A wireless device is configured to operate in at least a first serving cell on a first carrier, and a first downlink message requests that a second serving cell on a second carrier be added or released. In response to the first downlink message, the second serving cell on the second carrier is added or released. Within a time period starting from the time resource, wireless device transmits, on the second serving cell, a first uplink message indicating completion of the addition or release of the second serving cell. The time period starting from the time reserving source is of a length that is a function of at least one parameter related to a clear channel assessment (CCA) procedure.