Improved robust blind multiuser detection in flat fading nonGaussian channels

In many realistic wireless channels the ambient noise is known through experimental measurements to be decidedly nonGaussian, due largely to impulsive phenomenon. Frequently, code-division multiple-access (CDMA) transmissions are made over fading channels. Further, blind multiuser detection is effective for reducing intersymbol interference (ISI) and improving system throughput. Hence, this paper presents an improved robust blind multiuser detection technique based on subspace approach, which requires only the signature waveform and the timing of the desired user in order to demodulate that user´s signal, in direct-sequence CDMA flat-fading channels with impulsive noise. An M-estimator is proposed to robustify the blind multiuser detector for combating multiple access interference and impulsive noise in synchronous CDMA flat-fading channels. The approach is corroborated with simulation results. Simulation results show that, in highly impulsive noise, the proposed detector with significant performance gain outperforms the linear decorrelating detector, the Huber and the Hampel M-estimator based multiuser detectors. Finally, it was shown that the robust blind multiuser detection technique could be applied to both synchronous and asynchronous flat-fading CDMA channels.