Closed-Form Training-Based Blind Estimation of Frequency Offset for QAM Signals with Unknown Power and Signal-to-Noise Ratio

A method is proposed for blind estimation of the frequency offset for signals with quadrature amplitude modulation. The method allows to obtain the result in a closed form, it is a modified version of the Luise and Reggiannini method for harmonic signal frequency estimation. The main modification is the introduction of a two-dimensional weighting function that depends on the magnitudes of two signal samples. Optimization of this weighting function is carried out by training in batch mode on the simulated sequences of signal samples. Normalization of input signal power and the use of training sequences with various signal-to-noise ratios allow to adapt weighting function to varying reception conditions. The results of computer simulation confirmed the efficiency of the proposed method and showed the advantage of a two-dimensional weighting function over one-dimensional versions.