• The KIPS Transactions:PartC
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• v.13C no.2 s.105
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• pp.185-194
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• 2006

In this paper, we first propose a power-and-bandwidth efficient cooperative transmission protocol where a sensor node assists two others for their data transmission to a clusterhead in WSNs (Wireless Sensor Networks) using LEACH (Low-Energy Adaptive Clustering Hierarchy). Then we derive its closed-form BER expression which Is also a general BER one for the decode-and-forward protocol (DF) and Prove that the proposed protocol performs as same as the conventional DF but obtains higher spectral efficiency. A variety of numerical results reveal the cooperation can save the network power up to 11dB over direct transmission at BER of $10^{-3}$.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.3
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• pp.445-450
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• 2020

Cooperative networks provides the benefits of performance improvements and capacity increment when the source node transmits signal to the destination node using several relay nodes. In this paper, we consider the cooperative network where the transmission scheme between the source node and relay node use conventional binary signaling, whereas the transmission scheme between thee relay node and destination node adopt the differential space time coding signaling. We analyze the performance of the system depending on the modulation scheme, i.e., coherent and differential modulation, at the source-relay links. The performance depending on the relay location is also compared by considering modulation scheme and the number of relay node.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4A
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• pp.318-324
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• 2011

In this paper, three coordinated random beamforming (CRBF) schemes are analyzed in a two-cell symmetric interference channel. A simple partial coordination of RBF with base station selection (BSS) is shown to achieve the same average sum rate performance of CRBF with joint encoding (JE). To improve the sum rate performance further, we also propose a transmission mode selection (TMS) between the BSS and JE which is shown to have additional sum rate gain for the large number of users. Simulation results verify the eectiveness of the proposed CRBF schemes and accuracy of the proposed analysis.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.4
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• pp.17-22
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• 2013

In this paper, we propose a multi-hop cooperative transmission protocol over Rayleigh fading channels. In the proposed protocol, the multi-hop cooperative transmission is used to improve the system performance. Due to broadcast nature, we do not limit the receiving node to be only the next node, but the destination and all the nodes between the transmitting node and the destination. The proposed protocol can hence save the average transmit power, compared with multi-hop direct transmission protocol due to the skipped transmissions from some intermediate nodes or chosen relays. The proposed scheme is implemented and evaluated in mobile ad-hoc wireless networks.

• Journal of The Korean Association of Information Education
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• v.4 no.1
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• pp.24-31
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• 2000

This paper is a study on the design and implementation of cooperative monitoring agent using mobile agent for educational portal site. Generally educational portal sites have many addresses of teachers homepage. Therefore, portal site has a very difficult task with maintaining a consistent address of site and administration of portal is impossible while to be on the search for all dead sites. In order to overcome this problem, we designed and implemented a mutual cooperative monitoring agent in order to filter off dead site using mobile agent. The monitoring agent applies at Korean educational portal site (KEPS) for elementary student and makes an experiment efficient. Finally a cooperative mobile agent is compared with a stationary monitoring agent.

• The KIPS Transactions:PartC
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• v.13C no.3 s.106
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• pp.317-322
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• 2006

This paper presents an efficient user-cooperation protocol associated with cyclic coding for WSNs (Wireless Sensor Networks) using LEACH(Low-Energy Adaptive Clustering Hierarchy). Since the proposed user-cooperation requires no CSI(Channel State Information) at both transmitter and receiver, and encoding and decoding of cyclic codes are simple, the processing complexity of sensor nodes is significantly reduced. Simulation results reveal such a combination can save the network energy up to 10dB over single-hop transmission at BER of $10^{-4}$.

• Journal of the Korean Association of Geographic Information Studies
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• v.17 no.1
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• pp.70-79
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• 2014

Following the technology developments of traffic network and communication for the wide area, the importance of the cooperation system to vitalize the wide area economy is increasing. Therefore, in this study, DongNam Kwon industry information system is established for the industrial information sharing based on GIS in the DongNam Kwon wide area economy. The DongNam Kwon is an industrial integration area centered with the manufacturing so that the operation of effective industrial cluster and cooperation systems are required across the administrational boundaries. To establish the database of the information, the information system was established utilizing already established industrial databases in Busan, Ulsan and Gyeongnam. But, various issues caused by the discordances among the data of each local government and the insufficiency of GIS based location information have been found. According to the analysis, the standardization considering the courses of collection, distributions and utilization are required immediately to solve the issues. This study establishes an 2-way industrial information system enabling the information creation and the phased approach between the administrator and the user in the bi-directions on the web by utilizing cadastral and numerical maps. The result of this study would have a meaning in providing a fundamental frame for cooperative responses and cooperation system for DongNam Kwon's industrial promotion using industrial information sharing.

• Journal of the Korean Data and Information Science Society
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• v.24 no.4
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• pp.803-813
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• 2013

The purchase of items in e-commerce is a little bit different from that of items in off-line. The recommendation of items in off-line is conducted by salespersons' recommendation, However, the item recommendation in e-commerce cannot be recommended by salespersons, and so different types of methods can be recommended in e-commerce. Recommender system is a method which recommends items in e-commerce. Preferences of customers who want to purchase new items can be predicted by the preferences of customers purchasing existing items. In the recommender system, the items with estimated high preferences can be recommended to customers. The algorithm of collaborative filtering is used in recommender system of e-commerce, and the list of recommended items is made by estimated values, and then the list is recommended to customers. The dataset used in this research are 100k dataset and 1 million dataset in Movielens dataset. Similar results in two dataset are deducted for generalization. To suggest a new algorithm, distribution features of estimated values are analyzed by the existing algorithm and transformed algorithm. In addition, respondent'distribution features are analyzed respectively. To improve the collaborative filtering algorithm in neighborhood recommender system, a new algorithm method is suggested on the basis of existing algorithm and transformed algorithm.

• Journal of KIISE:Software and Applications
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• v.32 no.7
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• pp.581-591
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• 2005

Collaborative filtering systems have problems involving sparsity and the provision of recommendations by making correlations between only two users' preferences. These systems recommend items based only on the preferences without taking in to account the contents of the items. As a result, the accuracy of recommendations depends on the data from user-rated items. When users rate items, it can be expected that not all users ran do so earnestly. This brings down the accuracy of recommendations. This paper proposes a collaborative recommendation method for extracting typical group preferences using user-item matrix optimization and user profiles in collaborative tittering systems. The method excludes unproven users by using entropy based on data from user-rated items and groups users into clusters after generating user profiles, and then extracts typical group preferences. The proposed method generates collaborative user profiles by using association word mining to reflect contents as well as preferences of items and groups users into clusters based on the profiles by using the vector space model and the K-means algorithm. To compensate for the shortcoming of providing recommendations using correlations between only two user preferences, the proposed method extracts typical preferences of groups using the entropy theory The typical preferences are extracted by combining user entropies with item preferences. The recommender system using typical group preferences solves the problem caused by recommendations based on preferences rated incorrectly by users and reduces time for retrieving the most similar users in groups.

• Proceedings of the Korea Society for Simulation Conference
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• 2001.05a
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• pp.72-76
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• 2001

인터넷이 생활의 중요한 요소로 자리잡기 시작하면서 네트워크의 침해 사고가 급증하고 있는 현실이다. 이러한 침해 사고를 예방하기 위해 침입 탐지 시스템(IDS)과 방화벽(Firewall)이 많이 사용되고 있다. 방화벽과 침입 탐지 시스템은 연동은 서로의 단점을 보완하여 더 강력하게 네트워크를 보호할 수 있다. 방화벽과 침입 탐지 시스템을 위한 시뮬레이션 모델은 DEVS (Discrete Event system Specification) 방법론을 사용하여 구성하였다. 본 논문에서는 실제 침입 데이터를 발생시켜 실제 침입에 가까운 상황 가운데 침입 행위를 판별하도록 구성하였다. 이렇게 구성된 시뮬레이션 모델을 사용하여 침입탐지 시스템의 핵심 요소인 침입 판별이 효과적으로 수행되는지를 시뮬레이션 할 수 있다. 현재의 침입은 광범위해지고, 복잡하게 되어 한 침입 탐지 시스템이 독립적으로 네트워크의 침입을 판단하기 어렵게 되었다. 이를 위해 네트워크 내에 여러 침입 탐지 시스템 에이전트를 배치하였고, 에이전트들이 서로 정보를 공유함으로써 공격에 효과적으로 대응할 수 있도록 하였다. 침입 탐지 시스템이 서로 협력하여 침입을 탐지하고, 이런 정보를 침입 차단 시스템에게 넘겨주게 된다. 이와 같은 구성을 통해서 공격자로부터 발생된 패킷이 네트워크 내로 들어오는 것을 원천적으로 막을 수 있도록 하였다.