| Summary: | 碩士 === 國立高雄第一科技大學 === 電腦與通訊工程所 === 92 === The OFDM is a multi-carrier modulation technique. It inherits the robustness against the inter-symbol interference（ISI）effect, high spectrum efficiency and enhanced anti-multipath fading ability. The CDMA is a spread spectrum communication technique. It inherits the anti-interference capability and against the inter-channel interference（ICI）. Except the encryption, it although has the higher user capacity than other conventional multiple access techniques.
OFDM-CDMA is a technology that combines OFDM and CDMA. It inherits the anti-multipath fading ability of OFDM technology as well as the high user capacity of CDMA. Since OFDM-CDMA owns a lot of advantages, such as high spectrum efficiency, high capacity and low bit-error-rate (BER), and so on, many researchers have devoted their efforts on this new technology. And it is expected to be the possible solution of the fourth-generation mobile communication systems.
In this thesis our discussion is focused on the OFDM-CDMA system, and evaluate the performance in multi-path fading environment. The multi-carrier OFDM system is first analyzed over a multi-path fading channel. And then the performance of OFDM-CDMA is evaluated. The simulation result is compared with that of a direct-sequence (DS) CDMA system. The major emphasis of our investigation includes multi-path fading, clipping effect, different types of guard, delay spread, orthogonality and system capacity.
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