| Summary: | 碩士 === 國立臺北科技大學 === 電機工程系研究所 === 95 === The thesis focused on the performance of OFDM based MC-CDMA systems in Rayleigh slow fading channel. OFDM is a digital multi-carrier modulation scheme, which uses a large number of closely-spaced orthogonal sub-carriers. Each sub-carrier is modulated with a conventional modulation scheme like phase-shift keying and quadrature amplitude modulation to maintain the similar data rates compared to the conventional single-carrier modulation schemes under the same bandwidth. In implementaion, the OFDM signals are generated from the Fast Fourier transform (FFT) algorithm. The MC-CDMA system utilizes mutually orthogonal spreading codes to distincguish user data. The OFDM based MC-CDMA system shares the benefits of both OFDM and MC-CDMA systems. However, in the Rayleigh fading channel the system performance is degraded by the disruption of the user orthogonality. In this thesis, we’ve derived the bit error rate formula of the single user detection for the above system in Rayleigh fading channel. For the multiuser case, we explored two complexity MUD schemes. One is the lower complexity MUD scheme such as PIC, SIC, and the other is the higher performance but higher complexity MUD scheme such as MMSE, PDA. To provide a reliable performance analysis of multi-user detectors in OFDM based MC-CDMA system, we compared the approximated bit-error-probability formulas with bit error rates simulated by computer.
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