Wireless base station, user terminal and wireless communication system

In order to suppress decreases in system resource use efficiency in Licensed-Assisted Access (LLA) systems using Listen Before Talk (LBT), a wireless base station according to one embodiment of the present invention communicates with user terminals capable of using licensed bands and unlicensed bands, and is characterized by comprising an acquisition unit for acquiring information relating to the amount of available time resources as computed from the results of LBT on unlicensed bands, and a control unit for controlling communications with the user terminal on unlicensed bands based on the information relating to the amount of available time resources.