| Traditional Code Division Multiple Access (CDMA) communication system belongs to narrow-band spreading spectrum system, whose data rate is so low that it can not be competent to new generation mobile communication systems that need high data rate. And Multi-carrier CDMA (MC-CDMA) technology based on the combination of the advantage of CDMA and OFDM technologies can convert the frequency selective channel propagation of the broadband to flat channel of the sub-carriers. It has adaptive flexibility, high capacity, and high bandwidth efficiency and interference robustness.Firstly, the propagation characteristics of mobile radio channels are discussed in this paper. Secondly, the fundamental principle of OFDM technology and three schemes of multi-carrier CDMA technology are introduced. Then MC-CDMA is proposed to be the subject of the study. Thirdly, the structure of transmitter/receiver of MC-CDMA system is given and the simulation model of MC-CDMA is founded with MATLAB. Based on this model, the performance of MC-CDMA system is analyzed and compared with that of OFDM system by simulation. Finally, an adaptive modulation algorithm for MC-CDMA is presented. Simulation proves that BER (bit-error-ratio) performance of MC-CDMA system is improved by the use of this adaptive modulation algorithm. |
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