OFDM-CDMA versus DS-CDMA: performance evaluation for fading channels

In code division multiple access (CDMA) systems direct sequence (DS) applying maximum ratio combining (MRC) at the receiver has achieved high interest for mobile communications. A second and rather novel technique is orthogonal frequency division multiplexing (OFDM) applying maximum-likelihood detection (MLD) at the receiver. In this paper the performance of both techniques is compared considering the mobile radio environment. The analytical results for both DS-CDMA and OFDM-CDMA are confirmed by Monte Carlo simulations. The analysis enables a performance comparison between the DS-CDMA system and the OFDM-CDMA system with respect to the demands of low complexity receivers which is important for system design. The results show that OFDM-CDMA outperforms DS-CDMA in terms of spectral efficiency.