Reduced-rank interference suppression for DS-CDMA using adaptive interpolated FIR filters with adaptive interpolators

We propose reduced-rank receivers based on adaptive interpolated finite impulse response (FIR) filters and adaptive interpolators for direct sequence code division multiple access (DS-CDMA) systems, and examine the novel structures in multipath fading channels. We describe the interpolated minimum mean squared error (MMSE) and the interpolated least squares (LS) for both receiver and interpolator to mitigate multiple access interference (MAI) and multiple-path propagation effects in a downlink scenario. Based on the interpolated MMSE and LS solutions, we present normalised least mean squares (NLMS) and recursive least squares (RLS) algorithms for both receiver and interpolator filters. Simulation experiments show that the proposed structures achieve a superior convergence performance to previously reported reduced-rank techniques and to the full-rank receiver.