Performance of multicarrier CDMA technique combined with space-time block coding over Rayleigh channel

For future wideband wireless networks, space diversity schemes relying on multiple antennas at the receiver and/or at the transmitter are very attractive to combat fading and improve the transmission performance. In this paper, the multi-carrier code division multiple access (MC-CDMA) technique combined with space-time block code (STBC) is analyzed in the case of two transmit antennas and N_τ (equal to one or two) receive antennas to provide a diversity order of 2N_τ. In particular, four single-user detection techniques are studied and compared in the synchronous case of the downlink operating over the frequency selective Rayleigh channel. Among all these techniques, simulations results show that the minimum mean square error (MMSE) combining offers the best efficiency. Moreover, it is demonstrated that multi-user MC-CDMA systems performances are improved thanks to the transmit diversity exploited by STBC and the receive diversity exploited by multiple receive antennas.