Base station and user terminal

A base station used in a mobile communication system supporting a D2D proximity service which enables direct device to device communication, the base station comprising:

• a receiver configured to receive D2D range information from a user terminal, the D2D range information indicating a permissible communication range of the user terminal in the D2D proximity service;
• a controller configured to determine, based on the D2D range information, whether to allow the user terminal to execute transmission/reception operations of a D2D synchronization signal to directly establish device to device synchronization;
• and
• a transmitter configured to transmit information indicating results of the determination to the user terminal, wherein
• a plurality of classes including classes each corresponding to a plurality of levels of permissible communication ranges are defined,
• the D2D range information is information indicating a class of the plurality of classes,
• the plurality of classes includes:
• a first class that supports a wide range of the D2D proximity service including a serving cell and an adjacent cell;
• and
• a second class that supports only a narrow range of the D2D proximity service not including the adjacent cell,
• the controller is configured to determine to allow the user terminal to execute the transmission/reception operations of the D2D synchronization signal in response to the D2D range information indicating the first class, and
• the controller is configured to determine to allow the user terminal not to execute the transmission/reception operations of the D2D synchronization signal in response to the D2D range information indicating the second class.