Methods and apparatuses for handling uplink (re)transmission in NR-U

1. A base station (BS), comprising:

one or more non-transitory computer-readable media storing one or more computer-executable instructions; and

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

transmit a dynamic grant to a user equipment (UE) for scheduling a first uplink (UL) resource and a second UL resource, the first UL resource starting before the second UL resource in time domain, and the second UL resource indicated for a new transmission; and

receive a first Medium Access Control (MAC) protocol data unit (PDU) from the UE via the second UL resource in a case that transmission of the first MAC PDU to the BS via the first UL resource has failed and the second UL resource is available for transmitting the first MAC PDU.

2. The BS of claim 1 , wherein the at least one processor is further configured to execute the one or more computer-executable instructions to cause the BS to:

receive a second MAC PDU from the UE via the second UL resource in a case that the second UL resource is not available for transmitting the first MAC PDU, wherein the second MAC PDU is generated by the UE for the new transmission using the second UL resource.

3. The BS of claim 1 , wherein the second UL resource is available for transmitting the first MAC PDU if the following conditions are satisfied:

the first MAC PDU is generated by the UE for the transmission using the first UL resource scheduled by the dynamic grant;

the first UL resource is indicated for the new transmission;

a size of the second UL resource is equal to or greater than a size of the first UL resource;

the transmission of the first MAC PDU on the first UL resource has failed due to a UL Listen-Before-Talk (LBT) failure; and

a first hybrid automatic repeat request (HARQ) process identifier (ID) associated with the first UL resource is different from a second HARQ ID associated with the second UL resource.

4. The BS of claim 3 , wherein the first MAC PDU is stored in a HARQ buffer of the UE after being generated, and the HARQ buffer is associated with a HARQ process of the first UL resource.

5. The BS of claim 4 , wherein the received first MAC PDU is obtained by the UE from the HARQ buffer for transmission using the second UL resource.

6. The BS of claim 1 , wherein the second UL resource is immediately after the first UL resource in the time domain.

7. The BS of claim 1 , wherein the first UL resource and the second UL resource are physical uplink shared channel (PUSCH) resources.

8. The BS of claim 1 , wherein a size of the second UL resource is equal to or greater than a size of the first UL resource.

9. The BS of claim 1 , wherein the dynamic grant is transmitted in downlink control information (DCI).

10. A method performed by a base station (BS), the method comprising:

transmitting a dynamic grant to a user equipment (UE) for scheduling a first uplink (UL) resource and a second UL resource, the first UL resource starting before the second UL resource in time domain, and the second UL resource indicated for a new transmission; and

receiving a first Medium Access Control (MAC) protocol data unit (PDU) from the UE via the second UL resource in a case that transmission of the first MAC PDU to the BS via the first UL resource has failed and the second UL resource is available for transmitting the first MAC PDU.

11. The method of claim 10 , further comprising:

receiving a second MAC PDU from the UE via the second UL resource in a case that the second UL resource is not available for transmitting the first MAC PDU, wherein the second MAC PDU is generated by the UE for the new transmission using the second UL resource.

12. The method of claim 10 , wherein the second UL resource is available for transmitting the first MAC PDU if the following conditions are satisfied:

the first MAC PDU is generated by the UE for the transmission using the first UL resource scheduled by the dynamic grant;

the first UL resource is indicated for the new transmission;

a size of the second UL resource is equal to or greater than a size of the first UL resource;

the transmission of the first MAC PDU on the first UL resource has failed due to a UL Listen-Before-Talk (LBT) failure; and

a first hybrid automatic repeat request (HARQ) process identifier (ID) associated with the first UL resource is different from a second HARQ ID associated with the second UL resource.

13. The method of claim 12 , wherein the first MAC PDU is stored in a HARQ buffer of the UE after being generated, and the HARQ buffer is associated with a HARQ process of the first UL resource.

14. The method of claim 13 , wherein the received first MAC PDU is obtained by the UE from the HARQ buffer for transmission using the second UL resource.

15. The method of claim 10 , wherein the second UL resource is immediately after the first UL resource in the time domain.

16. The method of claim 10 , wherein the first UL resource and the second UL resource are physical uplink shared channel (PUSCH) resources.

17. The method of claim 10 , wherein a size of the second UL resource is equal to or greater than a size of the first UL resource.

18. The method of claim 10 , wherein the dynamic grant is transmitted in downlink control information (DCI).