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Electronic learning has produced a comfortable, sophisticated, interactive and adaptable teaching model. Moreover, the consistent technical progress in this field allows the development of increasingly interesting applications [1]. We chose to select those elements to create an e-learning environment. This paper presents a model of the multi-tiered e-learning system based on Web Services. It shows...
Current computer networks are challenged by the overwhelming multiplication of available content and the increasing requirements of the content delivery applications. Content caching is already playing its role in content delivery solutions. In this paper we identify the parameters and conditions that affect the performance of content caching solutions and the quality of the related multimedia services...
In this paper, we introduce the implementation ofthe Sporadic Server algorithm at the user level in Real TimeJava. That is, we do not modify the specification of the JavaVirtual Machine (JVM) so our proposal runs without problemson every JVM with support for real-time scheduling. The paperin- cludes an experimental evaluation of the aperiodic handlingmechanism using as benchmark the one developed...
A simple implementation for OPC XML-DA has been achieved by the traditional XML-DA server. However, little has been attracted to the design and improvement of the capability. An OPC-XML DA server system of high performance is designed in this paper. We use .net asynchronous framework to design asynchronous subscription mechanism which is based on the Comet. New caching mechanism is designed by non-relational...
In this paper, we study the algorithms to estimate the response times of service executions during real-time service composition. By using reservation schedules to derive server utilization, we can compute a more realistic response time for each service than its static execution time. Reservation schedules are kept in a system data structure called hierarchical TBTree (hTBTree). Using these response...
In this paper we focus on how Quality of Service guarantees are provided to virtualised applications in the Cloud Computing infrastructure that is being developed in the context of the IRMOS European Project. Provisioning of proper timeliness guarantees to distributed real-time applications involves the careful use of real-time scheduling mechanisms at the virtual-machine hypervisor level, of QoS-aware...
Service-oriented communication is a new trend in the industry, which opens a new paradigm of Web service based VoIP communication and can be easily integrated in end-to-end SOA solutions. In this paper, we proposed the service building block based multimedia conferencing Web service over IP networks, and mainly focus on the design and implementation of the multimedia conferencing service entities,...
Multiple servers as a mechanism for scheduling aperiodic tasks in heterogeneous environments can increase performance of real time systems. This paper describes implementation of the multiple total bandwidth server (MTBS) mechanism, a version of total bandwidth server (TBS) for distributed systems, in a simulation tool. The tool enables evaluation of the mechanism performance for arbitrary task sets...
Virtualization provides an excellent solution to resolve the portability, maintainability, development, and utilization problems in many system designs. In this paper, we are interested in energy-efficient designs for platform virtualization. In particular, we explore the computing resource mapping and the energy consumption relationship between virtual cores and physical cores when timing constraints...
Real-time performance is one of the most essential requirements in the field of Real-Time Operating System (RTOS). Meeting deadlines of the periodic tasks and optimizing response time of non-periodic tasks both are important reflections of high real-time performance. This paper analyzes the deficiency at real-time and schedulable performance of AUTOSAR Operating System (AUTOSAR OS) version 3.1.1....
In previous work we motivated the need for using the OSGi Framework with the RTSJ to develop real-time systems. We found a number of issues with using these technologies together. One of the issues we discovered was unbounded dynamism caused by the absence of admission control. Components can be uninstalled, installed and updated without regulation. This means that it is impossible to guarantee resources...
We propose two complementary methods to account for scheduler overhead in the schedulability analysis of Variable Bandwidth Servers (VBS), which control process execution speed by allocating variable CPU bandwidth to processes. Scheduler overhead in VBS may be accounted for either by decreasing process execution speed to maintain CPU utilization (called response accounting), or by increasing CPU utilization...
This paper aims to present a two phase scheduling algorithm that offers lesser energy consumption for real time systems modeled periodic as well as aperiodic tasks by utilizing the concept of dynamic voltage scaling and dynamic power down. The first phase is same as used in Sim et al. whereas, second phase has been modified by utilizing the concept of idle slot, available slack and power down in case...
This paper presents a preemption control based bandwidth preserving server approach to improve the quality of service in terms of better responsiveness to the aperiodic task and reduce their rejection ratio while ensuring the feasibility of periodic task at the same time. Feasibility analysis is done at offline by assigning the priority of periodic tasks as well as server to service the aperiodic...
Responsive Link, an ISO/IEC communication standard, provides many functional capabilities for distributed realtime systems. This paper is focused on periodic and aperiodic communication techniques for Responsive Link. In periodic communication, the priority is assigned to each packet so that the network utilization is improved. A schedulability test for connection establishments is also derived to...
Hierarchical scheduling has recently been used to provide temporal isolation to embedded virtualised systems. Response time analysis is a common way to derive a schedulability test for these systems. This paper points out that response time analysis for hierarchical fixed-priority scheduling found in the literature is only exact for tasks of the highest priority domain. For the rest of the tasks is...
On-line task scheduling is a very challenging issue for dual-core real-time embedded systems, because to control priority inversion and to manage system utilization are fundamentally at odds with each other. We propose an on-line dual-core scheduling framework for dynamic workloads with real-time constraints. The processor and the co-processor are dedicated to separate schedulers with different scheduling...
In this paper, we are interested by the integration of precedence and resources sharing constraints in the real time scheduling of periodic and aperiodic tasks. We also treat the problem of dynamic voltage scaling of the processor in the same context. Many dynamic voltage scaling algorithms have been proposed in the literature. However, these algorithms do not consider the constraints of precedence...
On-demand broadcast is an effective wireless data dissemination technique to enhance system scalability and capability to handle dynamic data access patterns. Previous studies on time-critical on-demand data broadcast were under the assumption that each client requests only one data item at a time. With rapid growth of time-critical information dissemination services in emerging applications, there...
Peer-to-peer mechanisms are considered as one of the key innovative and user-friendly solutions for real-time Internet communication services. Eliminating server-based architecture, reducing or eliminating configuration effort, and allowing end-user devices to bring resources into the network, will reshape the network as we currently know it. This presents substantial opportunities for networks and...
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