• Journal of the Korean Operations Research and Management Science Society
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• v.16 no.2
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• pp.118-127
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• 1991

In this paper, criteria and algorithms for the optimal service rate in a closed queueing network have been established. The objective is to minimize total cost. It is shown that system throughput is increasing concave over the service rate of a node and cycle time is increasing convex over the set of service times with a single calss of cubsomers. This enables developing an algorithm using a steepest descent method when the cost function for service rate is convex. The efficiency of the algorithm rests on the fact that the steepest descent direction is readily obtained at each iteration from the MVA algorithm. Several numerical examples are presented. The major application of this research is optimization of facility capacity in a manufacturing system.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1178-1180
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• 1987

The resequence delay is an important performance measure in a store-and-forword computer network where messages go out of order while traversing logical channel. An analysis of the total delay including resequence delay is presented for M/M/L queueing system with 2 class heterogeneous servers and improvement of delay performance is investigated by simulation.

• The Transactions of the Korea Information Processing Society
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• v.5 no.1
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• pp.33-39
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• 1998

A queueing model for performance evaluation of finite buffered inter-node communication system is proposed in this paper. Each components are modeled as M/M/I/B queues to obtain the steady state probabilities and ar-rival rate and to analyze finite buffer behavior, The overall sysrem is integrated as series queues with blocking. Average delay and throughput are the performance measures studied in this analysis. The analytical results are first validated through simulation. Next, the effect of buffer length is discussed using the proposed model.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.27 no.3
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• pp.26-30
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• 2004

We consider an AS/RS(Automated Storage/ Retrieval System) which performs both of single and dual commands. The service times of single and dual commands are assumed to be differently distributed. Steady-state probabilities at the service completion epochs are calculated. Then, we transform the arrival rates of storage and retrieval commands into those of single and dual commands. Using this, we propose a non-preemptive queueing model with priority for the performance analysis of an AS/RS, and obtain approximated means of queue lengths and waiting times.

• Management Science and Financial Engineering
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• v.12 no.2
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• pp.1-18
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• 2006

We consider an $M^x/G/1$ queueing system with Bernoulli vacation schedule under multiple vacation policy. where after each vacation completion or service completion the server takes sequence of vacations until a batch of new customer arrive. This generalizes both $M^x/G/1$ queueing system with multiple vacation as well as M/G/1 Bernoulli vacation model. We carryout an extensive analysis for the queue size distributions at various epochs. Further attempts have been made to unify the results of related batch arrival vacation models.

• Journal of applied mathematics & informatics
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• v.12 no.1_2
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• pp.395-408
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• 2003

Common Channel Signaling(CCS) networks need special controls to avoid overload of signaling networks and degradation of call process-ing rate, since they play an important role of controlling communication transfer networks. Congestion control and flow control mechanisms are well described in ITU-T recommendation on Signaling System No.7(SS7). For the practical provisions, however, we need an analysis on the relation among service objects, system requirements and implementation of congestion control algorithms. SS7 provides several options for controlling link congestion in CCS networks. In this paper we give a general queueing model of congestion control algorithm which covers both the international and national options. From the queuing model, we obtain the performance parameters such as throughput, message loss rate and mean delay for the international option. To show the performance of the algorithm, some numerical results are also given.

• Journal of Korean Institute of Industrial Engineers
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• v.22 no.3
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• pp.387-398
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• 1996

In this study the cell arrival processes from pre-buffer into multiplexer for MPEG(Motion Picture Experts Group) coding video sources are analyzed with consideration of the traffic periodicity in frame level. The analysis is performed by introducing the two arrival models, that is, periodic on/off source model and periodic uniform arrival model. Modulated $N^*D$/D/1 queueing system is utilized in periodic on/off source model, while ${\Sigma}{N_i}^*D_i$/D/1 queueing system is used in periodic uniform arrival model. The presented models are validated by comparing with computer simulations. Numerical results for periodic uniform arrival model are shown to be very accurate, but those of periodic on/off source model are shown to be inaccurate as the number of sources are increased.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.8
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• pp.779-788
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• 1992

The Input /output (I /0) subsystem is often the bottleneck in high performance computer system. Generally, system performance evaluation models were enhanced to include the effect of the I/0 system. In this paper, we modeled the terminal servers which are Indispensable devices In distribution of computer resources. We use M /M /1 Queueing model for find out the point of the system performance FIFO buffer sizes In the terminal server arc the Important fanctions of the system design and could be effected to the overall system functions. We have proposed the of optimal buffer sizes in the model of terminal server for increasing the system performance. We analizing the vatting time for terruanl server using Queueing model. and We find out the reference model result from simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.6
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• pp.545-553
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• 1987

An approximation algorithm has been obtained to analyze the network of single server tandem queues with a finite length. In the queueing network with a finite queue length, the blocking which is mutually dependent, occure due to the limitation of the queue length. Thus, it is difficults to analyze such a queueing network. In this paper each queue has been regarded as the independent M/M/1/K system to analyze the queueing network with the blocking, which is based on the assumption that an arrival rate to the present station is increased by the blocking of the following stations. The performance measures, such as state probability, average queue length and tha waiting time, can be easily obtained using the proposed algorithm. In order to justify this approximation algorithm, comparison of the results of this algorithm with those of state transition simultaneous equations has been made an verified with computer simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.9A
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• pp.2184-2196
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• 1998

Admission control is one of the most important congestion control mechanism to be executed at the call set up phase by regulating traffic into a network in a preventive way. An efficient QOS evaluation or bandwidth estimation method is required for call admission to be decided in real time. In this paper, we spropose a computtionally simple approximation method of estimating cell loss probability and mean cell delay for admission control of both delay sensitive and loss sensitive calls. Mixed input queueing system, where a new call combines with the existing traffic, is used as a queueing model for QOS estimation. Also traffic parameters are suggested to characterize both a new call and existing traffic. Aggregate traffic is approximated by a renewal process with these traffic parameters and then mean delay and cell loss probability are detemined using appropriate approximation formulas. The accuracy of this approximation approach is examined by comparing their results with exact analysis or simulation results of vrious mixed unput queueing systems. Based on this QOS estimation method, call admission control scheme which is traffic independent and computable in yeal time are proposed.