Method and apparatus for performing random access-less handover in ntn system

A method performed by a terminal in a wireless communication system, the method comprising:

• receiving, from a first non-terrestrial network (NTN) base station, a radio resource control (RRC) reconfiguration message including configuration information associated with a random access channel (RACH)-less handover to a second NTN base station and timing information applied to the second NTN base station;
• and
• performing physical uplink shared channel (PUSCH) transmission to the second NTN base station based on the timing information and the configuration information,
• wherein whether a timing adjustment value for the second NTN base station is equal to a timing adjustment value for the first NTN base station is indicated by the timing information.

A first non-terrestrial network (NTN) base station in a wireless communication system, the first NTN base station comprising:

• a transceiver;
• and
• a controller configured to:
• determine a random access channel (RACH)-less handover to a second NTN base station for a terminal,
• obtain, from the second NTN base station, configuration information associated with the RACH-less handover, and
• control the transceiver to transmit, to the terminal, a radio resource control (RRC) reconfiguration message including the configuration information and timing information applied to the second NTN base station,
• wherein whether a timing adjustment value for the second NTN base station is equal to a timing adjustment value for the first NTN base station is indicated by the timing information,
• wherein physical uplink shared channel (PUSCH) transmission from the terminal to the second NTN base station is performed based on the timing information and the configuration information.

A terminal in a wireless communication system, the terminal comprising:

• a transceiver;
• and
• a controller configured to:
• control the transceiver to receive, from a first non-terrestrial network (NTN) base station, a radio resource control (RRC) reconfiguration message including configuration information associated with a random access channel (RACH)-less handover to a second NTN base station and timing information applied to the second NTN base station, and
• control the transceiver to perform physical uplink shared channel (PUSCH) transmission to the second NTN base station based on the timing information and the configuration information,
• wherein whether a timing adjustment value for the second NTN base station is equal to a timing adjustment value for the first NTN base station is indicated by the timing information.