• Journal of Internet Computing and Services
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• v.19 no.2
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• pp.9-15
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• 2018

This paper proposes an energy efficient adaptive relay station ON/OFF scheme with different frequency reuse factors (FRFs) to enhance the system throughput and reduce the transmission energy consumption for the transparent mode of 2-hop cellular relay networks (CRNs) based on orthogonal frequency division multiple access and time division duplex. In the proposed scheme, the base station turns on or off the relay stations (RSs) when they are overutilized and undertuilized based on the traffic density of the cell coverage, respectively. Through the simulation results, we show that the proposed scheme outperforms the conventional CRN in terms of the energy consumption with the same system throughput. Further, in order to increase the system throughput with low energy consumption, the best way is FRF 1 when the number of operating RSs is up to 4 and FRF 2 otherwise.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.156-157
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• 2003

The wavelength converter is considered to be a key element of future dense WDM optical networks. It enables wavelength reuse and resolves contention problem. Moreover, the tunability of the wavelength converter enhance the flexibility of network systems by facilitating reconfigurable dynamic wavelength routing. In order to achieve optically tunable wavelength conversion, we recently proposed and experimentally demonstrated wavelength conversion and tuning based on cascaded sum and difference frequency generation in a Ti：PPLN channel waveguide. (omitted)

• Proceedings of the Optical Society of Korea Conference
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• 2006.02a
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• pp.135-136
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• 2006

We present a new binary data encryption and transmission technique based on 4-step phase-shifting interferometry for a security system. Phase-shifting interferometry is used for recording phase and amplitude information on CCD device. 4-step phase-shifting is implemented by moving the PZT mirror with equidistant phase steps of ${\pi}/2$. The basic idea is that we reuse a 256 gray-level digital hologram to encrypt binary data with 4-step phase-shifting interferometry.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.226-228
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• 2004

IEEE 802.15.3 High-Rate WPAN(Wireless Personal Area Network)는 l0m내외의 무선 환경에서 실시간 비디오, 고품질 오디오 및 대용량 파일 전송을 가능케 하는 기술이다 하나의 네트워크를 piconet 단위로 구성하고 하나의 Piconet에는 PNC(piconet coordinator)가 TOMA(Time Division Multiple Access) 방식으로 DEV(device)들에게 채널타임을 할당한다. 본 논문에서는 IEEE 802.15.3 High-Rate WPAN 환경에서 하나의 piconet 에 존재하는 각각 통신을 하려는 DEV 들이 서로의 신호에 간섭을 받지 않을 만큼 떨어져 있다면 한 개의 채널타임을 각각의 DEV 들에게 동시에 할당하여 여러 DEV들이 동시에 통신을 하는 공간 재활용방식을 통해 네트워크의 성능을 향상하는 방법을 제안하고 MAC의 공간재활용방식을 통한 네트워크의 성능향상 방법을 연구한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.04a
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• pp.83-85
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• 2016

C-RAN (Cloud Radio Access Network) structure is the most popular approach for 5G stander, it employs CoMP (Coordinated Multiple Points Transmission/Reception) to enhance frequency utilization and increase throughput for cell-edge users. C-RAN mainly includes two parts: baseband units (BBU) and remote radio heads (RRH). In this paper we propose a new resource block allocation (spectrum allocation) scheme by the permutation and combination of BBUs, and we also use the CoMP (Coordinated Multiple Points Transmission/Reception) technique according to the different environment to improve the spectrum utilization and reduce resource waste in different environment. The simulation results expound that the scheme significantly enhances throughput and improves the spectrum utilization.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.11a
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• pp.357-360
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• 2004

본 논문은 소프트웨어의 효율적인 재사용을 위해 소스 코드 기반 컴포넌트 검색 방법을 제안하였다. 제안한 방법은 2단계로 이루어지는데, 먼저 라이브러리에 저장된 클래스를 기반으로 한 컴포넌트는 파싱 과정을 거쳐 의미망을 구성하고, 다음으로 사용자가 질의한 소스 코드를 이용하여 검색이 이루어진다. 소스 코드에서 추출된 식별자가 컴포넌트의 의미망을 활성화시켜 연관된 컴포넌트를 검색한다. 본 연구에서 제안한 검색방법은 프로그래머의 관심을 라이브러리 내에 있는 컴포넌트로 유도하여 재사용성을 높일 수 있으며, 프로그래밍 패턴을 제공함으로써 프로그래머로 하여금 프로그램의 가이드 라인으로 사용할 수 있도록 도움을 줄 수 있다.

• Journal of information and communication convergence engineering
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• v.2 no.2
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• pp.106-109
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• 2004

This study designs a load balancer via direct routing that share a virtual service on a single IP address in the Linux system and suggests an efficient load balancing method to improve transmission speed in the web server cluster environment. It will increase performance and scalability with fast packet transfer and removing bottleneck problem by using TCP Splicing and Content-Aware Distributor method. This method is expected to be the noticeable technology that provides an important interface, which make application services for e-commerce effectively be applied to high-speed network infrastructure. At this time, it is required to study further on the optimum balancing method in the web server cluster environment so as to apply the hybrid (optimum load balancing method by software and hardware) method and improve the reuse of security cession based on high-speed TCP connections.

• ETRI Journal
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• v.40 no.6
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• pp.726-735
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• 2018

Femtocells are good examples of the ultimate networking technology, offering enhanced indoor coverage and higher data rate. However, the dense deployment of femto base stations (FBSs) and the exploitation of subcarrier reuse between macrocell base stations and FBSs result in significant co-tier and cross-tier interference, thus degrading system performance. Therefore, appropriate resource allocations are required to mitigate the interference. This paper proposes a discrete bacterial foraging optimization (DBFO) algorithm to find the optimal resource allocation in two-tier networks. The simulation results showed that DBFO outperforms the random-resource allocation and discrete particle swarm optimization (DPSO) considering the small number of steps taken by particles and bacteria.

• ETRI Journal
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• v.44 no.6
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• pp.955-965
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• 2022

A low Earth orbit (LEO) satellite constellation could be used to provide network coverage for the entire globe. This study considers multi-beam frequency reuse in LEO satellite systems. In such a system, the channel is time-varying due to the fast movement of the satellite. This study proposes an efficient power and bandwidth allocation method that employs two linear machine learning algorithms and take channel conditions and traffic demand (TD) as input. With the aid of a simple linear system, the proposed scheme allows for the optimum allocation of resources under dynamic channel and TD conditions. Additionally, efficient projection schemes are added to the proposed method so that the provided capacity is best approximated to TD when TD exceeds the maximum allowable system capacity. The simulation results show that the proposed method outperforms existing methods.

• Journal of the Korean Society for Library and Information Science
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• v.48 no.4
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• pp.267-295
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• 2014

The purpose of this study is to analyze empirically relationships between learners' psychological factors, knowledge sourcing behavior and knowledge utilization outcomes and to analyze the mediation effect of social learning and relationships among learners. Another purpose is to understand learners' attitude on social learning and knowledge sourcing behavior. The main results of this study are as follows: First, regression results on relationships among learners' psychological factors, knowledge sourcing behavior, knowledge utilization outcomes show that learners' self-efficacy has a positive effect on social learning activity participation, and goal orientation has a positive influence on group knowledge sourcing and social learning activity participation. Users' experiences of social media has a positive effect on group knowledge sourcing, social learning activity participation and social learning interaction. From a knowledge utilization perspective, published knowledge sourcing positively affects knowledge reuse, knowledge application and knowledge innovation. Dyadic knowledge sourcing has positive influence on knowledge reuse. Group knowledge sourcing affects positively knowledge application and knowledge innovation. Second, social learning activity participation factor has full mediation effect on relationship between learners' goal orientation and group knowledge sourcing, and the relationship between users' experiences of social media and group knowledge sourcing. A relationship among members factor has full mediation effect on the relationship between published knowledge sourcing and knowledge reuse, and relationship between published knowledge sourcing and knowledge innovation. Third, the results of in-depth interview show that learners trust and easily collect knowledge from social network services in general. Also, they get a variety of idea for solving information problem from interaction among members in social learning community.