A non-data-aided frequency offset estimation algorithm of two co-frequency 16QAM signals

For single-channel of 16QAM mixed signals, a non-data-aided (NDA) frequency offset estimation (FOE) algorithm is proposed. The frequency offset of signals after down conversion affects the phase of the signal and make the signal rotate so that the extremum of the in-phase components and the quadrature components of signals are changed. Calculation of the frequency offset by optimizing the object functions which is obtained from the extremums of the I-channel signals and the Q-channel signals, and the optimized process is accomplished by utilizing hierarchical search. This method does not require any prior information and it is insensitive for unknown parameters of mixed signals, for example, amplitude and timing offset. The simulation-results verify the effectiveness and practicality of the proposed algorithm.