Systems, apparatus, user equipment (UE), evolved node B (eNB), computer readable media, and methods are described for multi-carrier listen before talk operations. In various embodiments, a transmitting device may assign one or more primary carriers to perform listen before talk (LBT) operations, with non-primary carriers performing a channel sensing operation at the end of the LBT operations of at least one primary channel. In various embodiments, the LBT operations at the primary carriers may use a shared random countdown number or an independent random countdown.