Mobile communication system and user terminal

Abstract

In a mobile communication system that supports D2D communication in which radio communication is directly performed between a first user terminal and a second user terminal in a frequency and a time assigned from a base station, in a time in which data is to be received from the first user terminal, when the second user terminal does not receive the data from the first user terminal, the second user terminal transmits failure notification indicating reception failure in the D2D communication to the base station.

1 . A mobile communication system comprising a first user terminal and a second user terminal, wherein
 D2D communication is radio communication is directly performed between the first user terminal and the second user terminal in a frequency and a time assigned from a base station, and   in a time in which data is to be received from the first user terminal, when the second user terminal does not receive the data from the first user terminal, the second user terminal transmits failure notification indicating reception failure in the D2D communication to the base station.   
     
     
         2 . The mobile communication system according to  claim 1 , wherein, in a time in which data is to be transmitted to the second user terminal, when there is no data to be transmitted to the second user terminal, the first user terminal transmits predetermined data to the second user terminal. 
     
     
         3 . The mobile communication system according to  claim 2 , wherein, in the time in which the data is to be transmitted to the second user terminal, when there is no data to be transmitted to the second user terminal and a passage time after data is finally transmitted to the second user terminal is smaller than a threshold value, the first user terminal repeatedly transmits the finally transmitted data as the predetermined data. 
     
     
         4 . The mobile communication system according to  claim 2 , wherein, in the time in which the data is to be transmitted to the second user terminal, when there is no data to be transmitted to the second user terminal and a passage time after data is finally transmitted to the second user terminal is equal to or more than a threshold value, the first user terminal transmits dummy data as the predetermined data. 
     
     
         5 . The mobile communication system according to  claim 1 , wherein
 in a time in which data is to be transmitted to the second user terminal, when there is no data to be transmitted to the second user terminal, the first user terminal transmits, to the base station, data notification indicating that there is no data to be transmitted to the second user terminal, and   after the base station receives the data notification from the first user terminal, when the base station receives the failure notification from the second user terminal, the base station ignores the failure notification from the second user terminal.   
     
     
         6 . The mobile communication system according to  claim 1 , wherein, when the second user terminal determines that the reception failure is caused by interference from another D2D communication, the second user terminal includes information on the other D2D communication into the failure notification, and transmits the failure notification to the base station. 
     
     
         7 . A user terminal that performs D2D communication which is radio communication is directly performed with another user terminal in a frequency and a time assigned from a base station, comprising:
 a notification transmission unit that transmits failure notification indicating reception failure in the D2D communication to the base station when data is not received from the other user terminal in a time in which the data is to be received from the other user terminal.   
     
     
         8 . A user terminal that performs D2D communication which is radio communication is directly performed with another user terminal in a frequency and a time assigned from a base station, comprising:
 a data transmission unit that transmits predetermined data to the other user terminal when there is no data to be transmitted to the other user terminal in a time in which the data is to be transmitted to the other user terminal.