• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.8
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• pp.976-984
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• 2012

Ad hoc networks can be used under difficult conditions, where it is difficult to construct infrastructures, such as shadowing areas, disaster areas, war area, and so on. In order to support to considerable and various wireless services, more spectrum resources are needed. However, efficient utilization of the frequency resource is difficult because of spectrum scarcity and the conventional frequency regulation. Ad-hoc networks employing cognitive radio(CR) system that guarantee high spectrum utilization provide effective way to increase the network capacity. However, there is a problem that all CR user do not fairly use the primary user's idle bandwidth which has been sensed. In this paper, to solve this problem, we propose the spectrum sharing algorithm which uses the multiple orthogonal sequences based on the code division multiple access(CDMA). From the proposed algorithm, it is expected that system performance of CR based ad-hoc network is improved significantly and it can be applied to the implementation of CR based ad-hoc network system.

• Electronics and Telecommunications Trends
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• v.26 no.3
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• pp.14-24
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• 2011

본 동향은 최근 각광을 받고 있는 소셜 네트워크 서비스 기술과 관련하여 현재 사용자에게 제공되고 있는 서비스와 진행되고 있는 연구 분야 전반에 걸쳐 소개한다. 소셜 관계를 제공하는 역할인지, 소셜 관계를 사용하는 역할인지에 따라 서비스의 행태를 나눠 기술하고 그러한 서비스를 제공하기 위해 필요한 대표적인 기술 분야로 소셜 네트워크 분석, 소셜 미디어, 시맨틱 소셜 웹, 소셜 검색에 관한 연구 개요를 설명한다. 마지막으로 소셜 네트워크 서비스의 폭발적인 성장에 기여한 스마트폰과 관련하여, 모바일 소셜 네트워크 서비스 동향을 살펴본다.

• Journal of KIISE:Information Networking
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• v.37 no.3
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• pp.249-253
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• 2010

Resource of wireless frequency bandwidth is gradually going to be deficient due to explosive increase of traffic and saturated non-licensed frequency band such as ISM. In the contrary, many licensed frequency bands are revealed to be low in utilization by several measurement based researches. To alleviate this inefficiency, a concept of cognitive radio is suggested. Cognitive radio lets non-licensed user exploit the licensed frequency band as long as non-licensed user does not interfere licensed user and as a result, it is possible to harness wireless frequency more efficiently. IEEE 802.22 is the first standard network with cognitive radio technology and it employs Two-Stage channel sensing mechanism to accomplish both enough licensed user protection and efficient channel utilization. In this paper, we analyze the overhead of Two-Stage channel sensing mechanism and identify the influence of channel sensing time to the overhead.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.35-41
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• 2017

To solve the shortage of radio spectrum and utilize spectrum resource more efficiently, cognitive radio technologies are proposed, and many studies on cognitive radio have been conducted. Multi-hop routing is one of the important technologies to enable the nodes to transmit data further with lower power in ad-hoc cognitive radio networks. In a multi-channel cognitive radio networks, each channel should be allocated to minimize interference to primary users. In the multi-hop routing, channel allocation should consider the inter-channel interference to maximize network throughput. In this paper, we propose multi-channel scheduling scheme which minimizes inter-channel interferences and avoids collision with primary users for the multi-hop multi-channel cognitive radio networks. The proposed scheduling is designed to determine both of routing path and channel selection. The performance of proposed channel allocation scheme is evaluated by the computer simulation in the aspect of capacity and collision rate.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10d
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• pp.385-389
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• 2007

본 논문에서는 각종 센서를 탑재한 차량을 센서 네트워크의 노드로써 움직이는 하드웨어를 구현하였다. 센서 네트워크에서 이동할 수 있는 노드들은 주위의 환경을 인지하여 대처하며 그에 대한 정보를 컴퓨터에 전달하여 차량이 있는 곳의 지도를 만들어 낸다. 이러한 센서 차량의 하드웨어를 만들기 위해 정면에 존재하는 장애물을 인지하는 라인레이저와 그것을 인지할 수 있는 카메라, 초음파 센서를 설치하였다. 절대적인 지표 없이 정확한 좌표를 알아내기 힘들고 차량 이동 시 미끄러짐 등과 같은 오차가 생길 수 있으므로 정확한 방위각을 알아낼 수 있는 디지털 나침반을 차량 설계에 포함 시켰다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2017.11a
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• pp.41-43
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• 2017

본 논문에서는 IoS (Internet of Signage) 환경에서 실감형 데이터 전송을 위한 상황 인지 기반 적응형 전송기법을 적용하고 이를 분석한다. 사이니지 네트워크 환경에서는 임의적인 다중 경로 페이딩, 간섭 등과 같은 왜곡 요소가 존재할 수 있기 때문에 이를 대처하기 위해 무선 송신기에서는 채널 환경에 대한 인지 이후, 그에 따른 MCS (Modulation and Coding Scheme)를 선정 및 안테나 기법을 선정한다. MCS 및 안테나 기법 선정을 위해 무선 송신기에서는 사전에 알고 있는 통계적인 SNR (Signal-to-Noise Ratio) 값을 통해 문턱값을 계산하고, 수신 사이니지로부터 얻은 CSI (Channel State Information)와의 크기 비교를 한다. 시뮬레이션 결과에서는 상황 인지를 기반으로 매 순간 최적의 전송률을 달성할 수 있음을 볼 수 있다.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2006.05a
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• pp.397-401
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• 2006

트래픽 패턴-맵(PatternMap)은 전체/세부 도메인별 보안 상황을 근원지/목적지 IP 주소 범위로 이루어진 그리드 상에 표현하여 관리자에게 네트워크 보안상황을 실시간으로 인지시키는 도구이다. 각각의 그리드는 근원지-목적지 간의 연결을 의미하며, 최다 점유를 차지하는 트래픽의 포트를 식별력을 갖는 색으로 표현한다. 이상 트래픽 현상의 검출은 가로 및 세로 열에 나타난 동일 색의 막대그래프(포트)의 개수와 그것의 합에 따라 결정되며, 그 결과로 선택된 세로 열과 가로 열을 활성화시켜 관리자에게 그 현상을 인지시킨다. 일반적으로 인터넷 웜이 발생할 경우에는 특정 근원지 열이 활성화되고, DDoS와 같은 현상은 목적지 열이 활성화되는 특징이 있다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.1
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• pp.33-40
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• 2010

Recently, the spectrum scarcity is becoming a big issue because there are exponential growth of broadcasting and communication systems in the spectrum demand. Cognitive radio is a technology that is envisaged to solve the problems in wireless networks resulting from the limited available spectrum and the inefficiency in the spectrum usage by exploiting the existing wireless spectrum opportunistically. Kuroda et al. proposed a radio-independent authentication protocol for cognitive radio networks. This paper first shows the privacy weaknesses in the authentication protocol by Kuroda et al. and proposes a privacy aware authentication protocol to solve the weaknesses.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.1
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• pp.37-44
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• 2016

It is important that using of efficient radio resource because of deficiency spectrum problem, so that related to this problem many researches are have proceeded. To solve this problem, Cognitive Radio(CR) was suggested. The channels are allocated to the secondary users when the primary users don't use the channels, and unfairness of secondary users can be serious problem and channel quality of multichannel can be different due to the different traffic pattern of primary users. In this paper, we propose MAC prtocol both of the user's fairness and channel quality in CR networks. Simulation results show the comparison with CR MAC protocols.

• Journal of Korea Society of Industrial Information Systems
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• v.21 no.5
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• pp.55-72
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• 2016

This study aims at providing a methodology for retaining international technology competitiveness, marketable industry, and sustainable promising technology in a field of new growth engine industry such as national unmanned aerial vehicle industry. We draw a result by analysing with tools such as KrKwic, Excel, NetMiner, presenting methods of a Social Network Analysis, sub-group analysis, and cognitive map analysis based on patent data in a field of unmanned aerial vehicle industry. As a result, some future promising technologies are prospected as what worths concentrated investment, such as 'pilot control tech', 'identification of friend or foe tech'.