Hoon Kim

Korea Advanced Institute of Science and Technology

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Y. C. Chung

Korea Advanced Institute of Science and Technology

Tianwai Bo

Ministry of Industry and Information Technology

V. Vuong

University of Bradford

Youngnam Han

Korea Advanced Institute of Science and Technology

S. H. Bae

Kangwon National University

Byung Gon Kim

Korea Advanced Institute of Science and Technology

Zaineb Al-Qazwini

National University of Singapore

Daeho Kim

Korea Research Institute of Standards and Science

Sang-Wook Han

Korea Institute of Science and Technology

Yukui Yu

Xidian University

Cooperative Institutions

Korea Advanced Institute of Science and Technology

164

Samsung (South Korea)

106

Korea University

Seoul National University

Yonsei University

Sungkyunkwan University

Hanyang University

Electronics and Telecommunications Research Institute

Incheon National University

Kyungpook National University

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Nonlinear Optical Crosstalk in Analog Phase-Modulated Wavelength-Division-Multiplexed Systems

Hoon Kim H.C. Ji Jun Haeng Lee

We report on the nonlinear inter-channel crosstalk in analog phase-modulated wavelength-division-multiplexed systems. The two-channel experimental results show a reduction of the crosstalk by ~15 dB, compared to intensity-modulated systems.

Crosstalk

Frequency-division multiplexing

Time-division multiplexing

Cross-phase modulation

10.1109/ofc.2008.4528101

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Citations (1)

Radio over RSOA-based WDM-PON

Hoon Kim

Reflective semiconductor optical amplifiers (RSOAs) have recently received a lot of attention as cost-effective upstream optical transmitters for wavelength-division multiplexed passive optical networks. However, the modulation bandwidth of this semiconductor device is limited to ~1.5 GHz and the device is largely used to accommodate <; 2.5-Gbps baseband signals. Recently we have proposed and demonstrated 10-Gbps operation of the RSOA using an optical delay interferometer (DI). The simple passive optical device acts as an optical equalizer as well as a vestigial side-band filter. In this paper, we present upstream transmission of 2-Gbps, 6-GHz radio signal using a directly modulated RSOA and a DI. Although the modulation bandwidth of our uncooled, transistor-outlook-can packaged device is only 1.2 GHz, not only does a 25-GHz DI equalize the limited bandwidth of the RSOA, but it also helps to generate a single sideband signal to make it resilient to the dispersion-induced RF fading.

Gigabit

Modulation (music)

10.1109/mwp.2011.6088714

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Dust Collection Performance of Bag Filters in Rice Processing Facilities

Transactions of the ASABE (2019)

Hoon Kim Oui Woung Kim Hyo Jai Lee Jae Hwan Ahn

Highlights The rice dust collection performance of bag filters was investigated. The pressure drop and rice dust collection efficiency were measured with various parameters. Correlation equations are suggested for the pressure drop across a clean filter medium and across the dust cake. Abstract. Because rice dust constitutes a form of air pollution, bag filters are widely used in rice processing facilities. Rice dust has various particle sizes, and the dust concentration in air is low with rice dust. Research on the rice dust collection performance of bag filters is necessary for effective dust collection in rice processing facilities. The objective of this study was to investigate the rice dust collection performance of bag filters. The pressure drop and rice dust collection efficiency were measured with various face velocities, dust concentrations, and fabric filter media. The dust collection efficiency decreased slightly with increases in the face velocity and in the maximum pressure drop in normal conditions. In addition, correlation equations of the pressure drop across a clean filter medium and across the dust cake are suggested to predict the pressure drop in overloaded conditions in rice processing facilities. The average error was 20.2%, and it decreased with increasing pressure drop. Using the correlation equations, bag filters can be managed to remove the deposited dust before the pressure drop significantly increases or reaches its maximum value. Keywords: Bag filter, Dust collection efficiency, Pressure drop, Rice dust.

Dust collector

10.13031/trans.13456

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A Study on the Luminance Measuring Method and Regional Measured Results for Outdoor Signboards with Lighting Considering Light Pollution

Journal of the Korean Institute of Illuminating and Electrical Installation Engineers (2012)

Hyunji Kim Hoon Kim

To suggest lighting regulations to prevent light pollution, domestic and international standards were analyzed and the luminance of outdoor signboards of main street at night was measured. In addition, to regulate the methods of luminance measurement, experiments on the measuring distance and direction from the signboards were conducted. The regulations were set as maximum luminance for outdoor signboard lightings of channel letter type, and limitations were suggested on each of the four lighting zones.

Light Pollution

10.5207/jieie.2012.26.10.001

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A Survey on Fairness Provision Schemes for Federated Learning Networks

The Journal of Korean Institute of Communications and Information Sciences (2023)

Yeong-chan Kim Hoon Kim

연합학습(Federated Learning, FL) 네트워크는 데이터 등 인공지능 학습 자원이 부족한 단말들이 연합학습을 지원하는 서버와 연결되어 협력적으로 학습모델 파라미터를 완성해 가는 것으로, 데이터를 직접 보내지 않고 학습 성능이 개선될 수 있는 효과적인 방법이다. 연합 학습이 여러 단말의 참여를 바탕으로 하여 참여자 선택, 참여자간 비중 반영 등에서의 형평성 문제가 제기된다. 본 연구에서는 이와 같은 연합학습에서의 형평성 문제에 대한 연구 동향과 주요기법을 소개한다. 또한 비례 균등 형평성 알고리즘을 적용하는 방안을 제시한다.

Federated Learning

10.7840/kics.2023.48.6.677

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On Decision Aided Carrier Phase and Frequency Offset Estimation in Coherent Optical Receivers

Journal of Lightwave Technology (2013)

Adaickalavan Meiyappan Pooi Yuen Kam Hoon Kim

We investigate carrier estimation (CE) for coherent optical receivers where the received signal is impaired by additive white Gaussian noise, laser phase noise, and frequency offset. Best practical 4-, 8-, and 16-point constellations are identified. A generalized differential encoding rule for signal constellations is presented. Performance of our complex-weighted decision-aided maximum-likelihood (CW-DA-ML) phase noise and frequency offset estimator is analyzed at low signal-to-noise ratio (SNR) and the optimal filter lengths are found. CW-DA-ML CE is put in perspective with respect to two fundamental estimators in the literature: (i) differential frequency estimator followed by block M th power phase estimator (DiffFE- M th CE), and (ii) fast Fourier transform based frequency estimator followed by block M th power phase estimator (FFTbE- M th CE), in terms of laser linewidth tolerance, frequency estimation range and speed, SNR threshold, and cycle slip probability. CW-DA-ML CE is 2.5 and 10.5 times faster than DiffFE- M th CE in 4 phase-shift keying and 16 quadrature amplitude modulation signals, respectively, at a 1-dB system penalty for a bit-error rate of 10 ^-3 . Our CE has lower cycle slip probability and transmission overhead than DiffFE- M th and FFTbE- M th CE. Hence, our CE is shown to be favourable in pilot-assisted (PA) systems. A PA CW-DA-ML CE is introduced and shown to be robust against time-varying frequency offset with minimal training overhead. Analog-to-digital convertor quantization error on our CE performance is also addressed.

10.1109/jlt.2013.2260723

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Citations (41)

Optical RZ transmitter using directly modulated laser driven by NRZ signals

OECC 2010 Technical Digest (2010)

Zaineb Al-Qazwini Hoon Kim

We propose and demonstrate a simple and cost-effective method to generate optical return-to-zero signals using a directly-modulated laser and a delay interferometer. The laser is driven with 9B/10B-coded non-return-to-zero signals.

Source

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Optimal Cache Resource Allocation Based on Deep Neural Networks for Fog Radio Access Networks

網際網路技術學刊 (2020)

Sovit Bhandari Hoon Kim Navin Ranjan Hong Zhao Pervez Khan

Cache resource allocation is of great significance for the advanced cellular networks, especially for fog radio access networks (F-RANs). Many cache resource allocation schemes have been proposed to increase the performance of F-RANs optimally. However, it is still challenging to apply these schemes and attain live performance in F-RAN systems since most of them need accurate and real-time data which shows radio link information or other network information. This paper presents a cache resource allocation strategy based on deep neural network (DNN) along with the training method required to train the neural networks. Simulation results in terms of DNN accuracy are shown to validate that the performance of proposed method approaches to that of the conventional iterative method in most cases.

Resource Management

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Mitigation of scintillation in FSO communication using a temporally and spatially incoherent spectrum-sliced light source

Optics Letters (2022)

Daeseong Lee V. Vuong Hoon Kim

We propose and demonstrate a temporally and spatially incoherent spectrum-sliced light source for scintillation mitigation in free-space optical (FSO) communications. For the temporal incoherence, we utilize the spectrum-sliced incoherent light (SSIL) modulated by gain-saturated reflective semiconductor optical amplifiers for data modulation and the suppression of excess intensity noise inherent in a narrowband incoherent light source. We then employ offset launching from a single-mode fiber to a multi-mode fiber to add the spatial incoherence to the SSIL source. The experimental demonstration shows that this temporally and spatially incoherent light is effective in mitigating scintillation. For example, this light source reduces the transmitter power required to achieve a bit-error ratio of 10-3 by ∼6 dB in comparison with the laser source. This is an ∼3 dB larger reduction in the transmitter power than the reduction achieved by a temporally incoherent light source.

Narrowband

Free-Space Optical Communication

10.1364/ol.455825

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A Low-Complexity Carrier Phase and Frequency Offset Estimator with Adaptive Filter Length for Coherent Receivers

Adaickalavan Meiyappan Pooi Yuen Kam Hoon Kim

We present a low-complexity joint carrier phase and frequency offset estimator, with adaptive sample averaging length according to the modulation format, signal-to-noise ratio, and laser linewidth. No preset parameters are required. It also achieves complete frequency estimation range.

Carrier frequency offset

10.1049/cp.2013.1594

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