16.14.3.1 Mobility in RRC_IDLE and RRC_INACTIVE

The same principles as described in 9.2.1 apply to mobility in RRC_IDLE for NTN and the same principles as described in 9.2.2 apply to mobility in RRC_INACTIVE for NTN unless hereunder specified.

The network may broadcast multiple Tracking Area Codes (TACs) per PLMN in an NR NTN cell. A TAC change in the System Information is under network control, i.e. it may not be exactly synchronised with real-time illumination of beams on ground.

For the NTN-TN mobility, the network may broadcast cell information on NR TN and EUTRA TN coverage areas in SIB25. This is supported for Earth-Fixed, Quasi-Earth-fixed and Earth-Moving cells. The coverage information consists in a list of geographical TN areas, with associated frequency information also indicated. UE can skip TN measurement based on the broadcast TN coverage information.

The UE can determine the network type (terrestrial or non-terrestrial) implicitly by the existence of cellBarredNTN in SIB1.

The NTN ephemeris is provided in SIB19. In an NTN cell, it includes serving cell's NTN payload ephemeris and optionally neighbouring cell's NTN payload ephemeris.

The UE may be provided with NTN payload assistance to assist in searching for NTN cells for the purpose of redirection from TN to NTN or from NTN to NTN. The UE may also be redirected by an NTN cell to an NR TN cell or an E-UTRAN TN cell.

The network may provide assistance information (e.g., ephemeris information, carrier frequency), which a UE may use for cell selection from NR NTN to IoT NTN.