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 ...
详细信息
In this paper nonlinear trajectory morphing is introduced. We show how it can explore the trajectory space of a nonlinear system. A trajectory tracking projection operator is defined for practical implementation of mo...
详细信息
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 probabilis...
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.
The primary-backup replication model is one of the commonly adopted approaches to providing fault tolerant data services. Its extension to the realtime environment, however, imposes the additional constraint of timin...
详细信息
The primary-backup replication model is one of the commonly adopted approaches to providing fault tolerant data services. Its extension to the realtime 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.
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 s...
详细信息
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.
Presents a detailed characterization of Java application and applet workloads in terms of reuse and sharing of Java code at the program, class and method level. In order to expose more sharing opportunities, technique...
详细信息
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 ...
详细信息
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.
In the molecular-beam epitaxy (MBE) process precise control over thickness, composition, and doping profiles are critical for end device performance. This paper addresses the problem of accurately controlling the flux...
详细信息
In the molecular-beam epitaxy (MBE) process precise control over thickness, composition, and doping profiles are critical for end device performance. This paper addresses the problem of accurately controlling the flux sources (effusion cells) used in MBE. We present a nonlinear compensator based on exact input-output linearization via feedback to control the flux of an effusion cell. The unmeasured states, necessary for implementation of the controller, are estimated by a Kalman-Bucy observer. We present simulations of the composite observer/nonlinear controller system, showing successful flux command following and elimination of shutter induced flux transients.
This paper introduces the concept of cross-positivity for vector fields and explores ramifications of cross-positivity relative to solutions of ordinary differential equations. The motivation is to understand the dyna...
详细信息
Information on Fault-Tolerance Latency (FTL), which is defined as the total time required by all sequential steps taken to recover from an error, is important to the design and evaluation of fault-tolerant computers u...
详细信息
Information on Fault-Tolerance Latency (FTL), which is defined as the total time required by all sequential steps taken to recover from an error, is important to the design and evaluation of fault-tolerant computers used in safety-critical real-time control systems with deadline information. In this paper we evaluate FTL in terms of several random and deterministic variables accounting for fault behaviors and/or the capability and performance of error-handling mechanisms, while considering various fault-tolerance mechanisms based on the tradeoff between temporal and spatial redundancy, and use the evaluated FTL to check if an error-handling policy can meet the Control System Deadline (CSD) for a given real-time application.
暂无评论