METHOD OF HARQ PROCESS FOR MULTICAST BROADCAST SERVICE AND USER EQUIPMENT USING THE SAME

1 . A method of hybrid automatic repeat request (HARQ) process for multicast broadcast service (MBS), adapted to a user equipment (UE), wherein the method comprising:

receiving first downlink control information (DCI) on a first physical downlink control channel (PDCCH) scrambled by a first radio network temporary identifier (RNTI), wherein the first DCI comprises a first new data indicator (NDI) value and schedules a first downlink data reception on a first physical downlink shared channel (PDSCH) corresponding to a HARQ process;

receiving second DCI on a second PDCCH scrambled by a second RNTI, wherein the second DCI comprises a second NDI value and schedules a second downlink data reception on a second PDSCH corresponding to the HARQ process;

identifying a first type of the first RNTI and a second type of the second RNTI; and

determining, according to the first type and the second type, whether the first NDI value and the second NDI value are used for determining the second downlink data reception corresponds to an initial transmission or a retransmission of the first downlink data reception.

2 . The method of claim 1 , further comprising:

in response to the second type corresponding to a group RNTI and the first type corresponding to a UE specific RNTI, determining the second downlink data reception corresponds to the initial transmission or the retransmission without using the first NDI value and the second NDI value, wherein the group RNTI is configured by a gNB to associate with a first transmission type for a group of UE, and the UE specific RNTI is configured by the gNB to associate with a second transmission type for a single UE.

3 . The method of claim 2 , wherein the step of determining the second downlink data reception corresponds to the initial transmission or the retransmission without using the first NDI value and the second NDI value comprising:

in response to the second type being different from the first type, determining the second downlink data reception is the initial transmission.

4 . The method of claim 1 , further comprising:

receiving a radio resource control (RRC) message indicating a group RNTI associated with an MBS bearer.

5 . The method of claim 1 , further comprising:

in response to both of the first type and the second type corresponding to a group RNTI, determining the second downlink data reception corresponds to the initial transmission or the retransmission by using the first NDI value and the second NDI value.

6 . The method of claim 5 , wherein the step of determining the second downlink data reception corresponds to the initial transmission or the retransmission by using the first NDI value and the second NDI value comprising:

determining the second downlink data reception corresponds to the initial transmission in response to the second NDI value being different from the first NDI value; and

determining the second downlink data packet corresponds to the retransmission in response to the second NDI value being the same as the first NDI value.

7 . The method of claim 1 , further comprising:

in response to the second type corresponding to a UE specific RNTI, determining the second downlink data reception corresponds to the initial transmission or the retransmission by using the first NDI value and the second NDI value.

8 . The method of claim 7 , wherein the step of determining the second downlink data reception corresponds to the initial transmission or the retransmission by using the first NDI value and the second NDI value comprising:

determining the second downlink data reception corresponds to the initial transmission in response to the second NDI value being different from the first NDI value; and

determining the second downlink data reception corresponds to the retransmission in response to the second NDI value being the same as the first NDI value.

9 . The method of claim 1 , further comprising:

decoding data from the second downlink data reception in response to determining the second downlink data reception corresponds to the initial transmission; and

soft combining data received from the first downlink data reception and the second downlink data reception in response to determining the second downlink data reception corresponds to the retransmission.

10 . A user equipment, 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:

receive first downlink control information (DCI) on a first physical downlink control channel (PDCCH) scrambled by a first radio network temporary identifier (RNTI), wherein the first DCI comprises a first new data indicator (NDI) value and schedules a first downlink data reception on a first physical downlink shared channel (PDSCH) corresponding to a HARQ process;

receive second DCI on a second PDCCH scrambled by a second RNTI value, wherein the second DCI comprises a second NDI value and schedules a second downlink data reception on a second PDSCH corresponding to the HARQ process;

identify a first type of the first RNTI and a second type of the second RNTI; and

determine, according to the first type and the second type, whether the first NDI value and the second NDI value are used for determining the second downlink data reception corresponds to an initial transmission or a retransmission of the first downlink data reception.