Random access method using ndi and user equipment for the same

PURPOSE: A method for performing an random access using NDI and a terminal device for the same ignores a uplink authentication signal in a MAC(Medium Access Control) layer module if an random access is failed, thereby preventing a transmission of unnecessary uplink signal. CONSTITUTION: A UE(User Equipment) transmits an random access preamble to a eNB(evolved-NodeB)(S701). The eNB transmits a random access response to the terminal(S702). The CR timer of the terminal receives uplink authentication information which being operating(S706). The uplink authentication information is instructed through a temporal cell identifier of the terminal form the eNB. If NDI(New Data Indicator) of the received downlink signal is set to one, the terminal performs following process according to a random access procedure failure(S708).