• 정보처리학회논문지C
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• 제11C권4호
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• pp.555-562
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• 2004

근거리 무선 개인 네트워크 시스템 즉, 블루투스의 피코넷을 위한 전력 및 차등 대역폭 할당을 고려한다. 대역폭 요구는 어플리케이션/서비스에 또는 시간에 따라서 변할 수도 있으므로, 제한된 자원을 서비스 요구를 만족하면서 다양한 서비스 클래스로 어떻게 할당할 것인가를 결정 하는 것이 중요하다. 본 논문에서는 다양한 서비스 형태의 대역폭 요구를 만족하면서 전력 절약 모드 (즉, 스니프 모드)에 의해 전력 소비를 절약하는 간단하고 효율적인 대역폭 할당 메커니즘을 제안한다. 기존의 (가중치) 라운드 로빈 폴링 방법과 제안된 메커니즘을 비교하고, 전송율, 지연시간, 전력 소비 측면에서의 성능 향상을 보인다.

• 전자공학회논문지C
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• 제36C권4호
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• pp.17-29
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• 1999

본 논문은 데이터 의존적인 CMOS 회로(예: DSP) 의 전력량을 감축하기 위한 상위 수준 합성 기법에 대한 연구이다. 상위수준 합성은 스케줄링, 자원 및 레지스터 할당의 세가지로 나우어서 수행한다. 스케줄링시의 저전력 설계의 목적은 자원할당 시 입력을 재 사용할 수 있는 가능성을 증가시키는 것이다. 스케줄링 후에 자원 및 레지스터 할당 문제는 가중차기 부가된 앙립 그래프로 표현하여 최소비용흐름 알고리즘을 수행함으로써 스위칭 동작횟수가 적은 해를 얻는다. 제안된 알고리즘은 저전력 레지스터 및 자원 할당 문제에 대하여 O({{{{ { n}^{3 } }}}}) (n은 그래프의 노드수) 시간에 최적해를 제공한다. 벤치마크 회로에 대한 실험 결과는 15%의 전력 감축 효과를 나타낸다.

• 디지털융복합연구
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• 제10권4호
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• pp.251-256
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• 2012

본 논문에서는 EPON의 상향 대역폭 부족현상을 개선하기 위해 기존에 EPON의 상향 트래픽을 파장 분할 방식으로 확장한 모델을 설계하고 이에 적합한 파장 배정 방법을 제안한다. 시뮬레이션 모델은 OPNET으로 구현하며, 구현된 파장 분할 EPON 모델에 대해서 실험을 통하여 적절한 가중치를 산정하여, 단대단 지연(End to end delay), 처리율(Through put), 사용율(Utilization), 큐 크기, 타임슬롯 크기, 상향 스트림 크기 그리고 파장 배정 방법에 대한 성능분석을 통해서 제안된 방식의 우수성을 검증한다.

• Industrial Engineering and Management Systems
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• 제4권1호
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• pp.23-35
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• 2005

This paper aims to develop a practical finite capacity MRP (FCMRP) system based on the needs of an automotive parts manufacturing company in Thailand. The approach includes a linear goal programming model to determine the optimal start time of each operation to minimize the sum of penalty points incurred by exceeding the goals of total earliness, total tardiness, and average flow-time considering the finite capacity of all work centers and precedence of operations. Important factors of the proposed FCMRP system are penalty weights and dispatching rules. Effects of these factors on the performance measures are statistically analyzed based on a real situation of an auto-part factory. Statistical results show that the dispatching rules and penalty weights have significant effects on the performance measures. The proposed FCMRP system offers a good tradeoff between conflicting performance measures and results in the best weighted average performance measures when compared to conventional forward and forward-backward finite capacity scheduling systems.

• 한국멀티미디어학회논문지
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• 제17권12호
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• pp.1453-1460
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• 2014

WFQ (Weighted Fair Queuing) provides not only fairness among traffic flows in using bandwidth but also guarantees the Quality of Service (QoS) that individual flow requires, which is why it has been applied to the resource reservation protocol (RSVP)-capable router. The RSVP allocates an enough resource to satisfy both the rate and end-to-end delay requirements of the flow in the condition of no packet loss, and the WFQ scheduler guarantees those QoS requirements with the allocated resource. In practice, however, most QoS-guaranteed services allow a degree of packet loss, especially from 0.1% to 3% for Voice over IP. This paper discovers that the packet loss rate of each traffic flow is determined by only its time-stamp adjustment value, and then enhances the WFQ to provide a differentiated packet loss guarantee under general traffic conditions in terms of both traffic characteristics and QoS requirements. The performance evaluation showed that the proposed WFQ could increase the utilization of bandwidth by 8~11%.

• Journal of Astronomy and Space Sciences
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• 제18권3호
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• pp.209-218
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• 2001

과학위성 1호의 주 과학임무중의 하나인 전천탐사를 통해 얻어지는 천구의 각 지역별 노출시간을 모의 계산하였다. 현재 계획된 위성운용 시나리오에 의하면 노출시간은 친구적도 지역에서 최소가 되고 극 지역으로 갈수록 증가한다. 한편, SAA (South Atlantic Anomaly)와 달에 의한 영향으로 천구 적도지역에서의 노출시간 추가 감소가 불가피하다. SAA에 의한 노출시간 감소는 SAA의 영향이 별로 없는 고층대기 관측과의 궤도교체 등 간단한 관측 스케줄링을 통해 SAA의 영향을 배제할 수 있다. 그러나 현재의 노출시간 분포는 성찬물질의 진화를 구체적으로 연구하기 위해서는 적절치 않다. 친구의 극 지역에 치중된 노출시간의 효율적 분배를 위해서는 능동적인 지역별 노출시간 분배가 필요하고, 따라서 현재보다 진보된 운용 시나리오 및 관측 스케줄링에 대한 추가 연구가 요구된다

• 대한조선학회논문집
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• 제54권2호
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• pp.102-112
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• 2017

Many studies on dynamic positioning control algorithms using fixed feedback gains have been carried out to improve station keeping performance of dynamically positioned vessels. However, the control algorithms have disadvantages in that it can not cope with changes in environmental disturbances and response characteristics of vessels motion in real time. In this paper, the Fuzzy Gain Scheduling - PID(FGS - PID) control algorithm that can tune PID gains in real time was proposed. The FGS - PID controller that consists of fuzzy system and a PID controller uses weighted values of PID gains from fuzzy system and fixed PID gains from Ziegler - Nichols method to tune final PID gains in real time. Firstly, FGS - PID controller, control allocation algorithm, FPSO and environmental disturbances were modeled using Matlab/Simulink to evaluate station keeping performance of the proposed control algorithm. In addition, simulations that keep positions and a heading angle of vessel with wind, wave, current disturbances were carried out. From simulation results, the FGS - PID controller was confirmed to have better performances of keeping positions and a heading angle and consuming power than those of the PID controller. As a consequence, the proposed FGS - PID controller in this paper was validated to have more effectiveness to keep position and heading angle than that of PID controller.

• 산업경영시스템학회지
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• 제41권4호
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• pp.238-247
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• 2018

This paper considers the problem of scheduling loading and unloading operations of a crane in a railway terminal motivated from rail-road container transshipment operations at Uiwang Inland Container Depot (ICD). Unlike previous studies only considering the total handling time of containers, this paper considers a bi-criteria objective of minimizing the weighted sum of the total handling time and tenant service time. The tenant service time is an important criterion in terms of terminal tenants who are private logistics companies in charge of moving containers from/to the terminal using their trucks. In the rail-road container shipment yard, the tenant service time of a tenant can be defined by a time difference between beginning and finishing loading and unloading operations of a crane. Thus, finding a set of sequences and time of the crane operations becomes a crucial decision issue in the problem. The problem is formulated as a nonlinear program which is improved by linearizing a nonlinear constraint in the model. This paper develops a genetic algorithm to solve the problem and performs a case study on the Uiwang ICD terminal. Computational experiment results show that the genetic algorithm shows better performance than commercial optimization solvers. Operational implications in terms of tenants are drawn through sensitivity analyses.

• ETRI Journal
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• 제29권3호
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• pp.329-335
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• 2007

This paper considers a timeslot assignment problem in an interactive satellite multimedia (ISM) system with digital video broadcast-return channel via satellite (DVB-RCS). The timeslot assignment problem is formulated as a binary integer programming to maximize the overall weighted throughput and is shown to be NP-hard. Thus, three real-time heuristic algorithms including ratio-based, packet-size (PS)-based, and transmission gain (TG)-based are derived, and some computational experiments are made. Considering the results, the ratio-based heuristic algorithm is demonstrated to be the most effective and efficient. We propose adapting the ratio-based heuristic algorithm to the timeslot assignment problem to greatly improve the ISM system utilization.

• 한국통신학회논문지
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• 제40권12호
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• pp.2410-2418
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• 2015

In this paper, we consider the femto users and their mutual interference as graph elements, nodes and weighted edges, respectively. The total bandwidth is divided into a number of resource blocks (RBs) and these are assigned to the femto user equipment (FUEs) using a graph coloring algorithm. In addition, resources blocks are assigned to the femto users to avoid inter-cell interference. The proposed scheme is compared with the traditional scheduling schemes in terms of throughput and fairness and performance improvement is achieved by exploiting the graph coloring scheme.