1. A method for establishing multiple links through relay user equipments (UEs) by an UE which is out of coverage in a wireless communication system, the method comprising:transmitting a radio resource control (RRC) connection request to a temporary relay UE having a highest device-to-device (D2D) signal quality among relay UEs located adjacent to the UE;
receiving, from the temporary relay UE, an RRC connection setup indicating a first base station (BS) that will provide a serving link to the UE and a second BS that will provide a replacement link to the UE among BSs to which the relay UEs are connected;
establishing the serving link through a first relay UE by transmitting an RRC connection complete message to the first relay UE connected to the first BS among the relay UEs; and
establishing the replacement link, where unicast data transmission and reception is inactivated, through a second relay UE connected to the second BS among the relay UEs.