A base station according to the first embodiment and the second embodiment is included in a network in a mobile communication system that supports a cellular communication in which a data path passes through a network, and a D2D communication that is a direct device-to-device communication in which a data path does not pass through the network. The base station includes a transmitter configured to transmit broadcast information that enables the D2D communication even in a specific state in which a user terminal does not establish a connection with the network.

Hereinafter, with reference to the drawings, a description will be provided for an embodiment in a case where D2D communication is introduced to an LTE system which is one of mobile communication systems configured based on the 3GPP standards.

(LTE System)

FIG. 1 is a configuration diagram of an LTE system according to the first embodiment. As illustrated in FIG. 1, the LTE system includes a plurality of UEs (User Equipment) 100, E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) 10, and EPC (Evolved Packet Core) 20. The E-UTRAN 10 corresponds to a radio access network and the EPC 20 corresponds to a core network. The E-UTRAN 10 and the EPC 20 configure a network of the LTE system.

The UE 100 is a mobile communication device and performs radio communication with a cell (a serving cell) with which a connection is established. The UE 100 corresponds to the user terminal.