Long-term Krylov-prefilter for reduced-dimension receive processing in DS-CDMA systems

Currently, long-term channel properties are only used for reduced-dimension processing in eigen subspaces. We introduce a preRAKE at the transmitter in the uplink of a direct sequence (DS) CDMA system with non-orthogonal codes in order to exploit long-term channel properties for reduced-dimension Wiener filtering in Krylov subspaces at the receiver. Simulation results show that Krylov outperforms eigen prefiltering with and without previous correlation. Moreover, the long-term is better than or equal to short-term processing except for optimal filtering in Krylov subspaces assuming multipath environments.