Method and apparatus for device to device communication

A method of performing a device-to-device (D2D) communication by a user equipment (UE), the method comprising:

• receiving an expression broadcasted by a UE;
• acquiring a proximity service identifier (ProSe ID) of the UE or a user of the UE;
• sending a direct D2D connection request message to the UE via a core network;
• receiving a direct connection accept message in response to the direct D2D connection request message;
• and
• performing the D2D communication with the UE using the ProSe ID.

A method of supporting device-to-device (D2D) communication by a communication entity, the method comprising:

• receiving, from a first user equipment (UE), a direct connection request message for requesting a connection with a second UE;
• sending a paging message to the second UE;
• forwarding the direct connection request message to the second UE after the second UE is in a connected state;
• receiving a direct connection accept message from the second UE in response to the direct connection request message;
• and
• forwarding the direct connection accept message to the first UE.

A user equipment (UE) of performing a device-to-device (D2D) communication, the UE comprising:

• a controller configured to control acquiring a proximity service identifier (ProSe ID) of the UE or a user of the UE, which is used in the D2D communication, generate an expression using the ProSe ID and control broadcasting the generated expression;
• a receiver configured to receive a direct D2D connection request message from another UE via a core network;
• and
• a transmitter configured to send a direct connection accept message in response to the direct D2D connection request message,
• wherein the controller controls performing the D2D communication with the other UE.

A user equipment (UE) of performing a device-to-device (D2D) communication, the UE comprising:

• a receiver configured to receive an expression broadcasted by a UE;
• a controller configured to control acquiring a proximity service identifier (ProSe ID) of the UE or a user of the UE;
• and
• a transmitter configured to send a direct D2D connection request message to the UE via a core network,
• wherein when the receiver is configured to receive a direct connection accept message in response to the direct D2D connection request message, and the controller is configured to control performing the D2D communication with the UE using the ProSe ID.

A communication entity of supporting device-to-device (D2D) communication, the method comprising:

• a receiver configured to receive, from a first user equipment (UE), a direct connection request message for requesting a connection with a second UE;
• a transmitter configured to send a paging message to the second UE;
• and
• a controller configured to control forwarding the direct connection request message to the second UE after the second UE is in a connected state,
• wherein when the receiver is configured to receive a direct connection accept message from the second UE in response to the direct connection request message, and the controller is configured to control forwarding the direct connection accept message to the first UE.