  In this work we propose an adaptive linear receiver structure based on
interpolated finite impulse response (FIR) filters with adaptive interpolators
for direct sequence code division multiple access (DS-CDMA) systems in
multipath channels. The interpolated minimum mean-squared error (MMSE) and the
interpolated constrained minimum variance (CMV) solutions are described for a
novel scheme where the interpolator is rendered time-varying in order to
mitigate multiple access interference (MAI) and multiple-path propagation
effects. Based upon the interpolated MMSE and CMV solutions we present
computationally efficient stochastic gradient (SG) and exponentially weighted
recursive least squares type (RLS) algorithms for both receiver and
interpolator filters in the supervised and blind modes of operation. A
convergence analysis of the algorithms and a discussion of the convergence
properties of the method are carried out for both modes of operation.
Simulation experiments for a downlink scenario show that the proposed
structures achieve a superior BER convergence and steady-state performance to
previously reported reduced-rank receivers at lower complexity.
