1. A method for a User Equipment (UE) operating in a wireless communication system, the method comprising:receiving a Radio Link Control (RLC) Protocol Data Unit (PDU) including a Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU) from a peer UE;
establishing a RLC entity and a PDCP entity for a UE-to-UE direct communication;
initializing one or more state variables of the RLC entity to a sequence number (SN) of the RLC PDU when the RLC entity is established for the UE-to-UE direct communication;
processing the RLC PDU using the initialized state variables;
deciphering the PDCP SDU based on a PDCP SN of the PDCP SDU,
wherein deciphering the PDCP SDU does not requires a Hyper Frame Number (HFN) of the PDCP SDU to be incremented when the PDCP SN reaches to a maximum value.