Method of channel scheduling for narrowband internet of things in non-terrestrial network and user equipment using the same

1. A method of channel scheduling for narrowband Internet of Things (NB-IoT) in a non-terrestrial network (NTN), adapted to a user equipment (UE), wherein the method comprising:

transmitting an uplink signal ending in a first subframe;

determining a monitoring window starting from a second subframe according to the first subframe and a time offset;

monitoring a downlink signal corresponding to the uplink signal according to the monitoring window;

receiving a second downlink signal ending in a third subframe;

determining a fourth subframe according to the third subframe and a second time offset; and

transmitting a second uplink signal corresponding to the second downlink signal at the fourth subframe.

2. The method of claim 1 , wherein a difference between the first subframe and the second subframe is greater than or equal to the time offset.

3. The method of claim 2 , wherein the difference is equal to the time offset plus a default offset.

4. The method of claim 1 , wherein the uplink signal is a narrowband physical uplink shared channel (NPUSCH) and the downlink signal is a narrowband physical downlink control channel (NPDCCH).

5. The method of claim 1 , wherein the uplink signal is a random access (RA) preamble and the downlink signal is a random access response (RAR).

6. The method of claim 1 , wherein a step of transmitting the uplink signal ending in the first subframe comprising:

transmitting the uplink signal via a pre-configured uplink resource.

7. The method of claim 1 , further comprising:

determining the time offset according to a round trip time (RTT) between the UE and a serving base station.

8. The method of claim 1 , further comprising:

determining the time offset according to a round trip time (RTT) between a serving base station and a reference point in a coverage of the serving base station, wherein the reference point comprises one of a serving satellite in a space and a cell center on a ground.

9. The method of claim 1 , further comprising:

receiving a signal, wherein the signal comprises at least one of system information and a radio resource control (RRC) message; and

obtaining the time offset from the signal.

10. The method of claim 1 , wherein a difference between the third subframe and the fourth subframe is greater than or equal to the second time offset.

11. The method of claim 10 , wherein the difference is equal to the second time offset plus a default offset.

12. The method of claim 1 , wherein the second downlink signal is a narrowband physical downlink shared channel (NPDSCH) and the second uplink signal is a narrowband physical uplink shared channel (NPUSCH) carrying an acknowledgment (ACK) response or a negative-acknowledgment (NACK) response.

13. The method of claim 1 , wherein the second downlink signal is a narrowband physical downlink control channel (NPDCCH) order and the second uplink signal is a random access (RA) preamble.

14. The method of claim 1 , wherein the second downlink signal is a system information block (SIB) and the second uplink signal is a narrowband physical random access channel (NPRACH).

15. The method of claim 1 , further comprising:

receiving a second signal, wherein the second signal comprises at least one of a system information block (SIB), a radio resource control (RRC) message, and a medium access control (MAC) control element (CE) command; and

obtaining the second time offset from the second signal.

16. The method of claim 1 , further comprising:

determining the second time offset according to a round trip time (RTT) between the UE and a communication device, wherein the communication device comprises one of a serving base station and a serving satellite.

17. The method of claim 1 , further comprising:

determining an uplink transmission timing according to the second time offset and a timing advance (TA) value.

18. A user equipment (UE) comprising:

one or more non-transitory computer-readable media having computer-executable instructions embodied thereon; and

at least one processor coupled to the one or more non-transitory computer-readable media, and configured to execute the computer-executable instructions to:

transmit an uplink signal ending in a first subframe;

determine a monitoring window starting from a second subframe according to the first subframe and a time offset;

monitor a downlink signal corresponding to the uplink signal according to the monitoring window;

receive a second downlink signal ending in a third subframe;

determine a fourth subframe according to the third subframe and a second time offset; and

transmit a second uplink signal corresponding to the second downlink signal at the fourth subframe.