• Journal of the Optical Society of Korea
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• 제19권5호
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• pp.437-443
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• 2015

In this paper, we analyze the performance of the all-optical multihop radio over a free space optical (RoFSO) communication system with amplify-and-forward (AF) relays under varying weather conditions. The proposed channel model considers the propagation loss, attenuation and atmospheric fading modeled by the Gamma-Gamma (GG) distribution. Both the amplified spontaneous emission (ASE) noise in the all-optical relays and the background noise projected onto receiver apertures have been considered in the analysis. The lower bound analytical expressions for the end-to-end bit error rate (BER) and outage probability are derived for the multihop system employing the all-optical relays with the full channel state information (CSI). Meanwhile, the exact results for BER and outage probability are obtained via Monte Carlo simulation. Results indicate the performance of the proposed system will be improved by the multihop transmission technology. For a fixed number of relays, the BER and outage probability will be increased with the deterioration of the weather conditions.

• 한국전자통신학회논문지
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• 제12권2호
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• pp.261-266
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• 2017

본 연구는 디지털위성중계기용 SHF 대역 상향주파수변환장치의 설계 및 구현에 대해 기술하였다. SHF 대역 상향주파수변환장치는 PLDRO(: Phase Locked Dielectric Resonator Oscillator) 및 주파수변환기로 구현된다. 주파수변환기 내부에는 불요파 최소화를 위하여 사전 EM 시뮬레이션을 통하여 설계한 Microstrip BPF(: Band Pass Filter) 및 LPF(: Low Pass Filter)로 구현하였다. 제작 전 우주환경에 대한 사전 시뮬레이션 분석을 통하여 장비 오동작 가능성을 최소하였으며, 발사환경 시 발생하는 진동 및 우주 방사능에 의한 TID(: Total Ionizing Dose)에 대한 시뮬레이션을 통해 신뢰성 있는 상향주파수변환장치를 설계하였으며, 제작 후 주요 성능지표에 대해 만족여부 확인 및 사전 성능 시뮬레이션 결과와 비교하였다.

• 한국전자통신학회논문지
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• 제12권6호
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• pp.983-988
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• 2017

본 연구는 위성중계기용 SHF 대역 OMUX(: Output Multiplexer)의 설계 및 구현에 대해 기술하였다. SHF 대역 입력필터조립체는 LPF(: Low Pass Filter) + Manifolder + Channel Filter + LPF로 구성된다. 제작 전 우주환경에 대한 사전 시뮬레이션 분석을 통하여 장비 오동작 가능성을 최소하였으며, 발사환경 시 발생하는 진동에 대한 시뮬레이션을 통해 신뢰성 있는 OMUX를 설계하였으며, 제작 후 주요 성능지표에 대해 만족여부 확인 및 사전 성능 시뮬레이션 결과와 비교하였다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.263-265
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• 2003

The computation cost of image registration is affected by searching data size and space. This paper proposes an efficient image registration algorithm that uses multi-resolution wavelet decomposed image to reduce the data size search. The algorithm determines the correlation detection at low resolution on low-pass sub bands of wavelet and generate mask for higher resolution as part of a coarse to fine registration algorithm. The correlation matching is defined for coarse resolution similarity measurement, while mutual information (MI) is used at fine resolution. The results show that the new efficient mask-based algorithm improves computational efficiency and yields robust and consistent image registration results.

• Current Optics and Photonics
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• 제1권1호
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• pp.1-6
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• 2017

Degradation of bit-error-rate (BER), caused by atmospheric turbulence, seriously hinders the performance of coherent Free Space Optical (FSO) communication systems. An adaptive optics system proves to be effective in suppressing the atmospheric turbulence. The holographic modal wavefront sensor (HMWFS) proposed in our previous work, noted for its fast detecting rates and insensitivity to beam scintillation, is applied to the coherent FSO communication systems. In this paper, based on our previous work, we first introduce the principle of the HMWFS in brief and give the BER of the coherent FSO with homodyne detection in theory, and then analyze the improvement of BER for a coherent FSO system based on our previous simulation works. The results show that the wavefront sensor we propose is better for weak atmospheric turbulence. The most obvious advantages of HMWFS are fast detecting rates and insensitivity to beam scintillation.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2022년도 추계학술대회
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• pp.390-391
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• 2022

최근 미국에서는 민간 우주개발업체인 스페이스 x가 스타링크 사업을 통해 저궤도 위성을 발사할 계획이며, 현재까지는 900여개의 위성을 발사하였다. 구체적으로는 Ku 대역과 ka 대역을 갖는 위성을 운용할 계획이며 광대역 신호의 전송을 위해 V 대역을 갖는 7518개 위성을 고도 340 km에 발사할 계획이다. 따라서, 운항중인 선박에서도 저궤도 위성을 통한 무선통신이 가능하게 되며, 다양한 솔루션이 제공될 계획이다. 본 연구에서는 3차원 결합구조를 가지는 코프레너 선로 구조에 대한 RF 특성을 연구하였으며, 이를 통해 완전집적형 해양무선통신 반도체 SoC (System on Chip)를 구현하기 위한 RF소자의 개발가능성을 검토하였다.

• 한국실내디자인학회:학술대회논문집
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• 한국실내디자인학회 2007년도 춘계학술대회 논문집
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• pp.176-180
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• 2007

The stage space in theatre for the performance of a play requires two aspects of the physical space for a play and the image as the background or the theme of a play. This research focuses on the scene design that creates the background or the theme of a play and communicates it to the audience. The scene design is composed of various design elements of space and objects as the properties of a play. Design elements and the objects are the design languages in various form; plane, three-dimensional, multi-dimensional form. These design language have the significant meaning as a sign like human language. The scene design is completed with rhetorical expression for communication in theatre. This research defines the category of meaning that design elements of scene design can create and the rhetorical expression of the scene design language. King Lear directed by Robert G. Anderson was analyzed with the category of design elements as a sign and the pattern of the rhetorical expression. The scene design for a play is completed effectively by the rhetorical expression of design elements as the design language for communication with the audience in theatre.

• 한국콘텐츠학회논문지
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• 제7권10호
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• pp.115-125
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• 2007

본고는 유저 활동의 중요성, 유저간의 소통의 중요성, 플레이어 캐릭터의 성장과 변형을 통한 정체성 확립의 중요성을 중심으로 가상공간 커뮤니케이션의 특성을 분석하고, 이를 통해 원만한 사회관계를 활성화하고자 그 방안을 모색하고 유저들이 가상 사회 안에서 보다 책임 있는 행동을 유발하도록 제안하였다. 하루에도 수 천 명이 접속하여 교류하는 가상 공간에서 유저는 솔로스토리를 진행하며 타인과의 인간 관계를 통해 자신의 정체성을 찾게 된다. 무엇보다도 중요한 것은 가상 공간을 사회로 인식하고 타인에 대한 언행에 대해 연대 책임 의식을 갖는 유저들의 자세일 것이다.

• Journal of Communications and Networks
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• 제6권3호
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• pp.258-268
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• 2004

We demonstrate rotationally invariant space-time (ST) trellis codes with a 4-D rectangular signal constellation for data transmission over fading channels using two transmit antennas. The rotational invariance is a good property to have that may alleviate the task of the carrier phase tracking circuit in the receiver. The transmitted data stream is segmented into eight bit blocks and quadrature amplitude modulated using a 256 point 4-D signal constellation whose 2-D constituent constellation is a 16 point square constellation doubly partitioned. The 4-D signal constellation is simply the Cartesian product of the 2-D signal constellation with it-self and has 32 subsets. The partition is performed on one side into four subsets A, B, C, and D with increased minimum-squared Euclidian distance, and on the other side into four rings, where each ring includes four points of equal energy. We propose both linear and nonlinear ST trellis codes and perform simulations using an appropriate multiple-input multiple-output (MIMO) channel model. The 4-D ST codes constructed here demonstrate about the same frame error rate (FER) performance as their 2-D counterparts, having however the added value of rotational invariance.

• ETRI Journal
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• 제28권5호
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• pp.684-687
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• 2006

In this letter, we evaluate the system performance of a space-time block coded (STBC) multicarrier (MC) DS-CDMA system over a time selective fading channel, with imperfect channel knowledge. The average bit error rate impairment due to imperfect channel information is investigated by taking into account the effect of the STBC position. We consider two schemes: STBC after spreading and STBC before spreading in the MC DS-CDMA system. In the scheme with STBC after spreading, STBC is performed at the chip level; in the scheme with STBC before spreading, STBC is performed at the symbol level. We found that these two schemes have various channel estimation errors, and that the system with STBC before spreading is more sensitive to channel estimation than the system with STBC after spreading. Furthermore, derived results prove that a high spreading factor (SF) in the MC DS-CDMA system with STBC before spreading leads to high channel estimation error, whereas for a system with STBC after spreading this statement is not true.