A UE performs first control channel monitoring according to a first CORESET and first search space set configuration(s), the first control channel monitoring performed on n subbands, n>1, able to be transmitted by a base station in an unlicensed band carrier. The UE determines, in response to a detection of a control channel in the monitoring and from the control channel, transmission bandwidth configuration to be used by the base station in the unlicensed band carrier for control channels. The UE performs second control channel monitoring according to a second CORESET and at least one second search space set configuration. The second control channel monitoring is performed on m subbands, m≤n, in the unlicensed band carrier, the m subbands being a subset of the n of subbands. A base station determines which subbands are available for use and transmits the transmission bandwidth configuration to the UE based thereon.