  In this work we propose schemes for joint model-order and step-size
adaptation of reduced-rank adaptive filters. The proposed schemes employ
reduced-rank adaptive filters in parallel operating with different orders and
step sizes, which are exploited by convex combination strategies. The
reduced-rank adaptive filters used in the proposed schemes are based on a joint
and iterative decimation and interpolation (JIDF) method recently proposed. The
unique feature of the JIDF method is that it can substantially reduce the
number of coefficients for adaptation, thereby making feasible the use of
multiple reduced-rank filters in parallel. We investigate the performance of
the proposed schemes in an interference suppression application for CDMA
systems. Simulation results show that the proposed schemes can significantly
improve the performance of the existing reduced-rank adaptive filters based on
the JIDF method.
