• Journal of KIISE
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• v.43 no.2
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• pp.246-255
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• 2016

The orthogonal frequency-division multiple access (OFDMA) systems are well suited to multi-rate multicast transmission, as they allow flexible resource allocation across both frequency and time, and provide adaptive modulation and coding schemes. Unlike layered video coding, the multiple description coding (MDC) enables flexible decomposition of the raw video stream into two or more substreams. The quality of the video stream is expected to be roughly proportional to data rate sustained by the receiver. This paper describes a mathematical model of resource allocation and throughput in the multi-rate video multicast for the OFDMA wireless and mobile networks. The impact on mean opinion score (MOS), as a measurement of user-perceived quality (by employing a variety of scheduling disciplines) is discussed in terms of utility maximization and proportional fairness. We propose a pruning algorithm to ensure a minimum video quality even for a subset of users at the resource limitation, and show the optimal number of substreams and their rates can sustain.

• Journal of KIISE:Information Networking
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• v.29 no.2
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• pp.129-140
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• 2002

In this paper, we consider the problem of packet transmission in a wavelength division multiplexed(WDM) optical network. Our network model assumes that receivers are fixed-tuned and transmitters are tunable such that optical lasers assigned to transmitters have limited access to the network bandwidth: hence each node must be equipped with multiple optical lasers and/or multiple optical filters in order to maintain a single-hop network. We first analyze scheduling all-to-all packet transmissions and present optimum scheduling for all-to-all packet transmissions. We then extend the analysis to the case of arbitrary traffic demands. We show that the scheduling with arbitrary traffic demand is NP-hard. A heuristic algorithm based on list scheduling is presented. The upper bound so obtained is compared with the lower bound and provides performance guarantees with arbitrary demands. The result are applicable to arbitrary tuning delay, arbitrary number of wavelength channels and optical lasers of arbitrary tuning ranges.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.149-158
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• 2019

The scheduling of planned maintenance problem of a system consisting of a number of components was studied. The purpose of maintenance scheduling is to minimize the cost of maintaining long-term operations. On the system side, the cost of a system shutdown can be minimized by grouping and inspecting a number of components. In addition, proper inspection cycles can be selected for each component to identify the failure sufficiently early to minimize the cost of the failure. To reduce the complexity of the calculations, the 'base interval approach' used in previous studies was applied and, in addition, the inspection cost savings from simultaneous inspections of multiple components were considered. To compare the effectiveness of inspection cost savings, this paper presents the results of simulation analysis performed by referring to the cases in the existing studies.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.59-60
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• 2023

The automation of container terminals is an important factor that determines port competitiveness, and global advanced ports tend to strengthen their competitiveness through container terminal automation. The operational efficiency of the AGV, which is an essential transport equipment of the automated terminal, can improve the productivity of the automated terminal. The operation of AGVs in automated container terminals differs from that of conventional container terminals, as it is based on an automated system in which AGVs travel along designated paths and operate according to assigned tasks, requiring consideration of factors such as workload, congestion, and collisions. To prevent such problems and improve the efficiency of AGV operations, a more sophisticated model is necessary. Thus, this paper proposes an AGV scheduling model that takes into account the AGV travel path and task assignment within the terminal The model prevent the problem of deadlock and. various cases are generated by changing AGV algebra and number of tasks to create AGV driving situations and evaluate the proposed algorithm through algorithm and optimization analysis.

• Journal of Korea Society of Industrial Information Systems
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• v.29 no.3
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• pp.67-77
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• 2024

Increasing energy efficiency in factories is an activity aimed at optimizing resource allocation in manufacturing processes to establish production plans. However, this strategy may not apply effectively when night shifts are unavoidable. Additionally, continuous fluctuations in production requirements pose challenges for its implementation in the factory. Recently, with the rapid proliferation of electric vehicles (EVs), technology utilizing electric vehicle batteries as energy storage systems has gained attention. Technology using these batteries can be an alternative for factory energy management. In this paper, a factory energy management method using EV batteries is proposed. The proposed method is analyzed using PSCAD/EMTDC software, considering the state of charge of EV batteries and Time-of-Use (TOU) rates. The proposed method was compared with production scheduling established considering predicted power usage and TOU rates. As a result, production scheduling saved 4,152 KRW per day, while the proposed method saved 7,286 KRW in electricity costs. Through this paper, the possibility of utilizing EV batteries for factory energy management has been demonstrated.

• Proceedings of the KIPE Conference
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• 2019.11a
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• pp.234-235
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• 2019

최근 국내 ESS 시장은 정부의 강력한 지원에 힘입어 민간의 투자, 운영 수요가 크게 늘어나고 있으며, 연평균 27% 성장하여 20년 민간 544MWh, 한전 320MWh로 총 864MWh 확대 전망이다. 특히, ESS는 태양광 연계를 통한 매전수익, 피크컷 기능을 통한 전력요금 절감, 독립전원 공급 등 다양한 분야에 활용되고 있다. ESS의 활용이 다양해짐에 따라 PMS/EMS를 통한 PCS제어 및 모니터링 기능, 피크컷 기능이 중요해지고 있다. 이렇듯 사이트 특성에 따른 커스터마이징이 편리한 PMS/EMS IoT 플랫폼 구축이 필요하다. 따라서 본 논문에서는 사이트 특성에 따른 커스터마이징이 편리한 PMS/EMS IoT 플랫폼을 설계하고 개발하였다. 그 결과 운전 스케줄링, 실시간 모니터링, 피크컷, 수익분석, 독립전원 등의 기술이 적용 가능한 PMS/EMS IoT 플랫폼을 통해 최적의 운영으로 수익을 극대화할 것으로 기대한다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.207-209
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• 2007

본 논문은 내륙 운송 체계 하에서 공 컨테이너의 효율적인 운송관리 문제에 대하여 다루었다. 내부적으론 pickup and delivery 제약조건을 적용하여 특정 pick up 시간을 가지는 화물과 터미널에서의 적 컨테이너을 만족하는 차량의 스케줄링 문제이다. 차량의 내부 운송에서 공 컨테이너의 이동이나 공차의 이동 같은 불필요한 이동을 최소화함으로 효율적 운송을 할 수 있다. 또 한 모든 화물과 수입된 적 컨테이너의 pick up time 의 시간 제약으로 인한 차량의 이동 제약를 만족해야 한다. 이 문제를 해결하기 위해서 휴리스틱과 메타 휴리스틱 방법을 이용하여 근사해를 도출한다.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06d
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• pp.362-366
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• 2008

본 논문에서는 이동 에이전트의 이주 노드들에 대한 최적 경로 탐색을 통한 적응적 이주 경로 기법을 설계한다. 적응적 이주 경로 기법은 이동 에이전트가 사용자로부터 동일한 작업 요청을 부여 받았을 경우 일반적으로 전체 노드를 순회하지 않고 이주할 노드를 선택함으로써 수행되어진다. 그러나 이주 수행시 네트워크 환경 변화 및 부하로 인해 트래픽이 증가된 경우에는 스케줄링된 목적 노드로의 이주가 원활히 수행되지 못하므로 노드 순회 시간 비용이 증가하게 된다. 따라서 본 논문에서는 이러한 상황을 해결하기 위해 최적으로 이주 노드들의 경로를 지정하는 경로 탐색 알고리즘을 통해 에이전트의 노드 이주 시간 비용을 최소화할 수 있는 이주 기법을 제안한다. 제안된 기법은 이동 에이전트의 이주 신뢰성을 확보하며 순회 작업 처리 시 효율성을 높일 수 있다.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.2
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• pp.227-233
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• 2000

In this paper, we present a new high-level data path synthesis algorithm which solves the two design problems, namely, scheduling and allocation, with power minimization as a key design parameter. From the observations in previous works on data path synthesis for low power, we derive an integer programming (IP) formulation for the problem, from which we then develop an efficient heuristic to carry out the scheduling and allocation simultaneously. Our experimental results demonstrate that the proposed algorithm is very effective in saving power consumption of circuits significantly.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.8
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• pp.905-917
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• 1999

멀티미디어 시스템에서 수행되는 부하 중 상당 부분은 정해진 시간에 주기적으로 수행되어 연속 매체(continuous media)를 처리하는 주기 태스크들이다. 연속 매체들을 처리하는 두 주기 태스크의 수행 요청 시간(release time)간에 인공적인 위상(phase)을 줄 경우, 전체 부하의 처리 타이밍에 영향을 주게 되며, 특히, 적절한 위상을 부여할 경우 부하가 고르게 분산된다. 부하의 고른 분산은 태스크 간섭을 줄여 지터(jitter), 종료시한 초과(deadline miss), 그리고 긴 응답 시간(response time) 등의 문제를 해소시킨다. 본 논문에서는 새로운 위상 스케줄링(phased scheduling) 알고리즘 및 알고리즘을 개발하고 평가할 수 있는 실험 환경을 제안한다. 본 논문에 제시된 알고리즘은 저자들의 선행 논문 1 에서 제시한 알고리즘의 대안이다. 새로운 알고리즘은 정확하게 최적의 위상을 찾지는 않으나 기존 알고리즘보다 빠르게 수행되며 적용 범위가 넓다.Abstract A multimedia system consists of substantial amount of continuous media workload scheduled periodically at deterministic time points. Artificial phase between the invocation times of any two continuous media tasks affects the timing of the entire workload. A proper phase configuration distributes workload uniformly over time and reduces task interference that may otherwise result in jitter, deadline miss, and long response time. The objective of this paper is to work out a phased scheduling algorithm and to evaluate its effectiveness. The algorithm in this paper is an alternative approach to our previous work 1 . It is almost as accurate as the predecessor but two of three times faster in identifying the appropriate phase vector.