On the performance of multicarrier CDMA (MC-CDMA) systems with transmit diveristy

Abstract

Transmit diversity techniques combined with error control coding have explored new scheme called space-time (ST) block coding. Because of the orthogonal structure of the ST block code, the maximum-likelihood decoding could be used at the receiver without complicated non-linear operation. The space-frequency (SF) block coding and space-time-frequency (STF) block coding are developed on the basis of the ST block coding, but the encoding is carried out in different domains. In this thesis we use these three diversity schemes to multicarrier (MC)-CDMA system. The advantage and disadvantage of different transmit diversity schemes are discussed. Computer simulations are presented for BPSK signals to evaluate the performances. Another topic we discuss is multiuser detection. An iterative multiuser receiver is proposed for an asynchronous DS-CDMA system with transmit diversity. In the proposed system, decorrelating detector, space-time decoder and parallel interference canceller are used iteratively to remove the multiuser interference (MUI). It is shown that the system performance improves with the number of iterations. However, simulation results show the performance margin diminishes with number of iterations.