Mobile communication system, user terminal, and base station

Abstract

A mobile communication system according to an embodiment 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 mobile communication system comprises: an eNB 200 included in the network and configured to transmit D2D broadcast information; and a UE 100 configured to perform the D2D communication after receiving the D2D broadcast information from the eNB 200. The D2D broadcast information is information that enables the D2D communication even though the UE 100 is in a specific state in which a connection with the network is not established. The UE 100 performs the D2D communication in the specific state on the basis of the D2D broadcast information.

1 . A mobile communication system, which 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, comprising:
 a base station included in the network and configured to transmit broadcast information; and   a user terminal configured to perform the D2D communication after receiving the broadcast information from the base station, wherein   the broadcast information is information that enables the D2D communication even though the user terminal is in a specific state in which a connection with the network is not established, and   the user terminal performs the D2D communication in the specific state on the basis of the broadcast information.   
     
     
         2 . The mobile communication system according to  claim 1 , wherein the specific state is an idle state indicating a state in which the user terminal does not establish the connection in a coverage of the network. 
     
     
         3 . The mobile communication system according to  claim 1 , wherein the specific state is a state in which the user terminal exists out of a coverage of the network. 
     
     
         4 . The mobile communication system according to  claim 3 , wherein the base station is a base station that manages a termination cell included in a termination area of the coverage. 
     
     
         5 . The mobile communication system according to  claim 1 , wherein the broadcast information includes resource information indicating a radio resource permitted to be used in one of the D2D communication and a terminal discovery process for starting the D2D communication. 
     
     
         6 . The mobile communication system according to  claim 1 , wherein the broadcast information includes power information indicating a maximum transmission power permitted in one of the D2D communication and a terminal discovery process for starting the D2D communication. 
     
     
         7 . The mobile communication system according to  claim 5 , wherein the base station does not use the radio resource permitted to be used in one of the D2D communication and the terminal discovery process, in the cellular communication. 
     
     
         8 . The mobile communication system according to  claim 1 , wherein the user terminal performs the D2D communication after disconnecting the connection on the basis of the broadcast information, when the connection is established before the D2D communication is performed. 
     
     
         9 . The mobile communication system according to  claim 2 , wherein the user terminal performing the D2D communication transmits, to the network, information indicating a request to avoid an interference after establishing the connection or in a process of establishing the connection, in response to detection of the interference to the D2D communication from another user terminal. 
     
     
         10 . The mobile communication system according to  claim 3 , wherein the user terminal performing the D2D communication determines to stop the D2D communication and transmits information indicating stop of the D2D communication to a terminal with which the user terminal communicates, in response to detection of an interference to the D2D communication from another user terminal. 
     
     
         11 . The mobile communication system according to  claim 1 , wherein the user terminal performing the D2D communication performs negotiation between terminals such that a radio resource used in a D2D terminal group including the user terminal is different from a radio resource used in another D2D terminal group including another user terminal, in response to detection of an interference to the D2D communication from the another user terminal. 
     
     
         12 . The mobile communication system according to  claim 1 , wherein the user terminal performing the D2D communication changes a radio resource used in the D2D communication to another radio resource, in response to detection of an interference to the D2D communication from another user terminal. 
     
     
         13 . The mobile communication system according to  claim 12 , wherein the user terminal, which changes the radio resource used in the D2D communication to the another radio resource, broadcasts change information indicating a change to the another radio resource by using the another radio resource. 
     
     
         14 . The mobile communication system according to  claim 13 , wherein the another user terminal notifies a the another user terminal's serving cell of a fact that the change information is received, when the another user terminal, which belongs to a D2D terminal group different from a D2D terminal group including the user terminal, receives the change information during using the another radio resource. 
     
     
         15 . The mobile communication system according to  claim 13 , wherein the another user terminal notifies the user terminal of a fact that the another radio resource is being used, when the another user terminal, which belongs to a D2D terminal group different from a D2D terminal group including the user terminal, receives the change information during using the another radio resource, 
     
     
         16 . The mobile communication system according to  claim 1 , wherein the user terminal performs the D2D communication by using a frequency hopping scheme, and the broadcast information includes information indicating a hopping pattern permitted to be used in the D2D communication. 
     
     
         17 . A user terminal, which is used 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, comprising:
 a receiver configured to receive broadcast information from a base station included in the network; and   a controller configured to perform the D2D communication after the receiver receives the broadcast information, wherein   the broadcast information is information that enables the D2D communication even though the user terminal is in a specific state in which a connection with the network is not established, and   the controller performs the D2D communication in the specific state on the basis of the broadcast information.   
     
     
         18 . A base station, which is included in a network in a mobile communication system that supports a cellular communication in which a data path passes through the network, and a D2D communication that is a direct device-to-device communication in which a data path does not pass through the network, comprising:
 a transmitter configured to transmit broadcast information that enables the D2D communication even though a user terminal is in a specific state in which a connection with the network is not established.