Random access procedure(s) for radio system

A user equipment (UE), 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:
• initiate a random access (RA) procedure by a medium access control (MAC) layer of the UE for a system information (SI) request triggered by an upper layer of the UE;
• select a specific preamble index corresponding to the SI request from a group of RA preambles, the specific preamble index being associated with a specific Radio Network Temporary Identifier (RNTI) corresponding to the SI request;
• transmit, to a base station (BS), an RA preamble based on the specific preamble index using the specific RNTI on a physical random access channel (PRACH) resource during the RA procedure;
• receive, from the BS, a downlink assignment on a Physical Downlink Control Channel (PDCCH) for the specific RNTI, the downlink assignment scheduling a Physical Downlink Shared Channel (PDSCH);
• receive, from the BS, a Random Access Response (RAR) on the PDSCH, the RAR including a MAC protocol data unit (PDU) during the RA procedure, the MAC PDU including a first MAC subheader;
• consider the RAR reception successful in a case that the first MAC subheader includes a random access preamble identifier (RAPID) corresponding to the RA preamble;
• indicate, by the MAC layer of the UE, successful reception of the RAR for the SI request to the upper layer of the UE after the RAR reception is considered successful;
• and
• consider the RA procedure successfully completed in a case that the MAC PDU includes no MAC RAR corresponding to the first MAC subheader.