MOBILE COMMUNICATION SYSTEM, USER TERMINAL, PROCESSOR, AND BASE STATION

摘要

A mobile communication system, which supports D2D communication that is direct device to device communication, comprises: a user terminal that transmits a discovery signal that is used for discovering a communication partner terminal in the D2D communication, wherein the user terminal transmits the discovery signal when the user terminal accepts start of communication and the user terminal has difficulty to establish a connection with a base station.