Doppler Frequency-Offset Estimator for Multi-carrier Faster-than-Nyquist Signaling in Low-Earth-Orbit Satellite Communications

As the comming of the sixth generation (6 G) era, the Low-Earth-Orbit (LEO) satellite communications are expected to provide better service for massive terminals. With the rapid increasing of users, it will make the wireless spectrum resource more scarce. In this paper, in order to improve the spectrum efficiency, Multi-carrier Faster-than-Nyquist (MFTN) signaling is applied into downlink of LEO satellite communications. Further, we have proposed a Doppler frequency offset estimator, which can minimize the performance loss of MFTN signaling in the LEO satellite channel. For reducing computation complexity, the proposed estimator has been simplified by polynomial approximation. In LEO satellite channel, simulation results demonstrated that the proposed estimator can achieve satisfied estimation performance. It is also verified that our proposed estimator can reduce transmission performance loss for MFTN with different packing factors.