METHOD AND RELATED DEVICE FOR OPERATING IN A NON-TERRESTRIAL NETWORK (NTN)

1 - 16 . (canceled)

17 . A method for a user equipment (UE) operating in a non-terrestrial network (NTN), the method comprising:

receiving, from a base station (BS), assistance information;

starting or restarting a first timer upon receiving the assistance information;

applying the assistance information to perform uplink synchronization; and

determining that the UE has lost the uplink synchronization upon expiration of the first timer.

18 . The method of claim 17 , further comprising:

determining that the assistance information is invalid upon the expiration of the first timer.

19 . The method of claim 17 , further comprising:

treating other running timers associated with the uplink synchronization as expired upon the expiration of the first timer.

20 . The method of claim 17 , further comprising:

flushing all hybrid automatic repeat request (HARQ) buffers for at least one serving cell upon the expiration of the first timer.

21 . The method of claim 17 , further comprising:

notifying a radio resource control (RRC) layer of the UE to release a physical uplink control channel (PUCCH) for at least one serving cell upon the expiration of the first timer.

22 . The method of claim 17 , further comprising:

notifying a radio resource control (RRC) layer of the UE to release a sounding reference signal (SRS) for at least one serving cell upon the expiration of the first timer.

23 . The method of claim 17 , further comprising:

clearing a configured downlink assignment and a configured uplink grant for at least one serving cell upon the expiration of the first timer.

24 . The method of claim 17 , further comprising:

clearing a physical uplink shared channel (PUSCH) resource for semi-persistent channel state information (CSI) reporting for at least one serving cell upon the expiration of the first timer.

25 . A user equipment (UE) operating in a non-terrestrial network (NTN), the UE comprising:

a processor for executing a computer-executable program; and

a memory, coupled to the processor, for storing the computer-executable program that, when executed by the processor, causes the UE to:

receive, from a base station (BS), assistance information;

start or restart a first timer upon receiving the assistance information;

apply the assistance information to perform uplink synchronization; and

determine that the UE has lost the uplink synchronization upon expiration of the first timer.

26 . The UE of claim 25 , wherein the processor is further configured to execute the computer-executable program to cause the UE to:

determine that the assistance information is invalid upon the expiration of the first timer.

27 . The UE of claim 25 , wherein the processor is further configured to execute the computer-executable program to cause the UE to:

treat other running timers associated with the uplink synchronization as expired upon the expiration of the first timer.

28 . The UE of claim 25 , wherein the processor is further configured to execute the computer-executable program to cause the UE to:

flush all hybrid automatic repeat request (HARQ) buffers for at least one serving cell upon the expiration of the first timer.

29 . The UE of claim 25 , wherein the processor is further configured to execute the computer-executable program to cause the UE to:

notify a radio resource control (RRC) layer of the UE to release a physical uplink control channel (PUCCH) for at least one serving cell upon the expiration of the first timer.

30 . The UE of claim 25 , wherein the processor is further configured to execute the computer-executable program to cause the UE to:

notify a radio resource control (RRC) layer of the UE to release a sounding reference signal (SRS) for at least one serving cell upon the expiration of the first timer.

31 . The UE of claim 25 , wherein the processor is further configured to execute the computer-executable program to cause the UE to:

clear a configured downlink assignment and a configured uplink grant for at least one serving cell upon the expiration of the first timer.

32 . The UE of claim 25 , wherein the processor is further configured to execute the computer-executable program to cause the UE to:

clear a physical uplink shared channel (PUSCH) resource for semi-persistent channel state information (CSI) reporting for at least one serving cell upon the expiration of the first timer.