Patent ID: 8861460

Claim:
A method for performing a random access procedure in a mobile communication system supporting carrier aggregation using a primary carrier and one or more secondary carriers, the method performed by a User Equipment (UE) and comprising: transmitting a first message comprising a random access preamble to an evolved NodeB (eNB) through the primary carrier; receiving a second message including first uplink (UL) grant information as a response to the random access preamble through the primary carrier; transmitting a third message including identity information of the UE to the eNB through an uplink radio resource corresponding to the first UL grant information; and receiving a Physical Downlink Control Channel (PDCCH) indicated by the identity information of the UE from the eNB, wherein, when the PDCCH is received through the primary carrier, the UE considers a contention resolution procedure according to transmission of the third message as a successful procedure, and wherein, when the PDCCH is received through the one or more secondary carriers, the UE considers the contention resolution procedure as an unsuccessful procedure.