1,435 research outputs found
Iterative refinement approach for QOS-Aware service configuration
In heterogeneous environments, diversity of resources among the devices
may affect their ability to perform services with specific QoS constraints,
and drive peers to group themselves in a coalition for cooperative service
execution. The dynamic selection of peers should be influenced
by user’s QoS requirements as well as local computation availability,
tailoring provided service to user’s specific needs. However, complex
dynamic real-time scenarios may prevent the possibility of computing
optimal service configurations before execution. An iterative refinement
approach with the ability to trade off deliberation time for the quality
of the solution is proposed. We state the importance of quickly finding
a good initial solution and propose heuristic evaluation functions that
optimise the rate at which the quality of the current solution improves
as the algorithms have more time to run
Handling QoS dependencies in distributed cooperative real-time systems
Due to the growing complexity and adaptability requirements of real-time embedded systems, which often exhibit
unrestricted inter-dependencies among supported services and user-imposed quality constraints, it is increasingly
difficult to optimise the level of service of a dynamic task set within an useful and bounded time. This is even more
difficult when intending to benefit from the full potential of an open distributed cooperating environment, where service
characteristics are not known beforehand. This paper proposes an iterative refinement approach for a service’s QoS
configuration taking into account services’ inter-dependencies and quality constraints, and trading off the achieved
solution’s quality for the cost of computation. Extensive simulations demonstrate that the proposed anytime algorithm is
able to quickly find a good initial solution and effectively optimises the rate at which the quality of the current solution
improves as the algorithm is given more time to run. The added benefits of the proposed approach clearly surpass its
reducedoverhead
Time-bounded distributed QoS-aware service configuration in heterogeneous cooperative environments
The scarcity and diversity of resources among the devices of heterogeneous computing
environments may affect their ability to perform services with specific Quality
of Service constraints, particularly in dynamic distributed environments where the
characteristics of the computational load cannot always be predicted in advance.
Our work addresses this problem by allowing resource constrained devices to cooperate
with more powerful neighbour nodes, opportunistically taking advantage
of global distributed resources and processing power. Rather than assuming that
the dynamic configuration of this cooperative service executes until it computes
its optimal output, the paper proposes an anytime approach that has the ability
to tradeoff deliberation time for the quality of the solution. Extensive simulations
demonstrate that the proposed anytime algorithms are able to quickly find a good
initial solution and effectively optimise the rate at which the quality of the current
solution improves at each iteration, with an overhead that can be considered
negligible
Network layer access control for context-aware IPv6 applications
As part of the Lancaster GUIDE II project, we have developed a novel wireless access point protocol designed to support the development of next generation mobile context-aware applications in our local environs. Once deployed, this architecture will allow ordinary citizens secure, accountable and convenient access to a set of tailored applications including location, multimedia and context based services, and the public Internet. Our architecture utilises packet marking and network level packet filtering techniques within a modified Mobile IPv6 protocol stack to perform access control over a range of wireless network technologies. In this paper, we describe the rationale for, and components of, our architecture and contrast our approach with other state-of-the- art systems. The paper also contains details of our current implementation work, including preliminary performance measurements
Optimising and adapting the QoS of a dynamic set of inter-dependent tasks
Due to the growing complexity and adaptability requirements of real-time systems, which often exhibit
unrestricted Quality of Service (QoS) inter-dependencies among supported services and user-imposed
quality constraints, it is increasingly difficult to optimise the level of service of a dynamic task set within
an useful and bounded time. This is even more difficult when intending to benefit from the full potential
of an open distributed cooperating environment, where service characteristics are not known beforehand
and tasks may be inter-dependent.
This paper focuses on optimising a dynamic local set of inter-dependent tasks that can be executed
at varying levels of QoS to achieve an efficient resource usage that is constantly adapted to the specific
constraints of devices and users, nature of executing tasks and dynamically changing system conditions.
Extensive simulations demonstrate that the proposed anytime algorithms are able to quickly find a good
initial solution and effectively optimise the rate at which the quality of the current solution improves
as the algorithms are given more time to run, with a minimum overhead when compared against their
traditional versions
Distributed video coding for wireless video sensor networks: a review of the state-of-the-art architectures
Distributed video coding (DVC) is a relatively new video coding architecture originated from two fundamental theorems namely, Slepian–Wolf and Wyner–Ziv. Recent research developments have made DVC attractive for applications in the emerging domain of wireless video sensor networks (WVSNs). This paper reviews the state-of-the-art DVC architectures with a focus on understanding their opportunities and gaps in addressing the operational requirements and application needs of WVSNs
Cross-layer optimization of unequal protected layered video over hierarchical modulation
Abstract-unequal protection mechanisms have been proposed at several layers in order to improve the reliability of multimedia contents, especially for video data. The paper aims at implementing a multi-layer unequal protection scheme, which is based on a Physical-Transport-Application cross-layer design. Hierarchical modulation, in the physical layer, has been demonstrated to increase the overall user capacity of a wireless communications. On the other hand, unequal erasure protection codes at the transport layer turned out to be an efficient method to protect video data generated by the application layer by exploiting their intrinsic properties. In this paper, the two techniques are jointly optimized in order to enable recovering lost data in case the protection is performed separately. We show that the cross-layer design proposed herein outperforms the performance of hierarchical modulation and unequal erasure codes taken independently
AUTONOMIC MANAGEMENT OF SOFTWARE AS A SERVICE SYSTEMS WITH MULTIPLE QUALITY OF SERVICE CLASSES
In recent years the emergence of Software as a Service (SaaS) provision and cloud computing in general had a tremendous impact on corporate information technology. While the implementation and successful operation of powerful information systems continues to be a cornerstone of success in modern enterprises, the ability to acquire IT infrastructure, software, or platforms on a pay-as-you-go basis has opened a new avenue for optimizing operational costs and processes. In this context we target elastic SaaS systems with on-demand cloud resource provisioning and implement an autonomic management artifact. Our framework forecasts future user behavior based on historic data, analyzes the impact of different workload levels on system performance based on a non-linear performance model, analyzes the economic impact of different provisioning strategies, derives an optimal operation strategy, and automatically assigns requests from users belonging to different Quality of Service (QoS) classes to the appropriate server instances. More generally, our artifact optimizes IT system operation based on a holistic evaluation of key aspects of service operation (e.g., system usage patterns, system performance, Service Level Agreements). The evaluation of our prototype, based on a real production system workload trace, indicates a cost-of-operation reduction by up to 60 percent without compromising QoS requirements
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