• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.9
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• pp.2117-2123
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• 2014

To cope with the explosive growth of traffic which is considered as one of the most biggest threat to current mobile communication systems, various solutions such as small cell and device-to-device communication have been exploited. Directional transmission in which transmission power of base station is focused onto the direction where the mobile station is located, can be used to increase throughput of the system. In this work, we develop a system-level simulator for cellular mobile communication systems using directional transmission and adaptive interference estimation scheme for directional transmission has been proposed. By using the developed simulator, the performance of cellular mobile communication systems with directional transmission is examined. Moreover, it is shown that the overall throughput of cellular system can be improved by utilizing directional transmission.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.11
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• pp.2621-2627
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• 2014

Directional transmission is one of key technology to solve the utmost problem that current mobile communication system faces, which is explosively increasing data traffic, since directional transmission can maximize the throughput of mobile communication systems. In this work, we consider power allocation scheme for mobile communication system which utilizing directional transmission. Especially, we consider the case in which multiple users in the same sector of base station, are served at the same time by utilizing directional transmission. For this scenarios, we consider equal power allocation scheme, Water-filling based scheme and inverse SNR scheme. Moreover, we propose beam power allocation scheme whose objective is to maximize overall system throughput by taking into account interference between different directional transmissions. Moreover, we have examined the spectral efficiency and Jain's fairness index of various power allocation schemes for directional transmission by using system level simulator that has been developed in our previous work. Through simulations, it has been verified that the proposed power allocation scheme can improve the spectral efficiency of the system by 28%.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.47-52
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• 2011

Directional couplers based on plasmonic waveguides with nano-scale three channels are designed by utilizing mode coupling effect as well as rib-guiding structure. Longitudinal modal transmission-line theory(L-MTLT) is used for simulating the light propagation and optimizing the design parameters. The designed plasmonic coupler operating as power splitter has nano-scale size of about 200~250 nm width. In order to achieve the desired power splitting ratio, the refractive index of guiding modes is evaluated along the width variation of center channel. Finally, a power splitter based on triple rib directional coupler, which ensures maximum power transfer from one outermost guide to the other outermost guide, is designed.

• Journal of the Korea Society of Computer and Information
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• v.17 no.10
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• pp.99-105
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• 2012

ZigBee is the low power, low cost and low data rate wireless personal area network(LR-WPAN) standard. The Directed-Messaging is the protocol which improves the energy efficiency through reducing the redundant message transmission by transmitting messages with directional information toward the specified sub-network area in wireless sensor network using broadcasting. In this paper, we design and implement the experimental grid sensor network using ZigBee modified by the Directed-Messaging for the energy efficiency improvement. The experimental sensor network in this paper is configured with Nano24 supporting the ADV message and the routing management module modified to use the directional information. The energy efficiency improvement of the experimental sensor-network by evaluating the experimental results according to transmitting ADV message.

• Journal of Advanced Navigation Technology
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• v.12 no.6
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• pp.627-633
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• 2008

In the case of traffic accidents, the broadcasting methods used in the mobile ad hoc network (MANET) cannot applied to transmit reliable message since moving high-speed in vehicular ad hoc networks (VANET) environments. In this paper, in order to guarantee transmitting reliable messages, we propose a collision avoidance method based-on directional antenna in VANET. In order to reduce interference from omni-broadcasting and to avoid hidden node problem from moving high-speed, we employed a forward-handed and backward directional antenna. The authors simulated the proposed method based on directional antenna and showed that the proposed method has been improved in respect to network utilization compared to existing VANET protocols.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.11
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• pp.18-26
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• 1999

Recently, various simplified simulation techniques such as firite-difference beam propagation method and non-orthogonal coupled-mode theory have proposed to analyze the optical characteristics of tapered directional couplers supported by the coupling of two propagating modes. Although these approaches are often in sufficiently accurate, they do not provide the detailed solutions encountered in the analysis of tapered guiding structures. For this purpose, we introduce and utilize a newly developed modal transmission-line theory to analyze rigorously power transfer of the directional coupler. The numerical result reveals that the propagation constants of even and odd modes converge to a single value as increasing the spacer thickness between two symmetric tapered guides. Furthermore, 97% of the power incident into a guiding channel is transmitted to the other channel at the tapered angle ${\theta}=0.1^{\circ}$, and the efficiency of power transfer decreases dramatically as increasing the angle.

• Broadcasting and Media Magazine
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• v.26 no.1
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• pp.19-30
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• 2021

전 세계 모바일 데이터 트래픽은 지속적으로 증가하고 있으며 이 중 상당 부분을 모바일 비디오 서비스가 차지할 것으로 전망되고 있다. 최근 방송 및 통신 전송 기술에서 전송용량 및 대역폭의 증대와 스펙트럼 이용의 유연성 및 효율성이 크게 개선됨에 따라 다양한 모바일 방송 서비스에 대한 기대가 고조되고 있다. 증가하는 모바일 방송 수요와 더불어 미래에는 이동통신 및 차세대 방송 기술의 융합을 통하여 초고화질 콘텐츠, VR/AR 등 다양한 미디어 서비스가 가능할 것으로 전망된다. 본 고에서는 새로운 미디어 서비스를 위하여 이동통신과 지상파 방송에서 전송 기술들을 살펴보고, 이들 기술이 새로운 미디어 서비스를 제공하기 위한 발전 및 융합 방향에 대해 살펴보고자 한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.24-29
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• 2011

Comparing conventional one-way relaying, two-way relaying scheme with network coding can achieve high throughput by reducing the transmission time. Coded cooperation protocol, which is a algorithm that uses coding on physical layer, can achieve high reliability. In this paper, we propose coded cooperation protocol over two-way relay network. Simulation results show proposed protocol has better performance in terms of reliability and throughput compare with conventional amplify and forward protocol. Also, with same throughput, proposed protocol has better performance in terms of reliability compare with the conventional hybrid decoded and forward protocol.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.4
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• pp.187-192
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• 2017

Rigorous longitudinal modal transmission-line theory (L-MTLT) is applied to analyze maximum power transfer in asymmetric grating-assisted directional couplers(A-GADC). By defining a coupling efficiency amenable to rigorous analytical solutions and interference between symmetric and asymmetric supermodes, the power exchange of TE modes as a function of propagation distance is numerically evaluated. The numerical result reveals that maximum power transfer occurs at a grating period ${\Lambda}_{eq}$, in which the insertion loss of supermodes is equal to each other. That is, it is generally different from conventional phase-matching condition of GADC. Furthermore, as the asymmetric profile of grating change to symmetrical profile, the coupling length decreases and the coupling efficiency for power transmission increases.

• The Journal of the Convergence on Culture Technology
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• v.4 no.3
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• pp.287-291
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• 2018

The CNTFET, which is attracting attention as a next-generation semiconductor device, can obtain ballistic or near-ballistic transport at a lower voltage than that of conventional MOSFETs by depositing CNTs between the source and drain of the device. In order to increase the performance of the CNTFET, a large number of CNTs must be deposited at a high density in the CNTFET. Thus, various manufacturing processes to increase the density of the CNTs have been developed. Recently, the Directional Shrinking Transfer Method was developed and showed that the current density of the CNTFET device could be increased up to 150 uA/um. So, this method enhances the possibility of implementing a CNTFET-based integrated circuit. In this paper, we will discuss how to evaluate the performance of the CNTFET device compared to a MOSFET at the circuit level when the CNTFET is fabricated by the Directional Shrinkage Transfer Method.