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이종망 환경에서 능동 안테나 시스템 기반의 셀간 간섭 제어 방법
김병준(Byoung-June Kim),박해성(Haesung Park),김덕경(Duk Kyung Kim) 한국통신학회 2014 韓國通信學會論文誌 Vol.39 No.9(통신이론)
최근 급증하는 데이터 트래픽에 효율적으로 대응하기 위해 매크로 기지국 영역에 매크로 기지국과 같은 주파수를 사용하는 소형 기지국이 공존하는 이종망에 관한 연구가 활발하게 진행 중이다. 이때, 매크로셀로부터 소형셀로의 간섭을 줄이기 위해 시간 영역에서 ABS (Almost Blank Subframe)을 이용한 enhanced Inter-cell Interference Coordination (eICIC) 기법이 제안되어 있다. 그러나 간섭 문제 해결을 위해 데이터를 전송하지 않는 서브프레임들이 발생함으로써 매크로셀 입장에서는 자원 낭비 문제가 발생한다. 본 논문에서는 능동 안테나 시스템 (AAS)과 Genetic Algorithm (GA)을 이용하여 소형 셀 방향으로 안테나 이득을 줄인 매크로 기지국의 3D 섹터 빔을 형성하여 셀간의 간섭신호 세기가 감소 되도록 하고 데이터 전송에 모든 서브프레임을 이용하여 낭비되는 자원이 없도록 한다. LTE -Advanced 시스템 레벨 시뮬레이터를 통해 기존 eICIC 기법과의 성능을 비교 분석하며, 제안된 기법의 성능 향상을 확인한다. To cope with recently increasing demand for data traffics, heterogeneous networks have been actively studied, where small cells are deployed within a macro cell coverage with the same frequency band. To mitigate the interference from the macro cell to small cells, an enhanced Inter-cell Interference Coordination (eICIC) technique has been proposed, where ABS (Almost Blank Subframe) is used in time domain. However, there is a waste of resource since no data is transmitted in a macro-cell in ABS. In this paper, we propose a new interference management method by using a 3D sector beam based on Active Antenna System (AAS), where Genetic Algorithm (GA) is applied to reduce the antenna gain toward a small-cell. With the proposed scheme, the macro-cell and small cells can transmit data at the same time with the AAS antenna pattern generating reduced interference to small cells. The performance of the proposed scheme is evaluated by using an LTE-Advanced system level simulator.
CIGS 태양전지의 소수캐리어 확산 거리에 대한 새로운 측정 방안 연구
이돈환(Don Hwan Lee),김영수(Young Su Kim),모찬빈(Chan Bin Mo),남정규(Jung Gyu Nam),이동호(Dong Ho Lee),박성찬(Sung Chan Park),김병준(Byoung June Kim),김동섭(Dong Seop Kim) 한국태양광발전학회 2014 Current Photovoltaic Research Vol.2 No.2
Minority carrier diffusion length is one of the most important parameters of solar cells, especially for short circuit current density (Jsc). In this report, we proposed the calculating method of the minority carrier diffusion length (Ln) in CIGS solar cells through biased quantum efficiency (QE). To verify this method"s reliability, we chose two CIGS samples which have different grain size and calculated Ln for each sample. First of all, we calculated out that Ln was 56nm and 97nm for small and large grain sized-cell through this method, respectively. Second, we found out the large grain sized-cell has about 7 times lower defect density than the small grain sized-cell using drive level capacitance profiling (DLCP) method. Consequently, we confirmed that Ln was mainly affected by the micro-structure and defect density of CIGS layer, and could explain the cause of Jsc difference between two samples having same band gap.
플라즈마 화학기상증착법에 의해 제조된 TiN 피막의 색깔, 구조 및 특성에 미치는 반응기체 유량비의 영향에 대한 연구
이정중,김병준,나재웅,이동각 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.12
TiN coatings were deposited on M2 high speed steel by the plasma enhanced chemical vapor deposition(PECVD) process using a gas mixture of TiCl₄, NH₃, H₂ and Ar with various NH₃/TiCl₄ flow rate ratios(Q(NH₃)/Q(TiCl₄)), and the effect of the flow rate ratio on the color, structure and property of TiN coatings has been investigated. Structural and compositional analyses were conducted by X-ray diffraction method(XRD), transmission electron microscopy(TEM), Rutherford backscattering spectroscopy(RBS), as well as Auger electron spectroscopy(AES). At low flow rate ratios, bright gold coatings with high hardness and low resistivity could be formed. At higher ratios, on the other hand, coatings of brown color were formed. They showed porous microstructures with considerably decreased microhardness. Results from structural and compositional analyses showed that a large amount of oxygen had been substitutionally incorporated in the brown color TiN during the deposition process to form titanium oxynitride. It has been found, however, that the color change of TiN coatings is closely related with the surface roughness of the coating rather than with the presence of oxygen in the coating.