A method, performed by a terminal, in a wireless communication system, the method comprising: receiving, from a base station, a radio resource control, RRC, message including first uplink configuration information associated with a first message for a 2-step random access; transmitting the first message comprising a Physical Random Access Channel, PRACH, preamble and a Physical Uplink Shared Channel, PUSCH, based on the first uplink configuration information; receiving a random access response, RAR, as a response to the transmitted first message; identifying whether the received RAR is a fallback RAR or a success RAR; in case that the received RAR is the fallback RAR: determining a transport block size for a PUSCH scheduled by the fallback RAR, wherein the transport block size for the PUSCH scheduled by the fallback RAR is the same as a transport block size of the PUSCH included in the first message; determining a modulation and coding scheme for the PUSCH scheduled by the fallback RAR; and transmitting the PUSCH scheduled by the fallback RAR based on the determined transport block size and the determined modulation and coding scheme; and in case that the received RAR is the success RAR: transmitting information related to Hybrid Automatic Repeat request - Acknowledgment, HARQ-ACK, feedback based on a Physical Uplink Control Channel, PUCCH resource indicator included in the success RAR. receiving, from a base station, a radio resource control, RRC, message including first uplink configuration information associated with a first message for a 2-step random access; transmitting the first message comprising a Physical Random Access Channel, PRACH, preamble and a Physical Uplink Shared Channel, PUSCH, based on the first uplink configuration information; receiving a random access response, RAR, as a response to the transmitted first message; identifying whether the received RAR is a fallback RAR or a success RAR; in case that the received RAR is the fallback RAR: determining a transport block size for a PUSCH scheduled by the fallback RAR, wherein the transport block size for the PUSCH scheduled by the fallback RAR is the same as a transport block size of the PUSCH included in the first message; determining a modulation and coding scheme for the PUSCH scheduled by the fallback RAR; and transmitting the PUSCH scheduled by the fallback RAR based on the determined transport block size and the determined modulation and coding scheme; and determining a transport block size for a PUSCH scheduled by the fallback RAR, wherein the transport block size for the PUSCH scheduled by the fallback RAR is the same as a transport block size of the PUSCH included in the first message; determining a modulation and coding scheme for the PUSCH scheduled by the fallback RAR; and transmitting the PUSCH scheduled by the fallback RAR based on the determined transport block size and the determined modulation and coding scheme; and in case that the received RAR is the success RAR: transmitting information related to Hybrid Automatic Repeat request - Acknowledgment, HARQ-ACK, feedback based on a Physical Uplink Control Channel, PUCCH resource indicator included in the success RAR. <EOS>