scholarly journals An M /M /1 Queueing System with Server on Attacks and Repair

We consider a M M/ /1 queueing model of a communication system subject to random attacks on service station. In such attack system, the time interval between any two attacks is an exponentially distributed random variable with mean1/  . When the server fails by an attack, any customer getting service at that time becomes damaged. The failed server is immediately taken for repair and the damaged customer is washed out. Customers in the queue waiting for service are not washed out. The repair time of the server undergoing repair is assumed to be an exponentially distributed random variable with mean1/ . During repair time, the customers are allowed to wait for service maintain First Come First Served order. After the completion of repair, the server returns to the work-station immediately without any delay, even if there is no customer to render service. We derive explicit form of the state probabilities of the attack system in the long run. We also obtain measures of system performance and the model is validated by a numerical illustration.

1990 ◽  
Vol 27 (03) ◽  
pp. 693-700 ◽  
Author(s):  
Matthew J. Sobel

Assigning each arriving customer to the fastest idle server is shown to maximize throughput (equivalently, minimize blocking probability) in a queueing model with Poisson arrivals, heterogeneous exponential servers, and no waiting room. If a cost structure is imposed on this model, under specified conditions the same policy minimizes the expected discounted cost and the long-run average cost per unit time.


1990 ◽  
Vol 27 (3) ◽  
pp. 693-700 ◽  
Author(s):  
Matthew J. Sobel

Assigning each arriving customer to the fastest idle server is shown to maximize throughput (equivalently, minimize blocking probability) in a queueing model with Poisson arrivals, heterogeneous exponential servers, and no waiting room. If a cost structure is imposed on this model, under specified conditions the same policy minimizes the expected discounted cost and the long-run average cost per unit time.


Author(s):  
Viktor Afonin ◽  
Vladimir Valer'evich Nikulin

The article focuses on attempt to optimize two well-known Markov systems of queueing: a multichannel queueing system with finite storage, and a multichannel queueing system with limited queue time. In the Markov queuing systems, the intensity of the input stream of requests (requirements, calls, customers, demands) is subject to the Poisson law of the probability distribution of the number of applications in the stream; the intensity of service, as well as the intensity of leaving the application queue is subject to exponential distribution. In a Poisson flow, the time intervals between requirements are subject to the exponential law of a continuous random variable. In the context of Markov queueing systems, there have been obtained significant results, which are expressed in the form of analytical dependencies. These dependencies are used for setting up and numerical solution of the problem stated. The probability of failure in service is taken as a task function; it should be minimized and depends on the intensity of input flow of requests, on the intensity of service, and on the intensity of requests leaving the queue. This, in turn, allows to calculate the maximum relative throughput of a given queuing system. The mentioned algorithm was realized in MATLAB system. The results obtained in the form of descriptive algorithms can be used for testing queueing model systems during peak (unchanged) loads.


GIS Business ◽  
2019 ◽  
Vol 14 (6) ◽  
pp. 577-585
Author(s):  
T. Vivekanandan ◽  
S. Sachithanantham

In inventory control, suitable models for various real life systems are constructed with the objective of determining the optimal inventory level.  A new type of inventory model using the so-called change of distribution property is analyzed in this paper. There are two machines M1 and M2  in series and the output of M1 is the input of M2. Hence a reserve inventory between M1 and M2 is to be maintained. The method of obtaining the optimal size of reserve inventory, assuming cost of excess inventory, cost of shortage and when the rate of consumption of M2  is a constant, has already been attempted.  In this paper, it is assumed that the repair time of M1  is a random variable and the distribution of the same undergoes a change of distribution  after the truncation point X0 , which is taken to be a random variable.  The optimal size of the reserve inventory is obtained under the above said  assumption . Numerical illustrations are also provided.


1994 ◽  
Vol 31 (A) ◽  
pp. 115-129 ◽  
Author(s):  
W. Böhm ◽  
S. G. Mohanty

In this contribution we consider an M/M/1 queueing model with general server vacations. Transient and steady state analysis are carried out in discrete time by combinatorial methods. Using weak convergence of discrete-parameter Markov chains we also obtain formulas for the corresponding continuous-time queueing model. As a special case we discuss briefly a queueing system with a T-policy operating.


2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Bin Sun ◽  
Moon Ho Lee ◽  
Sergey A. Dudin ◽  
Alexander N. Dudin

We consider a multiserver queueing system with two input flows. Type-1 customers have preemptive priority and are lost during arrival only if all servers are occupied by type-1 customers. If all servers are occupied, but some provide service to type-2 customers, service of type-2 customer is terminated and type-1 customer occupies the server. If the number of busy servers is less than the thresholdMduring type-2 customer arrival epoch, this customer is accepted. Otherwise, it is lost or becomes a retrial customer. It will retry to obtain service. Type-2 customer whose service is terminated is lost or moves to the pool of retrial customers. The service time is exponentially distributed with the rate dependent on the customer’s type. Such queueing system is suitable for modeling cognitive radio. Type-1 customers are interpreted as requests generated by primary users. Type-2 customers are generated by secondary or cognitive users. The problem of optimal choice of the thresholdMis the subject of this paper. Behavior of the system is described by the multidimensional Markov chain. Its generator, ergodicity condition, and stationary distribution are given. The system performance measures are obtained. The numerical results show the effectiveness of considered admission control.


Author(s):  
С.А. Олейникова ◽  
И.А. Селищев

Статья посвящена разработке имитационной модели, позволяющей оценить вероятностно-временные показатели случайной величины, представляющей собой длительность выполнения комплекса последовательно-параллельных работ. В первую очередь, к таким показателям относятся закон распределения случайной величины (с точностью до параметров), вероятность завершения проекта в некотором временном интервале, а также математическое ожидание и дисперсия. Потребность в решении поставленной задачи возникает в случае, если длительности отдельных работ являются случайными величинами. В этом случае временные характеристики завершения комплекса работ необходимы не только для оценки вероятностно-временных характеристик, но и для простейшего планирования времени начала каждой из работ. В настоящее время существуют подходы к решению данной задачи, наиболее распространенным из которых является PERT (Program Evaluation and Review Technique, техника оценки и анализа проектов). Однако оценки метода базируются на центральной предельной теореме, основывающейся на предположениях, которые в условиях реального функционирования производственных или обслуживающих систем невыполнимы. В силу этого возникает необходимость в получении модели, позволяющей оценить требуемые характеристики в любых условиях. В результате получена имитационная модель, позволяющая получить вероятностно-временные характеристики случайной величины, представляющей собой длительность комплекса последовательно-параллельных работ и отличающейся повышенной точностью по сравнению с существующими аналогами. Для реализации модели выбрана среда AnyLogic The article is devoted to the development of a simulation model that allows you to estimate the probabilistic-time indicators of a random variable, which is the duration of the completion of the complex of sequential-parallel works. First of all, such indicators include: the law of the distribution of a random value (with an accuracy of parameters), the probability of completing the project in some time interval, as well as a mathematical expectation and dispersion. The need for solving the task arises in the case if the duration of individual works are random values. In this case, the time characteristics of the completion of the work complex are necessary not only to assess the probabilistic-time characteristics but also for the simplest planning of the start time of each work. Currently, there are approaches to solving this task, the most common of which is PERT (Program Evaluation and Review Technique, an evaluation and project analysis technique). However, the estimates of the method are based on the central limit theorem based on assumptions that are impracticable in the real functioning of industrial or serving systems. Because of this, it is necessary to obtain a model that allows one to estimate the required characteristics in any conditions. As a result, a simulation model was obtained, which allows one to obtain the probabilistic-time characteristics of a random variable, which is the duration of a complex of sequential-parallel works and characterized by increased accuracy compared to existing analogues. For the implementation of the model, we chose AnyLogic medium


2021 ◽  
pp. 2150001
Author(s):  
Kai Yao

In the queueing theory, the interarrival times between customers and the service times for customers are usually regarded as random variables. This paper considers human uncertainty in a queueing system, and proposes an uncertain queueing model in which the interarrival times and the service times are regarded as uncertain variables. The busyness index is derived analytically which indicates the service efficiency of a queueing system. Besides, the uncertainty distribution of the busy period is obtained.


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