• Industrial Engineering and Management Systems
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• 제6권1호
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• pp.55-63
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• 2007

Exchange of information is essential to the process of innovation such as product development. However, in many cases innovation fails because of a lack of knowledge sharing among parties concerned, even if parties individually have pieces of useful knowledge and skills. Besides physical factors like communication costs, the possibility of opportunistic behavior by parties like stealing ideas can discourage information exchange. This paper introduces a model to analyze incentives of information exchange. The model is a game by two players who alternately opt to offer information to the partner. It is suggested that information exchange can stop before reaching the efficient level. In order to attain the efficient information exchange, expectation of mutual benefit and absence of opportunistic motives in both players are needed. Methods for promoting information exchange include modifying payoff structure to meet the condition of information exchange. The fluidity of partnership may increase a variety of information exchange partners, but discourage building trust between partners which promotes information exchange.

• 한국정보통신학회논문지
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• 제17권6호
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• pp.1318-1323
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• 2013

본 논문은 비 슬롯 모드 인지 무선망에서 기회적 스펙트럼 접속 방식의 성능을 시뮬레이션을 통해 비교 분석한다. 비교 분석할 두 가지 기회적 스펙트럼 방식은 다음과 같다. 첫 번째 방식은 어떤 채널에서 전송을 성공한 경우 동일한 채널을 다시 센싱하고, 실패한 경우 가장 오래전에 선택했던 채널을 센싱하는 방식이다. 두 번째 방식은 어떤 채널에서 전송에 실패한 경우 동일한 채널을 다시 센싱하고, 성공한 경우 가장 오래전에 선택했던 채널을 센싱하는 방식이다. 본 논문에서는 일차 사용자가 채널을 점유하는 기간에 따라 두 방식 사이의 성능을 비교한다.

• Journal of Communications and Networks
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• 제12권4호
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• pp.346-357
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• 2010

Opportunistic scheduling provides the capability of resource management in wireless networks by taking advantage of multiuser diversity and by allowing delay variation in delivering data packets. It generally aims to maximize system throughput or guarantee fairness and quality of service (QoS) requirements. In this paper, we develop an extended proportional fair (PF) scheduling policy that can statistically guarantee three kinds of QoS. The scheduling policy is derived by solving the optimization problems in an ideal system according to QoS constraints. We prove that the practical version of the scheduling policy is optimal in opportunistic scheduling systems. As each scheduling policy has some parameters, we also consider practical parameter adaptation algorithms that require low implementation complexity and show their convergences mathematically. Through simulations, we confirm that our proposed schedulers show good fairness performance in addition to guaranteeing each user's QoS requirements.

• Journal of Communications and Networks
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• 제13권1호
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• pp.50-55
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• 2011

Spectrum leasing for cognitive radio (CR) networks is an effective way to improve the spectrum utilization. This paper presents an opportunistic relaying based spectrum leasing for CR networks where the primary users lease their frequency band to the cognitive users. The cognitive users act as relays for the primary users to improve the channel capacity, and this improved capacity is used for the transmission of secondary users' data. We show that the cognitive users can use a significant portion of the communication resource of primary networks while maintaining a fixed target data rate for the primary users. Moreover, the primary network is also benefited by the cooperating cognitive users in terms of outage probability. Information theoretic analysis and simulation results are presented to evaluate the performances of both primary and cognitive networks.

• 한국IT서비스학회지
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• 제11권2호
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• pp.93-106
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• 2012

Recently, a Game Shut-down policy, partially limiting the time for the use of online game service, has been implemented in order to protect the youth from the excessive use of games by limiting their access to games in the late hours, based on the serious side effects of online games on the youth. However, the effectiveness of a Game Shut-down policy becomes a social issue. Thus, this study aims to investigate the alternative policies through the levels of the communications suggested by the theory of excellence, for the successful implementation of the policy. As a result of the study, the government and students, the recipient of those policies, need to strengthen their two-way communication in respect of the Game Shut-down policy, breaking from the existing views on the perception. The problem is that the current government's way of the communication for the Game Shut-down policy is one-way and it is aiming at achieving the objectives only. Thus, the communication in this manner will cause the side effect. 'the opportunistic violation of the system in the future', even if the students seemingly accept the system. Two-way communication will enhance the motivation for the voluntary acceptance of the system and lower the motivation for the opportunistic violation of the system. Thus, the government needs to strengthen two-way communication in the future.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권10호
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• pp.3409-3422
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• 2014

The frequency spectrum available for the wireless communication is extremely crowded. In order to improve the spectral efficiency, the two-way relay networks have aroused great attention. A simple $N^{th}$ best-relay selection criterion for the opportunistic two-way relay networks is proposed, which can be implemented easily by extending the distributed timer technique in practice, since the proposed criterion is mainly based on the channel gains. The outage performance of the proposed relay selection scheme is analyzed under the outdated channel state information (CSI), and a tight closed-form lower bound and asymptotic value of the outage probability over Rayleigh fading channels are obtained. Simulation results demonstrate that the tight closed-form lower bound of the outage probability very closely matches with simulated ones in the whole SNR region, and the asymptotic results provide good tight approximations to the simulation ones, especially in the high SNR region.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제3권4호
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• pp.97-106
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• 2014

본 논문에서는 분산 무선인지 네트워크 환경에서 단일 홉 적용을 위하여 제안된 CR MAC 프로토콜들을 MANET 라우팅 프로토콜에 적용하기 위한 설계 방법을 제안한다. 고려하는 CR MAC 프로토콜들은 Opportunistic MAC (O-MAC)과 Opportunistic Periodic MAC (OP-MAC)이고, MANET 라우팅 프로토콜로서는 AODV를 사용한다. 이들은 OPNET을 사용하여 구현하였으며, O-MAC과 OP-MAC의 MAC 환경에서의 성능과 AODV를 적용하였을 때의 성능을 비교한다. 이를 통하여 단일 홉의 DCRN 환경을 기반으로 설계된 무선인지 MAC 프로토콜의 성능과 AODV 적용시의 성능의 관계를 분석한다.

• Journal of information and communication convergence engineering
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• 제8권3호
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• pp.273-276
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• 2010

Opportunistic spectrum access (OSA) allows unlicensed users to share licensed spectrum in space and time with no or little interference to primary users, with bring new research challenges in MAC design. We propose a cognitive MAC protocol using statistical channel information and selecting appropriate idle channel for transmission. The protocol based on the CSMA/CA, exploits statistics of spectrum usage for decision making on channel access. Idle channel availability, spectrum hole sufficiency and available channel condition will be included in algorithm statistical information. The model include the control channel and data channel, the transmitter negotiates with receiver on transmission parameters through control channel, statistical decision results (successful rate of transmission) from exchanged transmission parameters of control channel should pass the threshold and decide the data transmission with spectrum hole on data channel. The proposed protocol's simulation will show that proposed protocol does improve the throughput performance via traditional opportunistic spectrum access MAC protocol.

• 한국의류학회지
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• 제34권2호
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• pp.280-290
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• 2010

This study identifies the antecedents of trust in the examination of the effects of the antecedents of trust on trust in apparel manufacturer-contractor relationships. A total of 92 apparel manufactures participated in this study. A factor analysis, Cronbach's alpha coefficient, and multiple regression analysis were conducted for the statistical analysis. Five antecedents of trust were classified: flexibility, opportunistic behavior, communication, specific investment, reputation. Two factors of trust were identified: credibility and benevolence. Flexibility, communication, and reputation of a contractor positively influenced the credibility of an apparel manufacture in a contractor. Flexibility, communication, and specific investment of a contractor positively relate to the benevolence of an apparel manufacture in a contractor. However, the opportunistic behavior of a contractor did not relate to either the credibility of an apparel manufacture or the benevolence in a contractor. The results of this study provide empirical evidence of the impact of flexibility, communication, specific investment, reputation on trust in apparel manufacturer-contractor relationships, and additional insight for selecting contractors that seek to improve trust in apparel manufacturer-contractor relationships.

• 한국통신학회논문지
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• 제39C권7호
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• pp.546-551
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• 2014

본 논문에서는 릴레이 기반의 선박 통신 네트워크에서 데이터 전송률을 높이기 위한 기회주의적 서브채널 할당기법을 제안한다. 릴레이 시스템을 기반으로 하는 기존 연구에서, 릴레이는 매 프레임마다 기지국으로부터 수신 받은 데이터를 선박에게 즉시 전달 해준다. 이때, 이중 홉 네트워크(기지국과 릴레이, 릴레이와 선박 간 링크)에서 전송 가능한 최대 수율은 두 링크의 채널 상태에 의해 결정된다. 만약, 채널 상태에 따른 두 링크가 가지는 채널 용량의 차이가 크다면 자원이 낭비되는 상황이 발생하게 된다. 이러한 문제점은 시스템의 성능을 저하시키며, 제한된 무선 자원을 효율적으로 활용하지 못하는 문제점이 발생하게 된다. 따라서 본 논문에서는 두 링크 사이에서 발생하는 자원의 낭비를 최소화 시킴과 동시에 자원을 효율적으로 할당 할 수 있는 기법을 제안한다. 또한 제안하는 기법의 계산 복잡도를 줄이기 위해서 차선의 기법을 제안한다. 시뮬레이션 결과를 통해서, 제안하는 기법은 기존 연구 대비 계산의 복잡도는 증가하지만 시스템의 데이터 전송률 성능이 최대 14.0% 향상됨을 확인 할 수 있다.