The Time-Frequency Synchronization for 5G NR Based Non-Terrestrial Networks.

In order to meet the comprehensive and diverse service requirements of 5G, 3GPP has completed a study which focused on definition of Non-Terrestrial networks (NTN) and Orthogonal Frequency Division Multiplexing (OFDM) based candidate waveform is recommended. Existing synchronization technologies developed primarily for the ground fifth generation mobile communication (5G) communications cannot be readily applied to satellite high mobility communication scenarios, since high doppler frequency offset caused by the fast movement of wireless terminals or low earth orbit (LEO) satellites. In this paper, time-frequency synchronization scheme is proposed for OFDM based wireless communication over large doppler frequency offset NTN system. Firstly, the coarse symbol timing and frequency synchronization are realized based on the preamble; Secondly, the correlation operation between the PSS symbols is used to realize the fine symbol timing synchronization. Finally, the residual frequency offset is estimated and tracked by the first-order filter frequency locked loop. Simulation results show that the proposed scheme can perform well with large frequency offset estimation range and high accuracy. Further, the scheme has no complex matrix operation and has better engineering applicability than other methods.