• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권6호
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• pp.2709-2734
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• 2020

The growing demand to make wireless data services 5G compatible has necessitated the development of an energy-efficient approach for an effective new wireless environment. In this paper, we first propose a cognitive sensor node (CSN) based game theory for deriving energy via a primary user-transmitted radio frequency signal. Cognitive users' time was segmented into three phases based on a time switching protocol: energy harvest, spectrum sensing and data transmission. The proposed model chooses the optimal energy-harvesting phase as the effected factor. We further propose a distributed energy-harvesting model as a utility function via pricing techniques. The model is a non-cooperative game where players can increase their net benefit in a selfish manner. Here, the price is described as a function pertaining to transmit power, which proves that the proposed energy harvest game includes Nash Equilibrium and is also unique. The best response algorithm is used to achieve the green connection between players. As a result, the results obtained from the proposed model and algorithm show the advantages as well as the effectiveness of the proposed study. Moreover, energy consumption was reduced significantly (12%) compared to the benchmark algorithm because the proposed algorithm succeeded in delivering energy in micro which is much better compared to previous studies. Considering the reduction and improvement in power consumption, we could say the proposed model is suitable for the next wireless environment represented in 5G.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.709-713
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• 2009

Recently, a lot of research that applies data acquired from devices such as cameras and RFIDs to context aware services is being performed in the field on Life-Log and the sensor network. A variety of analytical techniques has been proposed to recognize various information from the raw data because video and audio data include a larger volume of information than other sensor data. However, manually watching a huge amount of media data again has been necessary to create supervised data for the update of a class or the addition of a new class because these techniques generally use supervised learning. Therefore, the problem was that applications were able to use only recognition function based on fixed supervised data in most cases. Then, we proposed a method of acquiring supervised data from a video sharing site where users give comments on any video scene because those sites are remarkably popular and, therefore, many comments are generated. In the first step of this method, words with a high utility value are extracted by filtering the comment about the video. Second, the set of feature data in the time series is calculated by applying functions, which extract various feature data, to media data. Finally, our learning system calculates the correlation coefficient by using the above-mentioned two kinds of data, and the correlation coefficient is stored in the DB of the system. Various other applications contain a recognition function that is used to generate collective intelligence based on Web comments, by applying this correlation coefficient to new media data. In addition, flexible recognition that adjusts to a new object becomes possible by regularly acquiring and learning both media data and comments from a video sharing site while reducing work by manual operation. As a result, recognition of not only the name of the seen object but also indirect information, e.g. the impression or the action toward the object, was enabled.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제9권5호
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• pp.530-540
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• 2003

인터넷 사이트의 정보량이 증가함에 따라 효율적인 정보제공의 필요성이 커지고 있으나, 대부분의 사이트에서 제공하는 핵심어의 불리언 조합에 기반을 둔 정보검색기법은 사용자의 의도를 제대로 표현하기 어렵기 때문에 지나치게 많거나 의도하지 않은 검색결과를 얻기 쉽다는 문제가 있다. 이 논문에서는 자연어 대화를 통하여 사용자에게 보다 정확하고 친절하게 정보를 제공할 수 있는 대화형 에이전트를 제안한다. 이 에이전트는 자연어 질의에 유한상태 오토마타를 적용하여 사용자의 질의의도를 파악하고 이를 답변지식의 구조적 패턴매칭에 활용함으로써, 어순변화에 강건하고 질의의도에 부합하는 답변을 제공한다. 제안한 시스템의 유용성과 가능성을 알아보기 위하여 간단한 웹 페이지를 소개하는 문제에 적용한 결과, 에이전트가 정확하고 친근하게 응답하는 것을 확인할 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권12호
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• pp.2957-2986
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• 2013

The traditional approach of fixed spectrum allocation to licensed networks has resulted in spectrum underutilisation. Cognitive radio technology is envisioned as a promising solution that can be used to resolve the ineffectiveness of the fixed spectrum allocation policy by accessing the underutilised spectrum of existing technologies opportunistically. The implementation of cognitive radio networks (CRNs) faces distinct challenges due to the fact that two systems (i.e., cognitive radio (CR) and primary users (PUs)) with conflicting interests interact with each other. Specially, in self-organised systems such as ad-hoc CRNs (AHCRNs), the coordination of spectrum access introduces challenges to researchers due to rapid utilisation changes in the available spectrum, as well as the multi-hop nature of ad-hoc networks, which creates additional challenges in the analysis of resource allocation (e.g., power control, channel and rate allocation). Instead, game theory has been adopted as a powerful mathematical tool in analysing and modelling the interaction processes of AHCRNs. In this survey, we first review the most fundamental concepts and architectures of CRNs and AHCRNs. We then introduce the concepts of game theory, utility function, Nash equilibrium and pricing techniques. Finally, we survey the recent literature on the game theoretic analysis of AHCRNs, highlighting its applicability to the physical layer PHY, the MAC layer and the network layer.

• 정보과학회 논문지
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• 제43권2호
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• pp.246-255
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• 2016

OFDMA는 주파수와 시간 축에 따라 융통성 있는 자원 할당이 가능하고, 적응적 변조와 코딩이 가능하기 때문에 다중률 멀티캐스트 전송에 적합하다. 계층적 코딩과 달리 MDC (multiple description coding)는 비디오 스트림을 서브 스트림으로 분해와 재조립이 용이하며, 수신율에 비례하여 비디오 품질도 증가하는 특성을 가지고 있다. OFDMA 무선 또는 이동통신망에서 비디오를 다중률로 멀티캐스트 전송할 때 자원 할당과 전송률에 관한 수학적 모델을 제시하고, 사용자가 느끼는 비디오 품질 인덱스인 MOS (mean opinion score)를 최대화 혹은 비례적 공평성을 극대화하는 스케줄링 방식에 대해, 평균값 분석 방법론을 통해 장기적 관점에서 비교 분석한다. 또한, 제한된 자원 내에서 일부 사용자에게 최저 품질을 보장하는 pruning 알고리즘을 제시하고, 비디오 세션 전 기간 또는 일부 기간에 최적으로 서브 스트림을 분할할 수 있음을 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권12호
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• pp.6214-6242
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• 2019

Routing in mobile ad hoc networks is performed in a distributed fashion where each node acts as host and router, such that it forwards incoming packets for others without relying on a dedicated router. Nodes are mostly resource constraint and the users are usually inclined to conserve their resources and exhibit selfish behaviour by not contributing in the routing process. The trust and reputation models have been proposed to motivate selfish nodes for cooperation in the packet forwarding process. Nodes having bad trust or reputation are detected and secluded from the network, eventually. However, due to the lack of proper identity management and use of non-persistent identities in ad hoc networks, malicious nodes can pose various threats to these methods. For example, a malicious node can discard the bad reputed identity and enter into the system with another identity afresh, called whitewashing. Similarly, a malicious node may create more than one identity, called Sybil attack, for self-promotion, defame other nodes, and broadcast fake recommendations in the network. These identity-based attacks disrupt the overall detection of the reputation systems. In this paper, we propose a reputation-based scheme that detects selfish nodes and deters identity attacks. We address the issue in such a way that, for normal selfish nodes, it will become no longer advantageous to carry out a whitewash. Sybil attackers are also discouraged (i.e., on a single battery, they may create fewer identities). We design and analyse our rationale via game theory and evaluate our proposed reputation system using NS-2 simulator. The results obtained from the simulation demonstrate that our proposed technique considerably diminishes the throughput and utility of selfish nodes with a single identity and selfish nodes with multiple identities when compared to the benchmark scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권5호
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• pp.1569-1586
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• 2015

This paper considers the optimal cell association and resource allocation for load balancing in a heterogeneous cellular network subject to user's quality-of-service (QoS) constraints. We adopt the proportional fairness (PF) utility maximization formulation which also accommodates the QoS constraints in terms of minimum rate requirements. With equal resource allocation this joint optimization problem is either infeasible or requires relaxation that yields a solution which is difficult to implement. Nevertheless, we show that this joint optimization problem can be effectively solved without any priori assumption on resource allocation and yields a cell association scheme which enforces single BS association for each user. We re-formulated the joint optimization problem as a network-wide resource allocation problem with cardinality constraints. A reweighted heuristic l₁-norm regularization method is used to obtain a sparse solution to the re-formulated problem. The cell association scheme is then derived from the sparsity pattern of the solution, which guarantees a single BS association for each user. Compared with the previously proposed method based on equal resource allocation, the proposed framework results in a feasible cell association scheme and yields a robust solution on resource allocation that satisfies the QoS constraints. Our simulations illustrate the impact of user's minimum rate requirements on cell association and demonstrate that the proposed approach achieves load balancing and enforces single BS association for users.

• 한국병원경영학회지
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• 제6권2호
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• pp.115-137
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• 2001

The purpose of this study is to find out the successful way of the hospital management focusing on the OCS. More than 40 educational hospitals have OCS. However, only five of them were chosen for the research. Questionnaires are collected from more than 750 persons working in five educational hospitals and some of them were interviewed. The major conclusions of the study can be summarized as follows: o The OCS has simplified the treatment procedure for outpatients, and the outpatients' waiting time has been shortened. o Higher rate of satisfaction was found among the personnel in general. o The number of patients who visited outpatients clinics has increased, so as the hospital profits: the personnel are rescheduled or sent to other departments the number of employees in hospitals have decreased. o The system has the positive effect on large hospitals with over 1000 beds, highly invested hospitals, well computerized hospitals and where the personnel are much interested in the system. o The managers' and the doctors' intention to utilize the OCS is the most important factor influencing the patients' convenience, the simplification of the work and the rate of the employees' satisfaction about their duties. The suggestions for more efficient hospital management through the OCS are as follows ; o The managers and the doctors are need to decide to make active use of the OCS. o The hospital can be run more effective under the clear management purpose. o The work in the hospital must be standardized based on patients' needs. o The OCS must be built and developed mainly for the users' utility. o The education of the personnel and the inspection of the program are necessary before the OCS is introduced. o The hardware should be thoroughly benchmarked before the purchase.

• 대한전자공학회논문지TC
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• 제49권7호
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• pp.23-31
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• 2012

스케쥴링 및 데이터율의 결합 제어와 같은 자원할당 기술은 전파인지 네트워크에서는 매우 중요한 문제이다. 그러나 전파인지 네트워크에서는 주사용자 채널의 스토케스틱 특성으로 인하여 데이터율 및 스케쥴링을 결합하여 제어하는 것은 매우 어렵다. 본 논문에서는 전파인지 네트워크에서 신뢰성 제한 조건들을 고려한 비대칭 데이터율 및 스케쥴링 결합 제어 기법을 제안한다. 데이터율 및 스케쥴링 문제를 컨벡스 최적화 기법으로 공식화하고 쌍대성 분해 기법을 사용하여 부분 문제로 변환하여 분산화 하였다. 본 논문에서는 전체 시스템의 효용함수를 최대화 하도록 분산 노드들의 데이터율을 분산적으로 제어하는 알고리즘을 제안 하였다. 반면, 스케줄링은 기지국이 최적화하는 비대칭 기법을 제안하였다. 본 논문에서 제안한 비대칭 결합 제어 알고리즘은 전체 최적화 해로 수렴하는 것을 수치해석 기법으로 검증하였다.

• 한국게임학회 논문지
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• 제17권3호
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• pp.107-116
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• 2017

샌드박스 게임은 높은 자유도를 기반으로 사용자 스스로 다양한 플레이패턴을 재창조하며 만족을 배가시킨다. 이러한 창조적 과정은 '커스터마이징'과 '행동자율성'을 통한 놀이의 확장성에 기인한다. 이는 즐거움을 느끼는 요소가 과정지향적이라는 말로 대변될 수 있다. 본고는 샌드박스형 게임이 다중경쟁 환경에서 가지는 구조적한계를 규명하고자 한다. 스텐드어론 기반에서는 다양한 커스터마이징을 통한 자유도의 확장성이 유저에게 월드지속성에 강한 동기를 부여한다. 반면 MMORPG와 같은 온라인 샌드박스 게임물에서는 다수유저의 경쟁 우위를 점하고자하는 목적지향적 성향이 샌드 박스형 게임 본연의 자유도와 확장성을 구사할 수 없는 태생적 한계임을 확인하였다. 본 연구에서는 온라인 기반의 샌드박스형 게임의 자유도와 확장성의 효용이 상쇄되는 원인과 성장한계를 옵티멀솔루션 요소에 기인함을 제시할 수 있었다.