An adaptive blind equalization algorithm for QAM and QPR modulations: The concentric ordered modulus algorithm, with results for 16 QAM and 9 QPR

The concentric ordered modulus algorithm (COMA) represents an approach to the blind equalization of QAM (quadrature amplitude modulation) and QPR signals. COMA's error is generated as a weighted minimum difference between a signal sample and a series of radii placed at the constellation points. COMA exhibits desired properties from the constant modulus algorithm and decision directed algorithm, such as an invariance to carrier modulation, probability distribution of constellation points, and correlation between symbols. COMA's nonlinear error generation precludes the use of classical closed-form analysis to insure an optimal weighting function design. Nevertheless, a simplified weighting function design algorithm is presented, which can be extended to high-order modulations.<
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