Blind 2-D RAKE receivers based on space-time adaptive MVDR processing for IS-95 CDMA system

Abstract

We previously presented a blind 2D RAKE receiver for CDMA that cancels strong multi-user access interference and optimally combines the desired user's 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 space-frequency (space-time) correlation matrix during that portion of the bit interval where the fingers of the RAKE occur, and the interference alone space-frequency (space-time) correlation matrix during that portion of the bit interval away from the fingers. The vector of space-frequency (space-time) weights yielding the optimum signal to interference plus noise ratio for bit decisions is the "largest" generalized eigenvector of the resulting matrix pencil. A reduced complexity scheme was also previously 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. A decision directed adaptation of this scheme for a commercial cellular CDMA system based on the IS-95 standard is presented herein. Only the uplink from mobile to base is considered.