Reduced complexity blind 2D RAKE receiver for CDMA

Abstract

We previously presented a blind 2D RAKE receiver for (direct sequence spread spectrum) CDMA that cancels strong multi-user access interference (MAI) and optimally combines multipath. After passing the output of each antenna through a matched filter based on the spreading waveform of the desired user, one estimates the signal plus interference spatio-frequency correlation matrix during that portion of the bit interval where the fingers of the RAKE occur, and the interference alone spatio-frequency correlation matrix during that portion of the bit interval away from the fingers. A reduced complexity scheme that outperforms the previous algorithm in a MAI dominant environment is presented based on a data adaptive transformation to a beamspace of dimension equal to the effective number of spatial degrees of freedom taken up by the desired user's multipath.