1. A method of device to device direct communication, the method comprising:receiving, by a user equipment (UE), one or more discovery messages on a physical sidelink discovery channel (PSDCH) for relay related discovery;
identifying an identifier (ID) of a relay UE that transmits a discovery message of the one or more discovery messages, wherein the discovery message is a discovery announcement message;
generating, by the UE, a reference signal received power (RSRP) measurement associated with the identified ID of the relay UE by measuring power of resource elements carrying demodulation reference signals (DMRSs) corresponding to the PDSCH on which the discovery message is received, if the discovery message is passed through cyclic redundancy check (CRC);
filtering, by the UE, RSRP measurements corresponding to a same ID among RSRP measurements corresponding to the one or more discovery messages; and
selecting a relay UE among relay UES corresponding to the one or more discovery messages based on the filtered RSRP measurements.