Methods and apparatuses for performing communication on an unlicensed band. A method, performed by a UE, of performing the communication on the unlicensed band, according to an embodiment, includes receiving SI (system information) scheduling information from a base station, identifying at least one of a primary SI window number or a secondary SI window number for a SI message based on the SI scheduling information, monitoring at least one window corresponding to the primary SI window number, and in response to the SI message being not received, monitoring at least one window corresponding to the secondary SI window number.