In a mobile communication system, an RRM measurement set is set as a collection of cells to become targets on which a UE performs a process of detecting whether or not radio communication is allowed. Among the cells in the RRM measurement set, a CoMP measurement set is set as a collection of cells to become candidates on which the UE performs a process of detecting whether or not coordinated communication (CoMP communication) is allowed. Among the cells of the CoMP measurement set, a CoMP active set is set as a collection of cells to become targets on which the UE performs the process of detecting whether or not CoMP communication is allowed.