• Journal of Communications and Networks
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• v.15 no.5
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• pp.457-463
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• 2013

In recent days, cooperative diversity and communication security become important research issues for wireless communications. In this paper, to achieve low probability of interception (LPI) and high throughput in the cooperative single-carrier frequency division multiple access (SC-FDMA) system, a new physical layer transmission scheme is proposed, where a new encryption algorithm is applied and adaptive modulation is further considered based on channel state information (CSI). By doing so, neither relay node nor eavesdropper can intercept the information signals transmitted from user terminal (UT). Simulation results show above new physical layer transmission scheme brings in high transmission safety and secrecy rate. Furthermore, by applying adaptive modulation and coding (AMC) technique according to CSI, transmission throughput can be increased significantly. Additionally, low peak-to-average power ratio (PAPR) characteristic can still be remained due to the uniform distribution of random coefficients used for encryption algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.6
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• pp.1334-1340
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• 2003

In this paper, We have proposed an Heterodyne technique to generate millimeter-wave signal. Microwave signals in cellular broadband mobile communication networks and distributed networks can favorably be generated and distributed by optical techniques. In principle, these techniques have already been investigated for optical control of phase- array antennas, characterization of photo-detector and phase locking of millimeter-wave oscillators and now being applied to wireless communications. The generation and transmission of millimeter-wave radio signals by optical means is of interest for future pico-cell broadband mobile communication system, especially for systems operating at frequencies of 300Hz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.466-471
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• 2003

In this paper, we introduce a new photodetector configuration that automatically aligns its receiving angle to the incident signal light. Around the central photodiode that receives the optical signal, 4 photodiodes on ${\Phi}$-axis and 2 photodiodes on $\theta$-axis are installed in order to drive 2 step motors in f and $\theta$ direction. The photodetector completes angle-alignment within Isec to the signal light from an arbitrary direction.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.9
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• pp.849-854
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• 2016

5G New Radio Access Technology(: RAT) is studied by many researchers because the current radio frequency is insufficient to accommodate the increased mobile communication data traffic. However, there are few researches to study on the issue whether the wired mobile network can accommodate the new RAT. Therefore, in the paper, the study on the issue whether the Radio over Fiber(: RoF) system can accommodate the new RATs such as millimeter wave communication, terahertz communication, and optical wireless communication. As a result of the study, only millimeter wave communication deserve to be considered in ten years and even RoF system may not support the increased bandwidth of the millimeter wave communication when beamforming is used.

• Journal of Advanced Information Technology and Convergence
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• v.8 no.2
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• pp.147-157
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• 2018

In this study, we analyzed an outdoor visible light communication system and implemented it through a simulation. We designed a Reed-Solomon encoder, a variable interleaver structure, and set it to the Institute of Electrical and Electronics Engineers (IEEE) 802.15.7 PHY I specification mode. We also analyzed the performance of an additive white gaussian noise (AWGN) channel environment using a root-raised-cosine (RRC) filter, implemented a MATLAB simulation and analyzed its performance. The results showed a requirement for an additional signal-to-noise ratio (SNR) of approximately 1.5 dB in a 3-ray multipath visible light channel environment than in an AWGN environment.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.5
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• pp.143-150
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• 2018

With the rapid development of RF based high speed wireless communication technology, devices that can be applied to IoT networks based on RF bandwidth are rapidly spreading, nevertheless, the development speed of the RF communication is not possible to keep up with the spread of the RF band for wireless communication. In this situation, OWC technology that uses visible light source as a transmitter is attracting attention as a technology that can overcome the band exhaustion problem of RF based wireless communication technology. Although, due to the distortion of the LED illumination shape by camera exposure time and LED blinking period, the LED illumination detection rate is degraded and the RoI setting is inaccurate. In this paper, we propose an adaptive median filter applied LED illumination detection algorithm for low rate CamCom, it is possible to detect a clear RoI and LED illumination. This research will be able to play a role as a complementary material of RF based wireless communication technology efficiently.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.425-430
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• 2013

Robust and high speed underwater communication is severely limited when compared to communications in terrestial. In free space, RF communication operates over long distances at high data rates. However, the obstacle in seawater is the severe attenuation due to the conducting nature. Acoustic modems are capable of long range communication up to several tens of kilometers, but it has low data-rate, high power consumption and low propagation speed. An alternative means of underwater communication is based on optics, wherein high data rates are possible. In this paper, the characteristics of underwater channel in the range of visible wavelength is investigated. And the possibility of optical wireless communication in underwater is also described. The LED-based transceiver and CMOS sensor module are integrated in the system, and the performance of image transmission was demonstrated.

• Information and Communications Magazine
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• v.28 no.12
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• pp.50-60
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• 2011

Visible light communication(VLC) is one type of short-range, optical, and wireless communication system utilizing light emitting diode(LED) and laser diode(LD) as optical source. In a VLC system, visible light is used as a transmission medium and used to illuminate. Using VLC has a lot of advantages: it is harmless to human body; it transmits with high power, and it has excellent security, a high data rate, and a license free frequency band. With such a unique blend of communication and illumination in one system, the most common application would be an indoor environment. We aim at reviewing key issues in VLC network such as : FOV(field of view), priority MAC, cooperative MAC, link switching, LED-ID technique, cell site diversity, and link recovery.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2766-2770
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• 2009

Recently, the Green IT is noticed because of the effects of greenhouse gas emissions, a drain on natural resources and pollution. In this paper, Visible Light Communication (VLC) systems with Turbo Coded scheme using LED is proposed and simulated in an optical wireless channel. As a forward error correction scheme to reduce information losses, turbo coding was employed. To decode the codewords, The Map (Maximum a Posteriori) algorism and SOVA (Soft Output Viterbi Algorithm) is used. The above mentioned schemes are described and simulation results are analyzed. As using turbo codes scheme, BER performance of proposed VLC systems is improved about 5 [dB].

• Journal of Advanced Navigation Technology
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• v.23 no.1
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• pp.61-68
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• 2019

Underwater wireless light communication system is quite necessary to retrieve recorded data from underwater devices or the black box without taking back it body. In this paper, a research on the light sensor technology in underwater wireless light communication under turbid sea was studied. A noise source under turbid sea for light communication was analysed, and a sensor system for light sensing using the reference light signal to remove the noises and to improve the output swing power wasstudied. Also, an underwater communication system was manufactured to validate the good performance of the development system, and using the system, the good performance of the developed system was validated through the light communication test in the tank containing the turbid sea water was presented.