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On credibility of simulation studies of telecommunication networks
 IEEE Communications Magazine
, 2002
"... In telecommunication networks, as in many other areas of science and engineering, proliferation of computers as research tools has resulted in the adoption of computer simulation as the most commonly used paradigm of scientific investigations. This, together with a plethora of existing simulation la ..."
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In telecommunication networks, as in many other areas of science and engineering, proliferation of computers as research tools has resulted in the adoption of computer simulation as the most commonly used paradigm of scientific investigations. This, together with a plethora of existing simulation languages and packages, has created a popular opinion that simulation is mainly an exercise in computer programming. In new computing environments, programming can be minimised, or even fully replaced, by the manipulation of icons (representing prebuilt programming objects containing basic functional blocks of simulated systems) on a computer monitor. One can say that we have witnessed another success of modern science and technology: the emergence of wonderful and powerful tools for exploring and predicting the behaviour of such complex, stochastic dynamic systems as telecommunication networks. But this enthusiasm is not shared by all researchers in this area. An opinion is spreading that one cannot rely on the majority of the published results on performance evaluation studies of telecommunication networks based on stochastic simulation, since they lack credibility. Indeed, the spread of this phenomenon is so wide that one can speak about a deep crisis of credibility. In this paper, this claim is supported by the results of a survey of over 2200 publications on telecommunication
Do not trust all simulation studies of telecommunications networks
 International Conference on Information Networking (ICOIN
, 2003
"... Since the birth of ARPANET and the first commercial applications of computer networks, through explosion of popularity of the Internet and wireless communications, we have witnessed increasing dependence of our civilization on information services of telecommunication networks. Their efficiency and ..."
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Since the birth of ARPANET and the first commercial applications of computer networks, through explosion of popularity of the Internet and wireless communications, we have witnessed increasing dependence of our civilization on information services of telecommunication networks. Their efficiency and reliability have become critically important for the wellbeing and prosperity of societies as well as for their security. In this situation, the significance of performance evaluation studies of current and future networks cannot be underestimated. Increasing complexity of networks has resulted in their performance evaluation studies being predominantly conducted by means of stochastic discreteevent simulation. This paper is focused on the issue of credibility of the final results obtained from simulation studies of telecommunication networks. Having discussed the basic conditions of credibility, we will show that, unfortunately, one cannot trust the majority of simulation results published in technical literature. We conclude with general guidelines for resolving this credibility crisis. 1
SimulationBased Estimation Of Proportions
 Manag. Sci
, 1994
"... this paper we propose a method for controlling the precision when several proportions are simultaneously estimated. In queueing network analysis, which is our primary application area of simulation, the need for several Manuscript of paper to appear in Management Science Kimmo E. E. Raatikainen: Si ..."
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Cited by 4 (2 self)
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this paper we propose a method for controlling the precision when several proportions are simultaneously estimated. In queueing network analysis, which is our primary application area of simulation, the need for several Manuscript of paper to appear in Management Science Kimmo E. E. Raatikainen: SimulationBased Estimation of Proportions 2 simultaneous proportions arises, for example, when the distribution of queue length is estimated or when the distribution of the system response times is approximated through a histogram. When simulation is used to estimate several proportions, the following two problems arise: 1) How do we specify the precision requirement for individual proportions? 2) How do we conclude that the individual requirements are simultaneously satisfied? The second problem can be solved by applying the Bonferroni inequality; see e.g. Kleijnen (1987, pp. 4143). The first problem is discussed below. When the mean of a response variable is estimated, the precision requirement is usually specified using the socalled relative halfwidth criterion. For simplicity in the following discussion, we assume that the unknown mean ` and its estimate
Sequential Estimation of Quantiles
, 1998
"... Quantiles are convenient measures of the entire range of values of simulation outputs. However, unlike the mean and standard deviation, the observations have to be stored since calculation of quantiles requires several passes through the data. Thus, quantile estimation (QE) requires a large amount o ..."
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Quantiles are convenient measures of the entire range of values of simulation outputs. However, unlike the mean and standard deviation, the observations have to be stored since calculation of quantiles requires several passes through the data. Thus, quantile estimation (QE) requires a large amount of computer storage and computation time. Several approaches for estimating quantiles in RS (regenerative simulation) and nonRS, which can avoid the difficulties of QE, have been proposed in [Igl76], [Sei82b], and [JC85].
Simultaneous Sequential Confidence Intervals Of Fixed Widths For Several Means Using Bonferroni Inequality
, 1992
"... this paper we examine asymptotic properties of sequentially constructed confidence regions based on the Bonferroni inequality. We also report empirical results when simultaneous confidence intervals for normal and transformed normal means are constructed. ..."
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this paper we examine asymptotic properties of sequentially constructed confidence regions based on the Bonferroni inequality. We also report empirical results when simultaneous confidence intervals for normal and transformed normal means are constructed.
Simulation Estimation of Dynamic Properties in Queueing Systems
, 1993
"... In simulation studies the focus has traditionally been on timeindependent characteristics of queueing systems, particularly on the steadystate mean. The systems, even if they are in stochastic equilibrium, have also timedependent or dynamic properties which are of great practical importance. Typic ..."
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In simulation studies the focus has traditionally been on timeindependent characteristics of queueing systems, particularly on the steadystate mean. The systems, even if they are in stochastic equilibrium, have also timedependent or dynamic properties which are of great practical importance. Typically, the dynamic properties are related to the variation of traffic or load during some period of time. In this paper we propose a way to examine dynamic properties of queueing systems through simulation. Our approach is based on the following idea: The original traffic rates are classified into low and heavy values. The resulting binary sequence of indicators characterize the traffic level of the system. The variation in the traffic level is summarized through estimating the two histograms of level durations. The rationale of translating the problem into simultaneous estimation of two histograms is that the estimates for the cell proportions are based on cumulative statistics. Therefore, w...
Accuracy of Estimates for Dynamic Properties of Queueing Systems in Interactive Simulation
 Int. J. of Computer Simulation
, 1993
"... Interactive graphics allows the analyst to view the output sequences during the simulation run. Therefore, the dynamic properties of queueing systems are more and more often examined. In this paper we propose an approach to characterize and estimate dynamic properties so that existing methods for es ..."
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Interactive graphics allows the analyst to view the output sequences during the simulation run. Therefore, the dynamic properties of queueing systems are more and more often examined. In this paper we propose an approach to characterize and estimate dynamic properties so that existing methods for estimating variances of means can be applied. The approach is based on transforming the original output sequence into several new sequences, the means of which together summarize important aspects of the dynamic properties in the original sequence. In addition, we propose a way of assessing the accuracy of estimates that is appropriate in interactive simulation. The method introduced is shown to have a sound theoretical basis. We also report experimental results of applying the method. Keywords Interactive Simulation, Dynamic Properties of Queueing Systems, Run Length Control, Confidence Estimation, Simultaneous Inference, Moving Range I. Introduction Interactive graphics that modern works...
Controlling The Precision Of Estimated Means In Interactive Simulation
 Annals of Operations Research
, 1994
"... The computing power of modern workstations has made it possible to simulate many queueing systems interactively. Recent development in simulation software has mainly concentrated on interactive facilities. Unfortunately the precision of estimates has widely been overlooked in interactive simulation. ..."
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The computing power of modern workstations has made it possible to simulate many queueing systems interactively. Recent development in simulation software has mainly concentrated on interactive facilities. Unfortunately the precision of estimates has widely been overlooked in interactive simulation. In this paper we propose a method for controlling the precisions of estimated means during an interactive simulation run. Since in a typical situation of interactive simulation the user is simultaneously interested in several means, we consider both the simultaneous precision and individual precisions of the estimated means. The method is based on the existing methods for estimating standard errors and on the Bonferroni inequality. The Bonferroni inequality is used to obtain a lower bound for the simultaneous precision. Key Words: Confidence estimation, Graphical user interface, Interactive simulation, Queueing network simulation, Runlength control, Sequential estimation, Simultaneous infe...
Exponentially Weighted Simultaneous Estimation of Several Quantiles
"... Abstract—In this paper we propose new method for simultaneous generating multiple quantiles corresponding to given probability levels from data streams and massive data sets. This method provides a basis for development of singlepass lowstorage quantile estimation algorithms, which differ in compl ..."
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Abstract—In this paper we propose new method for simultaneous generating multiple quantiles corresponding to given probability levels from data streams and massive data sets. This method provides a basis for development of singlepass lowstorage quantile estimation algorithms, which differ in complexity, storage requirement and accuracy. We demonstrate that such algorithms may perform well even for heavytailed data. Keywords—Quantile estimation, data stream, heavytailed distribution, tail index. I.
A DECISION SUPPORT MODEL FOR PASSENGER CAPACITY DESIGN OF BRT STATIONS
"... In this paper, a decision support model for capacity planning of bus rapid transit stations is proposed. Static, deterministic models are used at present for station capacity design, whereas bus passenger flow through stations is dynamic with an associated stochastic element. Passenger arrivals vary ..."
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In this paper, a decision support model for capacity planning of bus rapid transit stations is proposed. Static, deterministic models are used at present for station capacity design, whereas bus passenger flow through stations is dynamic with an associated stochastic element. Passenger arrivals vary over time, and are driven by bus schedules and process variation. The proposed model produces capacity design curves for given input data sets and bus schedules, and assists the station designer without being prescriptive. A case study of model application to the proposed Thibault Station in Cape Town, South Africa, is presented. OPSOMMING ’n Besluitsteunmodel vir kapasiteitsbeplanning van sneldiensbusstasies word in hierdie artikel voorgehou. Tans word statiese, deterministiese modelle gebruik vir stasiekapasiteitsontwerp, terwyl passasiersvloei deur busstasies dinamies is met ’n stochastiese element. Passasiersaankomste varieer oor tyd en word bepaal deur busskedules en prosesvariasie. Die voorgestelde model lewer kapasiteitontwerpkurwes vir gegewe insetdata en busskedules en ondersteun die stasieontwerper sonder om voorskriftelik te wees. Die toepassing van die model word geïllustreer met behulp van ’n gevallestudie by die beplande Thibaultstasie in Kaapstad, SuidAfrika. A