Abstract
Recently, the popular mobile communication systems are expected to support several kinds of service, like voice, video, and data transmission. Hence, the users may transmit their signal in different data rates. In this thesis, we introduce two kinds of accessing method, MC access and MPG access, and choose Code Division Multiple Access (CDMA) by use of direct-sequence spread spectrum (DSSS) to demodulate a multi-rate system.Besides, the most important shortcomings of CDMA system is the multiple access interference (MAI). The multiple access interference is produced because there are multiple users using the same frequency band simultaneously. This interference will degrade the performance of the system. Hence, in order to suppress the interference, the parallel interference cancellation (PIC) scheme is proposed in this thesis. This scheme uses the adaptive iteration to improve the performance of receiver. By using the PIC scheme, the interference projection method is introduced to estimate the transmitting amplitude for every user.During signal transmission, the receiver will receive many replicas of the transmitted signal with slightly time difference and amplitude decay because of the multi-path fading. This may cause the difficulty in demodulating the received signal. A method which can estimate path numbers and delay time simultaneously is introduced in this thesis. We can use this information together with the PIC scheme to obtain a more practical communication receiver.Finally, the multi-rate system using PIC scheme with path and delay estimator are discussed. Some results of simulation are given at last to illustrate the performance of MC and MPG system, and the performance of path and delay estimator.