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4th Annual ACM/IEEE International Conference on Mobile computing and Networking, MobiCom 1998

作者： Choi, Sunghyun Shin, Kang G. Real-Time Computing Laboratory Department Of Electrical Engineering And Computer Science The University Of Michigan Ann ArborMI48109-2122 United States

ISBN: (纸本)9781581130355

In this paper, we compare four distributed connection admission control schemes in cellular networks where the first two schemes are to keep the hand-off dropping probability below a target value, the third scheme is to guarantee no hand-off drops through a per-connection bandwidth reservation, and the fourth scheme uses another type of per-connection bandwidth reservation. The first scheme predicts the bandwidth required to handle hand-offs by estimating possible hand-offs from adjacent cells, then performs the admission control for each newly-requested connection. On the other hand, the second scheme predicts the total required bandwidth in the current cell by estimating both incoming and outgoing hand-offs at each cell. The third scheme requires the set of cells which the mobile with a newly-requested connection will traverse, and reserves bandwidth for each connection in each of those cells. The fourth scheme reserves bandwidth for each connection in the predicted next cell of a mobile. We adopt the history-based mobility estimation for the first two schemes. Using extensive simulations, the four schemes are compared quantitatively in terms of (1) important performance measures such as the hand-off dropping probability, connection-blocking probability, and bandwidth utilization, (2) dependency on the de-sign parameters, (3) dependency on the mobility estimation accuracy, and (4) complexity. The simulation results indicate that the first scheme is the most desirable in the sense that it achieves reasonably good performance while requiring much less memory and computation than the other three schemes. © Copyright ACM 1998.

关键词： Bandwidth

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Predictive and adaptive bandwidth reservation for hand-offs in QoS-sensitive cellular networks 98

Predictive and adaptive bandwidth reservation for hand-offs ...

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Proceedings of the ACM SIGCOMM '98 conference on Applications, technologies, architectures, and protocols for computer communication

作者： Sunghyun Choi Kang G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science The University of Michigan Ann Arbor Michigan

ISBN: (纸本)9781581130034

How to control hand-off drops is a very important Quality-of-Service (QoS) issue in cellular networks. In order to keep the hand-off dropping probability below a pre-specified target value (thus providing a probabilistic QoS guarantee), we design and evaluate predictive and adaptive schemes for the bandwidth reservation for the existing connections' handoffs and the admission control of new *** first develop a method to estimate user mobility based on an aggregate history of hand-offs observed in each cell. This method is then used to predict (probabilistically) mobiles' directions and hand-off times in a cell. For each cell, the bandwidth to be reserved for hand-offs is calculated by estimating the total sum of fractional bandwidths of the expected hand-offs within a mobility-estimation time window. We also develop an algorithm that controls this window for efficient use of bandwidth and effective response to (1) time-varying traffic/mobility and (2) inaccuracy of mobility estimation. Three different admission-control schemes for new connection requests using this bandwidth reservation are proposed. Finally, we evaluate the performance of the proposed schemes to show that they meet our design goal and outperform the static reservation scheme under various scenarios.

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Optimization of a real-time primary-backup replication service

Optimization of a real-time primary-backup replication servi...

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Reliable Distributed Systems

作者： Hengming Zou F. Jahanian Real-time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

The primary-backup replication model is one of the commonly adopted approaches to providing fault tolerant data services. Its extension to the real time environment, however, imposes the additional constraint of timing predictability, which requires a bounded overhead for managing redundancy. The paper discusses the trade-off between reducing system overhead and increasing (temporal) consistency between the primary and backup, and explores ways to optimize such a system to minimize either the inconsistency or the system overhead while maintaining the temporal consistency guarantees of the system. An implementation built on top of the existing RTPB model (H. Zou and F. Jahanian, 1998) was developed within the x-kernel architecture on the Mach OSF platform running MK 7.2. Results of an experimental evaluation of the proposed optimization techniques are discussed.

关键词： Fault tolerance Timing Redundancy Fault tolerant systems real time systems Laboratories Environmental management Buildings Protocols Application software

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End-host architecture for QoS-adaptive communication

End-host architecture for QoS-adaptive communication

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real-time Technology and Applications Symposium

作者： T. Abdelzaher K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

Proliferation of communication-intensive real-time applications with "elastic" timeliness constraints such as streaming stored video, requires a new design for end-host communication subsystems. The design should (i) provide per-flow or per-service-class guarantees, (ii) maximize the aggregate utility of the communication service across all clients, (iii) gracefully adapt to transient overload, and (iv) avoid, if possible, starving lower-priority service classes during the period of sustained overload. The authors propose a QoS-optimization algorithm and communication subsystem architecture that satisfy the above requirements. It provides each client its contracted QoS, while adapting gracefully to transient overload and resource shortage. A new concept of flexible QoS contract is introduced, specifying multiple acceptable levels of service (or QoS levels for short) and their corresponding rewards for each client. Allowing clients to specify multiple QoS levels permits the server to perform QoS-optimization and degrade client's QoS under transient overload predictable, as specified in the QoS contract. Clients receive a money-back guarantee if the contracted QoS is violated by the server. The proposed resource-management mechanism maximizes server's total reward under resource constraints. They implemented and evaluated the architecture on a Pentium-based PC platform running under The Open Group (TOG) MK7.2 kernel, demonstrating the capability of the communication subsystem in meeting its design goals.

关键词： Contracts Degradation Aggregates computer architecture Resource management Laboratories Application software Streaming media Kernel Monitoring

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Efficient all-to-all personalized exchange in multidimensional torus networks

Efficient all-to-all personalized exchange in multidimension...

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International Conference on Parallel Processing (ICPP)

作者： Young-Joo Suh K.G. Shin Department of Computer Science and Engineering Pohang University of Science and Technology Pohang South Korea Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

This paper presents new algorithms for all-to-all personalized exchange in multidimensional torus-connected multiprocessors. Unlike existing message-combining algorithms in which the number of nodes in each dimension should be power-of-two and square, the proposed algorithms accommodate non-power-of-two tori where the number of nodes in each dimension need not be power-of-two. In addition, destinations remain fixed over a larger number of steps in the proposed algorithms, thus making them amenable to optimizations. Finally, the data structures used are simple, hence making substantial saving of message-rearrangement time.

关键词： Intelligent networks Multidimensional systems Samarium computer science Propagation delay Scattering computer networks Laboratories Communication switching Data structures

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Inter-completion time scheduling (ICTS): non-preemptive scheduling to maximize the minimum inter-completion time

Inter-completion time scheduling (ICTS): non-preemptive sche...

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IEEE International Conference on Engineering of Complex computer Systems

作者： C.C. Amaro A.D. Stoyen S.K. Baruah Department of Computer & Information Science Dependable Real-Time Systems Laboratory New Jersey Institute of Technology Newark NJ USA Department of Computer Science University of Vermont Burlington VT USA

Temporal load-balancing, spreading out the executions of tasks over time, is desirable in many applications in complex systems. A form of temporal load balancing is discussed, scheduling to maximize minimum inter-completion time (MICT-scheduling) and minimum global inter-completion time (MGICT-scheduling). It is shown that MICT- and MGICT-scheduling are, in general, NP-hard. A number of restricted classes of task systems are identified, which can be efficiently MICT- and MGICT-scheduled.

关键词： Processor scheduling real time systems Load management

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Non-Preemptive Scheduling to Maximize the Minimum Global Inter-Completion time (MGICT) 1

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IFAC Proceedings Volumes 1998年第14期31卷 135-140页

作者： Carlos C. Amaro Sanjoy K. Baruah Alexander D. Stoyen Wolfgang A. Halang Dependable Real- Time Systems Laboratory Department of Computer & Information Science New Jersey Institute of Technology University Heights Newark NJ 07102 USA Department of Computer Science The University of Vermont Burlington VT 05405 Faculty of Electrical Engineering Fernuniversität 58084 Hagen Germany

Temporal load-balancing - "spreading out" the executions of tasks over time - is desirable in many applications. A form of temporal load-balancing is discussed: scheduling to maximize minimum global inter-completion time (MGICT-scheduling). It is shown that MGICT-scheduling is, in general, NP-hard. A number of restricted classes of task systems are identified, which can be efficiently MGICT-scheduled.

关键词： non-preemptive scheduling independent tasks multiple processors loadbalancing

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Continuous media filesystem services on a real-time JAVA server

Continuous media filesystem services on a real-time JAVA ser...

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IEEE International Conference on Embedded and real-time computing Systems and Applications (RTCSA)

作者： A. Molano A. Miyoshi H. Tokuda R. Rajkumar Real Time and Multimedia Laboratory Department of Computer Science Carnegie Mellon University Pittsburgh PA USA Faculty of Environmental Information Keio Research Institute at SFC Keio University Fujisawa Kanagawa Japan

We investigate filesystem support for continuous media on the Java language. We describe a prototype implementation on a real-time Java Server, developed as an application level server on the real-time Mach microkernel environment. The Java virtual machine has been extended to support filesystem bandwidth reservation facilities existing on real-time Mach. Such facilities allow continuous media applications to specify their disk bandwidth usage requirements by creating a disk bandwidth reservation. The operating system, upon acceptance of the requests, internally enforces and guarantees such a share of the disk bandwidth for every active reservation. We present a performance evaluation, including both a synthetic application and real multimedia application based on a Quicktime video player which make use of real time Java threads and filesystem bandwidth reservation facilities. Our experiments conclude that the proposed filesystem extensions to the Java language are suitable for continuous media application requirements.

关键词： Java File servers Bandwidth Application software Timing Contracts Prototypes Virtual machining Yarn Electrical capacitance tomography

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Load adjustment and filtering based on process criticality

Load adjustment and filtering based on process criticality

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IEEE International Conference on Embedded and real-time computing Systems and Applications (RTCSA)

作者： Tei-Wei Kuo Shie-Kai Ni Giun-Haur Huang Real Time Systems Laboratory Department of Computer Science and Information Engineering National Chung Cheng University Chiayi Taiwan Department of New Technology Development Platform Software Division Acer Incorporated Taipei Taiwan System Software Laboratory Institute for Information Industry Taipei Taiwan

ISBN: (纸本)081869209X

This paper generalizes the load scaling techniques proposed in (Kuo and Mok, 1991) for fixed-priority real-time applications. A framework is proposed to adjust the system workload by relating the criticality and flexibility of a process to the resource allocation problem. A load adjustment procedure based on the approximation algorithm (Ni et al., 1997) is proposed to maximize the system profit in an on-line fashion. When the list of allowable configurations is implicitly given by scalable periodic processes, the corresponding load filtering problem is shown to be NP-complete. We also prove the upper bound of the system profit and provide a mechanism to balance the schedulability and the maximum profit of the system.

关键词： Filtering Resource management Job shop scheduling Timing real time systems Approximation algorithms Upper bound Laboratories Frequency computer science

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Statistical real-time channels on multiaccess bus networks

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IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 1997年第8期8卷 769-780页

作者： Chou, CC Shin, KG the Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science The University of Michigan

real-time communication with performance guarantees is expected to become an important and necessary feature of future computer networks. In this paper, we present a scheme which can provide real-time communication services with both absolute and statistical performance guarantees on multiaccess bus networks for given input traffic characteristics and performance requirements. The proposed scheme reserves network bandwidth for real-time connections according to their needs. It also allows for independent addition and deletion of real-time connections while preserving existing guarantees. Our extensive simulation results for motion video communication have shown the proposed scheme to outperform the other well-known schemes.

关键词： real-time communication real-time connection/channel multimedia systems FieldBus (SP50) multiaccess networks digital video transmission

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