A low-complexity space-time RAKE receiver for DS-CDMA communications

An algorithm is presented for estimating the quantities needed by a space-time RAKE receiver for DS-CDMA to achieve maximum SINR for the desired user. The proposed algorithm, which is applicable in the case of either periodic or aperiodic spreading codes, asymptotically provides the exact time of arrival of each dominant multipath within a bit period, and the optimum beamformer for extracting each multipath. This is achieved by using cyclostationarity to exploit the difference between the respective spectra of the desired user and each multiuser access interferer at the output of the correlator based on the desired user's code. Estimates of the relative time delay and optimal beamformer for each RAKE finger are used by the space-time RAKE receiver to optimally combine the desired user's multipath while simultaneously canceling strong multiuser access interference. Simulations of a near-far scenario are presented demonstrating the efficacy of the proposed algorithm.