Dithered signed-error CMA: robust, computationally efficient blind adaptive equalization

Adaptive blind equalization has gained widespread use in communication systems that operate without training signals. In particular, the constant modulus algorithm (CMA) has become a favorite of practitioners due to its LMS-like complexity and desirable robustness properties. The desire for further reduction in computational complexity has motivated signed-error versions of CMA, which have been found to lack the robustness properties of CMA. This paper presents a simple modification of signed-error CMA, based on the judicious use of dither, that results in an algorithm with robustness properties closely resembling those of CMA. We establish the fundamental transient and steady-state properties of dithered signed-error CMA and compare them with those of CMA.