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주파수 선택성 다중경로 페이딩 채널에서 Near/Far 영향을 받는 Multi-Carrier CDMA Trellis Coded 16 QAM 시스템의 성능 해석
노재성,강희조,김춘길,김언곤,조성준 대전산업대학교 반도체기술연구소 2000 半導體技術硏究所報 Vol.2 No.-
본 논문에서는 주파수 선택성 다중경로 페이딩과 Near/Far 영향을 받는 Multi-Carrier CDMA 시스템의 성능을 분석하였다. 성능 분석을 위해 사용한 파라미터들은 Multi-Carrier의 수, 다중사용자의 수, RAKE 수신기의 가지수, 주파수 선택성 다중경로 페이딩의 감쇄지수, 그리고 CDMA 다중사용자의 분포와 세기이다. Multi-Carrier CDMA 시스템에서 Near/Far 영향을 분석하기 위하여 3가지의 간섭 분포 모델을 설정하였다. 첫 번째 모델은 다중사용자가 간섭과 대 반송파 비인 I/C를 -4 dB에서 4dB 사이에서 2dB씩의 차이를 가지며 20%씩 균일하게 분포하는 경우이다. 두 번째 모델은 다중사용자가 I/C 비를 -2 dB에서 2 dB 사잉에서 2 dB씩의 차이를 가지며 33.3%씩 균일하게 분포하는 경우이다. 그리고 세 번째 모델은 모든 다중사용자가 I/C가 0 dB로 신호 전력과 간섭 전력이 동일하게 분포하며 전력이 완전하게 제어된 경우이다. 그리고 본 논문에서는 주파수 선택성 다중경로 페이딩의 영향을 감소시키기 위하여 RAKE 수신기를 채용한 Multi-Carrier CDMA 시스템을 제안하였다. 이 시스템에서는 제시한 3가지의 간섭 분포 모델중에서 세 번째 모델(완전 전력제어가 된 경우)이 가장 좋은 성능을 나타내었고, 간섭파의 전력과 신호파의 전력차이가 적을수록 희망 신호에 영향을 주는 간섭 신호의 전력량이 적어서 Multi-Carrier CDMA 시스템의 성능이 향상됨을 알 수 있었다. The performance of a multi-carrier CDMA system is analyzed considering frequency selective multipath fading and Near/Far effects. The number of multicarrier, multiuser, and arms of RAKE receiver, and the decay ratio of frequency selective multipath fading are used as a parameter for the performance analysis. Moreover, the distribution and the strength of multiuser interference are also considered. To evaluate the Near/Far effects in a multi-carrier CDMA system, three distribution models are assumed. In the first model, Interference to Carrier Ratio, I/C, ranges from -4 dB to 4dB, and at each 2 dB interval, 20% of multiuser is assumed to be uniformly distributed. In the second one, I/C ranges from -2 dB to 2dB, and 33.3% of multiuser is assumed to be equally dispersed at each 2dB interval. The third model is 0 dB of I/c, that is, with perfect power control, multiuser are assumed to be evenly located. In this paper, multi-carrier CDMA system adopting RAKE receiver is proposed to mitigate the frequency selective multipath fading. From the results, the third model(i.e. perfect power control) shows the best perfomance, and the narrower range of I/C causes the less effects to the desired signal, which reads to the better performance.
Performance Analysis of 32-QAPM System with MRC Diversity in Rician Fading Channel
Chun, Jae Young,Kim, Eon Gon The Korea Institute of Information and Commucation 2016 Journal of information and communication convergen Vol.14 No.4
In this study, the performance of a 32-quadrature amplitude position modulation (QAPM) system is analyzed under a Rician fading channel condition when the maximal ratio combining (MRC) diversity technique is used in the receiver. The fading channel is modeled as a frequency non-selective slow Rician fading channel corrupted by additive white Gaussian noise (AWGN). QAPM is available to improve BER performance without amplifying transmit power, and MRC diversity makes the performance improvement of QAPM system even bigger by intentionally maximizing SNR. Error performances are shown for the 32-QAPM system and a 32-phase silence shift keying (PSSK) system in order to examine the effects of fading severity, for various values of the Rician parameter, K. The dependence of error rates on MRC diversity is also analyzed. The simulation results show that the BER performance of the 32-QAPM system is better than that of the 32-PSSK system under the above mentioned conditions.
Distributed Computer Control of Air Volume System using Variable Speed Fan Drive
Eon-Bin Song,Chun-Sam Kim,Yoon-Ho Kim,Byung-Do Yoon 전력전자학회 1992 ICPE(ISPE)논문집 Vol.1992 No.4
The distributed computer control of variable air volume system using variable speed fan drive is presented. The control system provides a hierarchical and distributed functions. The inverter can be programmable and communicate with the computer system in real time. The configuration of control system is proposed and the control program is developed. The new variable air volume system offers the improvement of indoor air quality and energy savings in office buildings.<br/>
Chun Hua Wei,Seong Eon Ryu 한국구조생물학회 2016 Biodesign Vol.4 No.3
Classical protein tyrosine phosphatases and dual specificity phosphatases share a common structural fold and constitute a major part of the protein tyrosine phosphatase family that dephosphorylate proteins involved in critical cellular processes such as cell growth and differentiation, immune regulation, and brain function. The active site of the enzyme family involves residues in several loops and the conformation of the active site residues and loops are critical in enzyme catalysis. A large number of structural studies have yielded various structures of classical protein tyrosine phosphatases and dual specificity phosphatases, which exhibit mobility of active site residues and loops depending on substrate/ligand binding and regulation states. The mobility is likely to play a role in the catalytic efficiency and cellular regulation processes of the enzymes. In this review article, we analyze currently available structures of classical protein tyrosine phosphatases and dual specificity phosphatases to understand the nature of structural mobility of the enzyme active site and its relationship with enzyme activity and cellular regulation.