targeted to periodic data acquisition. This protocol dynamically adjusts the sleep schedules of nodes to match the network demands, even in time-varying operating conditions. In addition, it does not require any a-priori knowledge of the network topology or traffic pattern. ASLEEP has been extensively studied with simulation. The results obtained show that, under stationary conditions, the protocol effectively reduces the energy consumption of sensor nodes (by dynamically adjusting their duty-cycle to current needs) thus increasing significantly the network lifetime. With respect to similar non-adaptive solutions, it also reduces the average message latency and may increase the delivery ratio. Under time-varying conditions the protocol is able to adapt the duty-cycle of single nodes to the new operating conditions while keeping a consistent sleep schedule among sensor nodes. The results presented here are also confirmed by an experimental evaluation in a real testbed.
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