| Summary: | 碩士 === 國立中山大學 === 電機工程學系研究所 === 86 ===
In mobile radilo systems, a multiple access interference (MAI) problem arises from the simultaneous transmisions of signals associated with several active users that share the same carrier, and an equalization problem which occurs in the frequency selective fading channel. An attractive solution to the MAI problem is Code Division Multiple Access (CDMA) .However, it is has a wide bandewidth, and when the bandwidth exceeds the coherence bandwidth of the channel, the fading tends to be frequency selective. Therefore, it need to use complicate equalization procedures to offer the possibility of coolecting signal energy from defferent paths.
In the multi-carrier of Orthogonal Frequency Division Multiplex (OFDM) systems ,each subcarrier can be considered as a narrowband channel and a simple one-tap equalizer can be used to combat channel fading. Recently, some proposals for a combination OFDM and CDMA have been made by Yee, Fazel and others[4],[10] The combined system ,called Multi-carrier CDMA system, has an attracted significant research interest. Since the complexity of the optimum Maximum Likelihood detector (MLD) in the Multi-carrier CDMA system grows exponentially with the number of user, simpler suboptimum detectors are therefore considered in practiacal applications.
In this thesis,we propose a new detection method in the Multi-carrier CDMA system. We will compare this mothod with other detection methods adn analyze tis performance in a Rayleigh fading channel. Furthermore, we apply this detection method to the multi-stage detector to improve the performance. Simulation results will demonstrate the performance improvement of the proposed detection method.
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