Obsie Mussa Yesuf

Bio: Obsie Mussa Yesuf is an academic researcher from Andhra University. The author has contributed to research in topics: Queue & M/G/1 queue. The author has an hindex of 2, co-authored 3 publications receiving 25 citations.

Renewal input infinite buffer batch service queue with single exponential working vacation and accessibility to batches

Abstract: This paper considers an infinite buffer single server batch service queue with single exponential working vacation policy. The inter-arrival times are generally independent and identically distributed random variables and the service times are exponential. The server accesses new arrivals even after service has started on any batch of initial number a. This operation continues till the service time of the ongoing batch is completed or the maximum accessible limit d of the batch being served is attained whichever occurs first. The supplementary variable technique and the recursive method are used to develop the steady-state queue length distributions at pre-arrival and arbitrary epochs. Some performance measures and numerical results are discussed.

Analysis of a finite buffer general input queue with Markovianservice process and accessible and non-accessible batch service

Abstract: Queues with Markovian service process ($MSP$) are mainly useful in modeling and performance analysis of telecommunication networks based on asynchronous transfer mode (ATM) environment. This paper analyzes a finite buffer single server batch service ($a, b)$ queue with general input and Markovian service process ($MSP$). The server accesses new arrivals even after service has started on any batch of initial number $a$. This operation continues till the service time of the ongoing batch is completed or the maximum accessible capacity $d ~(a\le d < b)$ of the batch being served is attained whichever occurs first. Using the embedded Markov chain technique and the supplementary variable technique we obtain the steady state queue length distributions at pre-arrival and arbitrary epochs. The primary focus is on the various performance measures of the steady state distribution of the batch service, special cases and also on numerical illustrations.

Finite buffer renewal input multiple exponential vacations queue with accessible and non-accessible batches

Abstract: In this paper, we study a finite buffer single server accessible and non-accessible batch service queue with multiple exponential vacations. The inter-arrival and service times are, respectively, arbitrarily and exponentially distributed. Using the supplementary variable technique (SVT) and the embedded Markov chain technique (EMCT), we obtain the steady state system (queue) length distributions at pre-arrival and arbitrary epochs. Some numerical results are presented in the form of table and graphs.

Fundamentals of Queueing Theory

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

Unreliable server M/G/1 queue with multi-optional services and multi-optional vacations

Abstract: This paper deals with an M/G/1 queue with multiple optional services and multiple optional vacations for an unreliable server queue. All arriving customers require a First Essential Service (FES), while only some of them ask for other optional services. The stability and ergodicity condition for the model has been discussed. By introducing supplementary variables and employing the generating function technique, we derive the system size distribution at the random epoch as well as the departure epoch. Waiting time distribution and some other queuing and reliability measures have also been obtained. The sensitivity analysis has been facilitated by taking numerical illustrations to explore the effect of the different parameters on various performance indices.

Analysis of finite-buffer bulk-arrival bulk-service queue with variable service capacity and batch-size-dependent service:

Abstract: Over the past few decades, bulk-arrival bulk-service queues have found wide application in several areas including computer-communication and telecommunication systems. In this paper, we consider a single server finite-buffer queue where customers arrive in batches according to the compound Poisson process and are served in batches of variable service capacity. The service times of the batches are arbitrarily distributed and depend on the size of the batch taken into for service. We obtain the joint distribution of the number of customers in the queue and number with the server, and other distributions such as number of customers in the queue, in the system, and number with the server. Various performance measures such as average number of customers in the system (queue), with the server, blocking probabilities, etc. are obtained. Several numerical results are presented and comparative studies of batch-size-dependent service with the one when service time of the batches are independent of the size of the batch have been carried out.

Threshold N-policy for (M, m) degraded machining system with K-heterogeneous servers, standby switching failure and multiple vacations

Abstract: This paper is concerned with multi-component machining system having online or operating units along with K-type of standby units under the facility of K-heterogeneous servers. The servers switch on one by one when the number of failed units in the system reaches to a predefined threshold policy (Ni for ith server: i = 1, 2, …, K). Once server returns from a vacation, he can leave the system and go for another vacation only if no failed unit available in the system for repair. Whenever any unit fails, it is immediately replaced by an available standby unit. In case when all standbys are used, the system works in degraded mode. The standby units have switching failure probability q. The governing equations are constructed by using appropriate birth-death rates. A cost function has also been constructed to calculate the optimal number of standby units for providing the desired efficiency to the system. The SOR method is employed to find the steady state probabilities, mean number of failed units in the system, reliability and throughput. Numerical results obtained by successive over relaxation (SOR) method are matched by the results evaluated using soft computing approach based on adaptive neuro-fuzzy inference system (ANFIS).