Adaptive Blind CDMA Receivers Based on ICA Filtered Structures

Abstract

Code division multiple access (CDMA) is a channel access method adopted by various radio technologies worldwide. In particular, CDMA is used as an access method in many mobile standards such as CDMA2000 and WCDMA. We address the problem of blind multiuser equalization in the wideband CDMA systems in the noisy multipath propagation environment. Herein, we propose three new blind receiver schemes based on variations of independent component analysis within several filtering structures. These adaptive blind CDMA receivers do not require knowledge of the propagation parameters or spreading code sequences of the users--they primarily exploit the natural assumption of statistical independence among the symbol signals. We also develop three semi-blind adaptive detectors by incorporating new adaptive methods into the standard Rake receiver structure. Extensive comparative case studies based on bit error rate performance are carried out as a function of (i) the number of users, (ii) the number of symbols per user, and (iii) the signal-to-noise ratio. The conventional detectors include the baseline linear minimum mean squared error detector. The results show that the proposed methods outperform other detectors in estimating the symbol signals from the received mixed CDMA signals. Moreover, the new blind detectors mitigate the multiaccess interference in CDMA.