Apparatus and method for performing device-to-device communication in wireless communication system

1. A method for performing device-to-device (D2D) communication, by a first device, in a wireless communication system, the method comprising:

receiving a discovery signal from one or more D2D devices while performing the D2D communication with a second device;

transmitting a report on the received discovery signal to a base station;

performing D2D link monitoring (DLM);

transmitting a D2D link failure (DLF) declaration to the base station, when the DLM result meets a predetermined condition; and

performing communication with the second device via a relay device determined by the base station based on the report and a response to a relaying request.

2. The method of claim 1 , wherein, in case the first device corresponds to a transmitting end of the D2D link, the predetermined condition corresponds to one of consecutively receiving a predetermined number of negative acknowledgements (NACKs) and failing to consecutively receive a predetermined number of acknowledgements (ACKs).

3. The method of claim 2 , wherein performing communication with the second device through the relay device comprises:

transmitting a signal that is to be transmitted to the second device to the relay device through a resource allocated by the base station; and

measuring a discovery signal from one or more D2D devices while performing the D2D communication with the relay device.

4. The method of claim 1 , wherein, in case the first device corresponds to a receiving end of the D2D link, the predetermined condition corresponds to a demodulation performance of the signal received through the D2D link being lower than a predetermined value.

5. The method of claim 2 , wherein the DLF includes information related to data corresponding to a last acknowledgement (ACK) transmitted by the second device.

6. The method of claim 5 , wherein the information related to data corresponding to a last acknowledgement (ACK) transmitted by the second device includes one or more of a transmission block number and an internet protocol packet sequence number.

7. The method of claim 3 , further comprising:

transmitting a handover request message to the base station based on the measured discovery signal while performing the D2D communication with the relay device.

8. A method for supporting device-to-device (D2D) communication, by a base station, in a wireless communication system, the method comprising:

receiving, from a first device, a report on a discovery signal received by a first device from one or more D2D devices while performing the D2D communication with a second device;

receiving a D2D Link Failure (DLF) declaration from the first device; and

determining a relay device that is to relay communication between the first device and a second device based on the received report and a response to a relaying request,

wherein the DLF declaration is transmitted when a D2D Link Monitoring (DLM) result of the first device meets a predetermined condition.

9. The method of claim 8 , wherein, in case the first device corresponds to a transmitting end of the D2D link, the predetermined condition corresponds to one of consecutively receiving a predetermined number of negative acknowledgements (NACKs) and failing to consecutively receive a predetermined number of acknowledgements (ACKs).

10. The method of claim 9 , further comprising:

having the first device allocate resources that is to be used when transmitting a signal to the second device through the relay device.

11. The method of claim 8 , wherein, in case the first device corresponds to a receiving end of the D2D link, the predetermined condition corresponds to a demodulation performance of the signal received through the D2D link being lower than a predetermined value.

12. The method of claim 9 , wherein the DLF includes information related to data corresponding to a last acknowledgement (ACK) transmitted by the second device.

13. The method of claim 12 , wherein the information related to data corresponding to a last acknowledgement (ACK) transmitted by the second device includes one or more of a transmission block number and an internet protocol packet sequence number.

14. The method of claim 8 , further comprising:

receiving a handover request message from the first device based on a discovery signal measured by the first device while performing the D2D communication with the relay device.