• Journal of Advanced Navigation Technology
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• v.15 no.2
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• pp.307-312
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• 2011

In the macro/femto cellular networks, the portion of channels assigned to each cell is a critical factor which sets the stability and the performance of the whole system. To grasp the concrete influence that the channel split portion have on the system, we present the queueing model for IP based macro/femto cellular networks, and find the stability conditions. Additionally we provide the strategy to decide the portion of channels allocated to each cell. Through the experiments, we prove that the proposed strategies operate feasibly in various network environments, and on the basis of these results we discuss the efficient system structure plan.

• Journal of the military operations research society of Korea
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• v.5 no.1
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• pp.155-162
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• 1979

GERT modeling is in a dynamic stage of development. One of the most exciting and useful new developments in GERT modeling and Simulation is the modeling technology and computer package called Q-GERT. As the name implies, this provides the capability to analyze complex networks of queueing systems. The modeling approach is quite similar to GERT, but includes queue nodes called 'Select' nodes, which allow a considerable amount of logic to be included in the analysis of complex networks of multichannel, multiphase queueing systems should find the Q-OERT package of considerable interest.

• Journal of Korean Institute of Industrial Engineers
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• v.23 no.4
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• pp.769-778
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• 1997

Assembly/Disassembly Queueing Networks (ADQNs) with finite buffers have been used as a major tool for evaluating the performances of manufacturing and parallel processing systems. In this study, we present simple but effective methods which yield throughput upper and lower bounds for ADQNs with exponential service times and finite buffers. These methods are based on the monotonicity properties of throughputs with respect to service times and buffer capacities. The throughput-upper bounding method is elaborated on with general network configuration (specifically acyclic configuration). But our lower bounding method is restricted to the ADQNs with more specialized configuration. Computational experiments will be performed to confirm the effectiveness of our throughput-bounding methods.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.5
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• pp.25-34
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• 1997

Relatively slow tuning speed of optical device causes the unwanted delay in high speed single-hop multiwavelength networks. To lessen the overhead, we present a channel access protocol with dynamjic message scheduling. Th eframe structure of proposed protocol adopts hybrid multiaccess scheme in which WDMA is used as a basic multiaccess technique and TDMA is used to provide subchannels within a wavelength band. This architecture has two merits : the network extention is not limited by available number of wavelengths, and the transmission delay caused by optical device tuning time can to minimize the number of tunings. It schedules messages that require same wavelength channels sequencely, so the total transmission delay is reduced by decreasement of wavelength changes. The performance of proposed protocol is evaluated through numerical analysis based on probability and queueing theory. The peformance of proposed protocol is evaluated through numerical analysis based on probability and queueing theory. The numeric results show that the peformance of proposed protocol is better than that of previous one.

• Journal of the Korean Operations Research and Management Science Society
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• v.29 no.4
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• pp.1-10
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• 2004

In this paper we study bounds for characteristics of stationary waiting times in (max, +)-linear systems with a Poisson arrival process. which are prevalent in manufacturing systems, kanban systems, cyclic and acyclic fork-and-join type systems, finite or infinite capacity tandem queues with various kinds of blocking, transportation systems, and telecommunication networks, and so on. Recently, some results on series expansion for characteristics, such as higher moments, Laplace transform, and tail probability, of transient and stationary waiting times in a class of (max, +)-linear systems via Taylor series expansions have been studied. In order to overcome the computational complexity in those results, we consider bounds for characteristics of stationary waiting times using valuable stochastic ordering results. Some numerical examples are also provided.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.469-475
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• 1991

In this paper, we suggest the exact perturbation analysis(Exact_PA) technique with respect to the buffer storage in tandem queueing networks, through which the optimal buffer storage design problem is considered. The discrete event dynamic equations for the departure time of a customer are presented together with the basic properties of Full Out(FO) and No Input(NI) with respect to the buffer storage. The new perturbation rules with respect to the buffer storage are suggested, from which the exact perturbed path can be obtained. The optimal buffer storage problem is presented by introducing a performance measure consisting of the throughput and the buffer storage cost. An optimization algorithm maximizing this performance measure is derived by using the Exact_PA technique. The proposed perturbation analysis technique and the optimization algorithm are validated by numerical examples.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.7 no.1
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• pp.15-23
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• 2003

ATM networks provide the various kinds of service which require the different Quality of Services(QoS) such as loss and delay. By statistically multiplexing of traffics and the uncertainty and fluctuation of source traffic pattern, the congestion may occur. The leaky bucket scheme is a representative policing mechanism for preventive congestion control. In this paper, we analyze the HOL(Head-of-Line) priority leaky bucket scheme. That is, traffics are classified into real-time and nonreal-time traffic. The real-time traffic has priority over nonreal-time traffic for transmission. For proposed mechanism, we obtain the system state distribution, finally the loss probability and the mean waiting time of real-time and nonreal-time traffic. The simple numerical examples also are presented.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1997.11a
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• pp.147-161
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• 1997

In the future, the performance of B-lSDN offering the multimedia and a various service depends on the performance of switch that is the important factor consisting of network. Bufferless banyan network consisted of MIN(multistage interconnection network) selected for- the fabric of ATM switch and has a limitation of performance because of blocking. Input buffered banyan networks with FIFO(first-in first-out) buffering scheme for the reduction of blocking and the cell bypass queueing theory for the reduction of HOL(head of line) blocking were seperately compared of the performance of switch. Specially input buffered banyan networks were applied monotonic buffering scheme that was proposed. As a result of simulation, Buffered Banyan Network with cell bypass queueing theory showed better performance than FIFO type input buffered Banyan network. Monotonic increase buffering scheme showed better performance than Monotonic decrease buffering scheme.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.841-844
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• 2002

Recently there has been an increasing interest in queueing models with disasters. Upon arrival of a disaster, all the customers present are noshed out. Queueing models with disasters have been applied to the problems of failure recovery in many computer networks systems, database systems and telecommunication networks in this paper, we suffest the steady state and sojourn time distributions of the M/G/l model with disaster and mass alway when the system is empty.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.547-547
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• 1996