• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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• pp.1336-1356
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• 2017

The spectrum scarcity crisis has resulted in a shortage of resources for many emerging wireless services, and research on dynamic spectrum management has been used to solve this problem. Game theory can allocate resources to users in an economic way through market competition. In this paper, we propose a bidding game-based spectrum allocation mechanism in cognitive radio network. In our framework, primary networks provide heterogeneous wireless service and different numbers of channels, while secondary users have diverse bandwidth demands for transmission. Considering the features of traffic and QoS demands, we design a weighted interference graph-based grouping algorithm to divide users into several groups and construct the non-interference user-set in the first step. In the second step, we propose the dynamic bidding game-based spectrum allocation strategy; we analyze both buyer's and seller's revenue and determine the best allocation strategy. We also prove that our mechanism can achieve balanced pricing schema in competition. Theoretical and simulation results show that our strategy provides a feasible solution to improve spectrum utilization, can maximize overall utility and guarantee users' individual rationality.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권1호
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• pp.421-433
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• 2015

Recently, there have been fast-growing social network services based on the Internet environment and web technology development, the prevalence of smartphones, etc. Social networks also allow the users to convey the information and news so that they have a great influence on the public opinion formed by social interaction among users as well as the spread of information. On the other hand, these social networks also serve as perfect environments for rampant malware. Malware is rapidly being spread because relationships are formed on trust among the users. In this paper, an effective patch strategy is proposed to deal with malicious worms based on social networks. A graph is formed to analyze the structure of a social network, and subgroups are formed in the graph for the distributed patch strategy. The weighted directions and activities between the nodes are taken into account to select reliable key nodes from the generated subgroups, and the Incremental PageRanking algorithm reflecting dynamic social network features (addition/deletion of users and links) is used for deriving the high influential key nodes. With the patch based on the derived key nodes, the proposed method can prevent worms from spreading over social networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권7호
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• pp.2231-2245
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• 2014

Cognitive Radio (CR) has very promising potential to improve spectrum utilization by allowing unlicensed Secondary Users (SUs) to access the spectrum dynamically without disturbing licensed Primary Users (PUs). Mitigating interference is a fundamental problem in CR scenarios. This is particularly problematic for deploying CR in cellular networks, when users are located at the cell edge, as the inter-cell interference mitigation and frequency reuse are critical requirements for both PUs and SUs. Further cellular networks require higher cell edge performance, then SUs will meet more challenges than PUs. To solve the performance decrease for SUs at the cell edge, a novel Dynamic Spectrum Allocation (DSA) scheme based on Game Theory is proposed in this paper. Full frequency reuse can be realized as well as inter-cell interference mitigated according to SUs' sensing, measurement and interaction in this scheme. A joint power/channel allocation algorithm is proposed to improve both cell-edge user experience and network performance through distributed pricing calculation and exchange based on game theory. Analytical proof is presented and simulation results show that the proposed scheme achieves high efficiency of spectrum usage and improvement of cell edge SUs' performance.

• 지능정보연구
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• 제15권4호
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• pp.141-158
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• 2009

다양한 정보자원들로부터 사용자가 요구하는 맞춤화된 정보를 추출해 내는 것은 더욱 어려워지고 있다. RSS를 비롯하여 개선된 다양한 정보 수집 방법들이 개발되었지만, 여전히 정보가공자인 사람의 도움 없이 필요한 정보들을 수집하여 정리 및 가공하는 작업이 쉽지는 않다. 따라서 본 연구에서는 정보사용자들이 사용 목적에 맞게 정보를 가공하는 부담을 줄여주기 위해 사례기반추론과 온톨로지에 기반한 맞춤형 통합정보생성 프레임워크를 제안한다. 본 프레임워크는 세 단계로 구성된다. 첫째, 수집된 웹 정보를 정보가공의 용이성을 위해 사례로 변환한다. 둘째, 동적 유사도 검색을 통해 수집된 사례들로부터 정보 사용자의 동적 요구사항에 적합한 사례를 검색한다. 셋째, 전 단계에서 추출된 사례를 정보사용자의 요구사항에 보다 적합한 지식으로 가공하기 위해 집중 유사도를 적용한다. 본 프레임워크는 여행자들의 정보수집을 위한 여행정보시스템에 적용되어 그 효과를 입증하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권3호
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• pp.749-761
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• 2014

Improving spectrum utilization efficiency is a fundamental goal of dynamic spectrum access technology. The definition of spectrum holes determines how to detect and exploit them. Current definitions of spectrum holes are ineffective in exploiting spatial-temporal spectrum holes. In this paper, a novel definition of spectrum holes is proposed, in which throughput loss indicates the impact of secondary users on primary users. The definition specifies spectrum holes, unifies the impact of secondary users on primary users and is effective exploiting spatial-temporal spectrum holes. Theoretical analysis and numerical simulations show that the new definition proposed in this paper significantly improves the spectrum utilization efficiency.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권11호
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• pp.5653-5672
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• 2019

In cloud computing era, an increasing number of resource-constrained users outsource their data to cloud servers. Due to the untrustworthiness of cloud servers, it is important to ensure the integrity of outsourced data. However, most of existing solutions still have challenging issues needing to be addressed, such as the identity privacy protection of users, the traceability of users, the supporting of dynamic user operations, and the publicity of auditing. In order to tackle these issues simultaneously, in this paper, we propose a traceable dynamic public auditing scheme with identity privacy preserving for cloud storage. In the proposed scheme, a single user, including a group manager, is unable to know the signer's identity. Furthermore, our scheme realizes traceability based on a secret sharing mechanism and supports dynamic user operations. Based on the security and efficiency analysis, it is shown that our scheme is secure and efficient.

• 한국경영정보학회:학술대회논문집
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• 한국경영정보학회 2008년도 춘계학술대회
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• pp.383-393
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• 2008

Online games are the popular topic due to the increased total online game market volume nowadays. And many studies on online games are released. But most studies used the questionnaire method that reveals only section of the situation like a snapshot. For this reason, previous studies have a little limitation that does not show dynamical changing issues like a product life cycle and changes in customer's mind Because of this, we studied on online games with the system dynamic model which can show dynamic simulations to analysis time series data. We chose MMORPG (Massively Multi-play Online) RPG (Role Playing Game) in sort of online games because it has many absorbing factors and enthusiastic users. We designed the simulation model which analyzes the influences of update and CRM strategy on users. We put the game developer who is ready for updated version game and released that periodically and focused on dormant users who used to be enthusiastic about MMORPG. The simulation results showed that the update has positive influences on new users gathering and hold established users. And CRM strategies help to prevent dormant users from transferring to rivals by offering them re-absorbing factors. Through this study, we confirmed the importance of update on online games and the necessity of introducing CRM strategy in the online game market.

• 한국정보시스템학회지:정보시스템연구
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• 제17권4호
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• pp.281-299
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• 2008

An online game is popular topic due to the increased total online game market volume nowadays. Even though many studies on an online game are released, most studies have used survey method that reveal only section of the situation like a snapshot. For this reason, previous studies have a little limitation that does not show dynamically changing issues like a product life cycle and change in customer's satisfaction. Because of this, we researched on an online game with the system dynamic model which can show dynamic simulation to analysis time series data. We chose MMORPG (Massively Multi-play Online Role Playing Game) in sort of an online game because it has many absorbing factors and enthusiastic users. We assumed that the game developer is ready for updated version game and release that periodically and focused on dormant users who used to be enthusiastic about MMORPG and designed simulation model which analyze how to influence of update and CRM strategy on users. The simulation results showed that the update has positive influences to gather new users and hold established users and CRM strategies help to prevent dormant users from transferring to rivals to offer them re-absorbing factors. Through this study, we confirmed importance of update on a online game and suggested the necessity to introduce CRM strategy in an online game market.

• 한국정보통신학회논문지
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• 제18권7호
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• pp.1628-1633
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• 2014

본 연구는 스마트폰환경에서 사용자의 관심주제와 읽기습관을 분석하여 읽기 습관을 분석하여 관심 있는 뉴스기사를 추천 시스템을 제안하였다. 사용자가 직접 관심영역의 가중치를 정함으로서 관심주제의 기사를 우선적으로 보여 주어 사용자가 쉽게 관심기사를 읽을 수 있도록 하였다. 또한 사용자가 사회적으로 이슈가 되는 기사에 관심을 갖는 경우 이를 반영하기 위해서 단순히 기사를 클릭하고 읽지 않은 경우는 가중치를 낮게 설정하였으며, 기사를 끝까지 스크롤을 하고 기사를 끝까지 읽은 경우는 가중치를 높게 설정하였다. 특정 분야의 기사를 자주 읽은 경우는 XML의 구조정보를 사용하여 관심주제영역의 가중치를 높게 설정함으로써 관련분야의 기사를 우선적으로 볼 수 있도록 하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.439-444
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• 1999

This paper presents an authoring system for users to create and edit multimedia documents more easily. Our system supports dynamic authoring to feedback the inconsistency that could be occurred when users authorize and flexible media synchronization. For these, we define a new time relation based on causal relation and provide an internal representation using trees and structured document parsing. The system consists of the components such as visual interface, parsing, and presentation engine. It has been implemented on Microsoft Windows 95 with Visual C++.