There is disclosed a method for operating a radio node for a wireless communication network, the radio node being adapted for transmitting communication data on at least one carrier based on a timing relative to a pre-defined time structure. The method comprises defining at least one freeze interval relative to the pre-defined time structure, performing a Listen-Before-Talk, LBT, procedure to determine whether accessing the at least one carrier for transmission is allowed, and, if accessing the at least one carrier for transmission is determined to be allowed based on performing the LBT procedure, starting transmission of communication data on the at least one carrier outside the at least one freeze interval. There are also disclosed a corresponding node, system, program product and storage medium.