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전형구(Hyoung-Goo Jeon),김경수(KyoungSoo Kim),안지환(JiWhan Ahn),Erchin Serpedin 한국통신학회 2008 韓國通信學會論文誌 Vol.33 No.3A
본 논문에서는 다중 경로 레이리 페이딩 시변 채널 환경의 Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (MIMO-OFDM) 시스템에서 효율적으로 채널 변화를 추적할 수 있는 채널 추적 방식을 제안하였다. 제안된 방식은 시변 채널에 대응할 수 있도록 블라인드 채널 예측기를 설계하였다. 또한 주파수 영역 채널 추정이 Minimum Mean Square Error (MMSE) 시간영역 채널 추정과 결합되어 있으며 이 방식은 매 OFDM 심벌마다 역행렬을 계산할 필요가 없다는 장점이 있다. 컴퓨터 시뮬레이션 결과 제안된 방식은 기존의 Li방식[4] 보다 성능이 우수함을 보였다. 도플러 주파수 100㎐ 및 10-4 BER에서 Eb/No이득이 약 2.5 ㏈ 정도 되었다. 도플러 주파수가 200㎐일 때 그 성능의 차이는 더욱 커졌다. This paper proposes an efficient scheme to track the time variant channel induced by multi-path Rayleigh fading in mobile wireless Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (MIMO-OFDM) systems with null sub-carriers. In the proposed method, a blind channel response predictor is designed to cope with the time variant channel. The proposed channel tracking scheme consists of a frequency domain estimation approach that is coupled with a Minimum Mean Square Error (MMSE) time domain estimation method, and does not require any matrix inverse calculation during each OFDM symbol. The main attributes of the proposed scheme are its reduced computational complexity and good tracking performance of channel variations. The simulation results show that the proposed method exhibits superior performance than the conventional channel tracking method [4] in time varying channel environments. At a Doppler frequency of 100㎐ and bit error rates (BER) of 10-4, signal-to-noise power ratio (Eb/N0) gains of about 2.5㏈ are achieved relative to the conventional channel tracking method [4]. At a Doppler frequency of 200㎐, the performance difference between the proposed method and conventional one becomes much larger.
Performance Enhancement of the Joint CDMA/PRMA Protocol Using Pseudo Bayesian Approach
Kim, Kyungsoo,Kook, Kwangho,Lee, Kangwon,Ahn, Jiwhan,Choi, Jeongrak 한국경영과학회 1999 韓國經營科學會誌 Vol.24 No.1
A new channel access function is proposed to enhance the performance of the joint CDMA/PRMA It is obtained in consideration of the number of terminals in reservation mode and the number of terminals in contention mode whose probability distribution is estimated by applying pseudo Bayesian approach Simulation results show that the performance of the joint CDMA/PRMA can be improved by applying new channel access function under voice-only traffic and mixed voice/random-data traffic