MC-CDMA In Mobile Communications

MC-CDMA is one of the key technologies in the next generation. It combines the advantages of OFDM and CDMA. It can convert the frequency selective channel propagation of the broadband to flat channel of the subcarrier. It has adaptive flexibility, high capacity, high bandwidth efficiency and interference robustness. This paper deeply research on the synchronization, peak-to-average power ratio, multiuser detection of the current MC-CDMA system. The main content is:1. We proposed a new time acquisition method, called adaptive subsection correlation time acquisition method of MC-CDMA system, the subsection correlation length is adapted according to the probable frequency offset. It is better than fixed correlation time acquisition method(SC method) . This advantage is shown that in AWGN and multipath channel, its estimation mean bias and estimation error square root is smaller than the SC method.2. Clipping is used to reduce the PAPR(Peak-to-Average Power Ratio) of multicarreir GMSK signal. The conclusion is that the moderate clipping introduces small performance degradation.3. We propose a new spreading sequence design scheme. In the uplink, using Golay sequence, CInew Sequence or Zadoff-Chu sequence, in the downlink, using WH sequence as the spreading sequence, we can control the PAPR of MC-CDMA below 7dB and BER below lE-3(SNR=20dB).4. We propose that the best detection method for the uplink MC-CDMA system is Decorrelating-Parallel Interference Cancellation(DEC-PIC) multiuser detection, and the best detection method for the downlink MC-CDMA system is Minimum Mean Square Error Combining (MMSEC)single user detection. We further analyze the effect of channel estimation error on multiuser detection. The conclusion is that it is only suitable for the occasion where channel estimation error is little.