Blind Detection in CDMA Systems Using Nonparametric Likelihood Ratio Criterion

In this paper we present a new approach for blind suppression of interference in a direct sequence code division multiple access (DS-CDMA) communication system. We use an independent component analysis (ICA) based method to detect the signal of the desired user. Classical ICA algorithms rely on simple assumptions on the source statistics. Therefore such algorithms can perform suboptimally or even fail to produce the desired source separation when the assumed statistical model is inaccurate. We propose to use ICA using nonparametric likelihood ratio (NLR) criterion as a tuning element which will be added to minimum mean-square error (MMSE) based detector. This method is completely blind to the sources and have the ability to separate the mixed sources simultaneously. We compare this new receiver structure named MMSE-nonparametric ICA with two other receiver structures, namely RAKE-fast ICA and MMSE-fast ICA. Simulation results show that the new technique provides better interference suppression than the other two methods.