Maximum Ratio Transmission 기법의 MIMO 다중경로 페이딩 채널로의 확장

이경규,이원철,신요안 崇實大學校 生産技術硏究所 2001 論文集 Vol.31 No.-

To effectively improve capacity on fading channels in the third generation and beyond mobile communication systems that require high quality and capacity, spatial diversity schemes utilizing MIMO (Multi-Input Multi-Output) concepts have been identified as an efficient way of improving the capacity without expanding the bandwidth. Among various MIMO spatial diversity schemes, MRT (Maximum Ratio Transmission) which maximizes signal-to-noise ratio at the reception has been recently proposed. In this paper, we extend the conventional MRT scheme which is restricted to flat fading channels to MIMO multipath fading channels, and analyze the bit error rate performance.

비등간격 입력을 갖는 변형된 Bernstein Polynomial과 이의 신경망적 해석

신요안 崇實大學校 生産技術硏究所 1994 論文集 Vol.24 No.-

This paper is concerned with a construction of modified Bernstein polynomials which allow unequally-spaced input points with slight constraints on their positions in the domain. We develop approximation theorems for the modified Bernstein polynomials and show that with slight constraints called well-positioned input points, the new polynomials can approximate arbitrary continuous functions defined on compact subsets in Euclidean spaces. The modified Bernstein polynomials have much plausible interpretation in the connectionist framework than classical ones discussed by Baldi.

OFDM 시스템을 위한 Look-Up Table 기반의 적응 사전왜곡 알고리즘

최종희,신요안 崇實大學校 生産技術硏究所 2001 論文集 Vol.31 No.-

In this paper, we propose a LUT (Look-Up Table) based adaptive predistorter for OFDM (Orthogonal Frequency Division Multiplexing) systems employing HPA (High Power Amplifier). In particular, an efficient and fast initialization algorithm for the LUT is proposed. Moreover, the proposed adaptive algorithm is based on the fixed point iteration method for updating the signal amplitudes and phases in the LUT accroding to time-variant property of the HPA. The simulation results show that the proposed scheme efficiently compensates for the nonlinearity of the HPA even with small sized LUTs and small number of iteration for the adaptive algorithm. Also the simulation indicates that the proposed scheme is quite beneficial for practical hardware implementation of the predistorters.

MIMO 시스템에서의 APP 디코딩의 성능

이경규,김산해,김홍철,이원철,신요안 崇實大學校 生産技術硏究所 2002 論文集 Vol.32 No.-

MIMO (multi-input multi-output) systems can achieve high data capacity and high data rate in the third generation (3G) or beyond-3G mobile communication systems. To effectively improve the performance of MIMO systems, new detection schemes which can mitigate mutual interferences from multiple transmit antennas, are highly required. In this paper, we consider a posteriori probability (APP) type detection schemes for the MIMO systems, and compare with other sub-optimal detection schemes based on zero forcing (ZF) and minimum mean square error (MMSE) - ordered successive interference cancellation (OSIC). Simulation results show that the APP outperforms ZF-OSIC and MMSE-OSIC, while the performance discrepancy becomes smaller as the number of receive antennas increases.

중압 배전망에서의 전력선 통신을 위한 OFDM 기법의 성능 분석

임장규,김산해,장희동,이원철,신요안 崇實大學校 生産技術硏究所 2002 論文集 Vol.32 No.-

Recently, PLC (Power Line Communication) on medium voltage power lines have been gaining much attention for high data rate access networking. In this paper, we evaluate the performance of OFDM (Orthogonal Frequency Division Multiplexing) schemes on medium voltage power line channels in the frequency range up to 20 ㎒. We analyze fading characteristics of multi-path channel models for medium voltage power lines, and simulations have been carried out for the OFDM using adaptive bit loading scheme. Simulation results indicate that the OFDM schemes with the adaptive bit loading show good bit error rate performance under harsh medium voltage power lines channel.

무선인지 시스템에서 협력 스팩트럼 센싱 성능 향상을 위한 경판정 결합 기법

신오순,신요안,Shin, Oh-Soon,Shin, Yo-An 한국통신학회 2009 韓國通信學會論文誌 Vol.34 No.2a

무선인지 기술은 비어있는 스펙트럼을 검출하고 이를 사용하여 통신하는 기술로서 주파수 부족 현상을 해소하기 위한 방안으로 활발히 연구가 이루어지고 있다. 무선인지 기술을 도입하기 위해 핵심적인 요소는 부사용자가 주사용자의 통신을 방해하지 않으면서 주파수 사용의 효율성을 최대화하는 것이다. 이를 위해서는 주사용자의 스펙트럼 점유 여부를 정확하게 판단하는 센싱 기술이 필요하다. 각각의 부사용자가 독립적으로 센싱을 수행하는 개별 센싱 기술은 음영지역, 잠복 터미널 문제 등이 있어서 최근 여러 부사용자가 협력하여 센싱을 수행하는 협력 스펙트럼 센싱 기술이 주목받고 있다. 본 논문은 협력 스펙트럼 센싱에 있어서 각 부사용자가 개별적으로 센싱한 결과의 경판정 값을 취합하여 이를 효과적으로 결합하는 방법을 제안한다. 제안한 방법은 과거의 협력 센싱 결과를 이용하여 각 부사용자의 개별 센싱 결과에 신뢰도를 나타내는 가중치를 부여하여 결합함으로써 협력 센싱 성능을 향상시킨다. 다양한 환경에서 제안한 방법의 검출 성능을 평가하여 기존의 가중치 없는 경판정 결합 방법과 비교한 결과를 제시한다. Cognitive radio is considered as a promising solution to scarce spectrum problem. The primary object of cognitive radio is to increase spectral efficiency, while causing limited interference to primary users who are using the spectrum. Hence, an essential part of cognitive radio systems is spectrum sensing which determines whether a particular spectrum is occupied or not by a primary user at a particular time. However, sensing decision of each individual secondary user alone may not be reliable enough due to shadowing and multipath fading of wireless channels. The so called hidden terminal problem makes the problem even worse, possibly yielding undesired interference to the primary users. Recently, cooperative spectrum sensing is emerging as a remedy to these problems of individual sensing. Cooperative sensing allows a group of secondary users to share local sensing information to extract a global decision with high fidelity. In this paper, we investigate a cooperative spectrum sensing algorithm based on hard decisions of local sensing outcomes. Specifically, we propose an effective scheme for combining local decisions by introducing weighting factors that reflect reliability of the corresponding secondary user. Through computer simulations, the performance of the proposed combining scheme is compared with that of the conventional scheme without weighting factors in various environments.

Cognitive Radio 시스템을 위한 간섭온도 인지 기반의 적응전송 기법

홍민기,김재운,김현욱,신요안,Hong, Min-Ki,Kim, Jae-Woon,Kim, Hyun-Wook,Shin, Yo-An 한국통신학회 2007 韓國通信學會論文誌 Vol.32 No.9c

In this paper, we present an adaptive transmission system model to establish the baseline for wireless adaptive transmission using CR (Cognitive Radio) systems, and propose an adaptive transmission scheme based on IT (Interference Temperature) cognition for CR systems in the presented system environment. The proposed CR adaptive transmission scheme is the method that provides the CR user with the maximum transmit power in the range of not causing any interference to the incumbent user and guaranteeing the optimal throughput by applying CR-AMC (CR-Adaptive Modulation and Coding) in the given channel state. Simulation results show that in case of using the proposed CR adaptive transmission scheme, there is little degradation of BER performance, while causing no interference to the incumbent user. At the same time, the proposed scheme guarantees the optimal throughput to the CR user in the given channel state. 본 논문에서는 CR (Cognitive Radio) 시스템의 무선 적응전송에 대한 연구 기반을 마련하기 위해 CR 시스템 환경 및 시나리오 모델을 제시하고, 제시된 시스템 환경 모델에서 CR 시스템을 위한 간섭온도 인지 기반의 적응 전송 기법을 제안한다. 제안된 CR 적응전송 기법은 CR-APC (CR-Adaptive Power Control)를 사용하여 주 사용자에게 간섭 영향을 미치지 않는 범위 내에서 CR 사용자에게 최대 전송전력을 제공하고, CR-AMC (CR-Adaptive Modulation and Coding)를 적용하여 주어진 채널 상태에서 CR 사용자에게 최적의 전송률을 보장할 수 있는 방식이다. 모의실험 결과, 제안된 CR 적응전송 기법을 사용한 경우 주 사용자에게는 간섭 영향을 거의 미치지 않아 비트오율 성능 열화가 거의 없었으며, CR 사용자에게는 주어진 채널 상태에서 최적의 전송률을 보장할 수 있음을 확인할 수 있다.

A Complex Radial Basis Function Network Based Equalizer for Nonlinear Digital Satellite Communication Channels

Yo An Shin,Byung Moon Yoon,Young Son Lim 대한전자공학회 1996 대한전자공학회 워크샵 Vol.1996 No.-

Enhancing Safety Awareness through Cigarette Waring Pictures: An Investigative Study

( Son-yo-han ),( Han-myoung-jun ),( Song-ji-hoon ),( Shin-ha-yeon ),( An-sun-min ),( Min-seung-nam ) 한국감성과학회 2023 한국감성과학회 국제학술대회(ICES) Vol.2023 No.-

This study focuses on depicting images, like those on cigarette packs, on safety and health signs. To this end, a survey was conducted, followed by a word cloud analysis. The results indicated that illustrating the cost of cigarettes on safety and health signs helps to increase awareness of the associated risks.

Effects of SnO₂ layer coated on carbon nanofiber for the methanol oxidation reaction

Kim, Dong Ha,Shin, Dong-Yo,Lee, Young-Geun,An, Geon-Hyoung,Han, Jeong Hwan,Ahn, Hyo-Jin,Choi, Byung Joon Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.16

<P><B>Abstract</B></P> <P>Carbon nanofibers (CNFs) are used as active materials for electrodes in various energy devices, such as lithium ion secondary batteries, supercapacitors, and fuel cells. Recent studies have shown that nanoscale coatings on carbon nanotubes increase the output and lifespan of these devices owing to the improvement of their mechanical and chemical properties. Among various coating methods, atomic layer deposition (ALD) can adjust the thickness of the coating layer conformally without any directional growth. Therefore, ALD can coat particles with high aspect ratios, such as CNFs, even at nanometer levels of thickness.</P> <P>In this work, we grew two different morphologies of a SnO<SUB>2</SUB> layer on CNF. We used two types of ALD equipment: flow-type ALD (static ALD), and fluidized bed reactor-type ALD (dynamic ALD). Static ALD could form a discontinuous SnO<SUB>2</SUB>, while a uniform SnO<SUB>2</SUB> layer was formed by pre-inserting a layer of Al<SUB>2</SUB>O<SUB>3</SUB>. On the other hand, dynamic ALD formed a uniform SnO<SUB>2</SUB> layer without pre-insertion of an Al<SUB>2</SUB>O<SUB>3</SUB> layer. X-ray photoelectron spectroscopy analysis revealed that both Sn<SUP>4+</SUP> and Sn<SUP>2+</SUP> were present in SnO<SUB>2</SUB> on the CNF deposited by static ALD, probably due to the formation of an interfacial layer between the SnO<SUB>2</SUB> and CNF. When the dynamic ALD method was used, only Sn<SUP>4+</SUP> was present in the SnO<SUB>2</SUB> on CNF. Cyclic voltammetry analysis was performed to characterize the electrochemical properties of the SnO<SUB>2</SUB>-coated CNF as an electrode on a direct methanol fuel cell. It was revealed that the discontinuous SnO<SUB>2</SUB> on CNF deposited by static ALD showed the highest current efficiency as well as enhanced electrocatalytic stability.</P>