Method and apparatus for handling MSGA retransmissions during two step random access procedures in wireless communication system

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

• receiving, from a terminal, a preamble for a message (MSG) A on a physical random access channel (PRACH);
• transmitting, to the terminal, a MSG B indicating fallback, in case that a medium access control (MAC) protocol data unit (PDU) for the MSG A is not received on a physical uplink shared channel (PUSCH);
• and
• receiving, from the terminal, a MAC PDU as a response to the MSG B, wherein the received MAC PDU is identified based on a buffer of the terminal,
• wherein a window for the MSG B starts at a first physical downlink control channel (PDCCH) monitoring occasion which is at least one symbol after a last symbol of the PUSCH.

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

• a transceiver;
• and
• a controller configured to:
• store a medium access control (MAC) protocol data unit (PDU) for a message (MSG) A in a buffer,
• transmit, to a base station, via the transceiver, a preamble for the MSG A on a physical random access channel (PRACH),
• transmit, to the base station, the MAC PDU for the MSG A on a physical uplink shared channel (PUSCH),
• receive, from the base station, via the transceiver, a MSG B indicating fallback, and
• transmit, to the base station, via the transceiver, a MAC PDU identified based on the buffer, as a response to the MSG B,
• wherein the MSG B is received by monitoring a window starting at a first physical downlink control channel (PDCCH) monitoring occasion, which is at least one symbol after a last symbol of the PUSCH.

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

• a transceiver;
• and
• a controller configured to:
• receive, from a terminal, via the transceiver, a preamble for a message (MSG) A on a physical random access channel (PRACH),
• transmit, to the terminal, via the transceiver, a MSG B indicating fallback, in case that a medium access control (MAC) protocol data unit (PDU) for the MSG A is not received on a physical uplink shared channel (PUSCH), and
• receive, from the terminal, via the transceiver, a MAC PDU as a response to the MSG B, wherein the received MAC PDU is identified based on a buffer of the terminal,
• wherein a window for the MSG B starts at a first physical downlink control channel (PDCCH) monitoring occasion which is at least one symbol after a last symbol of the PUSCH.