Distributed Real Time Systems

Front Distribution Centre (FDC) is a new terminal warehouse which is closer to customers, with its location selection being crucial for e-commerce and customer time satisfaction. We introduce in this paper a joint distribution function of demand based on time and space, which constructs two spatio-time models: spatio-time clustering model and spatio-time optimisation model. A staged clustering algorithm is designed to obtain the candidate FDCs, and an intelligent algorithm based on NSGA-II (Non-dominated Sorting Genetic Algorithm II) is applied to determine the final FDCs, in which the location selection problem is formulated as a bi-objective programming model to minimise total costs and maximise customer time satisfaction. Our results indicate that the model considering spatio-temporal joint attribute of demand performs better than the traditional spatial model. Furthermore, when compared with the k-means clustering algorithm, Multi-Objective Evolutionary Algorithm based on Decomposition (MOEA/D) and its improved algorithm Multi-Objective Evolutionary Algorithm based on the Adaptive Neighborhood Adjustment strategy (MOEA/D-ANA), Multi-Objective Particle Swarm Optimisation" (MOPSO) and its enhancing algorithm Competitive Multi-Objective Particle Swarm Optimiser (CMOPSO), the solving method based on staged clustering and NSGA-II absolutely performs more stable and can get a greater number of pareto-optimal solutions with higher qualities. Especially when compared with K-means clustering algorithms, it can reduce total costs by up to 38.84% and improve customer time satisfaction by up to 36.22%.

We propose static task allocation algorithms for the periodic tasks of a distributed real-time system. The cyclic task consists of task threads which may communicate and share resources. A graph partitioning process and a thread sequencing algorithm are applied to these threads to yield local schedules. The exact analysis is then obtained and further refinements are performed if the worst case response time of a task is greater than its deadline.

For testing of sequential software it is usually sufficient to provide the same input (and program state) in order to reproduce the output. For real-time systems, on the other hand, we need also to control, or observe, the timing and order of the inputs. If the system additionally is multitasking, we also need to take timing and the concurrency of the executing tasks into account. In this paper we present a method for deterministic testing of multitasking real-time systems, which allows explorative investigations of real-time system behavior. The method includes an analysis technique that given a set of tasks and a schedule derives all execution orderings that can occur during run-time. These orderings correspond to the possible interleavings of the executing tasks. The method also includes a testing strategy that using the derived execution orderings can achieve deterministic, and even reproducible, testing of real-time systems. Since, each execution ordering can be regarded as a sequential program, it becomes possible to use techniques for testing of sequential software in testing multi-tasking real-time system software. We also show how this analysis and testing strategy can be extended to encompass distributed computations, communication latencies and the effects of global clock synchronization. The number of execution orderings is an objective measure of the testability of a system since it indicates how many behaviors the system can exhibit during runtime. In the pursuit of finding errors we must thus cover all these execution orderings. The fewer the orderings the better the testability.

Industrial revolution is advancing, and the augmented role of autonomous technology and embedded Internet of Things (IoT) systems is at its vanguard. In autonomous technology, real-time systems and real-time computing are of core importance. It is crucial for embedded IoT devices to respond in real-time; along with fulfilling all the constraints. Many combinations for existing approaches have been proposed with different trade-offs between the resources constraints and tasks dropping rate. Hence, it highlights the significance of a task scheduler which not only takes care of complex nature task input; but also maximizes the CPU throughput. A complex nature task input is when combinations of hard real-time tasks and soft real-time tasks, with different priorities and urgency measures, arrive at the scheduler. In this work, we propose a custom tailored adaptive and intelligent scheduling algorithm for the efficient execution and management of hard and soft real time tasks in embedded ...

Industrial revolution is advancing, and the augmented role of autonomous technology and embedded Internet of Things (IoT) systems is at its vanguard. In autonomous technology, real-time systems and real-time computing are of core importance. It is crucial for embedded IoT devices to respond in real-time; along with fulfilling all the constraints. Many combinations for existing approaches have been proposed with different trade-offs between the resources constraints and tasks dropping rate. Hence, it highlights the significance of a task scheduler which not only takes care of complex nature task input; but also maximizes the CPU throughput. A complex nature task input is when combinations of hard real-time tasks and soft real-time tasks, with different priorities and urgency measures, arrive at the scheduler. In this work, we propose a custom tailored adaptive and intelligent scheduling algorithm for the efficient execution and management of hard and soft real time tasks in embedded ...

Real-time embedded systems have evolved during the past several decades from small customdesigned digital hardware to large distributed processing systems. As these systems become more complex, their interoperability, evolvability and cost-effectiveness requirements motivate the use of commercial-off-theshelf components. This raises the challenge of constructing dependable and predictable real-time services for application developers on top of the inexpensive hardware and software components which has minimal support for timeliness and dependability guarantees. We are addressing this challenge in the ARMADA project. ARMADA is set of communication and middleware services that provide support for fault-tolerance and end-toend guarantees for embedded real-time distributed applications. Since real-time performance of such applications depends heavily on the communication subsystem, the first thrust of the project is to develop a predictable communication service and architecture to ensure QoS-sensitive message delivery. Fault-tolerance is of paramount importance to embedded safety-critical systems. In its second thrust, ARMADA aims to offload the complexity of developing fault-tolerant applications from the application programmer by focusing on a collection of modular, composable middleware for fault-tolerant group communication and replication under timing constraints. Finally, we develop tools for testing and validating the behavior of our services. We give an overview of the ARMADA project, describing the architecture and presenting its implementation status.

In this work, we are interested in testing dynamic distributed information systems. That is we consider a decentralized information system which can evolve over time. For this purpose we propose a runtime standard-based test execution platform. The latter is built upon the normalized TTCN-3 specification and implementation testing language. The proposed platform ensures execution of tests cases at runtime. Moreover it considers both structural and behavioral adaptations of the system under test. In addition, it is equipped with a test isolation layer that minimizes the risk of interference between business and testing processes. The platform also generates a minimal subset of test scenarios to execute after each adaptation. Finally, it proposes an optimal strategy to place the TTCN-3 test components among the system execution nodes.

The IEEE 802.11 Wireless LAN standard is one of the most popular wireless standards in the market today. Since 1997 when the first version of the IEEE 802.11 was launched in the market, a lot of different versions has been announced and developed. In this paper, a comprehensive evaluation analysis of the IEEE 802.11b and IEEE 802.11g has been carried out, examining the performance of both standards at the MAC sub-layer, in terms of QoS, using two different simulation tools. Finally, the comparison for both cases is discussed.

The Wireless Sensor Networks (WSNs) have limited power and communication capabilities, combined with the requirement for long network lifetime. To increase it, methods to reduce energy consumption are highly required. To achieve this goal, we study a data aggregation technique without size reduction, i.e. data merge. It is a generic technique, since it is also usable in applications with heterogeneous data and requirements for high accuracy. This study presents the impact of the data merge technique on WSNs applications executed under various realistic data flow scenarios, traffic loads and wait time intervals. Our results show significant reductions in both packet loss and radio energy consumption.

Coordinated behavior of mobile robots is an important emerging application area. Different coordinated behaviors can be achieved by assigning sets of control tasks, or strategies, to robots in a team. These control tasks must be scheduled either locally on the robot or distributed across the team. An application may have many control strategies to dynamically choose from, although some may not be feasible, given limited resource and time availability. Thus, dynamic feasibility checking becomes important as the coordination between robots and the tasks that need to be performed evolves with time. This paper presents an on-line algorithm for finding a feasible strategy given a functionally equivalent set of strategies for achieving an application's goals. We present two algorithms for feasibility improvement. Both consider communication cost and utilization bound to make resource allocation and scheduling decisions. Extensive experimental results show the effectiveness of the approaches, especially in resource-tight environments. We also demonstrate the application of our approach to real world scenarios involving teams of robots and show how feasibility analysis also allows the prediction of the scalability of the solution to large robot teams.

Coordinated behavior of mobile robots is an important emerging application area. Different coordinated behaviors can be achieved by assigning sets of control tasks, or strategies, to robots in a team. These control tasks must be scheduled either locally on the robot or distributed across the team. An application may have many control strategies to dynamically choose from, although some may not be feasible, given limited resource and time availability. Thus, dynamic feasibility checking becomes important as the coordination between robots and the tasks that need to be performed evolves with time. This paper presents an online algorithm for finding a feasible strategy given a functionally equivalent set of strategies for achieving an application's goals. We present two heuristics for feasibility checking. Both consider communication cost and utilization bound to make allocation (of tasks to execution sites) and scheduling decisions. Extensive experimental results show the effectiveness of the approaches, especially in resource-tight environments. We also demonstrate the application of our approach to real-world scenarios involving teams of robots and show how feasibility analysis also allows the prediction of the scalability of the solution to large robot teams.

In this work, we are interested in formal Model-Based Testing for Real-Time Systems. The proposed approach is based on the use of the model of Timed Automata with continuous clocks for which we adopt the reset-point semantics. We remind the definition of timed conformance relation tioco. We extend the notion of soundness and completeness of test suites. We also consider specifications in form of one-clock input-complete timed automata. Moreover, we provide interesting decidability results for the considered classes of specifications. More specifically, we consider the case when some parameters of the timed-automaton tester are fixed in advance, namely the number of clocks of the timed-automaton and its maximal time-constraint constants. Finally, several possible extensions of the present work in different directions are proposed.

A method has been recently proposed for coordinating the testers that constitute a distributed test system. In the present article, we introduce the test method and then we explain how we can guarantee complete executability of test sequences by strengthening ...

Investigations into deadline guarantees in real-time systems have traditionally been dominated by scheduling using static and analytical approaches. This framework has been successfully applied to a wide range of applications. However, many realworld applications are too complex for such analysis and cannot be subject to absolute guarantees. Rigid analytical approaches are not practical when confronted with the degree of complexity and degrees of freedom of real software systems in use. In this paper we propose and employ a novel modeling technique based on Universal Basis Functions (UBF) to give probabilistic estimates of a system holding its deadlines (responsiveness). The algorithm is non-parametric and data driven rather than analytical. It builds a model of the system based on observations of system variables. We first show the practicality of our learning algorithm by modeling responsiveness of a simulated queuing system and by predicting CPU demand of the Baum-Welch algorithm based on its parametrization. We derive precise models to predict resource demand a-priori and give accurate responsiveness estimates for the queuing system. We then apply our modeling technique to real data of a commercial telecommunication platform. Deadlines in this system are introduced as serving incoming calls within a prespecified time frame. The data investigated includes time-continuously measured system states. We build probabilistic models and derive conditional probabilities of calls being processed within their prespecified deadline for given time intervals. Results are presented in terms of responsiveness, precision, recall and F-Measure. The models and results have been validated on synthetic as well as on a distributed real-world computing system. Our findings suggest significantly improved forecasting of timeliness compared to alternative approaches.

We propose a formal framework for black-box conformance testing for distributed real-time systems. Our framework is based on the model of partially-observable, non-deterministic timed automata. A given distributed system can be modeled either as a single timed automaton or a network of timed automata. We recall the definiton of the timed input-output conformance relation tioco. We consider two types of tests: analog-clock tests and digital-clock tests. Our algorithm for generating analog-clock tests is based on an on-the-fly determinization of the specification automaton during the execution of the test, which in turn relies on reachability computations. We also provide algorithms for static or on-the-fly generation of digital-clock tests. These tests measure time only with finite-precision digital clocks. Our testing architecture may be either centralized or not.

This paper describes ongoing investigations into algorithms for user-centric modular distributed real-time resource management. These investigations are being conducted in the context of the Rialto operating system - an object-based real-time kernel and programming environment currently being developed within Microsoft Research. A primary goal of this research is to develop appropriate real-time programming abstractions to allow multiple independent real-time programs

This paper describes ongoing investigations into algorithms for user-centric modular distributed real-time resource management. These investigations are being conducted in the context of the Rialto operating system -an object-based real-time kernel and programming environment currently being developed within Microsoft Research.

This paper describes ongoing investigations into algorithms for user-centric modular distributed real-time resource management. These investigations are being conducted in the context of the Rialto operating system -an object-based real-time kernel and programming environment currently being developed within Microsoft Research.

Workstations and personal computers are increasingly being used for applications with real-time characteristics such as speech understanding and synthesis, media computations and I/O, and animation, often concurrently executed with traditional nonreal-time workloads. This paper presents a system that can schedule multiple independent activities so that:

The goal of the Rialto project at Microsoft Research is to build a system architecture supporting coexisting independent real-time (and non-real-time) programs. Unlike traditional embedded-systems real-time environments, where timing and resource analysis among competing tasks can be done off-line, it is our goal to allow multiple independently authored real-time applications with varying timing and resource requirements to dynamically coexist and cooperate to share the limited physical resources available to them, as well as also coexisting with nonreal-time applications.

This paper describes ongoing investigations into algorithms for user-centric modular distributed real-time resource management. These investigations are being conducted in the context of the Rialto operating system — an object-based real-time kernel and programming environment currently being developed within Microsoft Research. A primary goal of this research is to develop appropriate real-time programming abstractions to allow multiple independent real-time programs to dynamically coexist and share resources on the same hardware platforms. Use of these abstractions is intended both to allow individual applications to reason about their own resource requirements and for per-machine system resource planner applications to reason about and control resource allocations between potentially competing applications. The set of resources being managed is dynamically extensible, and may include remote resources in distributed environments. The local planner conducts resource negotiations with individual applications on behalf of the user, with the goal of maximizing the user's perceived utility of the set of running applications with respect to resource allocations for those applications.

Workstations and personal computers are increasingly being used for applications with real-time characteristics such as speech understanding and synthesis, media computations and I/O, and animation, often concurrently executed with traditional nonreal-time workloads. This paper presents a system that can schedule multiple independent activities so that:

Workstations and personal computers are increasingly being used for applications with real-time characteristics such as speech understanding and synthesis, media computations and I/O, and animation, often concurrently executed with traditional nonreal-time workloads. This paper presents a system that can schedule multiple independent activities so that:

Workstations and personal computers are increasingly being used for applications with real-time characteristics such as speech understanding and synthesis, media computations and I/O, and animation, often concurrently executed with traditional nonreal-time workloads. This paper presents a system that can schedule multiple independent activities so that:

Workstations and personal computers are increasingly being used for applications with real-time characteristics such as speech understanding and synthesis, media computations and I/O, and animation, often concurrently executed with traditional nonreal-time workloads. This paper presents a system that can schedule multiple independent activities so that: