• 대한전자공학회논문지TC
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• 제38권10호
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• pp.24-33
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• 2001

패킷 통신에 있어서 주요 서비스 품질(QoS : Quality of Service) 요소로는 지연(delay), 지연 변이(delay variation), 패킷 손실율(loss rate) 등이 있다. 본 논문에서는 복수의 논리적 버퍼가 하나의 메모리 버퍼를 공유할 때, 논리버퍼의 손실율 성능을 향상시키기 위한 새로운 버퍼 할당 기법을 제안한다. 제안된 예방적 적응 한계치(PAT : Preventive Adaption Threshold) 버퍼 할당 기법은 기존의 동적 한계치 (Dynamic Threshold)기법에서 사용하는 패킷 폐기 한계치(threshold)의 직선적 변화 궤적과는 다른 한계치 동적 변화 궤적을 사용함으로써 패킷 손실율 성능을 개선하였다. 제안된 기법의 성능을 평가하기 위하여 기존의 무제어(NC : No Control), 고정 한계치(ST : Static Threshold), 동적 한계치(DT : Dynamic Threshold)등의 기법과 여러 측면에서 손실율 성능을 비교하였다.

• 정보처리학회논문지A
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• 제10A권6호
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• pp.677-684
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• 2003

VOD 서비스의 대부분 정책들은 주로 서버 시스템에 대해 연구되고 있고, 단절감 없는 재생과 재생질 보증의 근간이 되는 클라이언트의 버퍼 안정화 문제에 대해서는 언급되지 않고 있다. 본 논문에서는 클라이언트의 버퍼 상태가 스타베이션 또는 오버런인 경우 서버에 동적인 제어신호를 발하고, 서버에서는 수신된 제어 요구 신호에 따라 프레임을 생략하여 전송하는 정책을 제안한다. 그리고 시뮬레이션을 통하여 제안 정책이 클라이언트의 버퍼 상태 악화로 인한 프레임의 미수신 및 손실을 방지하여 클라이언트의 버퍼를 안정화시켜 재생질 보증에 더 효율적임을 보인다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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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.

• International Journal of Control, Automation, and Systems
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• 제6권2호
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• pp.214-222
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• 2008

Bode principle is applied to carry out traffic control for rate based ATM network, which guarantees the higher buffer utilization, buffer overflow-free, and well utilization of bandwidth. The principle confirms the relationship between the threshold of buffer queue and the network bandwidth, as well as the relationship between the threshold of buffer and source input rate. Theoretic warrant of the buffer threshold is proposed. The reference range of source input rate is provided in theory, which makes the source end respond to the change of network state rapidly and dynamically, and then the effect of time delay to the traffic control is avoided. Simulation results show that the better steady and dynamic performances of networks are obtained by Bode principle.

• 대한산업공학회지
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• 제21권1호
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• pp.103-118
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• 1995

This paper is concerned with developing flow control method for a dynamic multistage manufacturing system with interstage buffers and unreliable machines. For the effective control of proposed manufacturing system, the three-level hierarchical scheme is introduced. At the top level, we collect the system data and then, design the buffer sizes and hedging points. Short-term production rates are calculated at the middle level. At the bottom level, actual dispatching times are determined by Clear the Largest Buffer Level rule. The control method utilizes the material and the space in the buffers to alleviate the propagation of a failure to other machines in the system and keeps the production close to demand. Finally, a numerical example is provided to illustrate the mathematical control method developed and implemented in a dynamic manufacturing environment.

• 한국통신학회논문지
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• 제22권4호
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• pp.855-869
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• 1997

In this paper, we proposed two kids of dynamic priority control mechanisms controlling the cell service ratio in order to improve the QOS(Quality of Service). We also analyse theoretically the characteristics of cell loss probability and mean cell delay time by applying the proposed priority control mechanisms to ATM switch with output buffer. The proposed priority control mechanisms have the same principles of storing cells into buffer but the different principles of serving cells from buffer. The one is the control mechanism controlling the cell service ratio according to the relative cell occupancy ratio of buffer, the other is the control mechanism controlling the cell service ratio according to both the relative cell occupancy ratio of buffer and the average arrival rate. The two service classes of our concern are the delay sensitive class and the loss sensitive class. The analytical results show that the proposed control mechanisms are able to improve the QOS, the characteristics of cell loss probability and mean cell delay time, by selecting properly the relative cell occupancy ratio of buffer and the average arrival rate. conventional DLB algorithm does not support synchronous cells, but the proposed algorithm gives higher priority to synchronous cells. To reduce synchronous cell loss rate, the synchronous cell detector is used in the proposed algorithm. Synchronous cell detector detects synchronous cells, and passes them cells to the 2nd Leaky-Bucket. So it is similar to give higher priority to synchronous cells. In this paper, the proposed algorithm used audio/video traffic modeled by On/Off and Two-state MMPP, and simulated by SLAM II package. As simulation results, the proposed algorithm gets lower synchronous cell loss rate than the conventional DLB algorithms. The improved DLB algorithm for multimedia synchronization can be extended to any other cells which require higher priority.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.768-783
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• 2020

Typically, a Dynamic Positioning System (DPS) uses a PID feed-back system, and it often adopts a wind feed-forward system because of its easier implementation than a feed-forward system based on current or wave. But, because a ship's drifting motion is caused by wind, current, and wave drift loads, all three environmental loads should be considered. In this study, a motion predictive control for the PID feedback system of the DPS is proposed, which considers the three environmental loads by utilizing predicted drifted ship positions in the future since it contains information about the three environmental loads from the moment to the future. The prediction accuracy for the future drifted ship position is ensured by adopting deep learning algorithms and a replay buffer. Finally, it is shown that the proposed motion predictive system results in better station-keeping performance than the wind feed-forward system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권11호
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• pp.5271-5289
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• 2016

On large-scale data analysis platforms deployed on cloud infrastructures over the Internet, the instability of the data transfer time and the dynamics of the processing rate require a more sophisticated data distribution scheme which maximizes parallel efficiency by achieving the balanced load among participated computing elements and by eliminating the idle time of each computing element. In particular, under the constraints that have the real-time and limited data buffer (in-memory storage) are given, it needs more controllable mechanism to prevent both the overflow and the underflow of the finite buffer. In this paper, we propose an auto regulated data provisioning model based on receiver-driven data pull model. On this model, we provide a synchronized data replenishment mechanism that implicitly avoids the data buffer overflow as well as explicitly regulates the data buffer underflow by adequately adjusting the buffer resilience. To estimate the optimal size of buffer resilience, we exploits an adaptive buffer resilience control scheme that minimizes both data buffer space and idle time of the processing elements based on directly measured sample path analysis. The simulation results show that the proposed scheme provides allowable approximation compared to the numerical results. Also, it is suitably efficient to apply for such a dynamic environment that cannot postulate the stochastic characteristic for the data transfer time, the data processing rate, or even an environment where the fluctuation of the both is presented.

• 정보과학회 논문지
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• 제43권3호
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• pp.327-335
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• 2016

본 논문에서는 실감교류 멀티미디어 서비스에 적합한 버퍼 관리 방안을 제안한다. 수신 버퍼 크기가 왕복 시간 추정에 따라 달라질 수 있도록 전형적인 지연 최적화 환경을 고려한다. 이러한 환경에서, 버퍼 크기 단축 시 버퍼 내에 I/P/B 프레임을 드롭하는 경우 발생할 수 있는 정보 손실을 최소화하기 위한 최적화 기법을 제안한다. 근사 해를 찾기 위해 동적 프로그래밍을 이용하는 Knapsack Problem으로 문제를 모델링한다. 제안된 기법은 기존의 버퍼 관리 기법과 비교된다. 시뮬레이션 연구를 통해, 제안하는 접근 방식은 비디오 품질에 중요한 PSNR을 증가시킬 수 있음을 확인하였다.

• 대한수학회논문집
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• 제13권3호
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• pp.603-627
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• 1998

The leaky bucket scheme is a promising method that regulates input traffics for preventive congestion control. In the ATM network, the input traffics are bursty and transmitted at high-speed. In order to get the low loss probability for bursty input traffics, it is known that the leaky bucket scheme with static leaky rate requires larger data buffer and token pool size. This causes the increase of the mean waiting time for an input traffic to pass the policing function, which would be inappropriate for real time traffics such as voice and video. We present the leaky bucket scheme with dynamic leaky rate in which the token generation period changes according to buffer occupancy. In the leaky bucket scheme with dynamic leaky rate, the cell loss probability and the mean waiting time are reduced in comparison with the leaky bucket scheme with static leaky rate. We analyze the performance of the proposed leaky bucket scheme in discrete-time case by assuming arrival process to be Markov-modulated Bernoulli process (MMBP).