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Flick, Allen E. Liao Ming. "Time dependent queuing systems." Auburn, Ala., 2008. http://hdl.handle.net/10415/1487.
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Fountanas, Leonidas. "Active queue management mechanisms for real-time traffic in MANETs /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA401102.
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Thesis (Electrical Engineer and M.S. in Electrical Engineering) Naval Postgraduate School, Dec. 2001.<br>"December 2001." Thesis advisor(s): Tummala, Murali ; Ives, Robert W. ; Parker, Robert E. Includes bibliographical references (p. 101-104). Also available online.
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Gangalic, Catalin. "Improving Queuing Time in a Pull Based Containerized Continuous Integration Build System." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-303114.
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Most of the medium and big size software companies around the world are now using some form of continuous automatic build systems, with smaller companies following through. This approach, towards a more continuous flow, has pushed for more innovation in the domain and the adoption of various orchestration tools for these builds. At the same time, most continuous integration build systems do not leverage the data for improving the total building time. This thesis intends to decrease the overall building time in a pull based build system, named Blazar. This is obtained by decreasing the average time a build waits before being allocated a resource by the orchestration tool, Kubernetes. The improvement of average queuing time is done by leveraging the past data regarding the queue load of the system with the scope of predicting the amount of resources and preemptively allocating them. In the thesis, various time series prediction models are explored in order to find the most relevant one with regards to the available data. The final choice of the model is Facebook’s Prophet due to its ability to leverage multiple seasonalities, handle outliers, accommodate holidays, and provide fast predictions. By tuning various model’s parameters, it was possible to achieve satisfactory results. Thus, for some of the tested periods, the average queuing time was decreased with up to 20%, while maintaining a reasonable resource usage, compared to the time without using any prediction models. Finally, this thesis represents a practical approach that can be applied to other applications and systems. This thesis also details its limitations while discussing other solutions and ideas to further improve the results.<br>De flesta medelstora och större mjukvaruföretag runt om i världen använder idag någon form av kontinuerliga automatiska byggsystem, något som mindre företag även har börjat efterfölja. Detta tillvägagångssätt mot ett mer kontinuerligt flöde har drivit för mer innovation inom domänen och adopteringen av olika orkestreringsverktyg för dessa byggda program. Samtidigt utnyttjar de flesta kontinuerliga integrationssystem inte den data de samlar in för att förbättra den totala byggtiden. Denna uppsats avser att minska den totala byggtiden i ett pull-baserat byggsystem som heter Blazar. Detta uppnås genom att minska den genomsnittliga tid som ett byggt program väntar innan den tilldelas en resurs av orkestreringsverktyget, Kubernetes. Förbättringen av den genomsnittliga kötiden fås genom att utnyttja tidigare data om systemets köbelastning med omfattningen att förutsäga mängden resurser och fördela dem förebyggande. I avhandlingen undersöks olika tidsserieprognosmodeller för att hitta den mest relevanta med avseende på tillgänglig data. Det slutliga valet av modellen är Facebooks Prophet på grund av dess förmåga att utnyttja flera säsongsbestämmelser, hantera avvikelser, helgdagar och ge snabba förutsägelser. Genom att ställa in olika modellparametrar var det möjligt att uppnå tillfredsställande resultat. Under några av de testade perioderna minskade således den genomsnittliga kötiden med upp till 20%, samtidigt som en rimlig resursanvändning bibehölls, jämfört med tiden som ficks utan att använda någon förutsägelsemodell. Slutligen avser denna avhandling inte att ge en toppmodern lösning. Således slutar det med att beskriva sina begränsningar samtidigt som de tillhandahåller andra lösningar och idéer som kan förbättra resultaten.
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Brahimi, Mammar. "Approximating multi-server queues with inhomgeneous arrival rates and continuous service time distributions." Thesis, Lancaster University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254028.
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Liman-Tinguiri, Karim. "Using importance sampling to simulate queuing networks with heavy-tailed service time distributions." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66438.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 81-82).<br>Characterization of steady-state queue length distributions using direct simulation is generally computationally prohibitive. We develop a fast simulation method by using an importance sampling approach based on a change of measure of the service time in an M/G/1 queue. In particular, we present an algorithm for dynamically finding the optimal distribution within the parametrized class of delayed hazard rate twisted distributions of the service time. We run it on a M/G/1 queue with heavy-tailed service time distributions and show simulation gains of two orders of magnitude over direct simulation for a fixed confidence interval.<br>by Karim Liman-Tinguiri.<br>M.Eng.
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Siddiqui, Usman Ghani. "The impact of MAC service-time and route discovery time on packet queuing delay in saturated ad hoc networks." Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/3978.
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This thesis presents a quantitative analysis of packet queuing delays in saturated DCF
networks. It presents the relationship between medium access control (MAC) delays, routing
delays, and the packet queuing delays, in terms of MAC service-time and route discovery time.
The effects of network size and data transmission rates on the queuing delays were also
analyzed. The simulations reveal that the MAC service-time affects the packet queuing delay in
stationary networks; whereas the route discovery time along with the MAC service-time affects
the queuing delays in mobile networks. Also, the average queuing delay increased with an
increase in the network sizes and data transmission rates, especially for network sizes of 20 and
more.<br>Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science.
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Muthuvelu, Sethumadhavan. "Simultaneous Lot sizing and Lead-time Setting (SLLS)Via Queuing Theory and Heuristic search." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/9692.
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Materials requirements planning (MRP) is a widely used method for production planning and scheduling. Planned lead-time (PLT) and lot size are two of the input parameters for MRP systems, which determine planned order release dates. Presently, planned lead-time and lot size are estimated using independent methodologies. No existing PLT estimation methods consider factors such as machine breakdown, scrap-rate, etc. Moreover, they do not consider the capacity of a shop, which changes dynamically, because the available capacity at any given time is determined by the loading of the shop at that time. The absence of such factors in calculations leads to a huge lead-time difference between the actual lead-time and PLT, i.e., lead-time error. Altering the size of a lot will have an effect not only on the lead-time of that lot but also on that of other lots. The estimation of lot size and lead-time using independent methodologies currently does not completely capture the inter-dependent nature of lead-time and lot size.
In this research, a lot-sizing model is modified in such a way that it minimizes the combination of setup cost, holding cost and work-in-process cost. This proposed approach embeds an optimization routine, which is based on dynamic programming on a manufacturing system model, which is based on open queuing network theory. Then, it optimizes lot size by using realistic estimates of WIP and the lead-time of different lots simultaneously for single-product, single-level bills of material. Experiments are conducted to compare the performance of the production plans generated by applying both conventional and the proposed methods. The results show that the proposed method has great potential and it can save up to 38% of total cost and minimize lead-time error up to 72%.<br>Master of Science
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Yu, Fu. "On statistical analysis of vehicle time-headways using mixed distribution models." Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/d101df63-b7db-45b6-8a03-365b64345e6b.
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For decades, vehicle time-headway distribution models have been studied by many researchers and traffic engineers. A good time-headway model can be beneficial to traffic studies and management in many aspects; e.g. with a better understanding of road traffic patterns and road user behaviour, the researchers or engineers can give better estimations and predictions under certain road traffic conditions and hence make better decisions on traffic management and control. The models also help us to implement high-quality microscopic traffic simulation studies to seek good solutions to traffic problems with minimal interruption of the real traffic environment and minimum costs. Compared within previously studied models, the mixed (SPM and GQM) mod- els, especially using the gamma or lognormal distributions to describe followers headways, are probably the most recognized ones by researchers in statistical stud- ies of headway data. These mixed models are reported with good fitting results indicated by goodness-of-fit tests, and some of them are better than others in com- putational costs. The gamma-SPM and gamma-GQM models are often reported to have similar fitting qualities, and they often out-perform the lognormal-GQM model in terms of computational costs. A lognormal-SPM model cannot be formed analytically as no explicit Laplace transform is available with the lognormal dis- tribution. The major downsides of using mixed models are the difficulties and more flexibilities in fitting process as they have more parameters than those single models, and this sometimes leads to unsuccessful fitting or unreasonable fitted pa- rameters despite their success in passing GoF tests. Furthermore, it is difficult to know the connections between model parameters and realistic traffic situations or environments, and these parameters have to be estimated using headway samples. Hence, it is almost impossible to explain any traffic phenomena with the param- eters of a model. Moreover, with the gamma distribution as the only common well-known followers headway model, it is hard to justify whether it has described the headway process appropriately. This creates a barrier for better understanding the process of how drivers would follow their preceding vehicles. This study firstly proposes a framework developed using MATLAB, which would help researchers in quick implementations of any headway distributions of interest. This framework uses common methods to manage and prepare headway samples to meet those requirements in data analysis. It also provides common structures and methods on implementing existing or new models, fitting models, testing their performance hence reporting results. This will simplify the development work involved in headway analysis, avoid unnecessary repetitions of work done by others and provide results in formats that are more comparable with those reported by others. Secondly, this study focuses on the implementation of existing mixed models, i.e. the gamma-SPM, gamma-GQM and lognormal-GQM, using the proposed framework. The lognormal-SPM is also tested for the first time, with the recently developed approximation method of Laplace transform available for lognormal distributions. The parameters of these mixed models are specially discussed, as means of restrictions to simplify the fitting process of these models. Three ways of parameter pre-determinations are attempted over gamma-SPM and gamma-GQM models. A couple of response-time (RT) distributions are focused on in the later part of this study. Two RT models, i.e. Ex-Gaussian (EMG) and inverse Gaussian (IVG) are used, for first time, as single models to describe headway data. The fitting performances are greatly comparable to the best known lognormal single model. Further extending this work, these two models are tested as followers headway distributions in both SPM and GQM mixed models. The test results have shown excellent fitting performance. These now bring researchers more alternatives to use mixed models in headway analysis, and this will help to compare the be- haviours of different models when they are used to describe followers headway data. Again, similar parameter restrictions are attempted for these new mixed models, and the results show well-acceptable performance, and also corrections on some unreasonable fittings caused by the over flexibilities using 4- or 5- parameter models.
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Darshana, Dipika. "DELAY SENSITIVE ROUTING FOR REAL TIME TRAFFIC OVER AD-HOC NETWORKS." Master's thesis, University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2802.
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Wireless ad hoc network consists of inexpensive nodes that form a mobile communication network. Due to limitations of the transmission range, the nodes rely on each other to forward packets such that messages can be delivered across the network. The selection of the path along which a packet is forwarded from the source node to the destination node is done by the routing algorithm. Most commonly used routing algorithms, though effective for non-real time applications, cannot handle real-time applications that require strict delay bounds on packet delivery. In this thesis, we propose a routing protocol that ensures timely delivery of real time data packets. The idea is to route packets in such a way that irrespective of factors like traffic load and node density, the average delay remains within acceptable bounds. This is done by carefully accessing the resources available to a route before a session is admitted along that route. Each link in the route is checked for sufficient bandwidth not only for the new session to be admitted but also for the sessions that are already using that link. The new session is admitted only if the admission does not violate the delay bounds of any on-going sessions. This method of route selection coupled with per-hop link reservations allows us to provide bounds on the delay performance. Extensive simulation experiments have been conducted that demonstrate the performance of the proposed routing protocol in terms of throughput, session blocking probability, packet drop probability, average path length, and delay.<br>M.S.<br>School of Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Computer Engineering MSCpE
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Kim, Jung-Kyung. "Tail asymptotics of queueing networks with subexponential service times." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29734.
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Thesis (Ph.D)--Industrial and Systems Engineering, Georgia Institute of Technology, 2010.<br>Committee Chair: Ayhan, Hayriye; Committee Member: Foley, Robert D.; Committee Member: Goldsman, David M.; Committee Member: Reed, Joshua; Committee Member: Zwart, Bert. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Grannan, Benjamin. "Dispatch, Delivery, and Location Logistics for the Aeromedical Evacuation of Time-Sensitive Military Casualties Under Uncertainty." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3536.
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Effective aeromedical evacuation of casualties is one of the most important problems in military medical systems because high-priority casualties will not survive without timely medical care. The decision making process for aeromedical evacuation consists of the following components: (1) identifying which aeromedical evacuation asset (see figure 1) to dispatch to the casualty, (2) locating aeromedical evacuation assets strategically in anticipation of incoming demand, and (3) deciding which medical treatment facility to transport the casualty. These decisions are further complicated because prioritization of casualties is based on severity of injury while aeromedical evacuation assets and medical treatment facilities operate with varying capabilities. In this dissertation, discrete optimization models are developed to examine dispatch, delivery, and location logistics for the effective aeromedical evacuation of casualties in military medical systems.
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Lopes, Marcelo da Mota. "Uma arquitetura orientada a serviço para aplicações com restrições temporais." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3141/tde-19072011-164425/.
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Este trabalho apresenta uma proposta de Arquitetura Orientada a Serviço para desenvolvimento de aplicações com restrições temporais, isto é, aplicações em que o tempo de resposta a uma requisição deve respeitar limites máximos. No desenvolvimento da arquitetura proposta foram considerados os modelos de filas com um único servidor e com múltiplos servidores, por meio da utilização de serviços redundantes e do escalonamento de requisições para melhoria do determinismo no tempo de resposta das requisições efetuadas. Para avaliação da arquitetura proposta foi construído um sistema de testes de forma a ser observado o comportamento do tempo de resposta das requisições em função do número de servidores disponíveis e sua respectiva taxa de utilização. Os resultados obtidos indicam que é possível obter um aumento no determinismo do tempo de resposta das requisições efetuadas (diminuição da dispersão de valores), tendo sido obtidos resultados semelhantes para os dois algoritmos de escalonamento utilizados: por ordem de chegada das requisições e SRPT (Shortest Remaining Processing Time).<br>This thesis presents a proposal for a Service Oriented Architecture applied to development of time constrained systems, where the timeliness of the results is a major requirement. The development is based on the queuing theory (models using one and multiple servers) and requests scheduling to improve response time determinism. In order to verify the proposal, a test system had been developed to observe the dynamic behavior of the requests response time dispersion according to the number of servers available and associated processing rate. The results obtained show an improvement over the request response time determinism and almost similar performance for the two scheduling algorithms used: request arrival order and SRPT (Shortest Remaining Processing Time).
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Erasmus, Gert Botha. "Stochastic models of steady state and dynamic operation of systems of congestion." Thesis, Pretoria : [s.n.], 2006. http://hdl.handle.net/2263/28814.
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(i) The thesis sets out to address the problematic phenomenon of Systems of Congestion via Basic Queueing Theory. The theory, and its application in practice, appears to be a field of study which is the common domain of “theorists” and “practitioners”. (ii) This professional dichotomy has come about due to diverging interests in that one group is mainly interested in the purity of mathematical modelling, and the other group is motivated to use modelling, which conveniently employs applications oriented solutions. (iii) The schism between the groups has been accentuated by the “practitioners” who in addition to having an interest in steady state system behaviour make use of methods of modelling of the transient operation of complex Systems of Congestion. (iv) At the outset the thesis demonstrates how closed form solutions are obtained for steady state and transient state operation of a selection of Systems of Congestion. The attendant mathematical derivations are elegant and intricate. (v) Having revealed the limited utility of closed-form solutions the thesis proceeds to investigate the feasibility of using dynamical systems theory to study the transient behaviour of complex Systems of Congestion. (vi) The creation of Chaos Theory in recent decades suggests that it may be employed as a useful tool in analysing Systems of Congestion. Iterative Chaos Theory methods of orbit generation for complete Systems of Congestion are therefore examined. The use of such orbit generation methods is found to be satisfactory for simple Systems of Congestion. More than a perfunctory knowledge of chaos mapping is however required. The simplicity of modelling is emphasized. (vii) Based on the results of benchmarking the creation of dynamic system orbits against an existing simulation method, the research advances to modelling of the transient operation of complex systems. Once again the iterative method of orbit generation displays the ease of modelling while simultaneously unfolding system dynamics graphically. (viii) One may hopefully contend that a tool of eminent utility has been developed to aid practitioners in studying and optimizing Systems of Congestion.<br>Thesis (PhD (Industrial Engineering))--University of Pretoria, 2006.<br>Industrial and Systems Engineering<br>Unrestricted
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Komashie, Alexander. "Information-theoretic and stochastic methods for managing the quality of service and satisfaction in healthcare systems." Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4402.
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This research investigates and develops a new approach to the management of service quality with the emphasis on patient and staff satisfaction in the healthcare sector. The challenge of measuring the quality of service in healthcare requires us to view the problem from multiple perspectives. At the philosophical level, the true nature of quality is still debated; at the psychological level, an accurate conceptual representation is problematic; whilst at the physical level, an accurate measurement of the concept still remains elusive to practitioners and academics. This research focuses on the problem of quality measurement in the healthcare sector. The contributions of this research are fourfold: Firstly, it argues that from the technological point of view the research to date into quality of service in healthcare has not considered methods of real-time measurement and monitoring. This research identifies the key elements that are necessary for developing a real-time quality monitoring system for the healthcare environment.Secondly, a unique index is proposed for the monitoring and improvement of healthcare performance using information-theoretic entropy formalism. The index is formulated based on five key performance indicators and was tested as a Healthcare Quality Index (HQI) based on three key quality indicators of dignity, confidence and communication in an Accident and Emergency department. Thirdly, using an M/G/1 queuing model and its underlying Little’s Law, the concept of Effective Satisfaction in healthcare has been proposed. The concept is based on a Staff-Patient Satisfaction Relation Model (S-PSRM) developed using a patient satisfaction model and an empirically tested model developed for measuring staff satisfaction with workload (service time). The argument is presented that a synergy between patient satisfaction and staff satisfaction is the key to sustainable improvement in healthcare quality. The final contribution is the proposal of a Discrete Event Simulation (DES) modelling platform as a descriptive model that captures the random and stochastic nature of healthcare service provision process to prove the applicability of the proposed quality measurement models.
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Albana, Abduh-Sayid. "Choix du prix et du délai de livraison dans une chaîne logistique avec une demande endogène sensible au délai de livraison et au prix." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI004/document.
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Parallèlement au prix, le délai de livraison est un facteur clé de compétitivité pour les entreprises. De plus les entreprises sont plus que jamais obligées de respecter ce délai promis. La combinaison du choix du prix et du délai promis implique de nouveaux compromis et offre de nombreuses perspectives. Un délai plus court peut entraîner une augmentation de la demande, mais augmente également le risque de livraison tardive et donc décourager les clients. A contrario un délai plus long ou un prix plus élevé entraîne généralement une baisse de la demande. Or malgré le rôle stratégique conjoint du prix et des délais et leurs impacts sur la demande, dans la littérature en gestion des opérations on suppose très généralement une demande exogène (fixée a priori) même si la conception de la chaîne impacte fortement les délais (localisation des sites, positionnement des stocks,..) et donc la demande. Nous nous sommes donc intéressés à ces choix de fixation des délais promis et du prix dans un contexte de demande endogène.La littérature traitant du choix du délai et du prix sous demande endogène a principalement considéré un contexte de fabrication à la commande (Make to Order). Un papier fondateur de Palaka et al en 1998 a présenté cette problématique avec une modélisation de l’entreprise par une file d’attente M/M/1 et nos travaux se placent dans la suite de ce travail. Notre revue de la littérature a permis d'identifier de nouvelles perspectives et nous proposons trois extensions dans cette thèse.Dans notre première contribution, en utilisant le cadre de Palaka et al, nous considérons que le coût de production est une fonction décroissante du délai. Dans tous les articles publiés dans ce contexte, le coût de production unitaire a été supposé constant. Pourtant en pratique, le coût de production unitaire dépend du délai promis, l'entreprise pouvant mieux gérer le processus de production et réduire les coûts de production en proposant des délais plus longs aux clients.Dans la deuxième contribution, nous considérons toujours le cadre de Palaka et al, mais modélisons l'entreprise comme une file d'attente M/M/1/K, pour laquelle la demande est donc rejetée s'il y a déjà K clients dans le système. Dans la littérature issue du travail de Palaka seule la file d'attente M/M/1 a été utilisée, ce qui signifie que tous les clients sont acceptés, ce qui peut entraîner de longues durées de séjour dans le système. Notre idée est basée sur le fait que rejeter certains clients, même si cela peut apparaitre dans un premier temps comme une perte de demande, pourrait aider à proposer un délai plus court pour les clients acceptés, et finalement conduire à une demande et donc un profit plus élevé.Dans la troisième contribution nous étudions un nouveau cadre pour le problème du délai et du prix en fonction de la demande endogène, en modélisant une chaîne logistique composée de deux étapes de production, modélisée par un réseau de files d’attente tandem (M/M/1-M/M/1). Dans la littérature avec ce cadre multi-entreprise, tous les articles ont considéré qu'un seul acteur avait des opérations de production, l'autre acteur ayant un délai nul. Nous avons étudié les scénarios centralisés et décentralisés.Pour chacun des nouveaux problèmes nous avons proposé des formulations maximisant le profit composé du revenu diminué des coûts de production, de stockage et pénalité de retard, et fourni des résolutions optimales, analytiques ou numériques. Ces résolutions nous ont amenés à démontrer de nouveaux résultats (retard moyen dans une M/M/1/K ; condition pour que des contraintes de service locales permettent d’assurer une contrainte de service globale dans un système en tandem). Nous avons mené des expériences numériques pour voir l’influence des différents paramètres<br>Along with the price, the delivery lead time has become a key factor of competitiveness for companies and an important purchase criterion for many customers. Nowadays, firms are more than ever obliged to meet their quoted lead time, which is the delivery lead time announced to the customers. The combination of pricing and lead time quotation implies new trade-offs and offers opportunities for many insights. For instance, on the one hand, a shorter quoted lead time can lead to an increase in the demand but also increases the risk of late delivery and thus may affect the firm’s reputation and deter future customers. On the other hand, a longer quoted lead time or a higher price generally yields a lower demand. Despite the strategic role of joint pricing and lead time quotation decisions and their impacts on demand, in the operations management literature an exogenous demand (a priory a known demand) is generally used in supply chain models, even if the design of the supply chain has a strong impact on lead times (i.e., sites location, inventory position, etc.) and thus affects the demand. Therefore, we are interested in the lead time quotation and pricing decisions in a context of endogenous demand (i.e., demand sensitive to price and quoted lead time).The literature dealing with pricing and lead time quotation under an endogenous demand mainly considered a make to order (MTO) context. A pioneer paper, Palaka et al. (1998), investigated this issue by modeling the company as an M/M/1 queue, and our work follows their footsteps. Our review of the literature allowed to identify new perspectives for this problem, which led to three main contributions in this thesis.In our first contribution, using Palaka et al.’s framework, we consider the unit production cost to be a decreasing function in quoted lead time. In most published papers, the unit production cost was assumed to be constant. In practice, the unit production cost generally depends on the quoted lead time. Indeed, the firm can manage better the production process and reduce the production cost by quoting longer lead time to the customers.In the second contribution, we still consider Palaka et al.’s framework but model the firm as an M/M/1/K queue, for which demand is rejected if there are already K customers in the system. In the literature on single firm setting following Palaka et al.’s research, only the M/M/1 queue was used, i.e., where all customers are accepted, which might lead to long sojourn times in the system. Our idea is based on the fact that rejecting some customers, might help to quote shorter lead time for the accepted ones, which might finally lead to a higher profitability, even if in the first glance we lose some demand.In the third contribution, we study a new framework for the lead time quotation and pricing problem under endogenous demand as we model the supply chain by two production stages in a tandem queue (M/M/1-M/M/1). In the literature with multi-firm setting, all papers considered that only one actor has production operations and the other actor has zero lead time. We investigated both the centralized and decentralized decision settings.For each problem studied, we formulated a profit-maximization model, where the profit consists of a revenue minus the production, storage and lateness penalty costs, and provides the optimum result (analytically or numerically). These resolutions led us to demonstrate new theoretical results (such as the expected lateness in an M/M/1/K, and the sufficient condition required to satisfy the global service constraint in a tandem queue by only satisfying the local service constraints). We also conducted numerical experiments and derived managerial insights
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Ghaboosi, K. (Kaveh). "Intelligent medium access control for the future wireless networks." Doctoral thesis, University of Oulu, 2009. http://urn.fi/urn:isbn:9789514292187.
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Abstract
Medium access control (MAC) in wireless ad hoc networks has received considerable attention for almost a couple of decades; however, there are still open problems which deserve thorough study in order to facilitate migration to the next generation broadband wireless communication systems. In ad hoc networks, a detected frame collision can be due to the so-called unreachability problem, where the destination station is situated either in the transmission or interference range of an emitting station and is unable to receive connection establishment frames from any of its neighboring stations. Unreachability might also be due to the inability of a radio station to respond to any connection establishment request, though when the unreachable station receives the connection establishment requests, however, it is prohibited from responding to the requests due to being situated in the interference range of the emitting neighbor.
To investigate the impact of this problem, we have to be equipped with a proper analytical framework; therefore, as the first part of this thesis, a scalable framework called Parallel Space – Time Markov chain (PSTMC) is proposed, through which a finite load non-saturated ad hoc network can be easily modeled. At the first step, a single-hop ad hoc network is considered and the accuracy of the model is evaluated using extensive numerical results. Subsequently, the proposed framework is further extended to model multi-hop ad hoc networks. Several discussions are also given on how the framework can be deployed for an arbitrary network topology. One of the main key features of the PSTMC model is its remarkable scalability in modeling complex network configurations. In fact, it is shown that multi-hop ad hoc networks have bounded complexity in being modeled by the PSTMC framework due to its spectacular specifications. These features lead us to a powerful tool by which an arbitrary network topology can be studied. In addition, the proposed models clearly facilitate demonstrating the impact of the unreachability problem on the performance of multi-hop networks. The introduced framework shows how the unreachability problem degrades the achieved throughput and channel capacity by the contending radio stations depending on the deployed network topology.
In the remainder of the thesis the unreachability problem in mobile ad hoc networks is tackled and a new MAC protocol to enhance the performance of the network is proposed. This MAC scheme is equipped with smart decision-making algorithms as well as adaptive management mechanisms to reduce the impact of the unreachability problem in single channel scenarios. Subsequently, the problem of concurrent radio resource management and contention resolution in multi-channel cognitive ad hoc networks is considered. In particular, a multi-channel technique for traffic distribution among a set of data channels without centralized control, which is enabled by a probabilistic channel selection algorithm as well as a multi-channel binary exponential backoff mechanism, is proposed. It is shown through simulations that the suggested scheme outperforms the existing MAC protocols in multi-channel environments as well as cognitive networks coexisting with primary users. A mathematical model is also introduced to study the performance of the multi-channel MAC protocol in a single-hop non-saturated wireless network.
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Hagtvedt, Reidar. "Applications of Decision Analysis to Health Care." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22535.
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This dissertation deals with three problems in health care. In the first, we consider the incentives to change prices and capital levels at hospitals, using optimal control under the assumption that private payers charge higher prices if patients consume more hospital services. The main results are that even with fixed technology, investment and prices exhibit explosive growth, and that prices and capital stock grow in proportion to one another.
In the second chapter, we study the flow of nosocomial infections in an intensive care unit. We use data from Cook County Hospital, along with numerous results from the literature, to construct a discrete event simulation. This model highlights emergent properties from treating the flow of patients and pathogens in one interconnected system, and sheds light on how nosocomial infections relate to hospital costs. We find that the system is not decomposable to individual systems, exhibiting behavior that would be difficult to explain in isolation.
In the third chapter, we analyze a proposed change in diversion policies at hospitals, in order to increase the number of patients served, without an increase in resources. Overcrowding in hospital emergency departments is caused in part by the inability to send patients to main hospital wards, due to limited capacity. When a hospital is completely full, the hospital often goes on ambulance diversion, until some spare capacity has opened up. Diversion is costly, and often leads to waves of diversions in systems of hospitals, a situation that is regarded as highly problematic in public health. We construct and analyze a continuous-time Markov chain model for one hospital. The intuition behind the model is that load-balancing between various hospitals in a metro area may hinder full congestion. We find that a more flexible contract may benefit all parties, through the partial diversion of federally insured patients, when a hospital is very close to full. Discrete event simulation models are run to assess the effect, using data from DeKalb Medical Center, and also to show that in a two-hospital system, more federally insured patients are served using this mechanism.
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Kluth, Stephan. "Quantitative modeling and analysis with FMC-QE." Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5298/.
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The modeling and evaluation calculus FMC-QE, the Fundamental Modeling Concepts for Quanti-tative Evaluation [1], extends the Fundamental Modeling Concepts (FMC) for performance modeling and prediction. In this new methodology, the hierarchical service requests are in the main focus, because they are the origin of every service provisioning process. Similar to physics, these service requests are a tuple of value and unit, which enables hierarchical service request transformations at the hierarchical borders and therefore the hierarchical modeling. Through reducing the model complexity of the models by decomposing the system in different hierarchical views, the distinction between operational and control states and the calculation of the performance values on the assumption of the steady state, FMC-QE has a scalable applica-bility on complex systems.
According to FMC, the system is modeled in a 3-dimensional hierarchical representation space, where system performance parameters are described in three arbitrarily fine-grained hierarchi-cal bipartite diagrams. The hierarchical service request structures are modeled in Entity Relationship Diagrams. The static server structures, divided into logical and real servers, are de-scribed as Block Diagrams. The dynamic behavior and the control structures are specified as Petri Nets, more precisely Colored Time Augmented Petri Nets. From the structures and pa-rameters of the performance model, a hierarchical set of equations is derived. The calculation of the performance values is done on the assumption of stationary processes and is based on fundamental laws of the performance analysis: Little's Law and the Forced Traffic Flow Law. Little's Law is used within the different hierarchical levels (horizontal) and the Forced Traffic Flow Law is the key to the dependencies among the hierarchical levels (vertical). This calculation is suitable for complex models and allows a fast (re-)calculation of different performance scenarios in order to support development and configuration decisions.
Within the Research Group Zorn at the Hasso Plattner Institute, the work is embedded in a broader research in the development of FMC-QE. While this work is concentrated on the theoretical background, description and definition of the methodology as well as the extension and validation of the applicability, other topics are in the development of an FMC-QE modeling and evaluation tool and the usage of FMC-QE in the design of an adaptive transport layer in order to fulfill Quality of Service and Service Level Agreements in volatile service based environments.
This thesis contains a state-of-the-art, the description of FMC-QE as well as extensions of FMC-QE in representative general models and case studies. In the state-of-the-art part of the thesis in chapter 2, an overview on existing Queueing Theory and Time Augmented Petri Net models and other quantitative modeling and evaluation languages and methodologies is given. Also other hierarchical quantitative modeling frameworks will be considered. The description of FMC-QE in chapter 3 consists of a summary of the foundations of FMC-QE, basic definitions, the graphical notations, the FMC-QE Calculus and the modeling of open queueing networks as an introductory example. The extensions of FMC-QE in chapter 4 consist of the integration of the summation method in order to support the handling of closed networks and the modeling of multiclass and semaphore scenarios. Furthermore, FMC-QE is compared to other performance modeling and evaluation approaches. In the case study part in chapter 5, proof-of-concept examples, like the modeling of a service based search portal, a service based SAP NetWeaver application and the Axis2 Web service framework will be provided. Finally, conclusions are given by a summary of contributions and an outlook on future work in chapter 6.
[1] Werner Zorn. FMC-QE - A New Approach in Quantitative Modeling. In Hamid R. Arabnia, editor, Procee-dings of the International Conference on Modeling, Simulation and Visualization Methods (MSV 2007) within WorldComp ’07, pages 280 – 287, Las Vegas, NV, USA, June 2007. CSREA Press. ISBN 1-60132-029-9.<br>FMC-QE (Fundamental Modeling Concepts for Quantitative Evaluation [1]) ist eine auf FMC, den Fundamental Modeling Concepts, basierende Methodik zur Modellierung des Leistungsverhaltens von Systemen mit einem dazugehörenden Kalkül zur Erstellung von Leistungsvorhersagen wie Antwortzeiten und Durchsatz. In dieser neuen Methodik steht die Modellierung der hierarchischen Bedienanforderungen im Mittelpunkt, da sie der Ursprung aller dienstbasierenden Systeme sind. Wie in der Physik sind in FMC-QE die Bedienanforderungen Tupel aus Wert und Einheit, um Auftragstransformationen an Hierarchiegrenzen zu ermöglichen. Da die Komplexität durch eine Dekomposition in mehreren Sichten und in verschiedene hierarchische Schichten, die Unterscheidung von Operations- und Kontrollzuständen, sowie dazugehörige Berechungen unter Annahme der Stationarität reduziert wird, skaliert die Anwendbarkeit von FMC-QE auf komplexe Systeme.
Gemäß FMC wird das zu modellierende System in einem 3-dimensionalen hierarchischen Beschreibungsraum dargestellt. Die quantitativen Kenngrößen der Systeme werden in drei beliebig frei-granularen hierarchischen bi-partiten Graphen beschrieben. Die hierarchische Struktur der Bedienanforderungen wird in Entity Relationship Diagrammen beschrieben. Die statischen Bedienerstrukturen, unterteilt in logische und reale Bediener, sind in Aufbaudiagrammen erläutert. Außerdem werden Petri Netze, genauer Farbige Zeit-behaftete Petri Netze, dazu verwendet, die dynamischen Abläufe, sowie die Kontrollflüsse im System zu beschreiben. Anschließend wird eine Menge von hierarchischen Gleichungen von der Struktur und den Parametern des Modells abgeleitet. Diese Gleichungen, die auf dem stationären Zustand des Systems beruhen, basieren auf den beiden Fundamental Gesetzen der Leistungsanalyse, dem Gesetz von Little und dem Verkehrsflussgesetz. Das Gesetz von Little definiert hierbei Beziehungen innerhalb einer hierarchischen Schicht (horizontal) und das Verkehrsflussgesetz wiederum Beziehungen zwischen hierarchischen Schichten (vertikal). Die Berechungen erlauben Leistungsvorhersagen für komplexe Systeme durch eine effiziente Berechnung von Leistungsgrößen für eine große Auswahl von System- und Lastkonfigurationen.
Innerhalb der Forschungsgruppe von Prof. Dr.-Ing Werner Zorn am Hasso Plattner Institut an der Universität Potsdam ist die vorliegende Arbeit in einen größeren Forschungskontext im Bereich FMC-QE eingebettet. Während hier ein Fokus auf dem theoretischen Hintergrund, der Beschreibung und der Definition der Methodik als auch der Anwendbarkeit und Erweiterung gelegt wurde, sind andere Arbeiten auf dem Gebiet der Entwicklung einer Anwendung zur Modellierung und Evaluierung von Systemen mit FMC-QE bzw. der Verwendung von FMC-QE zur Entwicklung einer adaptiven Transportschicht zur Einhaltung von Dienstgüten (Quality of Service) und Dienstvereinbarungen (Service Level Agreements) in volatilen dienstbasierten Systemen beheimatet.
Diese Arbeit umfasst einen Einblick in den Stand der Technik, die Beschreibung von FMC-QE sowie die Weiterentwicklung von FMC-QE in repräsentativen allgemeinen Modellen und Fallstudien. Das Kapitel 2: Stand der Technik gibt einen Überblick über die Warteschlangentheorie, Zeit-behaftete Petri Netze, weitere Leistungsbeschreibungs- und Leistungsvorhersagungstechniken sowie die Verwendung von Hierarchien in Leistungsbeschreibungstechniken. Die Beschreibung von FMC-QE in Kapitel 3 enthält die Erläuterung der Grundlagen von FMC-QE, die Beschreibung einiger Grundannahmen, der graphischen Notation, dem mathematischen Modell und einem erläuternden Beispiel. In Kapitel 4: Erweiterungen von FMC-QE wird die Behandlung weiterer allgemeiner Modelle, wie die Modellklasse von geschlossenen Netzen, Synchronisierung und Mehrklassen-Modelle beschrieben. Außerdem wird FMC-QE mit dem Stand der Technik verglichen. In Kapitel 5 werden Machbarkeitsstudien beschrieben. Schließlich werden in Kapitel 6 eine Zusammenfassung und ein Ausblick gegeben.
[1] Werner Zorn. FMC-QE - A New Approach in Quantitative Modeling. In Hamid R. Arabnia, editor, Proceedings of the International Conference on Modeling, Simulation and Visualization Methods (MSV 2007) within WorldComp ’07, 280 – 287, Las Vegas, NV, USA, Juni 2007. CSREA Press. ISBN 1-60132-029-9.
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Debnath, Jayanta Kumar. "Development of Scheduling, Path Planning and Resource Management Algorithms for Robotic Fully-automated and Multi-story Parking Structure." University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1470399189.
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Liu, Liqiang Kulkarni Vidyadhar G. "Service systems with balking based on queueing time." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1454.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.<br>Title from electronic title page (viewed Apr. 25, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Statistics and Operations Research." Discipline: Statistics and Operations Research; Department/School: Statistics and Operations Research.
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Nasr, Walid. "Analysis and Approximations of Time Dependent Queueing Models." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/26090.
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Developing equations to compute congestion measures for the general G/G/s/c queueing model and networks of such nodes has always been a challenge. One approach to analyzing such systems is to approximate the model-specified general input processes and distributions by processes and distributions from the more computationally friendly family of phase-type processes and distributions. We develop numerical approximation methods for analysis of general time-dependent queueing nodes by introducing new approximations for the time-dependent first two moments of the number-in-system and departure-count processes.<br>Ph. D.
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Ha, Duy Hung. "Modélisation statistique et probabiliste du temps inter-véhiculaire aux différents niveaux de trafic." Thesis, Paris Est, 2011. http://www.theses.fr/2011PEST1140.
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Temps Inter-véhiculaire (TIV) est une variable microscopique fondamentale dans la théorie du trafic, et a été étudié depuis le début du développement de cette théorie, vers 1930. La distribution de probabilité du TIV décrit la répartition des arrivées des véhicules en un point donné et reflète dans une certaine mesure le comportement de conduite. Beaucoup d'applications en ingénierie du trafic viennent de la connaissance fine de cette variable. La thèse a pour but d'approfondir cette connaissance en modélisant la distribution du TIV dans différents contextes selon différents points de vue. Tout d'abord, deux méthodes d'échantillonnage, la méthode de groupement et la méthode de raffinement sont considérées. L'application numérique concerne deux bases de données, celle de la route nationale RN118 et celle de l'autoroute A6. Ensuite, trois types de modèles probabilistes sont analysés et classifiés. Une comparaison exhaustive des modèles et des méthodes d'estimation est réalisée ce qui conduit à considérer que le modèle gamma-GQM est supérieur aux autres modèles en matière de performance statistique et en efficacité de calcul. Différentes procédures d'estimation sont testées, celle qui est proposée et retenue favorise la stabilité des paramètres estimés. Six nouveaux modèles de TIV sont proposés, calibrés, analysés. Mis à part deux modèles de performance inférieure aux autres et au modèle gamma-GQM, quatre modèles sont équivalents voire meilleurs que le modèle gamma-GQM. Pour une raison pratique, le modèle Double Gamma est choisi à côté du modèle gamma-GQM, comme modèle de comparaison, dans toute la modélisation des TIV. Le calibrage des modèles et l'analyse des paramètres des modèles sont menés, à partir des données réelles, en considérant trois dimensions d'étude du trafic: les échelles macroscopique, mésoscopique et microscopique. Une quatrième dimension d'étude des TIV est constituée des facteurs exogènes au trafic. La prise en compte de ces facteurs exogènes, à chaque échelle macroscopique entraîne la distinction de deux types de facteur exogène : « empêchant » et « impulsant». Finalement, différentes approches de validation sont testées. L'approche proposée par « enveloppe des distributions » semble prometteuse pour le futur<br>Time Headway (TH) is a microscopic variable in traffic flow theories that has been studied since the 1930s. Distribution of this fundamental variable describes the arrival pattern of vehicles in traffic flow, so probabilistic modeling is the main approach to study TH and represent driving behaviour. The applications of the variable in traffic engineering are varied; include capacity calculation, microscopic simulation, traffic safety analysis, etc. This dissertation aims at modeling the TH distribution in different contexts. Firstly, the short-time sampling method and long-time sampling method are applied to obtain TH samples from the two data bases (the RN118 national roadway and the A6 motorway). Then, three probabilistic TH model types are analyzed and classified. An exhaustive comparison between the existing models and between the corresponding estimation methods lead to consider that the gamma-GQM is the best TH model in the literature. An estimation process is also proposed in order to obtain good and stable estimated results of the parameters. After that, the TH probabilistic modeling is developed by six new models. Except for the two ones which are worse, the four other models are statistically equivalent and/or better than the gamma-GQM. For practical reason, the Double Gamma model is selected, as a comparison model, with the gamma-GQM to calibrate all TH samples. Three traffic levels are considered: macroscopic, mesoscopic and microscopic. The effects of exogenous factors are also examined. Examining this factor in each macroscopic variable level leads to distinguish two following factor types: impeding factor and propulsive factor. Finally, different approaches for TH validation are tested. The proposed approach of “envelope of distributions” seems to be promising for future applications
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Desta, Alemayehu. "Energy Supply and Demand Side Management in Industrial Microgrid Context." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1234/document.
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En raison de l'augmentation des coûts d'énergie et des préoccupations environnementales telles que les empreintes de carbone élevées, les systèmes de la production d'électricité centralisée se restructurent pour profiter des avantages de la production distribuée afin de répondre aux exigences énergétiques toujours croissantes. Les microgrids sont considérés comme une solution possible pour déployer une génération distribuée qui inclut des ressources énergétiques distribuées DERs (Distributed Energy Resources)(e.g, solaire, éolienne, batterie, etc). Dans cette thèse, nous traitons les défis de la gestion d'énergie dans un microgrid industriel où les charges énergétique sont constituées de processus industriels. Notre plan consiste à diviser la gestion de l'énergie du microgrid en deux parties: la production et la demande d’énergie.Du côté de la production d'énergie, les défis incluent la modélisation des générations de puissance et le lissage des fluctuations des DER. Pour modéliser les générations de puissance, nous proposons un modèle basé sur les concepts de service courbé de Network Calculus. En utilisant cet outil mathématique, nous déterminons une quantité minimale de puissance que les DERs peuvent générer; leur agrégation nous donnera une production d'énergie totale dans le microgrid. Après cela, s'il existe un déséquilibre entre la production et la demande d'énergie, nous proposons des stratégies différentes pour minimiser les coûts d'approvisionnement énergétique. Sur la base des données réelles de la consommation d'énergie d'un site industriel situé en France, des économies significatives peuvent être réalisées en adoptant ces stratégies. Dans cette thèse, nous étudions également comment atténuer les effets des fluctuations de puissance des DERs en conjonction avec des systèmes de stockage d'énergie. Pour cela, nous proposons un algorithme de lissage gaussien et nous le comparons avec des algorithmes de lissage trouvés dans l'état de l'art. Nous avons trouvé que l'algorithme proposé utilise de batterie de moins de taille à des fins de lissage par rapport à d'autres algorithmes. À cette fin, nous sommes également intéressés à étudier les effets de la gamme admissible des fluctuations sur les tailles de la batterie.Du côté de la demande, l'objectif est de réduire les coûts de l'énergie grâce aux approches de gestion de la demande DSM (Demand Side Management) telles que Demand Response (DR) et Energy Efficiency. Comme les processus industriels consomment énormément, une petite réduction de la consommation d'énergie en utilisant les approches DSM pourrait se traduire par des économies cruciales. Cette thèse se concentre sur l'approche DR qui peut profiter des prix variables de l'électricité dans le temps pour déplacer les demandes énergétiques des heures de pointe aux heures creuses. Pour atteindre cet objectif, nous comptons sur un modèle basé sur la théorie de file d'attente pour caractériser les comportements temporels (arrivée et départ des tâches) d'un système de fabrication. Après avoir défini les processus d'arrivée et de départ de tâches, une fonction d'utilisation efficace est utilisée pour prédire le comportement de la machine dans un domaine temporel et qui peut afficher son statut (allumé/éteint) à tout moment. En prenant le statut de chaque machine dans une ligne de production comme une entrée, nous proposons également un algorithme de planification DR qui adapte la consommation d'énergie d'une ligne de production aux deux contraintes de puissance disponibles et de taux de production. L'algorithme est codé à l'aide d’une machine d’état fini déterministe (Deterministic Finite State Machine) dans laquelle les transitions d'état se produisent en insérant une tâche à l'entrée du tapis roulant (on peut aussi avoir des transitions sans insertion de taches). Nous définissons des conditions pour l'existence d’un planificateur réalisable et aussi des conditions pour accepter positivement des demandes DRs<br>Due to increased energy costs and environmental concerns such as elevated carbon footprints, centralized power generation systems are restructuring themselves to reap benefits of distributed generation in order to meet the ever growing energy demands. Microgrids are considered as a possible solution to deploy distributed generation which includes Distributed Energy Resources (DERs) (e.g., solar, wind, battery, etc). In this thesis, we are interested in addressing energy management challenges in an industrial microgrid where energy loads consist of industrial processes. Our plan of attack is to divide the microgrid energy management into supply and demand sides.In supply side, the challenges include modeling of power generations and smoothing out fluctuations of the DERs. To model power generations, we propose amodel based on service curve concepts of Network Calculus (NC). Using this mathematical tool, we determine a minimum amount of power the DERs can generate and aggregating them will give us total power production in the microgrid. After that, if there is an imbalance between energy supply and demand, we put forward different strategies to minimize energy procurement costs. Based on real power consumption data of an industrial site located in France, significant cost savings can be made by adopting the strategies. In this thesis, we also study how to mitigate the effects of power fluctuations of DERs in conjunction with Energy Storage Systems (ESSs). For this purpose, we propose a Gaussian-based smoothing algorithm and compare it with state-of-the-art smoothing algorithms. We found out that the proposed algorithm uses less battery size for smoothing purposes when compared to other algorithms. To this end, we are also interested in investigating effects of allowable range of fluctuations on battery sizes.In demand side, the aim is to reduce energy costs through Demand Side Management (DSM) approaches such as Demand Response (DR) and Energy Efficiency (EE). As industrial processes are power-hungry consumers, a small power consumption reduction using the DSM approaches could translate into crucial savings. This thesis focuses on DR approach that can leverage time varying electricity prices to move energy demands from peak to off-peak hours. To attain this goal, we rely on a queuing theory-based model to characterize temporal behaviors (arrival and departure of jobs) of a manufacturing system. After defining job arrival and departure processes, an effective utilization function is used to predict workstation’s (or machine’s) behavior in temporal domain that can show its status (working or idle) at any time. Taking the status of every machine in a production line as an input, we also propose a DR scheduling algorithm that adapts power consumption of a production line to available power and production rate constraints. The algorithm is coded using Deterministic Finite State Machine (DFSM) in which state transitions happen by inserting a job (or not inserting) at conveyor input. We provide conditions for existence of feasible schedules and conditions to accept DR requests positively.To verify analytical computations on the queuing part, we have enhanced Objective Modular Network Testbed in C++ (OMNET++) discrete event simulator for fitting it to our needs. We modified various libraries in OMNET++ to add machine and conveyor modules. In this thesis, we also setup a testbed to experiment with a smart DR protocol called Open Automated Demand Response (OpenADR) that enables energy providers (e.g., utility grid) to ask consumers to reduce their power consumption for a given time. The objective is to explore how to implement our DR scheduling algorithm on top of OpenADR
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Chen, Zhenyu. "Discrete-time queueing model for responsive network traffic and bottleneck queues." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/21314.
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The Internet has been more and more intensively used in recent years. Although network infrastructure has been regularly upgraded, and the ability to manage heavy traffic greatly increased, especially on the core networks, congestion never ceases to appear, as the amount of traffic that flow on the Internet seems to be increasing at an even faster rate. Thus, congestion control mechanisms play a vital role in the functioning of the Internet. Active Queue Management (AQM) is a popular type of congestion control mechanism that is implemented on gateways (most notably routers), which can predict and avoid the congestion before it happens. When properly configured, AQMs can effectively reduce the congestion, and alleviate some of the problems such as global synchronisation and unfairness to bursty traffic. However, there are still many problems regarding AQMs. Most of the AQM schemes are quite sensitive to their parameters setting, and these parameters may be heavily dependent on the network traffic profile, which the administrator may not have intensive knowledge of, and is likely to change over time. When poorly configured, many AQMs perform no better than the basic drop-tail queue. There is currently no effective method to compare the performance of these AQM algorithms, caused by the parameter configuration problem. In this research, the aim is to propose a new analytical model, which mainly uses discrete-time queueing theory. A novel transient modification to the conventional equilibrium-based method is proposed, and it is utilised to further develop a dynamic interactive model of responsive traffic and bottleneck queues. Using step-by-step analysis, it represents the bursty traffic and oscillating queue length behaviour in practical network more accurately. It also provides an effective way of predicting the behaviour of a TCP-AQM system, allowing easier parameter optimisation for AQM schemes. Numerical solution using MATLAB and software simulation using NS-2 are used to extensively validate the proposed models, theories and conclusions.
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Wall, Alan Douglas. "Extending the scope of discrete time models to provide practical results for continuous time queueing systems." Thesis, Lancaster University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307361.
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Sirviö, Marina. "Aspects of stationary processes : occupation times and queueing applications /." Åbo (Finland) : Åbo akademi, 2007. http://catalogue.bnf.fr/ark:/12148/cb409815260.
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Rueda, Javier Eduardo. "The Ph(t)/Ph(t)/s/c Queueing Model and Approximation." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/9637.
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Time-dependent queueing models are important since most of real-life problems are time-dependent. We develop a numerical approximation algorithm for the mean, variance and higher-order moments of the number of entities in the system at time t for the Ph(t)/Ph(t)/s/c queueing model. This model can be thought as a reparameterization to the G(t)/GI(t)/s. Our approach is to partition the state space into known and identifiable structures, such as the M(t)/M(t)/s/c or M(t)/M(t)/1 queueing models. We then use the Polya-Eggenberger distribution to approximate certain unknown probabilities via a two-moment matching algorithm. We describe the necessary steps to validate the approximation and measure the accuracy of the model.<br>Master of Science
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Barnes, John A. "Traffic processes and sojourn times in finite Markovian queues." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53907.
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This paper gives results on various traffic processes and on the sojourn time distribution for a class of models which operate as Markov processes on finite state spaces. The arrival and the service time processes are assumed to be independent renewal processes with interval distributions of phase-type. The queue capacity is finite. A general class of queue disciplines are considered. The primary models studied are from the M/E<sub>k</sub>/Φ/L class. The input, output, departure and overflow processes are analyzed. Furthermore, the sojourn time distribution is determined. Markov renewal theory provides the main analytical tools. It is shown that this work unifies many previously known results and offers some new results. Various extensions, including a balking model, are studied.<br>Ph. D.
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Dormuth, Darryl W. "Performance assessment of mixed methods for time integration using an assembly-type queueing model." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq23596.pdf.
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Kulkarni, Aditya Umesh. "Approximating Deterministic Changes to Ph(t)/Ph(t)/1/c and Ph(t)/M(t)/s/c Queueing Models." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/33460.
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A deterministic change to a time-varying queueing model is described as either changing the number of entities, the queue capacity, or the number of servers in the system at selected times. We use a surrogate distribution for N(t), the number of entities in the system at time t, to approximate deterministic changes to the Ph(t)/Ph(t)/1/c and the Ph(t)/M(t)/s/c queueing models. We develop a solution technique to minimize the number of state probabilities to be approximated.<br>Master of Science
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Sell, Nicole Lee. "Empirical Investigations of Queuing and Surface Street Times using Truck Probe Data around International Border Crossings." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1405682680.
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Baldwin, Rusty Olen. "Improving the Real-time Performance of a Wireless Local Area Network." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/28113.
Full textAbstract:
This research considers the transmission of real-time data within a wireless local area network (WLAN).
Exact and approximate analytic network evaluation techniques are examined. The suitability of using a given technique in a particular situation is discussed.
Simulation models are developed to study the performance of our protocol RT-MAC (real-time medium access control). RT-MAC is a novel, simple, and elegant MAC protocol for use in transmitting real-time data in point to point ad hoc WLAN. Our enhancement of IEEE 802.11, RT-MAC, achieves dramatic reductions in mean delay, missed deadlines, and packet collisions by selectively discarding packets and sharing station state information. For example, in a 50 station network with a normalized offered load of 0.7, mean delay is reduced from more than 14 seconds to less than 45 ms, late packets are reduced from 76% to less than 1%, and packet collisions are reduced from 36% to less than 1%. Stations using RT-MAC are interoperable with stations using IEEE 802.11. In networks with both RT-MAC and IEEE 802.11 stations, significant performance improvements were seen even when more than half of the stations in the network were not RT-MAC stations.
The effect of the wireless channel and its impact on the ability of a WLAN to meet packet deadlines is evaluated. It is found that, in some cases, other factors such as the number of stations in the network and the offered load are more significant than the condition of the wireless channel.
Regression models are developed from simulation data to predict network behavior in terms of throughput, mean delay, missed deadline ratio, and collision ratio. Telemetry, avionics, and packetized voice traffic models are considered.
The applicability of this research is not limited to real-time wireless networks. Indeed, the collision reduction algorithm of RT-MAC is independent of the data being transported. Furthermore, RT-MAC would perform equally well in wired networks. Incorporating the results of this research into existing protocols will result in immediate and dramatic improvements in network performance.<br>Ph. D.
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Kelly, Brian J. "Use of a simulation game and queuing model to achieve shorter lead times in stamping die development." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10923.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996, and Thesis (M.S.)--Massachusetts Institute of Technology, Sloan School of Management, 1996.<br>Includes bibliographical references (p. 129-130).<br>by Brian J. Kelly.<br>M.S.
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Zhang, Shu. "Stochastic orienteering on a network of queues with time windows." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/1944.
Full textAbstract:
Motivated by the management of sales representatives who visit customers to develop customer relationships, we present a stochastic orienteering problem on a network of queues, in which a hard time window is associated with each customer and the representative may experience uncertain wait time resulting from a queueing process at the customer.
In general, given a list of potential customers and a time horizon consisting of several periods, the sales representative needs to decide which customers to visit in each period and how to visit customers within the period, with an objective to maximize the total reward collected by the end of the horizon. We start our study with a daily orienteering problem, which is a subproblem of the general problem. We focus on developing a priori and dynamic routing strategies for the salesperson to implement during a day.
In the a priori routing case, the salesperson visits customers in a pre-planned order, and we seek to construct a static sequence of customers that maximizes the expected value collected. We consider two types of recourse actions. One is to skip a customer specified by an a priori route if the representative will arrive late in the customer's time window. The other type is to leave a customer immediately after arriving if observing a sufficiently long queue (balking) or to leave after waiting in queue for a period of time without meeting with the customer (reneging). We propose customer-specific decision rules to facilitate the execution of recourse actions and derive an analytical formula to compute the expected sales from the a priori route. We tailor a variable neighborhood search (VNS) heuristic to find a priori routes.
In the dynamic routing case, the salesperson decides which customer to visit and how long to wait at each customer based on realized events. To seek dynamic routing policies, we propose an approximate dynamic programming approach based on rollout algorithms. The method introduces a two-stage heuristic estimation that we refer to as compound rollout. In the first stage, the algorithm decides whether to stay at the current customer or go to another customer. If departing the current customer, it chooses the customer to whom to go in the second stage. We demonstrate the value of our modeling and solution approaches by comparing the dynamic policies to a priori solutions with recourse actions.
Finally, we address the multi-period orienteering problem. We consider that each customer's likelihood of adopting the representative's product stochastically evolves over time and is not fully observed by the representative. The representative can only estimate the adoption likelihood by meeting with the customer and the estimation may not be accurate. We model the problem as a partially observed Markov decision process with an objective to maximize the expected sales at the end of the horizon. We propose a heuristic that decomposes the problem into an assignment problem to schedule customers for a period and a routing problem to decide how to visit the scheduled customers within the period.
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Epp, Martin [Verfasser]. "Performance evaluation of shuttle-based storage and retrieval systems using discrete-time queueing network models / Martin Epp." Karlsruhe : KIT Scientific Publishing, 2018. http://www.ksp.kit.edu.
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Escobar, Fernández de la Vega Marcos. "Approximate solutions for multi-server queuing systems with Erlangian service times and an application to air traffic management." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9631.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.<br>Includes bibliographical references (p. 209-213).<br>This thesis is concerned with approximations of certain M(t)/G(t)/n(t)/n(t) + q queueing systems. More specifically, we are interested in such systems under very general conditions such as time-varying demand and capacity, and high utilization, including occasional oversaturation. Conditions such as these cannot be addressed with existing methodologies. We focus on M(t)/G(t)/n(t)/n(t) + q systems that can be approximated fairly well by M(t)/E&(t)/n(t)/n(t) + q systems. The latter have a large number of system states, that increase with the system parameters k, n, q and the utilization ratio, and involve complicated state transition probabilities. We propose numerical methods to solve the corresponding Chapman-Kolmogorov equations, exactly and approximately We first describe the exact solution technique of M(t)/Ek(t)/n(t)/n(t) + q queueing systems. Then, we develop two heuristic solution techniques of M(t)/E&(t)/ndt)/n(t) + q queueing systems, and provide the corresponding complete state descriptions. We compare the exact and approximate results to validate our heuristics and to select the heuristic that best approximates the exact results in steady-state and under stationary conditions. We also propose two algorithms to vary the number of servers in the system, since many real-life problems involve such changes in response to variations in demand. Further results using our ELC heuristic show that our practical approach behaves well under nonstationary conditions, including varying capacity, and during the transient period to steady-state. We conclude that our heuristic approach is an excellent alternative for studying and analyzing M(t)/E&(t)/n(t)/n(t)+q models and, as a by-product, many M(t)/G(t)/n(t)/n(t) +q systems that arise in practice. Finally, we present an application of the M(t)/E&(t)/n(t)/n(t) + q queueing model in the context of Air Traffic Management. This model appears to be a reasonable approach to estimating delays and congestion in an en-route sector in the air traffic system and can be used as an important building block in developing an analytical model of the entire Air Traffic Management system.<br>by Marcos Escobar Fernández de la Vega.<br>Ph.D.
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Moss, Blake Cameron. "On the Distribution of Inter-Arrival Times of 911 Emergency ResponseProcess Events." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8391.
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The 911 emergency response process is a core component of the emergency services critical infrastructure sector in the United States. Modeling and simulation of a complex stochastic system like the 911 response process enables policy makers and stakeholders to better understand, identify, and mitigate the impact of attacks/disasters affecting the 911 system. Modeling the 911 response process as a series of queue sub-systems will enable analysis into how CI failures impact the different phases of the 911 response process. Before such a model can be constructed, the probability distributions of the inter-arrivals of events into these various sub-systems needs to be identified. This research is a first effort into investigating the stochastic behavior of inter-arrival times of different events throughout the 911 response process. I use the methodology of input modeling, a statistical modeling approach, to determine whether the exponential distribution is an appropriate model for these inter-arrival times across a large dataset of historical 911 dispatch records.
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Mohamed, Mahmud H. Etbega. "Some Active Queue Management Methods for Controlling Packet Queueing Delay. Design and Performance Evaluation of Some New Versions of Active Queue Management Schemes for Controlling Packet Queueing Delay in a Buffer to Satisfy Quality of Service Requirements for Real-time Multimedia Applications." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4258.
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Traditionally the Internet is used for the following applications: FTP, e-mail and Web traffic. However in the recent years the Internet is increasingly supporting emerging applications such as IP telephony, video conferencing and online games. These new applications have different requirements in terms of throughput and delay than traditional applications. For example, interactive multimedia applications, unlike traditional applications, have more strict delay constraints and less strict loss constraints. Unfortunately, the current Internet offers only a best-effort service to all applications without any consideration to the applications specific requirements. In this thesis three existing Active Queue Management (AQM) mechanisms are modified by incorporating into these a control function to condition routers for better Quality of Service (QoS). Specifically, delay is considered as the key QoS metric as it is the most important metric for real-time multimedia applications. The first modified mechanism is Drop Tail (DT), which is a simple mechanism in comparison with most AQM schemes. A dynamic threshold has been added to DT in order to maintain packet queueing delay at a specified value. The modified mechanism is referred to as Adaptive Drop Tail (ADT). The second mechanism considered is Early Random Drop (ERD) and, iii in a similar way to ADT, a dynamic threshold has been used to keep the delay at a required value, the main difference being that packets are now dropped probabilistically before the queue reaches full capacity. This mechanism is referred to as Adaptive Early Random Drop (AERD). The final mechanism considered is motivated by the well known Random Early Detection AQM mechanism and is effectively a multi-threshold version of AERD in which packets are dropped with a linear function between the two thresholds and the second threshold is moveable in order to change the slope of the dropping function. This mechanism is called Multi Threshold Adaptive Early Random Drop (MTAERD) and is used in a similar way to the other mechanisms to maintain delay around a specified level. The main focus with all the mechanisms is on queueing delay, which is a significant component of end-to-end delay, and also on reducing the jitter (delay variation) A control algorithm is developed using an analytical model that specifies the delay as a function of the queue threshold position and this function has been used in a simulation to adjust the threshold to an effective value to maintain the delay around a specified value as the packet arrival rate changes over time. iv A two state Markov Modulated Poisson Process is used as the arrival process to each of the three systems to introduce burstiness and correlation of the packet inter-arrival times and to present sudden changes in the arrival process as might be encountered when TCP is used as the transport protocol and step changes the size of its congestion window. In the investigations it is assumed the traffic source is a mixture of TCP and UDP traffic and that the mechanisms conserved apply to the TCP based data. It is also assumed that this consists of the majority proportion of the total traffic so that the control mechanisms have a significant effect on controlling the overall delay. The three mechanisms are evaluated using a Java framework and results are presented showing the amount of improvement in QoS that can be achieved by the mechanisms over their non-adaptive counterparts. The mechanisms are also compared with each other and conclusions drawn.
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Gupta, Varun. "Stochastic Models and Analysis for Resource Management in Server Farms." Research Showcase @ CMU, 2011. http://repository.cmu.edu/dissertations/544.
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Server farms are popular architectures for computing infrastructures such as supercomputing centers, data centers and web server farms. As server farms become larger and their workloads more complex, designing efficient policies for managing the resources in server farms via trial-and error becomes intractable. In this thesis, we employ stochastic modeling and analysis techniques to understand the performance of such complex systems and to guide design of policies to optimize the performance. There is a rich literature on applying stochastic modeling to diverse application areas such as telecommunication networks, inventory management, production systems, and call centers, but there are numerous disconnects between the workloads and architectures of these traditional applications of stochastic modeling and how compute server farms operate, necessitating new analytical tools. To cite a few: (i) Unlike call durations, supercomputing jobs and file sizes have high variance in service requirements and this critically affects the optimality and performance of scheduling policies. (ii) Most existing analysis of server farms focuses on the First-Come- First-Served (FCFS) scheduling discipline, while time sharing servers (e.g., web and database servers) are better modeled by the Processor- Sharing (PS) scheduling discipline. (in) Time sharing systems typically exhibit thrashing (resource contention) which limits the achievable concurrency level, but traditional models of time sharing systems ignore this fundamental phenomenon. (iv) Recently, minimizing energy consumption has become an important metric in managing server farms. State-of-the-art servers come with multiple knobs to control energy consumption, but traditional queueing models don’t take the metric of energy consumption into account. In this thesis we attempt to bridge some of these disconnects by bringing the stochastic modeling and analysis literature closer to the realities of today’s compute server farms. We introduce new queueing models for computing server farms, develop new stochastic analysis techniques to evaluate and understand these queueing models, and use the analysis to propose resource management algorithms to optimize their performance.
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Thapa, Gyan. "Optimization of Just-in-Time Sequencing Problems and Supply Chain Logistics." Doctoral thesis, Mälardalens högskola, Utbildningsvetenskap och Matematik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-28849.
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This dissertation presents a comprehensive and comparative progress in sequencing approaches of mixed-model just-in-time (JIT) sequencing problem together with discrete apportioment problem (DAP). The goal of JIT sequencing problem (JITSP) is to keep the rate of usage of parts as constant as possible along the assembly lines, and the goal of DAP is to divide a given integer number of delegates proportionally among the states or the parties according to their population or votes. Furthermore, the supply chain logistics problem is also reported in here with some real life applications.The single-level JITSP, known as the product rate variation problem (PRVP), is pseudo-polynomially solvable. The total PRVP minimizes sum deviation and the bottleneck PRVP minimizes the maximum deviation between the actual production and the ideal production. The assignment approach solves total PRVP whereas the perfect matching works for bottleneck PRVP solving the problem in pseudo-polynomial time. The multi-level JITSP, known as the output rate variation problem (ORVP), is NP-hard in most of the cases. However, some sequencing heuristics and dynamic programming are devised for near optimal solutions. And the pegging assumption reduces the ORVP into weighted case of PRVP. In this dissertation, the total PRVP with square and absolute deviations are considered and mean-based divisor methods are devised for the equitably efficient solution. The simultaneous dealing to the PRVP and DAP establishes the interlink between the production sequencing problem and integer seat allocating problem. The new upper bottlenecks are investigated and the problems are solved comparatively. The bottleneck PRVP instances for small deviations and cyclic sequences for total PRVP are shown to be optimal. The bicriterion sequencing is discussed with Pareto optimal solutions.The production sequencing problem is simultaneously dealt with supply chain logistics to balance overall supply chain system. The cross-docking supply chain logistics problem is formulated with a proposition to be solved. The real-world applications of JITSP and supply chain are listed and some open problems are pointed out as the closing of the dissertation.
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Tribastone, Mirco. "Scalable analysis of stochastic process algebra models." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4629.
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The performance modelling of large-scale systems using discrete-state approaches is fundamentally hampered by the well-known problem of state-space explosion, which causes exponential growth of the reachable state space as a function of the number of the components which constitute the model. Because they are mapped onto continuous-time Markov chains (CTMCs), models described in the stochastic process algebra PEPA are no exception. This thesis presents a deterministic continuous-state semantics of PEPA which employs ordinary differential equations (ODEs) as the underlying mathematics for the performance evaluation. This is suitable for models consisting of large numbers of replicated components, as the ODE problem size is insensitive to the actual population levels of the system under study. Furthermore, the ODE is given an interpretation as the fluid limit of a properly defined CTMC model when the initial population levels go to infinity. This framework allows the use of existing results which give error bounds to assess the quality of the differential approximation. The computation of performance indices such as throughput, utilisation, and average response time are interpreted deterministically as functions of the ODE solution and are related to corresponding reward structures in the Markovian setting. The differential interpretation of PEPA provides a framework that is conceptually analogous to established approximation methods in queueing networks based on meanvalue analysis, as both approaches aim at reducing the computational cost of the analysis by providing estimates for the expected values of the performance metrics of interest. The relationship between these two techniques is examined in more detail in a comparison between PEPA and the Layered Queueing Network (LQN) model. General patterns of translation of LQN elements into corresponding PEPA components are applied to a substantial case study of a distributed computer system. This model is analysed using stochastic simulation to gauge the soundness of the translation. Furthermore, it is subjected to a series of numerical tests to compare execution runtimes and accuracy of the PEPA differential analysis against the LQN mean-value approximation method. Finally, this thesis discusses the major elements concerning the development of a software toolkit, the PEPA Eclipse Plug-in, which offers a comprehensive modelling environment for PEPA, including modules for static analysis, explicit state-space exploration, numerical solution of the steady-state equilibrium of the Markov chain, stochastic simulation, the differential analysis approach herein presented, and a graphical framework for model editing and visualisation of performance evaluation results.
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Abdel-Jaber, Hussein F. "Performance Modelling and Evaluation of Active Queue Management Techniques in Communication Networks. The development and performance evaluation of some new active queue management methods for internet congestion control based on fuzzy logic and random early detection using discrete-time queueing analysis and simulation." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4261.
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Since the field of computer networks has rapidly grown in the last two decades, congestion control of traffic loads within networks has become a high priority. Congestion occurs in network routers when the number of incoming packets exceeds the available network resources, such as buffer space and bandwidth allocation. This may result in a poor network performance with reference to average packet queueing delay, packet loss rate and throughput. To enhance the performance when the network becomes congested, several different active queue management (AQM) methods have been proposed and some of these are discussed in this thesis. Specifically, these AQM methods are surveyed in detail and their strengths and limitations are highlighted. A comparison is conducted between five known AQM methods, Random Early Detection (RED), Gentle Random Early Detection (GRED), Adaptive Random Early Detection (ARED), Dynamic Random Early Drop (DRED) and BLUE, based on several performance measures, including mean queue length, throughput, average queueing delay, overflow packet loss probability, packet dropping probability and the total of overflow loss and dropping probabilities for packets, with the aim of identifying which AQM method gives the most satisfactory results of the performance measures. This thesis presents a new AQM approach based on the RED algorithm that determines and controls the congested router buffers in an early stage. This approach is called Dynamic RED (REDD), which stabilises the average queue length between minimum and maximum threshold positions at a certain level called the target level to prevent building up the queues in the router buffers. A comparison is made between the proposed REDD, RED and ARED approaches regarding the above performance measures. Moreover, three methods based on RED and fuzzy logic are proposed to control the congested router buffers incipiently. These methods are named REDD1, REDD2, and REDD3 and their performances are also compared with RED using the above performance measures to identify which method achieves the most satisfactory results. Furthermore, a set of discrete-time queue analytical models are developed based on the following approaches: RED, GRED, DRED and BLUE, to detect the congestion at router buffers in an early stage. The proposed analytical models use the instantaneous queue length as a congestion measure to capture short term changes in the input and prevent packet loss due to overflow. The proposed analytical models are experimentally compared with their corresponding AQM simulations with reference to the above performance measures to identify which approach gives the most satisfactory results. The simulations for RED, GRED, ARED, DRED, BLUE, REDD, REDD1, REDD2 and REDD3 are run ten times, each time with a change of seed and the results of each run are used to obtain mean values, variance, standard deviation and 95% confidence intervals. The performance measures are calculated based on data collected only after the system has reached a steady state. After extensive experimentation, the results show that the proposed REDD, REDD1, REDD2 and REDD3 algorithms and some of the proposed analytical models such as DRED-Alpha, RED and GRED models offer somewhat better results of mean queue length and average queueing delay than these achieved by RED and its variants when the values of packet arrival probability are greater than the value of packet departure probability, i.e. in a congestion situation. This suggests that when traffic is largely of a non bursty nature, instantaneous queue length might be a better congestion measure to use rather than the average queue length as in the more traditional models.
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Horký, Miroslav. "Modely hromadné obsluhy." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232033.
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The master’s thesis solves models of queueing systems, which use the property of Markov chains. The queueing system is a system, where the objects enter into this system in random moments and require the service. This thesis solves specifically such models of queueing systems, in which the intervals between the objects incomings and service time have exponential distribution. In the theoretical part of the master’s thesis I deal with the topics stochastic process, queueing theory, classification of models and description of the models having Markovian property. In the practical part I describe realization and function of the program, which solves simulation of chosen model M/M/m. At the end I compare results which were calculated in analytic way and by simulation of the model M/M/m.
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Rýzner, Zdeněk. "Využití teorie hromadné obsluhy při návrhu a optimalizaci paketových sítí." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219285.
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This master's thesis deals with queueing theory and its application in designing node models in packet-switched network. There are described general principles of designing queueing theory models and its mathematical background. Further simulator of packet delay in network was created. This application implements two described models - M/M/1 and M/G/1. Application can be used for simulating network nodes and obtaining basic network characteristics like packet delay or packet loss. Next, lab exercise was created, in that exercise students familiarize themselves with basic concepts of queueing theory and examine both analytical and simulation approach to solving queueing systems.
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Ouyang, Wenzhuo. "Scheduling in Wireless Networks with Limited and Imperfect Channel Knowledge." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397819786.
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Duri, Christelle. "Etude comparative de gestions à flux tiré." Grenoble INPG, 1997. http://www.theses.fr/1997INPG0006.
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L'efficacite d'un systeme de production depend en grande partie de la gestion mise en oeuvre pour declencher les differentes operations necessaires a la fabrication des produits. Il est donc primordial de choisir une gestion bien adaptee au systeme a piloter. Cette these a pour but de comparer, qualitativement et quantitativement, trois gestions a flux tire : les gestions kanban, kanban generalise et base stock. Nous nous sommes tout d'abord interesses aux methodes analytiques permettant d'evaluer les performances des trois types de systemes etudies et nous avons propose des extensions de methodes deja existantes. Pour l'analyse des systemes base stock, nous presentons une nouvelle approche. Nous avons egalement propose une evaluation des nouvelles performances qui apparaissent dans le critere de comparaison que nous avons choisi. Pour pouvoir comparer les gestions, il faut trouver les valeurs optimales des parametres du systeme. Pour ne pas tester toutes les configurations possibles, nous avons mis au point des procedures de dimensionnement qui permettent d'eliminer certaines configurations non interessantes. La premiere comparaison a porte sur le comportement du systeme en regime stationnaire. Sur les exemples etudies, nous avons notamment remarque que, si l'on dispose d'un delai de livraison, les gestions kanban generalise et base stock donnent des couts optimaux proches et plus faibles que ceux de la gestion kanban, pour une meme qualite de service. On choisira alors la gestion base stock s'il n'est pas important de limiter l'encours maximum, et la gestion kanban generalise dans le cas contraire. La deuxieme comparaison a porte sur le comportement des systemes kanban et kanban generalise en regime transitoire. Cette etude, qui a ete faite en simulation, a permis de mettre en evidence la robustesse de la gestion kanban generalise face a un changement du niveau moyen de la demande, lorsqu'on s'autorise un delai de satisfaction des clients.
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Gannon, Mark Andrew. "Passeios aleatórios em redes finitas e infinitas de filas." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-16102017-154842/.
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Um conjunto de modelos compostos de redes de filas em grades finitas servindo como ambientes aleatorios para um ou mais passeios aleatorios, que por sua vez podem afetar o comportamento das filas, e desenvolvido. Duas formas de interacao entre os passeios aleatorios sao consideradas. Para cada modelo, e provado que o processo Markoviano correspondente e recorrente positivo e reversivel. As equacoes de balanceamento detalhado sao analisadas para obter a forma funcional da medida invariante de cada modelo. Em todos os modelos analisados neste trabalho, a medida invariante em uma grade finita tem forma produto. Modelos de redes de filas como ambientes para multiplos passeios aleatorios sao estendidos a grades infinitas. Para cada modelo estendido, sao especificadas as condicoes para a existencia do processo estocastico na grade infinita. Alem disso, e provado que existe uma unica medida invariante na rede infinita cuja projecao em uma subgrade finita e dada pela medida correspondente de uma rede finita. Finalmente, e provado que essa medida invariante na rede infinita e reversivel.<br>A set of models composed of queueing networks serving as random environments for one or more random walks, which themselves can affect the behavior of the queues, is developed. Two forms of interaction between the random walkers are considered. For each model, it is proved that the corresponding Markov process is positive recurrent and reversible. The detailed balance equa- tions are analyzed to obtain the functional form of the invariant measure of each model. In all the models analyzed in the present work, the invariant measure on a finite lattice has product form. Models of queueing networks as environments for multiple random walks are extended to infinite lattices. For each model extended, the conditions for the existence of the stochastic process on the infinite lattice are specified. In addition, it is proved that there exists a unique invariant measure on the infinite network whose projection on a finite sublattice is given by the corresponding finite- network measure. Finally, it is proved that that invariant measure on the infinite lattice is reversible.
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Chu, Hsuan Kai, and 褚宣凱. "Simulating Time-Varying Demand Services with Queuing Models." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/n6ck6f.
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Chung, Ming-Hung, and 鍾明宏. "A Study on Queuing Buffer Allocation in a Differentiated Service Queuing Scheme with Time Token Concept." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/21646031430106967012.
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碩士<br>國防大學管理學院<br>資訊管理學系<br>97<br>According to time token concept, this study proposes a priority-based queuing scheme to forward IP packets differentiatedly. The proposed queuing scheme tries to use a time token assignment mechanism to handle a queuing buffer allocation issue. In the proposed queuing scheme, 3 packet transmission priorities are adopted and a queuing buffer is divided into 3 logical queuing buffers which are corresponding to transmission priorities of IP packets. In each logical queuing buffer, there exist two types of queuing buffers; one is guaranteed queuing buffer and the other is dynamic queuing buffer. The guaranteed queuing buffer is a dedicated queuing buffer; the dynamic queuing buffer depends on received time tokens to allocate queuing buffer space. The proposed queuing scheme depends on transmission priorities of IP packets to assign time tokens to logical queuing buffers. With received time tokens, logical queuing buffers can allocate more queuing buffer space to enqueue arrival IP packets.
In this study, we use NS2 as a simulation platform. The proposed queuing scheme is implemented with C++ and is integrated in the NS2 simulator. Several scenarios are simulated to obverse packet forwarding behaviors among IP packets. After collecting simulation data, we can find that the proposed queuing scheme can base on packet transmission priorities to support a differentiated packet forwarding behavior among IP packets. Moreover, the IETF DiffServ scheme is used as a comparison to realize the packet forwarding performance of IP packets. After comparing simulation data, we find that the differentiated packet forwarding performance supported by the proposed queuing and the IETF DiffServ scheme is close.
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Kao, Jyh Han, and 高志瀚. "A PRELIMINARY QUEUING TIME MODEL OF REPETITIVE PROJECT SCHEDULING." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/80765333353792754244.
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碩士<br>國立臺灣科技大學<br>營建工程技術學系<br>82<br>The main purpose of this thesis is to establish a scheduling
model of repetitive project , Line of Balance assumes that the
queuing time of the same task of different units is zero and
unable to be controlled.However,in practice due to construction
logic and safety consideration the task internal has to be
controlled.This thesis builds the formul- ations of repetitive
project scheduling and queuing time.Fur- thermore,it applies
the queuing time research results to the scheduling analysis of
slurry-wall construction.