• Transactions on Control, Automation and Systems Engineering
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• 제3권3호
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• pp.139-145
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• 2001

In this paper, we consider the H$_2$(or guaranteed cost control) and H$_{\infty}$ controller design methods for singular(or descriptor) systems with input time delay. Also, a mixed H$_2$and H$_{\infty}$ controller design algorithm is treated by combination of the proposed H$_2$and H$_{\infty}$ controller design method. The sufficient conditions for the existence of controllers and controller design methods are introduced at each Lemma and Theorem. Furthermore, we present optimization problems to get the upper bound of performance measures. The proposed methods are checked by examples.

• 한국항해학회지
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• 제7권1호
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• pp.1-32
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• 1983

The delay due to congestion has recently attracted widespread attention with the analysis of over-all operation at the port. But, the complexity of the situation is evident in view of the large number of factors which impinge on the considerable end. Queueing theory is applicable to a large scale transportation system which is associated with arrivals of vessels in a large port. The attempt of this paper is to make an extensive analysis of the port transport system and its economic implications from the viewpoint that port is one of the physical distribution facilities and a kind of queueing system which includes ships and cargoes as port customer. By analyzing the real data on the Port of Pusan, it is known that this port can be represented as a set of multi-channel with identical setof Poisson arrival and Erlang service time, and also it is confirmed that the following formula is suitable to calculate the mean delay in this port, namely, $W_4={\frac{\rho}{\lambda(1-\rho)} {\frac{e_N(\rho{\cdot}N)}{D_{N-1}(\rho{\cdot}N)}$ where, ${\lambda}$: mean arrival rate $\mu$: mean servicing rate; N: number of servicing channel; ${\rho}$: utillization rate (${\lambda}/N{\mu}$) $e_N$: the Poisson function Coming to grips with the essentials of the cost of delay due to congestion, a simple ship journey cost model is adopted and the operating profit sensitivity to variation in port time is examined, and for purpose of a future development for port princing service the marginal cost is approximately calculated on the basis of queueing theory.

• 한국통신학회논문지
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• 제30권1A호
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• pp.46-54
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• 2005

본 논문은 사용자의 이동 패턴에 기반한 효율적인 이동 멀티캐스트 기법을 제안한다. 본 논문은 멀티캐스트 서비스를 받기 위해 소요되는 전체 지연 시간을 줄이기 위한 방법으로 이동 노드의 반복적인 이동 성향을 정의한다. 정의된 이동 성향을 바탕으로 지역의 범위에 속하는 외부 에이전트들은 멀티캐스트 라우팅 트리를 활성화된 상태로 유지함으로 이동 노드가 재방문 했을 경우 지연 없이 멀티캐스트 서비스를 즉시 받을 수 있다. 수학적 분석모델을 이용하여 제안된 방안의 성능을 증명하며, 분석 결과는 제안된 방식이 기존의 연동방식 보다 전체 처리 비용과 서비스 지연 시간 측면에서 우수하다는 것을 보여준다.

• 한국위성정보통신학회논문지
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• 제6권2호
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• pp.84-90
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• 2011

IP 기반의 이동 네트워크에서 페이징 메커니즘을 IP 계층에서 처리하는 기술(즉, IP 페이징)은 이동 단말의 전력 소모와 위치 등록 시그널링 부하를 감소시켜주며, 이기종 무선 액세스 기술들을 지원하는 것을 가능하게 한다. 그러나, 통신이 매우 빈번한 환경 하에서는 증가하는 페이징 시그널링 부하와 잦은 페이징 지연으로 인하여 오히려 IP 페이징의 사용은 역효과를 초래할 수도 있다. 따라서, 본 논문에서는, 이러한 IP 페이징의 문제점을 해결하고자, 이동 단말이 자신의 프로파일 정보에 기반하여 선택적인 위치 등록 및 페이징을 수행할 수 있도록 하는 비용 효율적인 IP 페이징 기법을 제안한다. 성능 평가 결과, 제안 기법은 IP 기반의 계층적 이동 네트워크에서 상당한 정도의 페이징 시그널링 부하와 잦은 페이징 지연을 감소시킬 수 있다는 것을 보여준다.

• 전기의세계
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• 제27권2호
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• pp.53-63
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• 1978

The problem of optimally controlling a time-delay control system to a function as the final target is inverstigated. Necessary conditions are presented in the form of Pontryagin's maximum principle, and it is further shown that they are also sufficient for linear systems with a convex cost functional. Several examples are given to illustrate the results.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2002년도 춘계학술대회
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• pp.237-241
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• 2002

This paper deals with the problem of determining the buyer's economic lot sizing policy for exponentially deteriorating products under trade credit. It is also assumed that the ordering cost consists of a fixed set-up cost and a freight cost, where the freight cost has a quantity discount offered due to the economies of scale. We formulate the mathematical model and the solution algorithm is developed based on the properties of an optimal solution.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.67-70
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• 2002

This paper presents an optimal robust LQ-PID controller design method for a second order system with time-delay to meet design specifications. By LQR formulation of the second order system with time-delay, tuning parameters of PID controller are related by the weighting factors Q and R of cost function. The selection of the weighting factors Q and R are chosen to satisfy such the design specifications as overshoot and settling time.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권9호
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• pp.2218-2230
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• 2012

In this paper, we propose an efficient channel delay estimation method for orthogonal frequency-division multiplexing (OFDM) systems, especially over doubly-selective fading channels which are selective in both the symbol time domain and subcarrier frequency domain. For the doubly-selective fading channels in single frequency network (SFN), long and strong echoes exist and thus the conventional discrete Fourier Transform (DFT) based channel delay estimation system often fails to produce the exact channel delay profile. Based on the analysis of the discrete-time frequency response of the channel impulse response (CIR) coefficients in the DFT-based channel delay estimation system, we develop a method to effectively extract the true CIR from the aliased signals by employing a simple narrow-band low-pass filter (NB-LPF). The performance of the proposed system is verified using the COST207 TU6 SFN channel model.

• Journal of the Optical Society of Korea
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• 제13권3호
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• pp.373-378
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• 2009

An Ethernet passive optical network (EPON) is a low-cost, high-speed solution to the bottleneck problem of a broadband access network. This paper analyzes the delay and the jitter performance of dynamic bandwidth allocation (DBA) schemes for differentiated services in EPONs. Especially, the average packet delay and the delay jitter of the expedited forwarding (EF) traffic class are compared, with consideration as to whether a cyclic or an interleaved polling scheme is superior. This performance evaluation reveals that the cyclic polling based DBA scheme provides constant and predictable average packet delay and improved jitter performance for the EF traffic class without the influence of load variations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권7호
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• pp.3057-3075
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• 2020

End-to-end network delay plays an vital role in distributed services. This delay is used to measure QoS (Quality-of-Service). It would be beneficial to know all node-pair delay information, but unfortunately it is not feasible in practice because the use of active probing will cause a quadratic growth in overhead. Alternatively, using the measured network delay to estimate the unknown network delay is an economical method. In this paper, we adopt the state-of-the-art matrix completion technology to better estimate the network delay from limited measurements. Although the number of measurements required for an exact matrix completion is theoretically bounded, it is practically less helpful. Therefore, we propose an online adaptive sampling algorithm to measure network delay in which statistical leverage scores are used to select potential matrix elements. The basic principle behind is to sample the elements with larger leverage scores to keep the traits of important rows or columns in the matrix. The amount of samples is adaptively decided by a proposed stopping condition. Simulation results based on real delay matrix show that compared with the traditional sampling algorithm, our proposed sampling algorithm can provide better performance (smaller estimation error and less convergence pressure) at a lower cost (fewer samples and shorter processing time).