On an efficient implementation of the multistage Wiener filter through Householder reflections for DS-CDMA interference suppression

The paper describes the implementation of the multistage Wiener filter (MWF) through a series of nested Householder transformations applied to the input signal as a means to form the analysis filter-bank part of the structure. The input signal is successively projected onto an appropriate subspace whereby the mutual information is maximized at each step, as required by the MWF structure. The method presented is described-as a constrained optimization problem, where the constraints are imposed on the input signal, and not on the coefficients of the filter. The method is applicable to reduced-rank as well as to full-rank implementations of the MWF. The Householder transformation assures that the equivalent blocking matrices for all the stages are efficiently implemented via single reflections and that only unitary reflections are employed; robustness against deleterious finite-precision effects is, therefore, improved. Simulations of a DS-CDMA interference suppression receiver illustrate the robust behavior of the proposed scheme when implemented in finite precision as compared to the conventional MWF using non-orthogonal blocking matrices.