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Iteration Algorithm (iteration + algorithm)

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Engineering100%

Selected Abstracts

CAC and routing for multi-service networks with blocked wide-band calls delayed, Part II: approximative link MDP framework

EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 1 2007
Ernst Nordström
In this paper, we study the call admission control (CAC) and routing issue in multi-service networks. Two categories of calls are considered: a narrow-band with blocked calls cleared and a wide-band with blocked calls delayed. The optimisation is subject to several quality of service (QoS) constraints, either on the packet or call level. The objective function is formulated as reward maximisation with penalty for delay. A suboptimal solution is achieved by applying Markov decision process (MDP) theory together with a three-level approximation. First, the network is decomposed into a set of links assumed to have independent Markov and reward processes respectively. Second, the dimensions of the link Markov and reward processes are reduced by aggregation of the call classes into call categories. Third, by applying decomposition of the link Markov process, the link MDP tasks are simplified considerably. The CAC and routing policy is computed by the policy iteration algorithm from MDP theory. The numerical results show that the proposed CAC and routing method, based on the approximate link MDP framework, is able to find an efficient trade-off between reward loss and average call set-up delay, outperforming conventional methods such as least loaded routing (LLR). Copyright © 2006 AEIT. [source]

CAC and routing for multi-service networks with blocked wide-band calls delayed, part I: exact link MDP framework

EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 1 2006
Ernst Nordström
In this paper, we study the call admission control (CAC) and routing issue in multi-service networks. Two categories of calls are considered: a narrow-band (NB) with blocked calls cleared and a wide-band (WB) with blocked calls delayed. The objective function is formulated as reward maximisation with penalty for delay. The optimisation is subject to quality of service (QoS) constraints and, possibly, grade of service (GoS) constraints. A suboptimal solution is achieved by applying Markov decision process (MDP) theory together with a two-level approximation. First, the network is decomposed into a set of links assumed to have independent Markov and reward processes respectively. Second, the dimensions of the link Markov and reward processes are reduced by aggregation of the call classes into call categories. The CAC and routing policy is computed by the policy iteration algorithm from MDP theory. The numerical results show that the proposed CAC and routing method, based on the exact link MDP framework, is able to find an efficient trade-off between reward loss and average call set-up delay, outperforming conventional methods such as the least loaded routing (LLR). Copyright © 2005 AEIT. [source]

Numerical analysis of Augmented Lagrangian algorithms in complementary elastoplasticity

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 14 2004
L. Contrafatto
The main subject of the paper is the investigation of Augmented Lagrangian algorithms and update formulas in the solution of elastoplastic problems. A stress rate formulation for elastoplastic models with internal variables and its finite increment form is employed to state the mechanical problem. In this formulation the Augmented Lagrangian is used to enforce the constraint of plastic admissibility directly on the stresses and thermodynamic forces. This is not a limitation of the Augmented Lagrangian approach, and the same framework can be built on more classical displacement formulations as well. The meaning and the derivation of various first and second order Lagrangian multipliers update formulas and iterative schemes is shown. A new diagonal iteration algorithm and the introduction of a scale factor for the Augmented Lagrangian term are proposed. Numerical examples compare the efficiency of several forms of Augmented Lagrangian algorithms and illustrate the influence of the scale factor and of the penalty parameter. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Simulation of general linear dielectric properties in TLM

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 5-6 2002
John Paul
Abstract The simulation of linear dispersive dielectric materials in time-domain TLM requires the inclusion of frequency-dependent material properties in the scattering process. For media having frequency dependencies described by a single pole or a pair of complex poles, for example Debye, Drude or Lorentz, it is straightforward to develop individual algorithms on a case-by-case basis. However, this approach lacks generality and when applied to the modelling of media displaying more complicated frequency dependencies, somewhat lengthy calculations need to be evaluated each time a new material is required. To address this difficulty, this paper describes methods for obtaining the iteration algorithm for general linear isotropic dielectric media. The results obtained using different ,,-transform methods are compared and an example of a frequency-dependent structure is simulated. Copyright © 2002 John Wiley & Sons, Ltd. [source]

An augmented system approach to static output-feedback stabilization with ,, performance for continuous-time plants

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 7 2009
Zhan Shu
Abstract This paper revisits the static output-feedback stabilization problem of continuous-time linear systems from a novel perspective. The closed-loop system is represented in an augmented form, which facilitates the parametrization of the controller matrix. Then, new equivalent characterizations on stability and ,, performance of the closed-loop system are established in terms of matrix inequalities. On the basis of these characterizations, a necessary and sufficient condition with slack matrices for output-feedback stabilizability is proposed, and an iteration algorithm is given to solve the condition. An extension to output-feedback ,, control is provided as well. The effectiveness and merits of the proposed approach are shown through several examples. Copyright © 2008 John Wiley & Sons, Ltd. [source]