QoS Constraints (qo + constraint)

Distribution by Scientific Domains


Selected Abstracts


QoS routing through alternate paths in wireless ad hoc networks

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 3 2004
Baoxian Zhang
Abstract Quality of service (QoS) routing plays an important role in QoS provisioning for mobile ad hoc networks. This work studies the issue of route selection subject to QoS constraint(s). Our method searches for alternate routes with satisfied QoS requirement(s) to accommodate each communication request when the shortest path connecting the source,destination pair of the request is not qualified. In order to effectively reduce protocol overhead, a directed search mechanism is designed to limit the breadth of the searching scope, which aims at achieving a graceful tradeoff between the success probability in QoS route acquisition and communication overhead. Efficient hop-by-hop routing protocols are designed for route selection subject to delay and bandwidth constraint, respectively. Simulation results show that the designed protocols can achieve high performance in acquiring QoS paths and in efficient resource utilization with low control overhead. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Specification, planning, and execution of QoS-aware Grid workflows within the Amadeus environment

CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 4 2008
Ivona Brandic
Abstract Commonly, at a high level of abstraction Grid applications are specified based on the workflow paradigm. However, majority of Grid workflow systems either do not support Quality of Service (QoS), or provide only partial QoS support for certain phases of the workflow lifecycle. In this paper we present Amadeus, which is a holistic service-oriented environment for QoS-aware Grid workflows. Amadeus considers user requirements, in terms of QoS constraints, during workflow specification, planning, and execution. Within the Amadeus environment workflows and the associated QoS constraints are specified at a high level using an intuitive graphical notation. A distinguishing feature of our system is the support of a comprehensive set of QoS requirements, which considers in addition to performance and economical aspects also legal and security aspects. A set of QoS-aware service-oriented components is provided for workflow planning to support automatic constraint-based service negotiation and workflow optimization. For improving the efficiency of workflow planning we introduce a QoS-aware workflow reduction technique. Furthermore, we present our static and dynamic planning strategies for workflow execution in accordance with user-specified requirements. For each phase of the workflow lifecycle we experimentally evaluate the corresponding Amadeus components. Copyright © 2007 John Wiley & Sons, Ltd. [source]


Adaptive resource allocation in OFDMA systems with fairness and QoS constraints,

EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 6 2007
Liang Chen
This paper describes several practical and efficient adaptive subchannel, power and bit allocation algorithms for orthogonal frequency-division multiple-access (OFDMA) systems. Assuming perfect knowledge of channel state information (CSI) at the transmitter, we look at the problem of minimising the total power consumption while maintaining individual rate requirements and QoS constraints. An average signal-to-noise ratio (SNR) approximation is used to determine the allocation while substantially reducing the computational complexity. The proposed algorithms guarantee improvement through each iteration and converge quickly to stable suboptimal solutions. Numerical results and complexity analysis show that the proposed algorithms offer beneficial cost versus performance trade-offs compared to existing approaches. Copyright © 2007 John Wiley & Sons, Ltd. [source]


A dynamic multicast routing satisfying multiple QoS constraints

INTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 5 2003
Debasish Chakraborty
In this paper we propose a QoS-based routing algorithm for dynamic multicasting. The complexity of the problem can be reduced to a simple shortest path problem by applying a Weighted Fair Queuing (WFQ) service discipline. Using a modified Bellman,Ford algorithm, the proposed routing builds a multicast tree, where a node is added to the existing multicast tree without re-routing and satisfying QoS constraints.,With user defined life-time of connection this heuristic algorthm builds multicast tree which is near optimum over the whole duration of session. Simulation results show that tree costs are nearly as good as other dynamic multicast routings that does not consider QoS. Copyright © 2003 John Wiley & Sons, Ltd. [source]