Methods and apparatuses for random access procedure in medium access control layer

1. A method performed by a base station for a 2-step random access (RA) procedure comprising a message A (MSGA) and a message B (MSGB), the method comprising:

receiving the MSGA of the 2-step RA procedure, wherein the MSGA comprising a common control channel (CCCH) media access control (MAC) service data unit (SDU);

transmitting, in response to the MSGA, the MSGB in a first slot, wherein the MSGB comprising a success random access response (RAR), wherein the success RAR comprising a hybrid automatic repeat request (HARQ) feedback timing indicator, a physical uplink control channel (PUCCH) resource indicator, and a user equipment (UE) contention resolution identity; and

receiving a HARQ feedback on an uplink (UL) resource within a second slot after transmitting the success RAR in response to the UE contention resolution identity in a MAC sub-protocol data unit (subPDU) of the success RAR matching the CCCH MAC SDU, wherein

the HARQ feedback timing indicator indicating the second slot to the UE, wherein the second slot is separated from the first slot by an offset, and the offset comprising a timing offset value corresponding to a list of PUCCH resource offset candidates; and

the PUCCH resource indicator indicates the UL resource to the UE, wherein the UE resource corresponds to one of a list of PUCCH resource candidates indicated to the UE by the PUCCH resource indicator, wherein the list of PUCCH resource candidates is associated with a UL bandwidth part (BWP), wherein the HARQ feedback is transmitted on the UL BWP.

2. The method of claim 1 , wherein the receiving the HARQ feedback on the UL resource within the second slot comprising:

receiving the HARQ feedback transmitted by a lower layer of the UE.

3. The method of claim 2 , wherein the lower layer comprising a physical layer of the UE.

4. The method of claim 1 , further comprising:

preconfigured, to the UE, the list of PUCCH resource candidates by a radio resource control (RRC) configuration.

5. The method of claim 1 , further comprising:

preconfigured, to the UE, the list of PUCCH resource offset candidates by a radio resource control (RRC) configuration.

6. The method of claim 1 , wherein the transmitting, in response to the MSGA, the MSGB in the first slot comprising:

generating the success RAR by a MAC entity of the base station; and

transmitting the success RAR via a downlink (DL) assignment.

7. The method of claim 6 , wherein the DL assignment is scrambled by an MSGB-radio network temporary identity (RNTI).

8. A base station (BS) configured to perform a 2-step random access (RA) procedure comprising a message A (MSGA) and a message B (MSGB), the BS 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 cause the BS to:

receive the MSGA of the 2-step RA procedure, wherein the MSGA comprising a common control channel (CCCH) media access control (MAC) service data unit (SDU);

transmit, in response to the MSGA, the MSGB in a first slot, wherein the MSGB comprising a success random access response (RAR), wherein the success RAR comprising a hybrid automatic repeat request (HARQ) feedback timing indicator, a physical uplink control channel (PUCCH) resource indicator, and a user equipment (UE) contention resolution identity; and

receive a HARQ feedback on an uplink (UL) resource within a second slot after transmitting the success RAR in response to the UE contention resolution identity in a MAC sub-protocol data unit (subPDU) of the success RAR matching the CCCH MAC SDU, wherein

the HARQ feedback timing indicator indicates the second slot to the UE, wherein the second slot is separated from the first slot by an offset, and the offset comprising a timing offset value corresponding to a list of PUCCH resource offset candidates; and

the PUCCH resource indicator indicates the UL resource to the UE, wherein the UE resource corresponds to one of a list of PUCCH resource candidates indicated to the UE by the PUCCH resource indicator, wherein the list of PUCCH resource candidates is associated with a UL bandwidth part (BWP), wherein the HARQ feedback is transmitted on the UL BWP.

9. The BS of claim 8 , wherein the at least one processor further configured to execute the computer-executable instructions to cause the BS to:

receive the HARQ feedback from a lower layer of the UE.

10. The BS of claim 9 , wherein the lower layer comprising a physical layer of the UE.

11. The BS of claim 8 , wherein the at least one processor further configured to execute the computer-executable instructions to cause the BS to:

preconfigure, to the UE, the list of PUCCH resource candidate by a radio resource control (RRC) configuration.

12. The BS of claim 8 , wherein the at least one processor further configured to execute the computer-executable instructions to cause the BS to:

preconfigure, to the UE, the list of PUCCH resource offset candidate by a radio resource control (RRC) configuration.

13. The BS of claim 8 , wherein the at least one processor further configured to execute the computer-executable instructions to cause the BS to:

generate the success RAR by a MAC entity of the BS; and

transmit the success RAR via a downlink (DL) assignment.

14. The BS of claim 13 , wherein the DL assignment is scrambled by an MSGB-radio network temporary identity (RNTI).