Time-frequency Joint Frequency Offset Estimation Algorithm for GMSK Modulation

As an emerging communication networking method, airborne data link plays an increasingly important role in the field of defense and civil use, and GMSK is widely used in airborne data link networking systems with its efficient frequency band utilization and power utilization. However, the high-speed movement of the UAV will inevitably produce Doppler frequency offset, which will greatly affect the performance of the communication system receiver, so this paper proposes a pilot-based time domain indirect estimation algorithm with low complexity implementation, and compares the performance of different pilot placement positions. At the same time, in order to make up for the shortcomings of the small estimation range of the algorithm, a time-frequency joint frequency offset estimation algorithm is further proposed, which first coarsely estimates and compensates the received signal through FFT and Quinn algorithms, and then uses the pilot-based frequency offset indirect estimation algorithm to accurately estimate the received signal. The algorithm not only takes into account the high estimation range of the frequency domain estimation algorithm, but also has the high accuracy of the time domain estimation algorithm, and can also have high performance under the condition of low SNR.