Multi-user detection in OFDM systems using CDMA and multiple antennas

In this paper multiuser detection in OFDM systems is examined. The separation of concurrently transmitted signals is based on space division and code division multiple access (SD/CDMA). The achievable bit error ratio and the peak to average power ratio (PAPR) are evaluated for different spreading strategies. A novel time domain spreading technique for OFDM systems is proposed for which the PAPR is independent of the processing gain. The examined OFDM techniques are compared with single-carrier transmission using equalization in the frequency domain (SC/FDE), which shows strong similarities to OFDM systems.