| Summary: | 碩士 === 國立清華大學 === 動力機械工程學系 === 98 === Because the Code Division Multiple Access (CDMA) mobile communication system, has the code division scheme in comparison with traditional frequency division multiple access (FDMA) and time division multiple access (TDMA), therefore, the system will have more serious multiple access interference (MAI). In order to cancel the interference, a interference cancellation scheme in demodulating is required. In this thesis the CDMA systems with direct-sequence (DS) spread spectrum modulation is discussed and the multi-carrier transmission and the orthogonal frequency division multiplexing (OFDM) to against the frequency-selective fading channel are used. In the receiver, the successive interference cancellation (SIC) scheme is used to reduce the interference, and then improves the performance of
receiver.
By using the SIC scheme efficiently, the transmitting amplitude for every user must be known. However, the receiver will receive many replicas of the transmitted signal with slightly time difference and amplitude decay because of the multi-path fading during signal transmission. This may cause the difficulty in estimating the amplitude. A method which can estimate the amplitude and channel gain simultaneously is introduced in this thesis. We can use this information together with the SIC scheme and the technique of maximum ratio combining (MRC) or equal gain combining (EGC) to obtain a more practical communication receiver.
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