Praise for the Third Edition: "This is one of the best books available. Its excellent organizational structure allows quick reference to specific models and its clear presentation . . . solidifies the understanding of the concepts being presented."IIE Transactions on Operations EngineeringThoroughly revised and expanded to reflect the latest developments in the field, Fundamentals of Queueing Theory, Fourth Edition continues to present the basic statistical principles that are necessary to analyze the probabilistic nature of queues. Rather than presenting a narrow focus on the subject, this update illustrates the wide-reaching, fundamental concepts in queueing theory and its applications to diverse areas such as computer science, engineering, business, and operations research.This update takes a numerical approach to understanding and making probable estimations relating to queues, with a comprehensive outline of simple and more advanced queueing models. Newly featured topics of the Fourth Edition include:Retrial queuesApproximations for queueing networksNumerical inversion of transformsDetermining the appropriate number of servers to balance quality and cost of serviceEach chapter provides a self-contained presentation of key concepts and formulae, allowing readers to work with each section independently, while a summary table at the end of the book outlines the types of queues that have been discussed and their results. In addition, two new appendices have been added, discussing transforms and generating functions as well as the fundamentals of differential and difference equations. New examples are now included along with problems that incorporate QtsPlus software, which is freely available via the book's related Web site.With its accessible style and wealth of real-world examples, Fundamentals of Queueing Theory, Fourth Edition is an ideal book for courses on queueing theory at the upper-undergraduate and graduate levels. It is also a valuable resource for researchers and practitioners who analyze congestion in the fields of telecommunications, transportation, aviation, and management science.

Fundamentals of Queueing Theory

Optimal design of fractional delay FIR filter using cuckoo search algorithm

The disclosed electrosurgical systems and methods accurately determine the power actually applied to a load by using equalizers to calibrate the power measurements. The electrosurgical systems include an electrosurgical generator and an electrosurgical instrument coupled to the electrosurgical generator through an electrosurgical cable. The electrosurgical generator includes an electrical energy source, voltage and current detectors, equalizers that estimate the voltage and current applied to a load, and a power calculation unit that calculates estimated power based upon the estimated voltage and current. The methods of calibrating an electrosurgical generator involve applying a resistive element across output terminals of the electrosurgical generator, applying a test signal to the resistive element, measuring the magnitude and phase angle of voltage and current components of the test signal within the electrosurgical generator, estimating the magnitude and phase angle of the voltage and current at the resistive element using equalizers, and determining gain correction factors and minimum phase angles for the equalizers.

Systems and methods for calibrating power measurements in an electrosurgical generator

This paper investigates the weighted least squares (WLS) and minimax design problems for variable fractional delay (VFD) FIR filters. For the WLS design, the general case of incorporating arbitrary nonnegative weighting functions is considered. The optimal solution is characterized by two matrix equations. An efficient algorithm using conjugate gradient (CG) techniques is proposed to solve the WLS solution. The proposed algorithm is guaranteed to converge to the optimal solution in a finite number of iterations. Moreover, an iterative reweighted least squares (IRLS) algorithm that uses the proposed CG algorithm as its iteration core is developed for the minimax design problem. In both of the algorithms, the filter coefficients are arranged as matrices, achieving a great saving in computations and memory space. The associated computational complexity is analyzed. Some design examples are provided and comparisons with existing methods show that the proposed ones are either computationally more efficient or can obtain the better filter performance, or both.

Matrix-Based Algorithms for the Optimal Design of Variable Fractional Delay FIR Filters

Motivated by accurate broadband steering vector requirements for applications such as broadband angle of arrival estimation, we review fractional delay filter designs. A common feature across these are their rapidly decreasing performance as the Nyquist rate is approached. We propose a filter bank based approach, which operates standard fractional delay filters on a series of frequency-shifted subband signals, such that they appear in the filters' lowpass region. We demonstrate the appeal of this approach in simulations.

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Implementation of accurate broadband steering vectors for broadband angle of arrival estimation

In this paper a numerically efficient method for designing a nearly optimal variable fractional delay (VFD) filter based on a simple and well-known window method is presented. In the proposed method a single window extracted from the optimal filter with fixed fractional delay (FD) is divided into even and odd part. Subsequently, the odd part is discarded and symmetric even part of the extracted window is used to design a family of nearly optimal filters with varying FD. In addition to window extraction, the proposed approach requires filter gain correction which is dependent on the desired FD. Optimum values of the gain correction factor as well as the extracted window can be computed beforehand, which allows us to design a nearly optimal FD filter with arbitrary FD at low numerical costs during runtime. On the basis of the proposed filter design method, the universal structure of VFD filter allowing for change of filter type and length has been proposed. In the paper, three FD filter optimality criteria are considered, which are maximal flatness, Chebyshev (minimax), and least squares.

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Variable Fractional Delay Filter Design Using a Symmetric Window

The window method is a fast and efficient approach to fractional delay filter design. However, gain of designed filter,
differs from the ideal value which should be equal one. This effect, called gain deficit, negatively affects filter quality.
The essence of the gain deficit problem as well as method and results of gain deficit correction are stated in this article.
The influence of gain deficit correction on frequency response of the fractional delay filter and approximation error is
discussed. An algorithm for finding optimum gain deficit correction factor has been proposed and relations between correction factor and filter and window parameters are presented in the paper.

Gain deficit effect in the fractional delay filter design by the window method

The paper describes our further research done with the proposed analytical and simulation traffic models of the Next Generation Network (NGN), which is standardized for delivering multimedia services with strict quality and includes elements of the IP Multimedia Subsystem (IMS). The aim of our models of a single IMS/NGN domain is to evaluate two standardized call processing performance parameters, which appropriate values are very important for satisfaction of users and overall success of the IMS/NGN concept. These parameters are mean Call Set-up Delay E(CSD) and mean Call Disengagement Delay E(CDD). Our latest investigations concern improving the conformity of the analytical results and experimental results obtained using the simulation model, which implements the operation of real network elements according to current standards and research. In this paper the results of calculations using PH/PH/1 queuing systems are presented, in which arrival and service distributions are phase-type distributions computed using maximum likelihood and distance minimization fitting algorithms based on experimental histograms. Presented latest results are compared to these obtained using other, previously investigated queuing systems. Additionally, computational complexity of all examined queuing systems is analyzed. As a result, some general remarks concerning all tested queuing systems and their applicability to NGN are provided.

Analysis of IMS/NGN Call Processing Performance Using Phase-Type Distributions Based on Experimental Histograms

In this paper we verify the previously proposed analytical traffic model of a multidomain Next Generation Network (NGN), which is standardized for delivering multimedia services based on the IP Multimedia Subsystem (IMS). For this reason a proper simulation model used, in which not theoretical queuing system models but the operation of real network elements and standardized call scenarios are accurately implemented. Consequently, the simulation model reflects the phenomena taking place in real IMS/NGN network and can be considered as a reference for evaluation of quality of the analytical results. The output variables assessed using both models are mean Call Set-up Delay (CSD) and mean Call Disengagement Delay (CDD), a subset standardized call processing performance parameters. The investigations are performed for various types of calls and sets of network parameters. As a result, conclusions regarding conformity of the analytical and simulation results in a multidomain IMS/NGN are presented.

Verification of the Analytical Traffic Model of a Multidomain IMS/NGN Using the Simulation Model

In current telecommunications it is assumed that demands of the information society for quickly delivered services will be satisfied by the Next Generation Network (NGN) architecture, which includes IP Multimedia Subsystem (IMS) elements. To guarantee Quality of Service (QoS), proper design and dimensioning of NGN is absolutely necessary, for which appropriate models have to be proposed. As the NGN architecture is very complicated, the most applicable are simulation models, which give more accurate results as well as allow investigation of more input and output parameters sets compared with analytical models. In the paper a scalable and extensible simulation model is presented, which allows evaluation of mean Call Set-up Delay (CSD) and mean Call Disengagement Delay (CDD) in a single domain of IMS-based NGN. Results obtained using the model are described and factors most influential on NGN call processing performance are indicated.

Maciej Sac

Papers

Variable Fractional Delay Filter Design Using a Symmetric Window

Gain deficit effect in the fractional delay filter design by the window method

Analysis of IMS/NGN Call Processing Performance Using Phase-Type Distributions Based on Experimental Histograms

Verification of the Analytical Traffic Model of a Multidomain IMS/NGN Using the Simulation Model

Simulation model of IMS/NGN call processing performance