• 한국통신학회논문지
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• 제32권1A호
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• pp.66-74
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• 2007

Cognitive Radio System은 주변 환경을 인지하여 시간적, 공간적으로 가용할 수 있는 채널을 확보하여 사용하는 시스템이다. CR시스템은 Incumbent User에 대한 간섭이 없는 조건 하에서 이용 가능한 채널을 효율적으로 써야한다는 엄격한 규정이 있다. 본 논문에서는 CR시스템에서 상향링크에서 일어날 수 있는 간섭을 회피하기 위한 방법으로 Reporter를 이용하여 이웃 셀로 Incumbent user의 상황을 보고하여 채널이용을 제한함으로서 간섭이 없는 상태에서 각 셀에서 보다 많은 채널을 이용하기 위한 방안을 알아본다. 이를 통해 같은 resource에 대해 보다 공간적으로 넓은 지역에서 채널을 이용할 수 있어 보다 높은 throughput을 확보할 수 있었다.

• 한국정보시스템학회지:정보시스템연구
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• 제23권2호
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• pp.109-137
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• 2014

As the fast development of information technology (IT), abundant attractive alternatives have showed up and challenged to the traditional information technology (IT). Cloud services, the hottest representative among these alternatives, has attracted the attention from all walks of life. Considering the diversity of cloud services, this study attempts to find out the important factors affected on individual's switching intention from incumbent IT to cloud services mainly based on two-factor theory (switching enablers and switching inhibitors) and explore the direct influences of these factors on individual's switching intention. According to our findings, individual's switching intention to cloud services is not only positively influenced by switching enablers but also negatively influenced by switching inhibitors. All the switching enablers in this study (perceived omnipresence, perceived collaboration support and perceived compatibility of cloud services) have positively significant influences on individual's switching intention as well as the switching inhibitors (usage habit of incumbent IT and perceived risk of cloud services) have negatively significant influences on individual's switching intention. It's noteworthy that satisfaction of incumbent IT has insignificant influence on individual's switching intention in this study. Moreover, as we expected, both social influence and personal innovativeness have significant influences on the generation of individual's switching intention.

• 산업경영시스템학회지
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• 제13권21호
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• pp.1-6
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• 1990

The paper analyzes how an agency problem in one industry affects the nature of equilibrium in another related industry facing potential entry. It is shown that, under certain situation, the incumbent allows for entry and charges a higher price than that without the agency problem. And the incumbent can reap more profits as a result of entry. The socially optimal price may be higher than, equal to or lower than the price the incumbent charges.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권11호
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• pp.1976-1996
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• 2011

Cognitive radio (CR) MAC protocol provides access control of unused spectrum resources without causing interference to primary users. To achieve this goal, in this paper a TDMA based cooperative multi-channel cognitive radio MAC (MCR-MAC) protocol is proposed for wireless ad hoc networks to provide reliable protection for primary users by achieving cooperative detection of incumbent system signals around the communication pair. Each CR node maintains transmission opportunity schedules and a list of available channels that is employed in the neighbor discovery period. To avoid possible signal collision between incumbent systems and cognitive radio ad hoc users, we propose a simple but efficient emergency notification message exchanging mechanism between neighbor CR nodes with little overhead. Our simulation results show that the proposed MCR-MAC can greatly reduce interference with primary users and remarkably improve the network throughput.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.905-913
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• 2008

The water resource depending on mostly surface water has many problems, such as contaminated and unpredicted contamination event. For this reason, it has been employed highly technical treatment method for them, such as ground water dam and river bank filtration. it has been developed the radial collector wells in kind of bank filtration to increase efficiency for in-taking the water resource insead of the vertical well needed many wells to take more resource. But it has many problems with the incumbent method to bore the horizontal hole for radial collector wells, such as filling with the filter material outside of a strainer by watering, jamming as retrieving the casing tube with the filter material, eccentric boring etc. To reduce the problems of incumbent equipment, it has been developed the horizontal boring equipment and performed the field trial tests several times, which have bits and water jetting system with rotating the cone-shaped front to be excavated easily. In this paper, it was compared the brand-new with the incumbent non-rotating pressing insertion method. Also it was shown the problems of the incumbent method was reduced effectively.

• ETRI Journal
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• 제38권1호
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• pp.112-122
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• 2016

This paper presents a set of candidate regulatory requirements for TV band devices (TVBDs) in the Rep. of Korea. To guarantee the protection of incumbent services, especially digital TV (DTV) and wireless microphones, in TV frequency bands, we suggest minimum separation distances of TVBDs from the noise-limited contour according to incumbent users and TVBD types. This paper also deals with multiple sets of separation distances of a co-channel TVBD network from a DTV protected contour on the basis of the radio propagation characteristics of different geographic areas to make good use of TV white space (TVWS) and safely protect the DTV service. We present a low-power transmission mode of TVBDs and the relevant separation distances for small-cell deployment. The service coverage reduction ratio of a TVBD network is investigated in the presence of DTV interference in four geographic areas. The TVWS field verification results, conducted on the island of Jeju (Rep. of Korea), show that incumbent services operate well without harmful interference from neighboring TVBDs with the proposed separation distances.

• 한국정보통신학회논문지
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• 제13권3호
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• pp.564-571
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• 2009

본 논문에서는 다중 주파수 채널이 운용중인 CR 기지국에서 외부대역 협력 스펙트럼 센싱 방식을 제안하였다. 그리고 ATSC 디지털 TV 신호인 경우에 대한 신호검출결과를 제시하였고 주파수 선택적 Rayleigh 페이딩 채널에서 외부대역 협력 센싱 방법에 대한 신호검출확률과 오경보 확률을 유도하였다. 수치해석 결과로는 CR 기지국에서 통신 중인 다중 주파수 채널의 CR단말기들이 측정한 incumbent 신호의 채널 전력이 유사한 경우에는 외부대역 협력 스펙트럼 센싱을 시행함으로써 incumbent 신호의 센싱 성능이 향상됨을 보여주고 있다.

• Asia pacific journal of information systems
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• 제20권2호
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• pp.39-62
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• 2010

As an engineered product, a software package has multiple dimensions that must be designed judiciously to enhance its competitive viability. Functionality, reliability and price are three such common dimensions. However, many software products are sold as bundles of individual components and the competitive impact of bundling has received less attention in the research literature. In this paper, we examine the implications of software vendors using bundling as an element of competitive strategy. A game theoretic model of the actions of an incumbent and a new entrant is developed and the impact on vendor and consumer welfare is analyzed. Numerical experiments with the model show that (i) increasing bundle size is an effective strategy for the incumbent to increase its payoff at the cost of the entrant's payoff and consumer surplus, especially when the entrant's quality is low (ii) in the presence of bundling, the entrant can still increase its own payoff and consumer surplus at the cost of the incumbent's payoff, by increasing product quality up to the level that best segments market demand with the incumbent and (iii) an increase in bundle size by the incumbent, or an increase in quality by the entrant, can both result in an increase of total surplus. Similar results are observed in a related case where the entrant offers free software bundles. Our results provide insights into how software vendors may strategically use bundling and quality as additional product dimensions in order to stay competitive in the market. These results also inform the competing vendors of the impact of bundling related public policy actions on their respective payoffs.

• 한국통신학회논문지
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• 제31권12B호
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• pp.1058-1067
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• 2006

무선 인지 기술 환경에서 CR 기지국이 숨겨진 인컴번트 시스템의 등장으로 인해 CR 사용자와 통신이 불가하고 인컴번트 사용자가 간섭을 받을 때, 이를 해결하기 위한 시그널링 방법에 관한 것으로 숨겨진 인컴번트 시스템의 검출을 위한 프로토콜을 제안한다. 특히 아웃밴드 시그널링 검출 방법을 통해 상향링크 및 하향링크 프레임 구조를 이용하여 단말의 채널상태 보고 방법과 이에 대한 기지국의 확인방법 및 절차를 제안한다. 서로 다른 CR 기지국이 공존하는 방법으로 낮은 충돌 확률로 아웃밴드 시그널링 메시지를 전송할 수 있도록 하고 이 때 주파수 사용 효율을 높이기 위해 분할 주파수 대역을 사용한다. 이를 통해 무선 인지 기술에서의 신뢰성 있고 효율적인 아웃밴드 시그널링 프로토콜을 제안한다.

• 한국통신학회논문지
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• 제37B권11호
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• pp.1050-1057
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• 2012

Super Wi-Fi는 TV white space 대역을 이용하여 Wi-Fi 네트워크를 구성하는 무선 인터넷 서비스 기술이다. 하지만, TV white space 대역 이용자는 기존 ISM 대역에서와 달리 incumbent user가 활성화될 때마다 Super Wi-Fi로 사용 중인 채널을 양보해야 하므로 Wi-Fi 서비스의 연속성을 보장하기 어렵다. 본 논문에서는 Super Wi-Fi 서비스 영역에서 AP (access point)가 운용채널을 비워 주어야 할 때 다른 이용 가능한 TV 채널을 AP의 운용채널로 선택하고 이 결과를 MS (mobile station)에게 제공함으로써 Wi-Fi의 서비스의 연속성이 보장될 수 있는 방법을 제시하였다. 즉, AP의 운용채널에 incumbent user가 나타나면 즉시 운용채널을 비우지 않고 incumbent user에 간섭을 주지 않는 subcarrier들의 그룹인 active subchannel을 이용하여 MS에게 AP 자신이 운용할 다른 채널의 정보를 제공한다. 이 채널정보를 공유한 MS는 AP의 운용할 다른 채널로 빠른 채널 핸드오버를 할 수 있으므로 Super Wi-Fi 서비스 연속성 보장성능이 향상될 수 있다. 제시한 채널 핸드오버 방법을 기존 Wi-Fi 방법과 비교하여 핸드오버 지연시간이 개선됨을 확인하였다.