User equipment and method for timing alignment

1. A method performed by a User Equipment (UE) for timing alignment, the method comprising:

receiving, from a Base Station (BS), a first configuration indicating at least one of a scheduling offset, a common Timing Advance (TA), and satellite ephemeris information;

receiving, from the BS, a second configuration indicating a TA offset for a TA variable;

determining a UE-specific TA based on the satellite ephemeris information;

determining a total TA based on at least one of the TA variable, the TA offset for the TA variable, the common TA, and the UE-specific TA;

determining the scheduling offset to be zero if the scheduling offset is not provided by the BS, wherein the scheduling offset includes a feeder link Round Trip Time (RTT); and

starting, from a transmission by the UE, a time window after an additional time based on the total TA and the scheduling offset.

2. The method of claim 1 , wherein the time window is a Random Access (RA) response window or a Message B (MsgB) response window.

3. The method of claim 1 , wherein the transmission by the UE occurs on a Physical Random Access Channel (PRACH).

4. The method of claim 1 , wherein the TA variable is a TA between a Downlink (DL) transmission of the UE and an Uplink (UL) transmission of the UE.

5. The method of claim 1 , wherein the first configuration is a Non-Terrestrial Network (NTN) configuration.

6. The method of claim 1 , wherein the first configuration is received via System Information (SI).

7. The method of claim 1 , wherein a unit of the scheduling offset comprises a number of slots.

8. The method of claim 1 , further comprising:

setting a length of a timer by increasing a value based on the UE-specific TA and the scheduling offset.

9. The method of claim 8 , wherein the timer is a Discontinuous Reception (DRX) Hybrid Automatic Repeat Request (HARD) RTT timer.

10. A User Equipment (UE) in a wireless communication system for timing alignment, the UE comprising:

at least one processor; and

at least one memory coupled to the at least one processor, the at least one memory storing computer-executable instructions that, when executed by the at least one processor, cause the UE to:

receive, from a Base Station (BS), a first configuration indicating at least one of a scheduling offset, a common Timing Advance (TA), and satellite ephemeris information;

receive, from the BS, a second configuration indicating a TA offset for a TA variable;

determine a UE-specific TA based on the satellite ephemeris information;

determine a total TA based on at least one of the TA variable, the TA offset for the TA variable, the common TA, and the UE-specific TA;

determine the scheduling offset to be zero if the scheduling offset is not provided by the BS, wherein the scheduling offset includes a feeder link Round Trip Time (RTT); and

start, from a transmission by the UE, a time window after an additional time based on the total TA and the scheduling offset.

11. The UE of claim 10 , wherein the time window is a Random Access (RA) response window or a Message B (MsgB) response window.

12. The UE of claim 10 , wherein the transmission by the UE occurs on a Physical Random Access Channel (PRACH).

13. The UE of claim 10 , wherein the TA variable is a TA between a Downlink (DL) transmission of the UE and an Uplink (UL) transmission of the UE.

14. The UE of claim 10 , wherein the first configuration is a Non-Terrestrial Network (NTN) configuration.

15. The UE of claim 10 , wherein the first configuration is received via System Information (SI).

16. The UE of claim 10 , wherein a unit of the scheduling offset comprises a number of slots.

17. The UE of claim 10 , wherein the computer-executable instructions, when executed by the at least one processor, further cause the UE to:

set a length of a timer by increasing a value based on the UE-specific TA and the scheduling offset.

18. The UE of claim 17 , wherein the timer is a Discontinuous Reception (DRX) Hybrid Automatic Repeat Request (HARD) RTT timer.