Blind adapted, pre-whitened constant modulus algorithm

We examine the use of a blind adaptive “pre-whitening” filter to precede an equalizer adapted by the constant modulus algorithm (CMA). The idea is based on results presented in which the use of a (fixed, or non-adaptive) pre-whitening filter provides an isometry (i.e. geometry preserving transformation) between the combined channel-equalizer (or global space) and the equalizer tap space. As much analysis found in CMA literature is done in “global space” now applies to the pre-whitened “equalizer tap space”, considerable exploitation of a known geometric structure is now possible. This paper’s main result demonstrates a method for improving the convergence rates of CMA adapted equalizers using the results of prewhitening analysis. The slow convergence of CMA equalizers is a common negative point associated with this well-known, robust blind equalization algorithm. Keywords— Constant Modulus Algorithm (CMA), Blind Equalization, Whitening, Convergence Analysis