Space-frequency multiuser detection for multirate MC-CDMA systems

Multicarrier code-division multiple-access (MC-CDMA) is a promising candidate for future wireless communication systems. In this paper, after the development of a unified signal model that applies to different multirate MC-CDMA schemes (multicode and variable spreading factor (VSF)), a novel space-frequency minimum mean-squared error based hybrid serial/parallel interference cancellation receiver (SF-MMSE/HIC) is developed. The signal processing of this new detector is jointly carried out in space and frequency domain which leads to the advantage of combating the interference resulting from different sources simultaneously. Furthermore, the impact of subcarrier interleaving is investigated for VSF MC-CDMA systems. Based on the characteristic function (CF) of a complex Gaussian random vector (CGRV), a bit error rate (BER) performance analysis method is developed. Several representative simulation examples of the detector are provided to demonstrate the performance of the proposed receiver. Moreover, results indicate that taking into account the subcarrier interleaving gain, VSF MC-CDMA systems can offer similar performance as that of multicode systems.