The design, implementation, and evaluation of a distributedreal-time architecture called HARTS (hexagonal architecture for real-timesystems) are discussed, emphasizing its support of time-constrained, fault-tolerant...
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The design, implementation, and evaluation of a distributedreal-time architecture called HARTS (hexagonal architecture for real-timesystems) are discussed, emphasizing its support of time-constrained, fault-tolerant communications and I/O (input/output) requirements. HARTS consists of shared-memory multiprocessor nodes, interconnected by a wrapped hexagonal mesh. This architecture is intended to meet three main requirements of real-time computing: high performance, high reliability, and extensive I/O. The high-level and low-level architecture is described. The evaluation of HARTS, using modeling and simulation with actual parameters derived from its implementation, is reported. Fault-tolerant routing, clock synchronization and the I/O architecture are examined
This paper presents an integrated approach for specification and design of software for distributed hard real-timesystems. The approach adopts a graph-based model, combined with a pre-run-time scheduling. This gives ...
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This paper addresses issues related to transfer protocols of distributed RT-UNIX automation systems. The wide-scale application possibilities of ATM have been considered in order to generate ideas for an improved tran...
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This paper addresses issues related to transfer protocols of distributed RT-UNIX automation systems. The wide-scale application possibilities of ATM have been considered in order to generate ideas for an improved transfer protocol and to embed it into the operating system. A proposal to transform an existing RT-UNIX operating system (QNX 4.2) in order to provide ATM features is described and analyzed. For the analysis, prototyping models of the operating system, the net adapter, net driver and the net manager have been developed. Remote interprocess communication can be simulated and analyzed, to see whether the imposed timing constraints are fulfilled. Some case-studies of simulations have shown that the approach represents a powerful and expressive instrument for the remote interprocess communication in distributedreal-time automation systems.
Replicated data consistency is a key issue in the design of distributedrealtime groupware applications, In this paper, we propose a new protocol to cope with this problem. The proposed algorithm guarantees an optima...
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Replicated data consistency is a key issue in the design of distributedrealtime groupware applications, In this paper, we propose a new protocol to cope with this problem. The proposed algorithm guarantees an optimal response time while ensuring data consistency at system quiescence. The originality of our proposition relies on the fact that neither locks nor clocks nor global information are required to establish data consistency. Instead, direct dependency relations between generated operations as well as operation transformation mechanism are used. The coupling of the above two mentioned mechanisms is shown to realize a good trade-off between the different requirements of groupware applications. Advantages of our approach are illustrated by comparing the algorithm to two well known optimistic concurrency control protocols for groupware applications: dOPT and ORESTE.
The automation of today's large-scale industrial systems relies on the operation of distributed controller devices that perform local computations and exchange information via communication networks. The subject o...
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The automation of today's large-scale industrial systems relies on the operation of distributed controller devices that perform local computations and exchange information via communication networks. The subject of this paper is the development of a family of shared-medium industrial communication protocols that support the transmission of real-time (RT) and nonreal-time (nRT) data among distributed controller devices. Different from existing protocols, we suggest to incorporate information that is available from the control application in the protocol definition. As a result, our protocols dynamically change the bandwidth allocation on the shared medium according to the instantaneous communication requirements while ensuring hard RT guarantees. Following the recent developments in industrial automation, our protocols can be realized as software layers on top of low-cost conventional Ethernet.
Formation flying synthetic aperture radar (FF-SAR) systems, as an important development direction of multichannel SAR, can achieve high-resolution wide-swath imaging. Coherently combining data from satellite receivers...
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Formation flying synthetic aperture radar (FF-SAR) systems, as an important development direction of multichannel SAR, can achieve high-resolution wide-swath imaging. Coherently combining data from satellite receivers puts a strain on the traditional real-time processing systems based on individual satellites. Characteristics, such as the power of real-time on-orbit processing platform, must be properly balanced with constrained memory and parallel computational resources. This article proposes a distributed SAR real-time imaging method based on the embedded graphics processing units (GPUs). The parallel computing method of the chirp scaling algorithm is designed based on the parallel programming model of compute unified device architecture, and the optimization methods of memory and performance are proposed for the hardware architecture of embedded GPUs. In particular, the unified memory management method is used to avoid data copying and communication delays between the CPU and GPU. A hardware verification system for distributed SAR real-time imaging processing based on multiple embedded GPUs is constructed. The proposed algorithm takes 5.86 s to process single-precision floating-point complex imaging with a data size of 8192 x 8192 on a single Jetson Nano platform. The actual power consumption is less than 5 W, and the performance-to-power ratio is greater than 1.7%. The experimental results show that the real-time processing method based on the embedded GPUs proposed in this article has high performance and low-power consumption.
This paper presents a novel technique for establishing a highly accurate global time in fault-tolerant, large-scale distributedreal-timesystems. Unlike the usual clock synchronization approaches, the proposed clock ...
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This paper presents a novel technique for establishing a highly accurate global time in fault-tolerant, large-scale distributedreal-timesystems. Unlike the usual clock synchronization approaches, the proposed clock validation technique provides a precise system time that also relates to an external time standard like UTC with high accuracy. The underlying idea is to validate time information of external time sources like GPS-receivers against a global time maintained by the local clocks in the system. As an example, a promising interval-based clock validation algorithm ICV that exhibits excellent fault-tolerance properties is outlined and analyzed. It requires only a few highly accurate external time sources and provides each node with the actual accuracy of its clock.
In a real-time database system, an application supports a mix of transactions. These include the real-time transactions that require completion by a given deadline. time-critical requirements also exist in many distri...
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In a real-time database system, an application supports a mix of transactions. These include the real-time transactions that require completion by a given deadline. time-critical requirements also exist in many distributed multi-media system applications. Existing concurrency control procedures introduce excessive delays due to non-availability of data resources. In this study, we ignore the delays incurred by ordinary transactions, in order to achieve a non-interference mode of execution (near parallel) for the time-critical transactions. For this purpose, a data allocation model has been studied. It is a stochastic process model based on the use of two-phase locking. It highlights the available possibilities for reductions of delays for time-critical transactions within a distributedreal-time database systems. Based on the new conceptual model, modified synchronization techniques for time-critical transactions have been proposed.
This paper presents a survey of results in developing real-time CORBA, a standard for rear-time management of distributed objects. This paper includes background on two areas that have been combined to realize Rear-Ti...
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This paper presents a survey of results in developing real-time CORBA, a standard for rear-time management of distributed objects. This paper includes background on two areas that have been combined to realize Rear-time CORBA: the CORBA standards that have been produced by the international Object Management Group;and techniques for distributedreal-time computing that have been produced in the research community. The survey describes major RT CORBA research efforts, commercial development efforts, and standardization efforts by the Object Management Group.
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