Reduced-complexity multi-stage blind clustering equaliser

A multi-stage blind clustering algorithm is proposed for equalization of M-quadrature amplitude modulated (QAM) channels. A hierarchical decomposition divides the overall task of equalizing a high-order QAM channel into much simpler sub-tasks. Each sub-task can be accomplished fast and reliably using a blind clustering algorithm derived originally for 4-QAM signals. The constant modulus algorithm (CMA) is used as a benchmark to assess this multi-stage blind equalizer. It is demonstrated that the new blind adaptive algorithm achieves much faster convergence. This multi-stage clustering equalizer only requires slightly more computations than the very simple CMA and, like the latter, its computational complexity does not increase as the levels of digital symbols increase