Time and Frequency Synchronization of GFDM Waveforms

Generalized frequency division multiplexing (GFDM) is a waveform for the next-generation communication but requires a step dedicated to time and frequency synchronization. The current time and frequency synchronization methods of GFDM do not fully address the requirements on accuracy, robustness to a large frequency offset, and low complexity. This study develops an accurate synchronization method tailored to large time and frequency offsets. The proposed method jointly synchronizes time and frequency, and derives a decision variable from the real part of an inner product. The accuracy of time and frequency synchronization increases because an error in the frequency offset is corrected simultaneously during the process of time synchronization, and because the decision variable does not depend on the imaginary part, which we show to be noise. The proposed method can correct the full range of frequency offsets. We compare synchronization accuracy of the proposed method to the state of the art analytically, numerically, and experimentally in terms of the discriminant probability, the range of correctable frequency offsets, the probability of perfect time synchronization, the root mean square error (RMSE) between estimates and actual offsets, and the bit error ratio. The proposed method outperforms the existing methods in all of these metrics. Moreover, it has practical utility, and increases the transmission reliability of GFDM-based communication systems.