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

A user equipment (UE) configured to perform a 2-step random access (RA) procedure including a message A (MSGA) and a message B (MSGB), the UE 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, and configured to execute the one or more computer-executable instructions to cause the UE to:
• transmit the MSGA of the 2-step RA procedure, the MSGA including a Common Control Channel (CCCH) Media Access Control (MAC) Service Data Unit (SDU);
• monitor an MSGB-Radio Network Temporary Identity (RNTI) within an MSGB time window, the MSGB time window starting from an earliest symbol of an earliest Physical Downlink Control Channel (PDCCH) occasion after an end of the MSGA transmission;
• receive, in response to transmitting the MSGA, the MSGB in a first slot, the MSGB including a success random access response (RAR), the success RAR containing a Hybrid Automatic Repeat reQuest (HARQ) Feedback Timing Indicator, a Physical Uplink Control Channel (PUCCH) Resource Indicator, and a UE Contention Resolution Identity;
• determine, by a MAC entity of the UE, to instruct a lower layer to transmit a HARQ feedback in response to the reception of the success RAR, wherein:
• the HARQ feedback is transmitted in a second slot determined by the HARQ Feedback Timing Indicator, and
• the second slot is separated from the first slot by an offset, the offset comprising a timing offset value determined from a list of PUCCH resource offset candidates;
• deliver, by the MAC entity of the UE, the HARQ Feedback Timing Indicator and the PUCCH Resource Indicator to the lower layer;
• and
• transmit, by the lower layer, the HARQ feedback on an uplink (UL) resource within the second slot, the UL resource being determined by the PUCCH Resource Indicator when the UE Contention Resolution Identity in a MAC sub-Protocol Data Unit (subPDU) of the success RAR matches the CCCH MAC SDU, the UL resource corresponding to one of the list of PUCCH resource candidates indicated by the PUCCH Resource Indicator, wherein the list of PUCCH resource candidates is associated with a UL bandwidth part (BWP).