Method of non-terrestrial network assistance information update procedure and related device

1. A method for performing, by a user equipment (UE), a non-terrestrial network (NTN) assistance information update procedure, the method comprising:

receiving, from a first cell, a handover command comprising first NTN assistance information associated with the first cell, the handover command indicating a second cell as a target cell for a handover procedure;

storing the first NTN assistance information;

performing the NTN assistance information update procedure based on the handover command;

selecting the second cell to camp on according to the handover command that comprises the first NTN assistance information;

receiving, from the second cell, an NTN-specific system information block (SIB) after selecting the second cell to camp on, the NTN-specific SIB indicating a validity time period;

obtaining, from the second cell, second NTN assistance information associated with the validity time period;

replacing the stored first NTN assistance information with the second NTN assistance information; and

counting down an NTN validity timer corresponding to the validity time period to zero.

2. The method of claim 1 , wherein the first cell and the second cell are supported by either an Evolved Universal Terrestrial Radio Access (E-UTRA) network or a New Radio (NR) network.

3. The method of claim 1 , wherein the first NTN assistance information includes at least one of a common timing advance value, location information associated with a serving cell and a reference point, or a feeder link delay between the serving cell and the reference point.

4. A user equipment (UE) for performing a non-terrestrial network (NTN) assistance information update procedure, the UE comprising:

at least one processor; and

at least one non-transitory computer-readable medium coupled to the at least one processor and storing one or more computer-executable instructions that, when executed by the at least one processor, cause the UE to:

receive, from a first cell, a handover command comprising first NTN assistance information associated with the first cell, the handover command indicating a second cell as a target cell for a handover procedure;

store the first NTN assistance information;

perform the NTN assistance information update procedure based on of the handover command;

select the second cell to camp on according to the handover command that comprises the first NTN assistance information;

receive, from the second cell, an NTN-specific system information block (SIB) after selecting the second cell to camp on, the NTN-specific SIB indicating a validity time period;

obtain, from the second cell, second NTN assistance information associated with the validity time period;

replace the stored first NTN assistance information with the second NTN assistance information; and

count down an NTN validity timer corresponding to the validity time period to zero.

5. The UE of claim 4 , wherein the first cell and the second cell are supported by either an Evolved Universal Terrestrial Radio Access (E-UTRA) network or a New Radio (NR) network.

6. The UE of claim 4 , wherein the first NTN assistance information includes at least one of a common timing advance value, location information associated with a serving cell and a reference point, or a feeder link delay between the serving cell and the reference point.