A MIMO approach for increasing spectrum efficiency of OFDM-CDMA system with pilot tone

In this paper, MIMO OFDM-CDMA downlink scheme is proposed as a solution for increasing the spectrum efficiency of the OFDM-CDMA downlink system with pilot tone and threshold detection combining (optimum TDC). The new presented system with MIMO included uses space-time block coding applied to two, three and four transmit antennas. BER (Bit Error Rate) performance in the case of Ricean frequency selective fading is evaluated for the original system as well as for the one with MIMO included. For that reason an adequate simulation model is developed. The results show that for the same data rate the proposed system with two times less subcarriers, i.e. narrower occupied frequency band provides better BER performance than the OFDM-CDMA system with pilot tone.