A method for a user equipment, UE, to perform communication in an unlicensed band, the method comprising: detecting a channel occupancy failure for an unlicensed band radio resource for transmitting uplink data; when the channel occupancy failure meets a predetermined criterion, determining that channel access fails for the unlicensed band radio resource; and upon the channel access failure, transmitting a higher layer signaling to a base station, the method further comprising, in a case where two or more bandwidth parts of the unlicensed band radio resource are configured, if one bandwidth part is determined to be the channel access failure, performing bandwidth part switching using another bandwidth part, wherein if the channel access failure occurs in a primary SCell, PSCell, or a secondary cell, SCell, the higher layer signaling is a secondary cell group, SCG, failure information message, the SCG failure information message being transmitted via a master cell group, MCG, wherein the base station performs the PSCell change or SCG change or SCG release procedure, wherein determining that the channel access fails includes determining that the channel access fails when a number of channel occupancy failures in the unlicensed band radio resource for transmitting the uplink data exceeds a threshold configured by the base station, and wherein determining that the channel access fails includes calculating the number of channel occupancy failures by increasing a value of a counter associated with the channel occupancy failure if the channel occupancy failure in the unlicensed band radio resource for transmission of the uplink data is detected. detecting a channel occupancy failure for an unlicensed band radio resource for transmitting uplink data; when the channel occupancy failure meets a predetermined criterion, determining that channel access fails for the unlicensed band radio resource; and upon the channel access failure, transmitting a higher layer signaling to a base station, the method further comprising, in a case where two or more bandwidth parts of the unlicensed band radio resource are configured, if one bandwidth part is determined to be the channel access failure, performing bandwidth part switching using another bandwidth part, wherein if the channel access failure occurs in a primary SCell, PSCell, or a secondary cell, SCell, the higher layer signaling is a secondary cell group, SCG, failure information message, the SCG failure information message being transmitted via a master cell group, MCG, wherein the base station performs the PSCell change or SCG change or SCG release procedure, wherein determining that the channel access fails includes determining that the channel access fails when a number of channel occupancy failures in the unlicensed band radio resource for transmitting the uplink data exceeds a threshold configured by the base station, and wherein determining that the channel access fails includes calculating the number of channel occupancy failures by increasing a value of a counter associated with the channel occupancy failure if the channel occupancy failure in the unlicensed band radio resource for transmission of the uplink data is detected.