Space-time adaptive reduced-rank processor for interference mitigation in DS-CDMA systems

A space-time adaptive reduced-rank processor for interference mitigation in DS-CDMA systems is proposed based on interpolated finite impulse response filters with time- varying interpolators. The proposed space-time processor allows a significant reduction in the number of estimation elements, thereby increasing the convergence and tracking performance of the estimation algorithms. In order to compute the parameters of the proposed space-time processor, a least squares design is presented and computationally efficient recursive least-squares (RLS) algorithms are developed for estimating the parameters of both reduced-rank receiver and interpolator. A linear and successive interference cancellation space-time receivers based on the proposed reduced-rank processor for mitigating multi-access and intersymbol interference in an uplink scenario are proposed. An analysis of the convergence properties of the proposed space-time processor is carried out and analytical expressions are derived for predicting the mean squared error performance of the proposed RLS algorithm. Simulation results show that the proposed reduced-rank space-time processor and RLS algorithms outperform existing techniques at lower complexity.