Method and apparatus for switching between 2 step and 4 step random access (RA) procedures and contention resolutions

A method performed by a base station in a wireless communication system, the method comprising:

• receiving, from a terminal, a message A (MsgA) associated with a 2 step random access (RA) procedure, the MsgA including a cell-radio network temporary identifier (C-RNTI);
• and
• transmitting, to the terminal, a physical downlink control channel (PDCCH),
• wherein the 2 step RA procedure is successfully completed, in case that a time alignment timer (TAT) is running and the PDCCH scheduling an uplink transport block (TB) is addressed to the C-RNTI, and
• wherein the 2 step RA procedure is successfully completed, in case that the TAT is not running, the PDCCH scheduling a downlink TB is addressed to the C-RNTI and a timing advance (TA) command is transmitted based on the downlink TB.

A terminal in a wireless communication system, the terminal comprising:

• a transceiver;
• and
• at least one processor configured to:
• transmit, to a base station, a message A (MsgA) associated with a 2 step random access (RA) procedure, the MsgA including a cell-radio network temporary identifier (C-RNTI),
• receive, from the base station, a physical downlink control channel (PDCCH), and
• identify whether the 2 step RA procedure is successfully completed,
• wherein the 2 step RA procedure is successfully completed, in case that a time alignment timer (TAT) is running and the PDCCH scheduling an uplink transport block (TB) is addressed to the C-RNTI, and
• wherein the 2 step RA procedure is successfully completed, in case that the TAT is not running, the PDCCH scheduling a downlink TB is addressed to the C-RNTI and a timing advance (TA) command is received based on the downlink TB.

A base station in a wireless communication system, the base station comprising:

• a transceiver;
• and
• at least one processor configured to:
• receive, from a terminal, a message A (MsgA) associated with a 2 step random access (RA) procedure, the MsgA including a cell-radio network temporary identifier (C-RNTI), and
• transmit, to the terminal, a physical downlink control channel (PDCCH),
• wherein the 2 step RA procedure is successfully completed, in case that a time alignment timer (TAT) is running and the PDCCH scheduling an uplink transport block (TB) is addressed to the C-RNTI, and
• wherein the 2 step RA procedure is successfully completed, in case that the TAT is not running, the PDCCH scheduling a downlink TB is addressed to the C-RNTI and a timing advance (TA) command is transmitted based on the downlink TB.