• 한국통신학회논문지
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• 제30권7A호
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• pp.620-627
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• 2005

OFDMA 하향링크 시스템에서 단말의 불균등한 위치 분포와 다양한 QoS 요구사항의 변화에 따라 시스템에 끼치는 부정적인 영향을 줄이기 위한 적응적 hot-spot 운용 기법에 대해 제안하였다. 매크로셀의 기지국은 셀 내 피고셀의 운용을 조절하며, 예측된 user outage probability와 AHOS 이득 파라미터 값에 의해 피코셀을 켜고 끄게된다. 제안된 AHOS 기법은 다양한 시스템 환경에서 QoS outage probability를 유지하면서 시스템의 throughput을 최대화 시키는 이득을 보였다.

• 산업공학
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• 제18권3호
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• pp.317-326
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• 2005

Staff scheduling is an important area, both from an academic and industrial point of view. It has become increasingly important as business becomes more service oriented and cost conscious in a global environment. There has been a lot of study to develop new and efficient staff scheduling models and methods. The purpose of this paper is not to develop new theoretical results but to develop a comprehensive user-friendly staffing model that can be applied to the real-world practice. The developed staffing software, OptStaff, provides the optimal configuration of the customer support center including the selection of customer support center locations, the allocation of staffs to each selected location, and schedules of staffs, so as to minimize the total cost while maximizing the customer satisfaction level. OptStaff also has capability to do scenario analysis by varying the levels of parameters and to create a variety of graphs and reports with user-friendly interfaces.

• 한국게임학회 논문지
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• 제16권6호
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• pp.69-78
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• 2016

FPS 게임 속 시가지 맵에서 간판, 현수막, 벽보 등의 옥외광고가 흔히 등장한다. 본 논문은 실제 상권들의 옥외광고를 FPS 게임의 시가지 맵에 자동으로 배치하는 방법을 제안한다. 옥외광고는 실제 제품이나 기업의 광고이며 서버에서 관리된다. 실제 광고가 업데이트 되는 경우 게임 소스를 수정하지 않고도 자동으로 배치된다. 광고의 배치에 있어서 플레이어의 위치와 실제 상권의 위치의 관계, 실제 상점의 서비스 형태 등을 활용한다. 수집한 속성들에 우선순위 점수를 부여하여 높은 순위가 우선적으로 맵에 배치된다. 제안하는 배치 방법은 플레이어의 위치를 기반으로 광고를 배치하므로 친근감 유발과 함께 광고 효과를 높일 수 있다.

• Architectural research
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• 제17권2호
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• pp.65-74
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• 2015

The habitual rooms and other structures related to everyday life are almost always grouped around the courtyard and together make up a house. There are many kinds of variety in types of courtyard houses depending on location, composition, allocation and relationship with inner space of the house. Every type of courtyard house accumulates many factors, which are social and economic circumstances, weather and geographical conditions. They are still well harmonized with life style and weather conditions in each area and basic unit of city organization. A courtyard can be shown as a place for everyday conversation like a community. Everyday space is the connective tissue that binds daily lives together, amorphous and so persuasive that it is difficult even to perceive. In spite of its ubiquity, everyday space is nearly invisible in the professional discourses of the city, like everyday life. Therefore Courtyards are special places that are outside yet almost inside, open to the sky, - a microcosm which gives relief to the inner rooms, gives the inhabitants a sense of ease and calm, and the feeling that they have their own piece of sky to use and protect them. This research will explore a variety of space use and dwelling types through courtyards based on field research and design projects.

• 한국통신학회논문지
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• 제33권9C호
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• pp.661-668
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• 2008

본 논문에서는 STO(Symbol Timing Offset)를 갖는 cooperative SFBC-OFDM 시스템에 적합한 파일럿 톤 기반의 채널 추정 기법을 제안한다. Cooperative SFBC-OFDM 시스템에서는 MS(Mobile Station)의 위치에 따라 RS(Relay Station)와 MS간 STO가 다르게 발생하며 이 STO가 위상 회전 형태로 왜곡을 발생시키기 때문에 orthogonal 파일럿 사용시 위상과 크기에 대하여 선형 보간을 취하여 채널을 추정하는 방법을 제안한다. 또한 orthogonal code를 사용하는 파일럿 구조에서는 비선형 방정식의 해를 구함으로써 채널 추정을 수행하는 방법을 제안한다. STO를 갖는 cooperative SFBC-OFDM 시스템에서 제안된 기법을 적용할 경우에 채널 추정 성능이 크게 개선될 수 있음을 모의실험을 통하여 확인한다.

• Management Science and Financial Engineering
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• 제19권2호
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• pp.19-29
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• 2013

Refuse collection network design, one of major decision problems in reverse logistics, is the problem of locating collection points and allocating refuses at demand points to the opened collection points. As an extension of the previous models, we consider capacity and maximum allowable distance constraints at each collection point. In particular, the maximum allowable distance constraint is additionally considered to avoid the impractical solutions in which collection points are located too closely. Also, the additional distance constraint represents the physical distance limit between collection and demand points. The objective is to minimize the sum of fixed costs to open collection points and variable costs to transport refuses from demand to collection points. After formulating the problem as an integer programming model, we suggest an optimal branch and bound algorithm that generates all feasible solutions by a simultaneous location and allocation method and curtails the dominated ones using the lower bounds developed using the relaxation technique. Also, due to the limited applications of the optimal algorithm, we suggest two heuristics. To test the performances of the algorithms, computational experiments were done on a number of test instances, and the results are reported.

• 한국구조물진단유지관리공학회 논문집
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• 제6권2호
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• pp.145-155
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• 2002

It is essential for health monitoring of a cable-stayed bridge to provide more accurate and enough information from the sensors. In experimental modal testing, the chosen measurement locations and the number of measurements have a major influence on the quality of the results. The choice is often difficult for complex structures like a cable-stayed bridge. It is extremely important a cable-stayed bridge to minimize the number of sensing operations required to monitor the structural system. In order to obtain the desired accuracy for the structural test, several issues must take into consideration. Two important issues are the number and location of response sensors. There are usually several alternative locations where different sensors can be located. On the other hand, the number of sensors might be limited due to economic constraints. Therefore, techniques such as methodologies, algorithms etc., which address the issue of limited instrumentation and its effects on resolution and accuracy in health monitoring systems are paramount to a damage diagnosis approach. This paper discusses an optimum sensor placement criterion suitable to the identification of structural damage for continuous health monitoring. A Kinetic Energy optimization technique and an Effective Independence Method are analyzed and numerical and theoretical issues are addressed for a cable-stayed bridge. Its application to a cable-stayed bridge is discussed to optimize the sensor placement for identification and control purposes.

• Journal of Communications and Networks
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• 제17권6호
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• pp.568-581
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• 2015

Predicting locations of users with portable devices such as IP phones, smart-phones, iPads and iPods in public wireless local area networks (WLANs) plays a crucial role in location management and network resource allocation. Many techniques in machine learning and data mining, such as sequential pattern mining and clustering, have been widely used. However, these approaches have two deficiencies. First, because they are based on profiles of individual mobility behaviors, a sequential pattern technique may fail to predict new users or users with movement on novel paths. Second, using similar mobility behaviors in a cluster for predicting the movement of users may cause significant degradation in accuracy owing to indistinguishable regular movement and random movement. In this paper, we propose a novel fusion technique that utilizes mobility rules discovered from multiple similar users by combining clustering and sequential pattern mining. The proposed technique with two algorithms, named the clustering-based-sequential-pattern-mining (CSPM) and sequential-pattern-mining-based-clustering (SPMC), can deal with the lack of information in a personal profile and avoid some noise due to random movements by users. Experimental results show that our approach outperforms existing approaches in terms of efficiency and prediction accuracy.

• ETRI Journal
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• 제28권3호
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• pp.282-290
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• 2006

In vertically overlaid cellular systems, a temporary traffic concentration can occur in a hot-spot area, and this adversely affects overall system capacity. In this paper, we develop an adaptive hot-spot operating scheme (AHOS) to mitigate the negative effects from the nonuniform distribution of user location and the variation in the mixture of QoS requirements in orthogonal frequency division multiple access downlink systems. Here, the base station in a macrocell can control the operation of picocells within the cell, and turns them on or off according to the system overload estimation function. In order to determine whether the set of picocells is turned on or off, we define an AHOS gain index that describes the number of subcarriers saved to the macrocell by turning a specific picocell on. For initiating the picocell OFF procedure, we utilize the changes in traffic concentration and co-channel interference to the neighboring cells. According to computer simulation, the AHOS has been proved to have maximize system throughput while maintaining a very low QoS outage probability under various system scenarios in both a single-cell and multi-cell environments.

• 한국통신학회논문지
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• 제25권10A호
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• pp.1512-1520
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• 2000

무선 통신망은 음성위주의 아날로그 방식에서 출발하여, 다양한 서버스 능력을 갖는 디지럴 방식으로 진화되고 있으며 궁극적으로는 멀티미디어 서비스가 가능한 IMT -2000으로 발전할 것이다. 무선망에서 멀티미디어 서비스를 제공하기 위해서는 한정된 무선 대역폭을 트래픽 특성에 따라 동적으로 활용할 수 있는 방안이 요구된다. 본 논문에서는 IMT - 2000 환경에서 이동체의 이동 방향을 추정하여 이를 근거로 대역폭을 예약하고, 멀티미디어 트래픽을 전송하는 대역 할당 및 호 수락 제어 기법을 제안한다. 이 기법은 수신 신호 세기(RSS: Received Si맹a1 Strength) 이외에 이동체와 기지국간이 거리, 이동체의 이동방향, 이동체의 이전위치와 같은 부정확한 다수의 파라미터를 동시에 고려하는 퍼지 다기준(multi-criteria) 의사 결정 방법을 이용하여 이동체의 위치를 추정한다. 시뮬레이션에 의해 성능을 분석하였다.