• 한국전자통신학회논문지
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• 제5권5호
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• pp.428-434
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• 2010

본 논문에서는 유선 통신의 광 네트워크와 무선 통신의 Zigbee의 통합으로 신뢰성 있는 전송이 가능한 지능형 SAN(Ship Area Network) 네트워크 모델을 제시하고, SAN 통합 네트워크와 연결된 각종 센서와 제어기를 구성 및 관리 하고 원격제어를 하기 위한 모듈을 구현한다. 이는 선박 내부의 주요구획 및 장비에 대한 실시간 모니터링 및 열악한 선박 내부의 작업환경을 감시하여 선박의 사고예방에 도움을 줄 수 있을 것이며, 선박 내부의 노동 경감, 운항 안전성 향상, 운항 경제성 향상 등에 활용할 수 있을 것이다.

• Journal of Communications and Networks
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• 제17권6호
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• pp.634-646
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• 2015

Assuming perfect channel state information (CSI) at the transmitter and receiver, the optimization problem of maximizing the minimum Euclidean distance between two received signals by a linear precoder is considered for multiple-input multiple-output (MIMO) systems with arbitrary dimensions and arbitraryary quadrature amplitude modulation (QAM) input. A general precoding framework is first presented based on the Gram matrix, which is shown for 2-dimensional (2-D) and 3-dimensional (3-D) MIMO systems when employing the ellipse expanding method (EEM). An extended precoder for high-dimensional MIMO system is proposed following the precoding framework, where the Gram matrix for high-dimensional precoding matrix can be generated through those chosen from 2-D and 3-D results in association with a permutation matrix. A complexity-reduced maximum likelihood detector is also obtained according to the special structure of the proposed precoder. The analytical and numerical results indicate that the proposed precoder outperforms the other precoding schemes in terms of both minimum distance and bit error rate (BER).

• 한국정보통신학회논문지
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• 제7권6호
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• pp.1334-1340
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• 2003

본 논문에서는 밀리미터파 대역의 신호 발생을 위한 헤테로다인 방식을 제안하였다. 향후, 무선 이동통신, 광대역 통신망에 사용되어질 밀리미터파 신호는 전기적 요소의 한계로 광학적인 요소에 의해 신호를 생성하는 방법을 연구 중에 있다. 광학적인 요소에 의한 여러 가지의 연구들이 광검출기의 기능, 밀리미터파 대역의 발진기의 개발 등이 이루어지고 있으며, 무선 통신망에 적용하기 위한 소자기술 등이 발전되고 있다. 본 논문에서는 향후 밀리미터파 대역에서 사용되어질 LMDS(Local Multi-point Distribution Service) 등의 시스템에서 광원으로 응용 가능한 방법을 제안하였다.

• Journal of the Optical Society of Korea
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• 제19권6호
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• pp.586-591
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• 2015

In recent years, along with the rapid development of LED technology, indoor positioning systems based on visible light communication (VLC) have been researched. In this paper, we propose an accurate indoor positioning method using white-light LEDs and a dual image sensor. Indoor LED lights are located at the ceiling in a room and broadcast information on their positions using VLC technology. A mobile device with a dual image sensor receives LED position information by VLC and estimates its position and azimuth angle. Simulation and experimental results are given to show the performance of the proposed indoor positioning system.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.95-96
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• 2006

A variety of systems have been attempted for effective urban management. In this paper, we introduce integrated urban management system (IUMS), which mainly consists of optical line terminal (OLT), optical network terminal (ONTs) and wireless access points (APs), by combining passive optical network (PON) and radio over fiber (RoF) technologies so as to take advantages of both two systems. Further, several IUMS services including disaster detection and prevention system (DDPS), bus information system (BIS) and real time location system (RTLS) are demonstrated in order to employ IUMS for the realization of future ubiquitous city (U-city).

• 전자공학회논문지
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• 제53권2호
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• pp.3-9
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• 2016

본 논문에서는 무선 및 이동통신을 위한 클라우드 무선 가입자 네트워크를 지원하는 프론트홀에서 무선 라디오파의 광섬유 전송망의 기술을 제안하고 구현한다. 하향 링크는 OFMD (orthogonal frequency division multiplexing) (O기법을 사용하였고 상향방향의 전송은 SC-FDMA (single carrier-frequency multiple access) 방식으로 구현하였다. 64, QAM, 16QAM, QPSK 등 다양한 변조 방식에 대해 시스템 파라메터를 도출하고 측정치를 기반으로 성능을 분석하였다.

• ETRI Journal
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• 제44권6호
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• pp.966-976
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• 2022

Optical wireless communication, or free space optics, is a promising solution for backhauls in sixth-generation mobile systems. However, the susceptibility of optical links to weather conditions has led to FSO links being furnished with radio frequency (RF) backups. These Hybrid FSO/RF systems provide enhanced link availability but lead to RF resource wastage. Cognitive radio technology, in contrast, is well known for its optimal use of RF resources and may be combined with an FSO link to create a Cognitive Hybrid FSO/RF system. This work uses such a system to analyze a configuration for a mobile backhaul in sixth-generation mobile systems. This configuration can seamlessly coexist with established large scale RF cellular networks. The performance of this configuration is analyzed with respect to outage probability and average bit error by considering the impact of optical channel turbulence, misalignment loss, RF interference, and noise. Mathematical closed-form expressions are verified by simulations.

• 한국전자파학회논문지
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• 제10권1호
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• pp.54-62
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• 1999

본 논문에서는 실내 무선광연결에 사용될 수 있는 차동검출기에서 잡음광의 결합비와 차동이득비에 따른 신호대 잡음비의 개선에 대하여 분석하고 실험하였다. 차동검출기는 2개의 포토다이오드와 1개의 차동증폭기 로 이루어지며, 차동이득비가 잡음광의 결합비와 같을 때 잡음광이 소거되어 약 20 dB의 선호대잡음비를 개 선하였다. 차통검출기는 실내의 무선광연결에서 주변의 강한 잡음광의 영향을 개선하거나 인접된 채널광에 의한 혼선의 영향을 없애는 데에 매우 효과적이다. 이 방법은 선호광과 유사한 파장의 잡음광이 발생하는 경 우에도 잡음개선효과가 았다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권3호
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• pp.1136-1151
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• 2018

This paper proposes a new hybrid scheme to decrease the high peak to average power ratio (PAPR) of optical orthogonal frequency division multiplexing (OFDM) signals in visible light communication (VLC) systems. The PAPR causes nonlinear signal distortions and high power requirements for the VLC transmitter (light emitting diode, LED). The proposed method is applicable for both direct current-biased optical OFDM (DCO-OFDM) and asymmetrically clipped optical OFDM (ACO-OFDM). In the proposed scheme, the PTS method is firstly modified to fit both optical OFDM approaches transmission and then combined with signal clipping method for further PAPR reduction and bit error rate (BER) improvement of the VLC system. The performance of hybrid scheme has been evaluated and compared with the original OFDM based VLC system, conventional PTS and clipping methods. The results show that the hybrid scheme outperforms other methods in terms of both the PAPR reduction and BER performance.

• 한국군사과학기술학회지
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• 제27권2호
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• pp.238-246
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• 2024

Modern military operations rely heavily on broadband communication and data transmission. Recently, the rising use of intelligent unmanned technology necessitates more frequencies. Free-space optical(FSO) communication can offer high-data-rate communications with high security and no need for licensing. Therefore, the FSO communication holds significant interest and potential in the defense industry. In this paper, we present design of a FSO communication terminal taking Korean domestic weather conditions into account. The domestic atmospheric attenuation is analyzed using several models and two-year meteorological information for a city in Korea, and this analysis is utilized to design the FSO communication terminal. The design results were verified using an FSO communication test bed, and we achieved an Ethernet bandwidth of approximately 1.86 Gbps at a distance of 1.3 km with the optical amplifier output power of the test bed set to about 20 dBm.