Method of performing hybrid automatic repeat request process for deprioritized uplink grant and related device

1. A method for a user equipment (UE) performing a Hybrid Automatic Repeat Request (HARQ) process of an uplink (UL) grant for scheduling a retransmission, the method comprising:

receiving, from a base station (BS), a first UL grant scheduling a first UL transmission on a first UL resource and a second UL grant scheduling a second UL transmission on a second UL resource, the second UL resource at least partially overlapping the first UL resource in time domain;

determining the first UL grant as a prioritized UL grant;

determining the second UL grant as a deprioritized UL grant;

performing the first UL transmission scheduled by the prioritized UL grant;

receiving a third UL grant scheduling a third UL transmission on a third UL resource; and

before generating a first transport block for the third UL transmission in response to determining that the third UL grant is for indicating a retransmission of a second transport block stored in a HARQ buffer of the HARQ process:

determining whether a size of the third UL resource is different from a size of the second transport block corresponding to the second UL transmission, and

flushing the HARQ buffer and determining that a new data indicator (NDI) for the third UL transmission is toggled if the size of the third UL resource is different from the size of the second transport block, wherein:

the third UL resource is not overlapping the first UL resource in the time domain and is not overlapping the second UL resource in the time domain, and

the second UL grant is a configured grant (CG) and the third UL grant is a dynamic grant (DG).

2. The method of claim 1 , wherein the first UL grant comprises the DG or the CG.

3. The method of claim 1 , wherein any of the first UL resource, the second UL resource, and the third UL resource is used for a physical uplink shared channel (PUSCH) transmission, a physical uplink control channel (PUCCH) transmission, or a physical random access channel (PRACH) transmission.

4. The method of claim 1 , wherein flushing the HARQ buffer further comprises:

flushing the HARQ buffer when the second transport block corresponding to the second UL transmission has not been generated by the UE.

5. The method of claim 1 , further comprising:

generating a Medium Access Control (MAC) Protocol Data Unit (PDU) associated with the second transport block corresponding to the second UL transmission; and

transmitting, to the BS, the MAC PDU on the third UL resource.

6. A user equipment (UE) for performing a Hybrid Automatic Repeat Request (HARQ) process of an uplink (UL) grant for scheduling a retransmission, the UE comprising:

at least one processor; and

at least one non-transitory machine-readable medium coupled to the at least one processor and 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 UL grant scheduling a first UL transmission on a first UL resource and a second UL grant scheduling a second UL transmission on a second UL resource, the second UL resource at least partially overlapping the first UL resource in time domain;

determine the first UL grant as a prioritized UL grant;

determine the second UL grant as a deprioritized UL grant;

perform the first UL transmission scheduled by the prioritized UL grant;

receive a third UL grant scheduling a third UL transmission on a third UL resource; and

before generating a first transport block for the third UL transmission in response to determining that the third UL grant is for indicating a retransmission of a second transport block stored in a HARQ buffer of the HARQ process:

determine whether a size of the third UL resource is different from a size of the second transport block corresponding to the second UL transmission, and

flush the HARQ buffer and determine that a new data indicator (NDI) for the third UL transmission is toggled if the size of the third UL resource is different from the size of the second transport block, wherein:

the third UL resource is not overlapping the first UL resource in the time domain and is not overlapping the second UL resource in the time domain, and

the second UL grant is a configured grant (CG) and the third UL grant is a dynamic grant (DG).

7. The UE of claim 6 , wherein the first UL grant comprises the DG or the CG.

8. The UE of claim 6 , wherein any of the first UL resource, the second UL resource, and the third UL resource is used for a physical uplink shared channel (PUSCH) transmission, a physical uplink control channel (PUCCH) transmission, or a physical random access channel (PRACH) transmission.

9. The UE of claim 6 , wherein flushing the HARQ buffer further comprises:

flushing the HARQ buffer when the second transport block corresponding to the second UL transmission has not been generated by the UE.

10. The UE of claim 6 , wherein the computer-executable instructions, when executed by the at least one processor, further cause the UE to:

generate a Medium Access Control (MAC) Protocol Data Unit (PDU) associated with the second transport block corresponding to the second UL transmission; and

transmit, to the BS, the MAC PDU on the third UL resource.