Performance of the MIMO-MC-CDMA System with MMSE Equalization

Multipath fading and spectral crowding are the major challenges in dealing higher data rate in future broadband wireless communication system. Multi-carrier Modulation like Multicarrier code division multiple access (MC-CDMA) can tackle the problem and provide higher data rate for future wireless communication system. However, through a frequency selective fading channel, the subcarriers in MC-CDMA signal have different amplitude levels and phase shifts which result in loss of the orthogonality among users and generates Multiple access interference (MAI). To combat the MAI, various amplitude and phase equalizing techniques such as Maximum Ratio Combining (MRC), Equal Gain Combining (EGC), Orthogonal Restoring Combining (ORC), Threshold Orthogonal Restoring Combining or Minimum Mean Square Error (MMSE) may be used. Out of these MMSE offers better performance since the MMSE criterion is applied independently on each subcarrier. Further improvement in performance is possible through space–time block coding, which offers maximum diversity gain and multiplexing gain. This paper combines MC-CDMA with MMSE equalization and space–time block coding which proves to be a powerful physical layer solution in combating delay spread and inter symbol interference (ISI).