distributed real time system

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A DDS/SDN Based Communication System for Efficient Support of Dynamic Distributed Real-Time Applications

A DDS/SDN Based Communication System for Efficient Support of Dynamic Distributed Real-Time Applications

introduce dynamicity in the data flows that are delivered/consumed by each simulator and on the QoS requirements related to the delivery of these data flows. The dynamic nature of these applications is one of the major challenges for the underlying communication system and in particular for the communication network that adds other challenges such as scalability and high QoS support. Indeed, if network resource utilization is a concern, the network must be flexible enough to be reprogrammed in accordance with any change in the application. Current approaches neither address the dynamicity of applications nor care about resource utilization. They are either based on static and overprovisioned dedicated networks or overlay networks (that are difficult to set up on demand and costly), or require from the application to adapt to network’s performance. The main reason is that current networks are rather static because of their complexity, the specificities of each network device, etc. An emerging class of communication networks named Software Defined Networks (SDN) have the ability to build flexible networks whose behavior can be programmed and reprogrammed on demand and in a fine grained manner. They are a promising answer to the efficient support of dynamic distributed real-time applications from a network resource utilization perspective
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Real time distributed shop floor scheduling using an agent-based service-oriented architecture

Real time distributed shop floor scheduling using an agent-based service-oriented architecture

2.1. Workcell Scheduling Problem In the workcell scheduling problem setting, workcells are implemented by FMS systems. Among many FMS scheduling models, we focus our attention on a class of problems in which machines have Partially Overlapping capabilities [Kamel and Ghenniwa, 1995]. As illustrated in Figure 2, a workcell consists of various types of resources, such as computer numerical controlled machines, automated guided vehicles (AGV) and a workpiece storage system. These resources are controlled by resource controllers and the whole workcell is controlled by a real time controller. An operator can program the processing of the workcell through the interaction with the real time controller. In this paper, we are interested in the impacts of partially overlapped characteristics of the workcell scheduling problem. We have simplified the workcell scheduling model by assuming that the transportation times of jobs between machines are equal and have been modeled in machine processing times. Therefore, there is no need to explicitly model the AGV. At the same time, storage and port are treated as independent resources, like machines.
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Real-Time Distributed Aircraft Simulation through HLA

Real-Time Distributed Aircraft Simulation through HLA

Ecole Polytechnique de Montr´eal Montr´eal,Canada Email: david.saussie@polymtl.ca Abstract—This paper presents some ongoing researches car- ried out in the context of the PRISE (Research Platform for Embedded Systems Engineering) Project. This platform has been designed to evaluate and validate new embedded system concepts and techniques through a special hardware and soft- ware environment. Since many actual embedded equipments are not available, their corresponding behavior is simulated using the HLA architecture, an IEEE standard for distributed simulation, and a Run-time infrastructure called CERTI and developed at ONERA. HLA is currently largely used in many simulation applications, but the limited performances of the RTIs raises doubts over the feasibility of HLA federations with real-time requirements. This paper addresses the problem of achieving real-time performances with HLA. Several experi- ments are discussed using well-known aircraft simulators such as the Microsoft Flight Simulator, FlightGear, and X-plane connected with the CERTI Run-time Infrastructure. The added value of these activities is to demonstrate that according to a set of innovative solutions, HLA is well suited to achieve hard real time constraints.
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Running real time distributed simulations under Linux and CERTI

Running real time distributed simulations under Linux and CERTI

All seems to be in a good real time programming. The experiments performed in this study showed that programming practices are also determining to take real time policies into account. For example programming changes in the protocol of exchanges between federates and RTI permitted to eliminate busy waiting loops in programs. By this way processors can be allocated to other federates that need them in order to progress. In other words, programmed mechanisms inside middleware have been devised to introduce some asynchronism in it. This asynchronism can permit to release processors and to allocate them to tasks that really need them. Moreover, experiments showed that system calls are costly. The cost comes from the overhead due to the system call itself. But while running a system call, a federate can reach a preemption point. At this point the kernel scheduler is invoked and the federate may lose its processor. So system calls must be used only when there is no mean to do otherwise, and in particular I/O system calls must be prohibited. The lesson here is that the algorithmic structure of programs has a great influence on the real time behaviour of federates.
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Real-time distributed simulations in an HLA framework: Application to aircraft simulation

Real-time distributed simulations in an HLA framework: Application to aircraft simulation

and Martin Adelantado 3 Abstract This paper presents some ongoing research carried out in the context of the PRISE Project (Research Platform for Embedded Systems Engineering). This platform has been designed to evaluate and validate new embedded system con- cepts and techniques through a special hardware and software environment. Since much actual embedded equipment is not available, corresponding behavior is simulated within a high-level architecture (HLA) federation implemented with a run-time infrastructure (RTI) called CERTI and developed at ONERA. HLA is currently largely used in many simulation applications, but the limited performances of the RTIs raise doubts over the feasibility of HLA federations with real-time requirements. This paper addresses the problem of achieving real-time performances with the HLA standard. Several experiments are discussed using well-known aircraft simulators such as Microsoft Flight Simulator, FlightGear, and X-plane connected with the CERTI RTI. The added value of these activities is to demonstrate that according to a set of innovative solutions, HLA architecture is well suited to achieve hard real-time constraints. Finally, a formal model guaran- teeing the schedulability of concurrent processes is also proposed.
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Flexible and Distributed Real-Time Control on a 4G Telecom MPSoC

Flexible and Distributed Real-Time Control on a 4G Telecom MPSoC

Traditional telecom chipset are designed with dedicated hardwired solutions which are cost-ineffective for multi- standard mobile handset. For more flexibility, MPSoCs (Mul- tiprocessor System-on-Chip) [3] with multiple programmable processors as system components have been introduced in the telecom field. MPSoCs are well suited for systems with concurrent algorithms like telecom applications. The imple- mentation of such algorithms on two heterogeneous SDR platforms [4] [5] has proven the efficiency of MPSoCs to provide a valuable solution. In the context of SDR platforms, the flexibility and reconfigurability is the key challenge. Ho- mogeneous MPSoCs, which are based on the replication of
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Model-Based Testing of Dynamic and Distributed Real-Time Systems

Model-Based Testing of Dynamic and Distributed Real-Time Systems

procedures, which focus on testing a system based on a small number of users. In fact, load testing is one of the testing types with high importance. It is usually accompanied by performance monitoring of the hosting environment. Typically, industry software testing practice is to separate load testing from functional testing. Different teams with different expertise and skills execute their testing at different times, and each team evaluates the results against its own criteria. It is exceptional to get the two testing types together and to evaluate load test results for functional correctness or incorporate sustained load in the functional testing. In this work, we propose a formal model-based framework to combine functional and load tests. Moreover, we study BPEL (Business Process Execution Language) compositions behaviors under various load conditions using the proposed framework.
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Model-based Synthesis of Distributed Real-time Automotive Architectures

Model-based Synthesis of Distributed Real-time Automotive Architectures

The concept of end-to-end deadline has been discussed in many research works. This applies both to single-processor and distributed architectures. In particular, for data-driven activation models end-to-end deadlines were considered in the context of schedulability analysis test such as holistic analysis with jitter propagation used in this work [34], or model with offsets as in [35]). Timing analysis techniques advanced significantly, considering new activation models, communication protocols or more expressive tasks representations (e.g. digraph model [41]). The optimization of deployment has not received comparable attention. [42] and [43] proposes a heuristics-based design optimization algorithm for mixed time-triggered and event-triggered systems. Its main assumption is that the nodes (in our case ECUs) are synchronized. An integrated framework for optimization is proposed in [44] for systems with periodic tasks on a network of processor nodes connected by a time-triggered bus. Authors use Simulated Annealing (SA) combined with geometric programming to hierarchically explore task allocation and assignment of tasks’ priority and period. In [45] the process of allocation of tasks and priority assignment targets the optimization of system flexibility, i.e. ability to adapt to changes which is important for real-time systems. The possible change this is introduction of new tasks into the system which obviously impacts the response-times of already deployed tasks. To solve the problem, just as in the previous work, authors are using simulated annealing. Work of Hamann et al. [46] optimizes multi-dimensional robustness criteria in a complex embedded system. Their approach is based on the stochastic multi-dimensional sensitivity analysis technique. Authors consider multiple problems affecting system performance such as changes in the execution times of tasks but also period speed-ups, etc. Azketa et al. [47] delivers an approach based on the genetic algorithms that optimizes the assignment of priorities to tasks and messages and then it maps them on the execution platform. Similarly allocation and scheduling decisions are being optimized in [48] and [49] under the real-time constraints. There are also approaches which consider only mono-processor architectures such as [50], [51] or [52] hence for all of them allocation is out of scope.
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Toward Real-time, Many-Task Applications on Large Distributed Systems

Toward Real-time, Many-Task Applications on Large Distributed Systems

Dedicated supercomputers can run real-time tasks, but volunteer computing could be an low-cost alternative if it could support real-time guarantees. In the domain of complex strategy games, Deep Blue [3] was the first machine defeat the human world champion in 1996. IBM developed a dedicated server system for Deep Blue, and the server achieved about 11.38 GFLOPS on the LINPACK benchmark. Since 2006, several researchers in the world have been developed MoGo, which is software to find the next move in the game of Go. They adapted Monte-Carlo-based algorithms, and now, they are as strong as the professional Go players in the 9 × 9 small board based on the cluster computing machines[2]. Grid gaming middleware [11] have been developed and address issues such as adaptive redirection of communication or computation given variable load. They also address issues such as high-level easy-to-use programming interfaces, and monitoring tools for capacity planning. We believe our work on giving worst-case bounds on execution time is complementary with those methods. For example, our techniques guarantee performance given that the data can be store entirely in the server’s memory; this in turn could be used with capacity planning tools to determine when to replicate a server.
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How to solve ODEs in real-time HLA distributed simulation

How to solve ODEs in real-time HLA distributed simulation

solutions used by S IMULINK when a global solving is not possible. 5. Formalization and Application 5.1 Discussion Through this non exhaustive list of simple examples, we raised the issue of direct feedthrough within HLA federations. If this problem is not taken into account, it usually introduces delays between federate models (state and output equation calculations). Obviously, this put into question the validity of the global simulation semantics and, depending on the size of the simulation step, this can have a significant impact on the overall system response. For example, suppose 50 federates involved in a communication sequence (as depicted in Figure 2) where each one is related with the previous by a direct feedthrough relation. If we do not care of direct feedthrough, the 50 th federate will receive its input value with a delay of 49 time units, whereas it should have received it during its first cycle. For sure, this example is a little exaggerated but it illustrates quite well the issue introduced by the presence of direct feedthrough, and why, one should apply the proper functional scheduling strategy. To resume, there are three main cases to consider:
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Real-Time Fair Resource Allocation in Distributed Software Defined Networks

Real-Time Fair Resource Allocation in Distributed Software Defined Networks

In this paper, we study the problem of nding a global fair resource allocation when the control plane is distributed over several domain controllers. More specically, we consider the case where the size of ows evolves over time and bandwidth allocations have to be quickly adjusted towards the novel fair solution (in the sense of α-fairness dened by Mo et al. in [13]). In distributed SDN architectures, controllers operate with full information in their domain and communicate (e.g., system states or optimization variables) with adjacent domain controllers or a central gathering entity. Exchanges between controllers are expensive in terms of communication delay and overhead. In this setting, a distributed algorithm may not have enough time to converge to optimum before it has to provide a feasible answer due to the scale of networks. Therefore, the main challenge is to produce very quickly good quality feasible solutions. Local mechanisms such as Auto-Bandwidth [15] have been proposed to greedily and distributedly adjust the allocated bandwidth to support time-varying IP trac in Multi Protocol Label Switching (MPLS) networks. However, they do not ensure fairness and do not optimize resources globally. On the other hand, centralized algorithms have been proposed to solve the problem but fail at quickly providing good and feasible solution in a distributed setting [12].
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Distributed Simulation of Heterogeneous and Real-time Systems

Distributed Simulation of Heterogeneous and Real-time Systems

The process of integrating components and evaluating their interaction with the target architecture requires knowl- edge of several domains (e.g. hardware, software) that are typically described in heterogeneous models (e.g. continuous models, discrete models, timed properties). Analyzing worst case execution times is insufficient in order to validate the system. Formal analysis cannot usually handle systems of that complexity. As a result, simulations are performed to analyze the functional behaviour of high level specifications mixed with more low level elements. Imagine, for instance, a flight control composed of two sub-functions distributed on two calculators communicating via an Ethernet network. To observe the real behavior on the platform, it is necessary to describe the functional behavior of each component as well as the timing of the network that communicates the data between the two sub-functions.
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Real-time distributed systems dimensioning and validation: The TURTLE method

Real-time distributed systems dimensioning and validation: The TURTLE method

{Ahlem.Mifdaoui, pdss}@isae.fr RÉSUMÉ. A d ˝ Ofinir par la commande \resume{...} ABSTRACT. The TURTLE language and toolkit offer a UML framework for service descrip- tion, protocol modeling and communication architecture validation. The method associated with TURTLE uses an architectural design pattern where two or several protocol entities rely on a pre-existing communication service. Modeling the pre-existing service with empirical val- ues is error-prone and hampers large space exploration during the communication architecture validation. The paper relies on the Network Calculus theory to parameterizes the service with realistic upper bounds. The revisited TURTLE method includes a dimensioning step between the requirement and analysis steps. This new step is based on a "Dimensioning Diagram" that de- scribes the network in terms of traffic and equipments behavior, and a "Dimensioning-oriented Use Case Diagram" that categorizes the flows conveyed by the network. The paper applies this method to a video conference system as example.
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Ensuring Timed Validity of Distributed Real Time Data

Ensuring Timed Validity of Distributed Real Time Data

8. Conclusion We proposed an approach focused on variables instead of task and process to model and analyse distributed real time systems. Based on the state transition system semantics extended by a timed ref- erential, we express timed properties of variables, and of communications. These properties are used to check the freshness of values, their stability and the compatibility of requirements. The analysis is done using propositions to derive simple proof or in more complex case using model checking. The complexity of model checking is a problem when analysing large systems so we work on combining proofs, to reduce the problem size, and model checking, to easily analyse simple models. For that purpose we will extend the number of properties and of proved propositions binding these properties.
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Proving Determinacy of the PharOS Real-Time Operating System

Proving Determinacy of the PharOS Real-Time Operating System

2.2 The TLA + Specification Language TLA + [6] is a formal specification language that is mainly intended for model- ing concurrent and distributed algorithms and systems, and that has successfully been used in academic and industrial environments [3, 7, 13]. It is based on un- typed Zermelo-Fraenkel set theory for modeling the data manipulated by the system, and on the Temporal Logic of Actions, a variant of linear-time temporal logic, for describing executions. Formulas of temporal logic serve for specifying system behavior as well as properties of systems. Systems are modeled as state machines. In particular, the system state is represented by a tuple of variables. State predicates (i.e., first-order formulas containing state variables) represent sets of system states, such as the initial condition or system invariants. Tran- sition predicates, also called actions, are first-order formulas that contain both ordinary (unprimed) and primed occurrences of state variables; they describe state transitions where unprimed variables denote the value in the first state and primed variables denote the value in the second state. For example, x 0 = x − y 0 is true of any pair hs, t i of states such that the value of x in state t equals the difference between the values of x in state s and y in state t . The canonical form of the safety part of a system specification in TLA + is a temporal formula of the form
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The real time product quality intelligent forecasting and analysis system

The real time product quality intelligent forecasting and analysis system

The thesis, combining the method of neural network and other systems, develops product quality online forecasting and analysis systems of fluidized catalytic cracking uni[r]

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Time-Resolved Fluorescence Measurement System for real-Time high-Throughput Microfluidic Droplet Sorting

Time-Resolved Fluorescence Measurement System for real-Time high-Throughput Microfluidic Droplet Sorting

(FLT) measurement system for real-time microfluidic droplet sorting in high throughput conditions. This system is implemented using a low cost System-on-Chip (SoC) Field- Programmable Gate Array (FPGA) platform, that combines a Cyclone V FPGA with a dual-core ARM Cortex-a9 Hard Processor System (HPS). A time-correlated single photon counting system is implemented in the FPGA part and the data are transferred to the SDRAM of the HPS part to be processed by a developed bare-metal C program to extract the FLT of each droplet passing through the detection spot. According to the droplet’s measured FLT, an action could be taken to sort this droplet. The system automatically detects the droplets and extracts their FLT values at different simulated droplet flow rates; from a few droplets up to 1 thousand droplets per second. Thanks to the use of a maximum Likelihood-based algorithm, the standard deviation of the measured FLTs of simulated droplets of the same material is only 30% above the theoretical quantum photon shot noise limit.
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Privacy Protection in Real Time HEVC Standard Using Chaotic System

Privacy Protection in Real Time HEVC Standard Using Chaotic System

Received: 26 April 2020; Accepted: 18 June 2020; Published: 24 June 2020    Abstract: Video protection and access control have gathered steam over recent years. However, the most common methods encrypt the whole video bit stream as unique data without taking into account the structure of the compressed video. These full encryption solutions are time and power consuming and, thus, are not aligned with the real-time applications. In this paper, we propose a Selective Encryption (SE) solution for Region of Interest (ROI) security based on the tile concept in High Efficiency Video Coding (HEVC) standards and selective encryption of all sensitive parts in videos. The SE solution depends on a chaos-based stream cipher that encrypts a set of HEVC syntax elements normatively, that is, the bit stream can be decoded with a standard HEVC decoder, and a secret key is only required for ROI decryption. The proposed ROI encryption solution relies on the independent tile concept in HEVC that splits the video frame into independent rectangular areas. Tiles are used to pull out the ROI from the background and only the tiles figuring the ROI are encrypted. In inter coding, the independence of tiles is guaranteed by limiting the motion vectors of non-ROI to use only the unencrypted tiles in the reference frames. Experimental results have shown that the encryption solution performs secure video encryption in a real time context, with a diminutive bit rate and complexity overheads.
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Designing real-time dependable distributed systems

Designing real-time dependable distributed systems

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignemen[r]

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A real time vision system for robotic arc welding

A real time vision system for robotic arc welding

/ La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur. Access and use of [r]

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