A wireless device receives message(s) configuring transmissions of sounding reference signals on a secondary cell in a secondary cell group. The wireless device receives an activation command to activate the secondary cell. The wireless device transmits one or more of the sounding reference signals on the secondary cell after applying a timing advance command to the secondary cell group. The wireless device is configured to not transmit any of the sounding reference signals on the secondary cell during a period between receiving the message(s) and applying the timing advance command to the secondary cell group.