• Journal of Communications and Networks
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• v.12 no.1
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• pp.11-18
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• 2010

Diversity-multiplexing tradeoff (DMT) is an efficient tool to measure the performance of multiple-input and multiple-output (MIMO) systems and cooperative systems. Recently, cooperative multicast system with wireless network coding stretched tremendous interesting due to that it can drastically enhance the throughput of the wireless networks. It is desirable to apply DMT to the performance analysis on the multicast system with wireless network coding. In this paper, DMT is performed at the three proposed wireless network coding protocols, i.e., non-regenerative network coding (NRNC), regenerative complex field network coding (RCNC) and regenerative Galois field network coding (RGNC). The DMT analysis shows that under the same system performance, i.e., the same diversity gain, all the three network coding protocols outperform the traditional transmission scheme without network coding in terms of multiplexing gain. Our DMT analysis also exhibits the trends of the three network coding protocols' performance when multiplexing gain is changing from the lower region to the higher region. Monte-Carlo simulations verify the prediction of DMT.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.07a
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• pp.306-307
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• 2015

본 논문에서는 ATSC (Advanced Television Systems Committee) 3.0 시스템을 위한 LDM (Layered Division Multiplexing) 기술을 제안하고, 그 성능을 전산실험을 통해 분석한다. 제안된 LDM 시스템은 기존의 TDM (Time Division Multiplexing) / FDM (Frequency Division Multiplexing) 기술에 비해 약 3 에서 9 dB 의 성능 이득을 나타낸다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.9
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• pp.797-801
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• 2013

Visible light communication (VLC) is a rapidly growing area of research and applications, due to the potential and predicted high efficiency of bandwidth. One of the key challenges in VLC technology is the choice of devices which are going to be deployed VLC features. Smartphone rationally uses the most widely deployed visible light sensor i.e. image sensor in camera, which could be used to receive the intensity modulated data. Image sensor based VLC system would be the most deployable scenario but initially the capacity was not much attractive compared with photodetector based VLC system. Here, the spatial multiplexing is proposed in MIMO based VLC system to increase the system capacity by utilizing the property of spatial separation of optical light sources in smartphone's camera module. The active pixels of imaging plane act as the multiple receivers which could be able to use on MIMO spatial multiplexing to enhance the system performance.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.5
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• pp.205-215
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• 2006

In this paper an optical power meter using Hadamard transform, which can be used in multiple channel optical elements alignment system, is proposed. A traditional optical power meter in multiple channel optical elements alignment system is able to judge how well the elements are aligned each other by measuring optical power of the first and the last two channels with at least two detectors. It has critical drawback that the alignment accuracy per channel is dependent on the number of detectors. The proposed optical power meter can get noise reduction by the Hadamard transform based multiplexing technique. The Hadamard transform based multiplexing technique using spatial light modulators is distinguished by the best enhancement of signal-to-noise ratio (SNR) for the reconstructed signals. Moreover, the noise reduction increases with increasing the order of multiplexing, namely the number of optical element channels. The proposed system is implemented by PDLC (Polymer Dispersed Liquid Crystal) mask which is operated by electric filed and generates optimal multiplexing patterns based on the Hadamard transform and single detector. It means that we obtain not only the each channel's optical power of multiple channel elements at once but also the best enhancement of SNR with single detector. Experimental results show that the proposed optical power meter is suitable for an active optical alignment system for multiple channel optical elements.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.338-341
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• 2005

This paper proposes a control system for a Galvano meter which can be used in angle multiplexing for a holographic data storage. Due to the small angle multiplexing selectivity and the exposure/delay time of a CCD camera, the system needs to be controlled to satisfy the performance specification. First, the mathematical model is derived by combining the electrical and mechanical dynamic equations. Then, the obtained model was tuned by the experiments. Finally, a PID controller using DSP was designed and was applied the holographic system. From this approach, we successfully meet the performance specification.

• Current Optics and Photonics
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• v.1 no.5
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• pp.440-455
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• 2017

In this paper, we carry out a performance analysis of a two-user free-space optical (FSO) communication system with photodetector multiplexing, in which the two users are defined as the primary user (PU) and secondary user (SU). Unlike common single-user FSO systems, our photodetector multiplexing FSO system deploys a shared detector at the receiver and enables PU and SU to send their own data synchronously. We conduct the performance analysis of this FSO system for two cases: (1) in the absence of background radiation, and (2) in the presence of background radiation. Decision strategies for PU and SU are presented according to the two scenarios above. Exact and approximate conditional symbol-error probability (SEP) expressions for both PU and SU are derived, in an ideal channel with no fading. Average SEP expressions are also presented in the no-background-radiation scenario. Additionally, in some particular cases where the power ratio tends to 0.5 or 1, approximate SEP expressions are also obtained. Finally, numerical simulations are presented under different conditions, to support the performance analysis.

• Proceedings of the Optical Society of Korea Conference
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• 1998.08a
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• pp.218-219
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• 1998

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.128-129
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• 2002

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2339-2345
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• 2020

Radiation imaging systems consisting of a large number of channels greatly benefit from multiplexing methods to reduce the number of channels with minimizing the system complexity and development cost. In conventional pixelated radiation detector modules, such as anger logic, is used to reduce a large number of channels that transmit signals to a data acquisition system. However, these methods have limitations of electrical noise and distortion at the detector edge. To solve these problems, a multiplexing concept using a digital signal encoding technique based on a time delay method for signals from detectors was developed in this study. The digital encoding multiplexing (DEM) method was developed based on the time-over-threshold (ToT) method to provide more information including the activation time, position, and energy in one-bit line. This is the major advantage of the DEM method as compared with the traditional ToT method providing only energy information. The energy was measured and calibrated by the ToT method. The energy resolution and coincidence time resolution were observed as 16% and 2.4 ns, respectively, with DEM. The position was successfully distributed on each channel. This study demonstrated the feasibility that DEM was useful to reduce the number of detector channels.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.4
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• pp.652-657
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• 2003

In this paper, Adaptive Modulation and Coding (AMC) is combined with Multiple Input Multiple Output (MIMO) multiplexing to improve the throughput performance of AMC. In addition, a system that adopts Selection Transmit Diversity (STD) in the AMC-MIMO multiplexing system is proposed. The received SNR is improved by adopting STD techniques. And it increases probability of selecting MCS (Modulation and Coding Scheme) level that supports higher data rate. This leads to an increased throughput of the AMC-MIMO system. STD in our simulation selects 2 transmission antennas from 4 antennas and AMC-MIMO multiplexing process operates with the selected antennas. The computer simulation is performed in flat Rayleigh fading channel. The results show that the proposed system achieves a gain of 1Mbps over the AMC-MIMO multiplexing system with the same number of antennas at 15dB SNR.