Adaptive blind 2D RAKE receiver for multiuser detection

A novel blind 2D RAKE receiver for multiuser detection with interference rejection in DS-CDMA cellular communication systems is presented. The receiver consists of an array of receiving antennas and each antenna is connected to K filters where K is the number of users. The filter outputs are combined and despread to suppress both multiuser interference and intersymbol interference. The outputs are subsequently fed into a decorrelator to further suppress the multiuser interference. The complex weighting factors of the tap delays of these filters are adaptively determined by a hybrid combination of the constant modulus algorithm and the decision-directed algorithm. No training sequence is required, and beamforming and equalization are performed simultaneously. The blind adaptive scheme converges approximately after 100 symbol periods when the input SNR of the desired signal is 10 dB. A 30 dB reduction of the output mean square error or, equivalently, an 30 dB improvement of the output SINR is obtained even when the maximum difference of the received signal power is up to 9 dB.