Blind carrier frequency offset estimation for cross QAM constellations

This paper introduces a novel blind frequency offset estimator for signaling using cross Quadrature Amplitude Modulated constellations. The estimator is based on the tentative frequency offset compensation of nonlinearly transformed received signal samples and on their accumulation in different angular windows. When the compensation perfectly removes the frequency offset, the measurements are suitably clustered and their accumulation, that we call the "Constellation Phase Signature" (CPS), is a peaked function of the window orientation. Hence, the frequency offset estimator is obtained by adjusting the compensation so that the peakness of the sample CPS is maximized. The performance of the estimator has been evaluated by numerical simulations. Comparison of the CPS based estimator with a selected existing estimator shows that it performs well for medium to high values of SNR.