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1

A queueing system with heterogeneous impatient customers and consumable additional items

Baek J., Dudina O., Kim C.

International Journal of Applied Mathematics and Computer Science

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2017

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Vol. 27, no. 2

367--384

EN

A single-server queueing system with a marked Markovian arrival process of heterogeneous customers is considered. Type-1 customers have limited preemptive priority over type-2 customers. There is an infinite buffer for type-2 customers and no buffer for type-1 customers. There is also a finite buffer (stock) for consumable additional items (semi-products, half-stocks, etc.) which arrive according to the Markovian arrival process. Service of a customer requires a fixed number of consumable additional items depending on the type of the customer. The service time has a phase-type distribution depending on the type of the customer. Customers in the buffer are impatient and may leave the system without service after an exponentially distributed amount of waiting time. Aiming to minimize the loss probability of type-1 customers and maximize throughput of the system, a threshold strategy of admission to service of type-2 customers is offered. Service of type-2 customer can start only if the server is idle and the number of consumable additional items in the stock exceeds the fixed threshold. Stationary distributions of the system states and the waiting time are computed. In the numerical example, we show some interesting effects and illustrate a possibility of application of the presented results for solution of optimization problems.

2

Fitting traffic traces with discrete canonical phase type distributions and Markov arrival processes

Mészáros A., Papp J., Telek M.

International Journal of Applied Mathematics and Computer Science

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2014

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Vol. 24, no. 3

453--470

EN

Recent developments of matrix analytic methods make phase type distributions (PHs) and Markov Arrival Processes (MAPs) promising stochastic model candidates for capturing traffic trace behaviour and for efficient usage in queueing analysis. After introducing basics of these sets of stochastic models, the paper discusses the following subjects in detail: (i) PHs and MAPs have different representations. For efficient use of these models, sparse (defined by a minimal number of parameters) and unique representations of discrete time PHs and MAPs are needed, which are commonly referred to as canonical representations. The paper presents new results on the canonical representation of discrete PHs and MAPs. (ii) The canonical representation allows a direct mapping between experimental moments and the stochastic models, referred to as moment matching. Explicit procedures are provided for this mapping. (iii) Moment matching is not always the best way to model the behavior of traffic traces. Model fitting based on appropriately chosen distance measures might result in better performing stochastic models. We also demonstrate the efficiency of fitting procedures with experimental results.

3

Analysis of an MMAP/PH1, PH2/N/∞ queueing system operating in a random environment

Kim C., Dudin A., Dudin S., Dudina O.

International Journal of Applied Mathematics and Computer Science

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2014

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Vol. 24, no. 3

485--501

EN

A multi-server queueing system with two types of customers and an infinite buffer operating in a random environment as a model of a contact center is investigated. The arrival flow of customers is described by a marked Markovian arrival process. Type 1 customers have a non-preemptive priority over type 2 customers and can leave the buffer due to a lack of service. The service times of different type customers have a phase-type distribution with different parameters. To facilitate the investigation of the system we use a generalized phase-type service time distribution. The criterion of ergodicity for a multi-dimensional Markov chain describing the behavior of the system and the algorithm for computation of its steady-state distribution are outlined. Some key performance measures are calculated. The Laplace–Stieltjes transforms of the sojourn and waiting time distributions of priority and non-priority customers are derived. A numerical example illustrating the importance of taking into account the correlation in the arrival process is presented.

4

Probability of ruin for a dependent, two-dimensional Poisson process

Heilpern S.

Badania Operacyjne i Decyzje

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2009

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nr 1

77-90

EN

A two-dimensional, dependent Poisson risk process is investigated in the paper. Claims are divided into two classes. Within each class claims have the same distribution, but claims belonging to different classes can have different distributions and the corresponding counting processes can be dependent. This dependence is induced by a common factor. Three models of ruin and the probabilities of ruin are investigated. The influence of the degree of class dependence on the probability of ruin are studied for each model.

PL

W pracy rozpatrywany jest dwuwymiarowy, zależny proces ryzyka Poissona. Wielkości wypłat podzielono na dwie klasy. W każdej klasie wypłaty mają ten sam rozkład, natomiast wypłaty należące do różnych klas mogą mieć różne rozkłady, a procesy liczące wypłaty mogą być zależne. Zależność ta jest generowana przez wspólny czynnik. Rozpatrywane są trzy modele ruiny, oparte na różnych sposobach wyznaczania czasu ruiny: czas wystąpienia pierwszej ruiny, pierwszy moment wystąpienia ruiny w obydwu klasach oraz ruina dla sumy procesów. Badane jest prawdopodobieństwo wystąpienia ruiny oraz wpływ stopnia zależności klas na to prawdopodobieństwo. Rozpatrzono przykłady, w których wypłaty mają rozkłady wykładnicze. W dwóch pierwszych modelach prawdopodobieństwa ruiny zostały wyznaczone metodami symulacyjnymi. W trzecim modelu wykorzystano metodę opartą na rozkładach fazowych.