New channel estimation schemes exploiting reliable decision feedback symbols for OFDM systems = OFDM 시스템에서의 신뢰도가 높은 되먹임 심볼을 이용한 새로운 채널 추정 기법

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The conventional pilot-aided orthogonal frequency division multiplexing (OFDM) systems use the fixed number of pilots to estimate the channel. In this thesis, we propose new channel estimation schemes that exploit reliable decision feedback symbols in the OFDM systems. The reliability of the decision feedback symbols depends on its error rate. In other words, the reliable symbol has a low symbol error rate. The process of the proposed scheme is follows. In the first place, the channel estimation process is performed by the conventional pilot-aided estimation scheme. Next, the estimated channel equalizes the channel distortion, and then the symbol detection process is operated. From the decision symbols, quasi-pilots are extracted based on their reliability. The quasi-pilot means the decision symbols that will be employed as pilots to estimate the channel. The reliable quasi-pilots are the symbols whose subcarrier’s channel gain is greater than the threshold value. These reliable quasi-pilots and pilots are used to estimate the channel again. This method gives more accurate estimated channel and lower bit error rate (BER) than conventional method. In order to prove these results, we calculate the Cramér Rao Lower Bound (CRLB) of estimated channel, and computer simulations are performed. Simulation results show that the mean square error of estimated channel is closed to CRLB, and BER of the proposed scheme is lower than conventional method.
Park, Dong-Joresearcher박동조researcher
한국과학기술원 : 전기및전자공학전공,
Issue Date
249571/325007  / 020043234

학위논문(석사) - 한국과학기술원 : 전기및전자공학전공, 2005.8, [ [iii], 74 p. ]


decision feedback; channel estimation; OFDM; reliable; 되먹임; 신뢰도; 채널추정; 직교 주파수 다중분할 시스템

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