• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.59-62
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• 2000

현재 CDMA 시스템에서 통화채널의 주파수 할당 방식에 Hashing 알고리즘이 사용되며, Hashing알고리즘에 의해 FA(frequency assignment)간 부하 균형을 유지하고 있다. Hashing 알고리즘은 모든 가입자 번호를 각 FA에 균일하게 할당하지만, 개별 기지국의 가입자 분포는 각 FA별로 반드시 균일하게 분포되지는 않는다. 이런 FA간 가입자 분포의 불균형은 해당 기지국의 과부하로 인식되어 조기 FA 증설이 요구되며, 해당 과부하 FA의 통화품질 열화를 일으킨다. 따라서 부하 균형에 따라 통화채널의 FA할당을 조절하기 위한 Hashing 후 강제 할당 방식인 OFD(optional forced distributio)을 제안하고 이를 CDMA 시스템에 적용하여 부하 균형의 개선 효과를 얻었다.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.448-455
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• 2003

본 논문에서는 MF-TDMA(Multi Frequency - Time Division Multiple Access)체계를 이용하는 광대역 위성 시스템의 리턴 링크를 대상으로 최저타임슬롯 할당 체계를 제시한다. 이를 위해 먼저 clear-sky RCST와 rain-fade RCST가 존재하고 복수의 서비스 및 지연 클래스가 존재하는 광대역 위성 시스템을 대상으로 MF-TDMA 체계 하에서 최적 타임슬롯 할당 체계를 제시한다. Phase 1에서는 clear-sky TRF타임슬롯들의 집합과 rain-fade TRF타임슬롯들의 집합을 결정하고, Phase 2에서는 각 RCST의 각 서비스/지연 클래스에 할당되는 타임슬롯의 수를 결정하고, Phase 3에서는 각 RCST의 각 서비스/지연 클래스에 할당된 타임슬롯들의 스케줄을 결정한다. 마지막으로 불균등 수요 데이터를 활용하여 제시한 최적 타임슬롯 할당 체계의 성능을 분석한다. 성능 분석 결과 제시한 최적 타임슬롯 할당 체계는 빠른 시간 내에 최적해 또는 최적해와 아주 가까운 해를 안정적으로 구한다는 사실을 확인할 수 있었다.

• Korean Institute of Interior Design Journal
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• v.18 no.4
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• pp.116-123
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• 2009

This research aims at the provision for all of the basic data upon the arrangement of organization and allocation which include the details of required spaces and adequate area in the design of Multipurpose Senior Centers. This analyzed research is to be proposed for Multipurpose Senior Center in various local areas in the city, it aims to clarify the existing condition in the operation of each organizational required space. Further more this research examines their relationship between the facilities available and the population use of the local elderly age. Consequently, the Daejeon Multipurpose Senior Center, including participation in the program and the very high frequency of use of the room entails a smooth progress of the program, improves the quality of space and based on the initial design is fully reflected in the step.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4356-4371
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• 2014

When the load in a multi-cell orthogonal frequency division multiple access (OFDMA) system is allowed to excessively increase in face of frequent handover, the cell area becomes smaller than the designed size, and thus continuity of quality of service (QoS) for handover requests cannot be guaranteed. To efficiently support the mobility of a mobile terminal (MT), we should adaptively cope with the resource demand of handover calls. This paper proposes a twofold resource-reservation scheme for OFDMA systems to guarantee continuity of QoS for various mobile multimedia services during MT handover from lightly to heavily loaded cells. Our twofold scheme attempts to guarantee service continuity for handover and to maximize resource allocation efficiency. We performed a simulation to evaluate our scheme in terms of outage probability, handover failure rate, total throughput, and blocking rate.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06d
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• pp.219-220
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• 2011

본 논문은 LTE-Advanced 망에서의 D2D(Device-to-Device) 통신을 효율적으로 하기 위한 주파수 할당 절차를 소개하고 그 메커니즘을 제안하였다. 제안한 메커니즘은 기지국에서 셀 내 주파수의 상태에 따라 주파수에 우선순위를 적용한 뒤, 높은 우선순위를 가지는 주파수를 D2D 통신에 할당한다. 성능평가에서는 D2D 통신, 주파수 할당 메커니즘을 적용하지 않은 D2D 통신, 주파수 할당 메커니즘을 적용한 D2D 통신의 처리량을 비교하여 제안한 메커니즘의 우수성을 증명하였다.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.1
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• pp.102-109
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• 2015

In Korea, Lunar exploration program has been prepared with the aim of launching in the 2020's. As a part of it, a lunar lander demonstrator was developed, which was the model for verifying the system such as structure, propulsion, and control system, before launching into the deep space. This paper deals with the path tracking performance of the lunar lander demonstrator with respect to the thruster controller based on Pulse Width Pulse Frequency Modulator (PWPFM) and Pulse Width Modulator (PWM). First, we derived equations of motion, considering the allocation of the thrusters, and designed the path tracking controller based on Euler angle. The signal generated from the path tracking controller is continuous, so PWPFM and PWM modulator are adopted for generating ON/OFF signal. Finally, MATLAB simulation is performed for evaluating the path tracking ability. We compared the path tracking performances of PWPFM and PWM based thrust controller, using performance measures such as the total impulse and the position error with respect to the desired path.

• Journal of Communications and Networks
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• v.4 no.4
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• pp.302-313
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• 2002

In order to facilitate and to meet the ever increasing demands for the wireless communication in the next decade and also to satisfy the high data rates for the new services, the future development of 3G (IMT2000) and systems beyond 3G (B3G) are foreseen. This article presents the need for these developments and motivations for systems beyond 3G taking into account both strategic and technological challenges to be faced. Moreover, the concepts and potential technologies involved including multiple airinterfaces, efficient spectrum allocation and utilisation for the success of systems B3G are briefly reviewed.

• Journal of the Korea Society of Computer and Information
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• v.20 no.6
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• pp.29-35
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• 2015

The heterogeneous LTE (Long Term Evolution)-Advanced networks comprising a macrocell and femtocells can provide an efficient solution not only to extend macrocell coverage but also to deal with packet traffics increasing explosively within macrocells. An efficient resource management scheme is necessary to maintain the QoS (Quality of Service) of mobile multimedia services because the LTE-Advanced system should support not only voice but also mobile applications such as data, image and video. This paper proposes a resource management scheme to guarantee QoS continuity of multimedia services and to maximize the resource utilization in OFDMA (Orthogonal Frequency Division Multiple Access) based LTE-Advanced systems. This scheme divides the resources into several service blocks and allocates those resources based on the competition between macrocell and femtocell. Simulation results show that it provides better performances than the conventional one in respect of handover failure rate and blocking rate.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.175-177
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• 2003

본 논문에서는 직교 주파수 분할 다중화 전송방식(OFDM:Orthogonal Frequency Division Multiplexing)에서 비트 오류율(BER)과 시스템에서 사용할 수 있는 총 송신 파워가 제한된 상태에서 데이터 전송률을 최대화 시키는 기법을 제안한다. 제안한 기법은 미리 계산된 비트수별 신호대잡음비 임계값(threshold)과 부반송파의 신호대잡음비를 비교한 후 부반송파별 송신 파워를 최적화 시켜 비트를 할당한다. 이 기법은 송신 파워 및 비트를 할당하는 최적의 기법이라고 알려진 Hughes­Hartogs 기법과 거의 동일한 데이터 전송률을 가질 수 있으면서, 부반송파의 송신 파워 및 비트수를 할당하기 위해 필요한 반복작업을 줄일 수 있다.

• Journal of the Ergonomics Society of Korea
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• v.25 no.4
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• pp.1-7
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• 2006

The purpose of this study is to develop an efficient algorithm for the management of the shift schedule in nuclear power plants in consideration with the ergonomic criteria and the regulatory codes. The ergonomic criteria considered are the work hours, overtime-work frequency and working time, start and finishing time of works, allocation of rest times and duty-offs, rotating of shifts, etc. to comply with the regulations such as the Labor Standard Act, the ILO Convention No. 171, 178, "the detailed content of a periodic safety review," enforcement regulations 19-2 of the Atomic Energy Act. The developed algorithm for the shift schedule program adopts a heuristic method to minimize the difference the workload for shift workers in nuclear power plants.