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On the Standardization of Key Enabling Technologies in Non-Terrestrial Network Air-interface Design

The requirements of seamless connection and extensive coverage, especially in rural and isolated areas have dramatically driven the development of Non-Terrestrial Networks (NTN) in 5G New Radio (NR). However, NTN faces some unique challenges such as extremely long propagation delay due to the long distance between satellites and user terminals and the significant Doppler effect caused by the fast movement of satellites. The current 5G NR standards cannot cope with such challenges and thus need to be enhanced to integrate NTN with the terrestrial network of 5G NR. In this paper, we introduce the latest development of 5G standards for NTN including deployment scenarios and system architectures in the 3rd Generation Partnership Project (3GPP). We also investigate the enabling technologies in NTN air-interface design, such as time and frequency synchronization, Hybrid Automatic Repeat Request (HARQ), physical layer procedures, etc., to enhance 5G NR standards. Some evaluations results are provided as well.