The present invention relates to a wireless communication system and a user equipment (UE) providing wireless communication services, and more particularly, a method of preventing transmission error of data while maintaining its security and a method of controlling an access of a Relay Node (RN) to a Donor eNB (DeNB) and an access of the UE to the RN during a process of transmitting and receiving user data when the RN as a radio network node is connected to the DeNB in an Evolved Universal Mobile Telecommunications System (E-UMTS), a Long Term Evolution (LTE) system, and a LTE-Advanced (LTE-A) system that have evolved from a Universal Mobile Telecommunications System (UMTS).