• The Journal of the Korea Contents Association
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• v.16 no.8
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• pp.671-680
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• 2016

This research suggested a new real-time traffic signal control algorithm using fusion data of the travel time and the occupancy rate. This research applied the travel time data of traffic information system to traffic signal operation, and developed the signal control process using the degree of saturation that was estimated from the travel time data. This algorithm estimates a queue length from the travel time based on a deterministic delay model, and includes the process to change from the queue length to the degree of saturation. In addition, this model can calculate the traffic signal timings using fusion data of the travel time and the occupancy rate based on the saturation degree. The micro simulation analysis was conducted for effectiveness evaluation. We checked that the average delay decreased by up to 27 percent. In addition, we checked that this signal control algorithm could respond to a traffic condition of oversaturation and detector breakdown effectively and usefully. This research has important contribution to apply the traffic information system to traffic signal operation sectors.

• Journal of the Korea Society for Simulation
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• v.33 no.1
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• pp.19-26
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• 2024

The phase-type, PH, distribution is defined as the time to absorption into a terminal state in a continuous-time Markov chain. As the PH distribution includes family of exponential distributions, it has been widely used in stochastic models. Since the PH distribution is represented and generated by an initial probability vector and a generator matrix which is called the Markovian representation, we need to find a vector and a matrix that are consistent with given set of moments if we want simulate a PH distribution. In this paper, we propose an approach to simulate a PH distribution based on distribution function which can be obtained directly from moments. For the simulation of PH distribution of order 2, closed-form formula and streamlined procedures are given based on the Jordan decomposition and the minimal Laplace transform which is computationally more efficient than the moment matching methods for the Markovian representation. Our approach can be used more effectively than the Markovian representation in generating higher order PH distribution in queueing network simulation.

• Proceedings of the KOR-KST Conference
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• 1998.10a
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• pp.226-235
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• 1998

본 논문에서는 추종 모형을 이용한 미시 교통류 시뮬레이션 모형을 개발하고, 이 모형을 통한 시뮬레이션을 통하여 단속류에서 검지기의 설치 위치에 따른 검지 특성을 알아보고, 교통정보 수집용의 검지기의최적 위치에 대해 평가하였다. 검지기로부터 발생하는 교통량, 점유율, 속도 자료중 링크의 통행시간을 가장 잘 반영하는 것은 점유율에 의한 검지기의최적위치는 정지선으로부터 150∼250m이다. 점유율 다음으로 통행시간을 잘 반영하는 자료는 지점속도로서 점유율보다는 상관관계가 낮지만, 양호한 설명력을 가지는 것으로 보인다. 교통량 자료는 상관관계가 낮으며, 교통량에 의한 위치 선정은 각 모의 실험 결과에서 일관적이지 않아 적절한 설명변수가 아니라고 판단하였다. 모든 경우에서, 정지선이나 링크 최상류에 위치한 검지기로부터의 자료는 통행시간과 독립적이므로 이러한 검지기는 교통정보 수집용을 사용할 수 없으며, 일반적인 검지기의최적 위치는 정상상태의 교통류 뿐만 아니라 대기행렬내에 존재하여 매우 혼잡한 상태를 경험할 수 있는 위치라고 할수 있다.

• 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 Korean Operations Research and Management Science Society
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• v.30 no.2
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• pp.131-142
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• 2005

This paper proposes queueing models for a Web server system which is composed of an infinite-buffer main server and finite-buffer auxiliary server(s). The system is modeled by the level-dependent quasi-birth- death (QBD) process. Utilizing the special structure of the QBD, we convert the infinite level-dependent QBD into a finite level-independent QBD and compute the state probabilities. We then explore the operational characteristics of the proposed web-server models and draw some useful conclusions.

• Journal of the Korean Operations Research and Management Science Society
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• v.22 no.2
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• pp.45-65
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• 1997

We build a queueing model for buffered leaky bucket system. First, we set up system equations and them calculate the steady-state probabilities at an arbitrary time epoch by recursive method. We derive the mean waiting time and the mean number of cells in the input buffer, and evaluate the performance of the buffered leaky bucket system to find the optimal queue capacity and token generation rate that meet the quality of service(QoS).

• Journal of the Korean Operations Research and Management Science Society
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• v.21 no.2
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• pp.203-213
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• 1996

A system is considered which is required to perform tasks that arrive randomly during a fixed mission duration. We develop queueing models to obtain the mission effectiveness and the blocking probabilities. Exact probabilities are computed by using the Finite Fourier Cosine Transform.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.30 no.4
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• pp.39-45
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• 2007

The BMAP/M/N/0 queueing system operating in Markovian random environment is investigated. The stationary distribution of the system is derived. Loss probability and other performance measures of the system also are calculated. Numerical experiments which show the necessity of taking into account the influence of random environment and correlation in input flow are presented.

• Journal of Korean Institute of Industrial Engineers
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• v.16 no.1
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• pp.107-114
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• 1990

A queueing system with compound Poisson arrival and server vacation is analyzed by including supplementary variables. We consider a vacation system in which the server leaves for a vacation as soon as the system empties. When he returns, if no customer is waiting for service, he waits until a group of customers arrive and then begins to serve. We obtain the system size distribution and the waiting time distribution. Additional performance measures will be also considered.

• Journal of Korean Institute of Industrial Engineers
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• v.24 no.3
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• pp.381-386
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• 1998

We frequently encounter stopped random sums when modelling queueing systems. We also notice occasional mishandling of stopped random sums in the literature. The purpose of this note is to prevent further mistakes by identifying and correcting typical mistakes about stopped random sums. As an example model, we use the two-phase M/G/1 queue with multiple vacations.