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Real-Time Technology and Applications Symposium, 1995. Proceedings

Date 15-17 May 1995

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Displaying Results 1 - 25 of 36
  • Proceedings Real-Time Technology and Applications Symposium

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  • Author index

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    Freely Available from IEEE
  • A configurable adjunct for real time systems (CARTS)

    Page(s): 48 - 49
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    CARTS is a set of system services targeted to real time distributed systems and spanning a variety of architectures. CARTS was designed to support rapid application code generation through generic user interfaces, to facilitate incremental system integration and reconfiguration via file-based data, and to provide tailored functionality appropriate to each project utilizing it. The CARTS postal system controls intertask communication within and between processors using optimal transfer methods such as shared memory, backplane I/O, or network I/O. The CARTS clock services supply high resolution time of day and mission clocks synchronized system wide at initialization and maintained through all levels of interface loading and across processor restarts View full abstract»

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  • Applying imprecise algorithms to real-time image and video transmission

    Page(s): 96 - 101
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    One major requirement for multimedia systems is the efficient transmission of multimedia information over a communication or computer network. Current image/video transmission techniques works well if sufficient processing power and network bandwidth are available, but do not adapt properly to a reduction in one or more of these resources. This paper proposes an image/video transmission technique, based on the imprecise computation model, which yields a balanced tradeoff between the quality of the image/video transmitted and the available time for transmission. Our experiments show that the proposed algorithm has favorable results compared to non-imprecise computation-based algorithms View full abstract»

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  • Paradigm for building robust real-time distributed mission-critical systems

    Page(s): 33 - 40
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    We demonstrate a new computing paradigm for the evolution of the long life-cycle defense system with stringent safety, timing and dependability requirements, namely, the multiple target tracking (MTT) part of a surveillance radar system. We demonstrate the new paradigm's capability for the support of system upgrades in system software, hardware, and application software while maintaining the existing baseline performance. This new paradigm shares many characteristics with the SEI/CMU Simplex Architecture whose applicability has been demonstrated for a prototypical industrial feedback control application. We present the concepts of our paradigm, lessons learned in applying the paradigm to surveillance radar, and lessons learned implementing the paradigm by integrating standard technologies View full abstract»

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  • The design and implementation of a Real-Time Object Management Interface

    Page(s): 192 - 201
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    Describes the design of the Real-Time Object Management Interface (RTOMI), a distributed real-time data-access interface which runs on multiprocessor platforms. RTOMI is designed to facilitate the implementation of real-time data-intensive applications by providing process scheduling and data distribution mechanisms that exploit the concept of “similarity”. RTOMI is implemented to run on a multi-board Intel System 520 which is used as a testbed for evaluating our real-time transaction scheduling and data distribution algorithms View full abstract»

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  • An interactive interface and RT-Mach support for monitoring and controlling resource management

    Page(s): 134 - 139
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    Real-time applications in dynamic systems such as multimedia systems may change their timing characteristics on the fly and may be created and terminated at any time. A priori resource allocation decisions may not hold throughout the lifetime of such applications because of changing user needs and interests. The ability to monitor and control system resources dynamically is fundamental to building flexible and dynamic multimedia systems. In this paper, we describe the mechanisms and tools we have built for monitoring and controlling operating system resource reserves in Real-Time Mach. The system supports a resource reservation abstraction called `processor capacity reserves', and an interactive tool named `rmon' uses these mechanisms to display the processor usage for each reserved activity in the system and to allow the user to change the processor reservation dynamically; it can also coordinate the reservation change requests with a separate quality-of-service manager which makes policy decisions regarding which requests are granted View full abstract»

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  • Real-time optimistic concurrency control protocol with dynamic adjustment of serialization order

    Page(s): 174 - 179
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    Proposes a new real-time optimistic protocol. By using a dynamic adjustment of the serialization order by backward-adjusting the non-serious conflicting transactions before the committing transactions, many unnecessary restarts can be eliminated. In the protocol, no conflict or serialization constraints have to be recorded during the read phase of a transaction. Different priority conflict resolution methods can be easily incorporated in the protocol. In addition, with the use of Thomas's write rule, the number of transaction restarts can further be much reduced View full abstract»

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  • Real-time communication in FieldBus multiaccess networks

    Page(s): 86 - 95
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    There has been an increasing need of timely and predictable communication services for embedded real-time systems in automated factories and industrial process controls. Work has been done on real-time communication with deadline guarantees in point-to-point, token bus/token ring/FDDI, and DQDB (Distributed Queue Dual Bus) networks. However, due to the random access nature of the CSMA/CD type multiaccess networks, they are not suitable for applications with stringent timing constraints. We consider real-time communication services with absolute deadline guarantees in multiaccess local area networks equipped with a centralized scheduler, such as the SP-50 FieldBus, an industrial standard protocol for process control and manufacturing applications. Similar to most token-passing networks, in a centralized scheduling multiaccess network, the access to the bus is controlled by a token. Only the station currently holding the token has the exclusive right to use the multiaccess bus. Unlike the token bus, token ring, or FDDI network, the multiaccess network uses a centralized token scheduling scheme and the token need not be allocated to the stations in a cyclic fashion. We show that the pinwheel and the distance-constrained scheduling techniques can be adapted to schedule the token in centralized-scheduling multiaccess networks to guarantee message deadlines View full abstract»

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  • A model and tools for supporting parallel real-time applications in Unix environments

    Page(s): 126 - 133
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    As real-time applications become more complex, it becomes increasingly important to provide both a clean model for their development and the ability to verify that their execution matches the development model. In addition to becoming more complex, soft real-time programs are becoming more mainstream, and as such are being run on platforms running some variant of Unix. It is even more important in these environments to be able to monitor a program and understand its behavior. We describe a frame scheduler that provides a simple model to the real-time programmer while maintaining considerable flexibility. We motivate and describe the implementation of FrameView, a set of tools closely coupled with the frame scheduler. Since FrameView and the frame scheduler were developed in conjunction with each other and are tightly coupled, they provide a powerful and efficient means for programmers to implement, analyze and modify soft parallel real-time applications. The frame scheduler is fully implemented in IRIX 5.3, and FrameView is in beta release. In this paper, we describe our experiences building and using the frame scheduler and FrameView View full abstract»

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  • Probabilistic performance guarantee for real-time tasks with varying computation times

    Page(s): 164 - 173
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    Describes how the scheduling algorithms and schedulability analysis methods developed for periodic tasks can be extended to provide performance guarantees to semi-periodic tasks. Like periodic tasks, the requests in a semi-periodic task are released regularly. However, their computation times vary widely. We focus on systems where the total maximum utilization of the tasks on each processor is larger than one. Hence, according to the existing schedulability conditions for periodic tasks, we cannot guarantee that the semi-periodic tasks are schedulable, even though their total average utilization is very small. We describe two methods of providing probabilistic schedulability guarantees to the semi-periodic tasks. The first method, called probabilistic time-demand analysis, is a modification of the exact schedulability test for periodic tasks. The second method, called the transform-task method, transforms each task into a periodic task followed by a sporadic task. The transform-task method can provide an absolute guarantee to requests with shorter computation times and a probabilistic guarantee to the longer requests View full abstract»

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  • From single to multiprocessor real-time kernels in hardware

    Page(s): 42 - 43
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    The article presents three different implementations of a traditional real-time kernel in hardware. All approaches improved performance and determinism by several orders of magnitude when compared with software-based real time kernels. The first implementation provides an integrated deterministic CPU and a deterministic and high performance multitasking real time kernel in hardware. The second implementation provides a deterministic and high performance standalone multitasking real time kernel in hardware and the last implementation provides a deterministic and high performance real time kernel for homogeneous and heterogeneous multiprocessor real-time systems View full abstract»

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  • ControlShell: component-based real-time programming

    Page(s): 54 - 55
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    Real-time system software is notoriously hard to share and reuse. The paper walks through the methodology and application of ControlShell, a component-based programming system real-time system software development. ControlShell combines graphical system-building tools, an execution-time configuration manager, a real-time matrix package, and an object name service into an integrated development environment. It targets complex systems that require on-line reconfiguration and strategic control. ControlShell takes advantage of functional object hierarchies to enable code sharing and reuse. It gains flexibility by supporting easy interconnectivity of these objects. It features a unique configuration control system for changing operating modes View full abstract»

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  • Real-time optimization at diamond interchanges

    Page(s): 250 - 255
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    Due to the complexity of road traffic movements occurring within urban interchanges and increasing levels of demand, many diamond interchanges on roads are experiencing serious congestion. The closely spaced traffic signals with high volume turning traffic create a complex control scenario. The diamond interchange offers the unique opportunity to integrate many innovative technologies into a system that is small enough to be manageable, yet complex enough to present a challenging control environment. Developing a real time, multi modal, traffic adaptive interchange control system is a research objective of the Intelligent Vehicle Highway System (IVHS) Research Center of Excellence Program of the Texas Transportation Institute. This research effort will integrate a variety of technologies into a single control system that will increase traffic performance and demonstrate IVHS concepts in advanced traffic management systems. Through the use of video imaging equipment, traffic information processing, and real time optimization and control, road users will experience less delay, less congestion and fewer safety problems at diamond interchanges View full abstract»

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  • Real-time UNIX application filestores

    Page(s): 44 - 45
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    From the inception of real-time computing, there has been concern about the performance of disk I/O, especially as it relates to application filestores such as those running under variants of the UNIX operating system. We present a brief discussion of UNIX filestores and show how one can easily bound the number of physical file I/Os that the UNIX operating system must perform to execute a given application process. Using the established bound for the number of physical disk I/Os, one can develop close analytical approximations of application processes elapsed running time which is of critical importance for real-time applications View full abstract»

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  • The real-time behavior of dynamic memory management in C++

    Page(s): 142 - 153
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    Dynamic memory management is an important aspect of modern software engineering techniques based on object-oriented methodologies. Additionally, dynamic management of memory serves important roles in improving the flexibility and functionality of large software systems. However, developers of current real-time systems avoid the use of dynamic memory because they fear that the worst-case time and space requirements of typical dynamic memory managers are insufficiently bounded. The degree to which these concerns are valid is quantified by detailed measurements of several real-world workloads. A special hardware-assisted real-time garbage collection system has been designed to facilitate reliable use of dynamic memory in hard real-time systems. By analyzing the dynamic memory use of application software, the real-time developer can prove compliance with time and space constraints. Analysis techniques are presented and the real-time performance of the hardware-assisted garbage collection system is compared to that of the traditional allocators View full abstract»

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  • An efficient implementation of the Hough transform for detecting vehicle license plates using DSP'S

    Page(s): 58 - 59
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    The paper addresses the general problem of the detection of vehicle license plates from road scenes, for the purpose of vehicle tracking. It describes an algorithm for detecting a license plate from a road scene acquired by a CCD camera, using image processing techniques, where the authors have used the Hough transform (HT) for line detection (the shape of the license plates is defined by lines) because it fits well into this application as it facilitates the selection of lines from specific areas and specific orientations within the image. This is followed by a brief description of the image processing system on which this algorithm has been implemented. Lastly, the results and conclusions of the application of the license plate detection algorithm to a real vehicle are discussed View full abstract»

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  • The real-time publisher/subscriber inter-process communication model for distributed real-time systems: design and implementation

    Page(s): 66 - 75
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    Distributed real-time systems are becoming more pervasive in many domains including process control, discrete manufacturing, defense systems, air traffic control, and online monitoring systems in medicine. The construction of such systems, however, is impeded by the lack of simple yet powerful programming models and the lack of efficient, scalable, dependable and analyzable interfaces and their implementations. We argue that these issues need to be resolved with powerful application-level toolkits similar to that provided by ISIS. We consider the inter-process communication requirements which form a fundamental block in the construction of distributed real-time systems. We propose the real-time publisher/subscriber model, a variation of group-based programming and anonymous communication techniques, as a model for distributed real-time inter-process communication which can address issues of programming ease, portability, scalability and analyzability. The model has been used successfully in building a software architecture for building upgradable real-time systems. We provide the programming interface, a detailed design and implementation details of this model along with some preliminary performance benchmarks. The results are encouraging in that the goals we seek look achievable View full abstract»

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  • A feasibility decision algorithm for rate monotonic scheduling of periodic real-time tasks

    Page(s): 212 - 218
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    The rate monotonic scheduling algorithm is a commonly used task scheduling algorithm for periodic real time task systems. The paper discusses feasibility decision for a given real time task system by the rate monotonic scheduling algorithm. It presents a new necessary and sufficient condition for a given task system to be feasible, and a new feasibility decision algorithm based on that condition. The time complexity of this algorithm depends solely on the number of tasks. This algorithm can be applied to the inverse deadline scheduling algorithm, which is an extension of the rate monotonic scheduling algorithm View full abstract»

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  • Efficient timing management for user-level real-time threads

    Page(s): 27 - 32
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    Timing management for user-level real-time threads can be done with appropriate support of the kernel. When a specified time comes, the kernel makes a virtual processor to upcall a user-level scheduler for its timing management. Then, the timing management can suffer from the overhead of a user-level scheduler. The paper presents an efficient timing management mechanism for user-level real-time threads. By sharing user-level timers through the shared kernel/user structure and keeping the appropriate hints for them, redundant processing of them and events can be eliminated. The results of the performance evaluations show that the upcall performance of our user-level real-time threads is comparable to and more stable than that of kernel-provided real-time threads View full abstract»

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  • Design and evaluation of a window-consistent replication service

    Page(s): 182 - 191
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    Real-time applications typically operate under strict timing and dependability constraints. Although traditional data replication protocols provide fault tolerance, real-time guarantees require bounded overhead for managing this redundancy. This paper presents the design and evaluation of a window-consistent primary-backup replication service that provides timely availability of the repository by relaxing the consistency of the replicated data. The service guarantees controlled inconsistency by scheduling update transmissions from the primary to the backup(s); this ensures that client applications interact with a window-consistent repository when a backup must supplant a failed primary. Experiments on our prototype implementation show that the service handles a range of client loads while maintaining bounds on temporal inconsistency View full abstract»

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  • Support for real-time computing within general purpose operating systems-supporting co-resident operating systems

    Page(s): 4 - 14
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    Distributed multimedia applications are typical of a new class of workstation applications that require real-time communication and computation services to be effective. Unfortunately, there remains a wide gap between the development of real-time computing technology in the research community and the deployment of real-time solutions in commercial systems. We explore technology for allowing two operating systems, a general purpose operating system and a predictable real-time kernel, to co-exist on the same hardware. We discuss the problems of multiplexing shared devices and partitioning shared data structures to accommodate two operating systems, and present a CPU executive that allows the IBM Microkernel (a derivative of the Mach microkernel) with an OSF/1 server to co-exist with a simple real-time kernel we have built. We also extend the traditional theory of scheduling periodic tasks on a uniprocessor to accommodate the case where a real-time kernel is allocated only a fraction of the total CPU capacity View full abstract»

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  • Non-preemptive scheduling of messages on controller area network for real-time control applications

    Page(s): 240 - 249
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    Scheduling messages on the controller area network (CAN) corresponds to assigning identifiers (IDs) to messages according to their priorities. If fixed priority scheduling such as deadline monotonic (DM) is used to calculate these priorities, then in general, it will result in low schedulability. Dynamic scheduling schemes such as earliest deadline (ED) can give greater schedulability, but they are not practical for CAN because if the ID is to reflect message deadlines then a long ID must be used. This increases the length of each message to the point that ED is no better than DM. Our solution to this problem is the mixed traffic scheduler (MTS), which is a cross between ED and DM, and provides high schedulability without needing long IDs. Through simulations, we compare the performance of MTS with that of DM and ED* (an imaginary scheduler which works like ED, except it needs only short IDs). We use a realistic workload in our simulations based on messages typically found in computer integrated manufacturing. Our simulations show that MTS performs much better than DM and at the same level as ED*, except under high loads and tight deadlines, when ED* is superior View full abstract»

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  • A new generation modechart verifier

    Page(s): 116 - 125
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    We have implemented a new-generation modechart verifier called vf3. The new verifier is capable of dealing with modecharts with arbitrary hierarchy. More importantly, it employs several novel strategies to effectively reduce the search space while speeding up the verification process. It represents the computation graph for a modechart in a more compact form called a `zone-based computation graph'. It uses on-the-fly deterministic pruning to reduce the outgoing edges from nodes in a graph. Finally, it builds on-the-fly a quotient graph based on a given real-time logic (RTL) formula. Our experimental results show that vf3 reduces the sizes of computation graphs by factors ranging from 2 to 10 View full abstract»

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  • Real-time communications scheduling for massively parallel processors

    Page(s): 76 - 85
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    Can general purpose commercial massively parallel processors (MPPs) be used for computationally intensive real-time applications that have traditionally required a custom arrangement of special-purpose computers and mainframes? If so, then the enormous lifecycle costs of many systems needed by, for instance, the Government could potentially be reduced. The components would be commercially available and continuing technological advances could more easily be incorporated into existing systems. Relevant applications have requirements not found in large-scale scientific computing, which has up to now provided most of the motivation for the development of MPPs. Perhaps the most important difference is the need for real-time processing. Depending on the application, multi-level security, fault tolerance and other features may also be necessary. There have already been hardware advances that may make such a high performance computing solution possible. However, daunting software challenges remain. We focus on one critical problem, the real-time scheduling of the communications between processing nodes. We discuss real-time MPP application benchmarks View full abstract»

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