Patent ID: 8406179

Claim:
A method for performing a random access by a User Equipment (UE) in a mobile communication system, the method comprising: transmitting a preamble to an Evolved Node B (ENB) via a first message when performing the random access, the preamble including at least one of a size of a third message that the UE will transmit and information indicating a channel condition; receiving a second message from the ENB in response to the first message, the second message including at least one of uplink (UL) transmission resource information by which the UE will transmit the third message and a size of the third message designated by the ENB; comparing the size of the third message designated by the ENB with a predetermined size, and designating a message format of the third message according to the comparison result; and generating and transmitting the third message according to the designated message format, wherein responsive to the designated message format, the third message is configured in the designated message format to include a normal MAC Packet Data Unit (PDU) or a transparent Radio Resource Control (RRC) message indicating that a UE having no RRC connection to the ENB transmits for the first time.