The present invention relates to a method for transmitting signals by a transmission end in a wireless communication system. In particular, the method includes the steps of: configuring one Packet Data Convergence Protocol (PDCP) entity, at least one first RLC entity related to the one PDCP entity and at least one second RLC entity related to the one PDCP entity; determining whether a service data unit (SDU) to be transmitted is a special SDU or not; if the SDU is the special SDU, transmitting the SDU to the at least one first RLC entity; and if the SDU is not the special SDU, transmitting the SDU to the at least one second RLC entity.