Patent ID: 8406180

Claim:
A method of performing a random access procedure by a user equipment in a wireless communication system, the method comprising: transmitting, by the user equipment, a random access preamble to a base station; receiving, by the user equipment, a random access response from the base station as a response to the random access preamble; generating, by the user equipment, a temporary identifier that is selected based on a set of random access preambles and a plurality of temporary identifiers reserved for each random access preamble; transmitting, by the user equipment, a radio resource control (RRC) connection request message comprising information on the temporary identifier and information on a unique identifier of the user equipment to the base station on an uplink shared channel (UL-SCH); receiving, by the user equipment, the temporary identifier on a physical downlink control channel (PDCCH) from the base station; if the temporary identifier on the PDCCH is confirmed, receiving, by the user equipment, a first contention resolution message including the unique identifier of the user equipment within a cell from the base station on a downlink shared channel (DL-SCH), the first contention resolution message being addressed to the temporary identifier on the PDCCH; transmitting, by the user equipment, a non-acknowledgement (NACK) signal to the base station if the first contention resolution message is not successfully received; receiving, by the user equipment, a second contention resolution message from the base station, the second contention resolution message being a retransmission of the first contention resolution message, a time interval between the first contention resolution message and the second contention resolution message being pre-determined, and the second contention resolution message being received under synchronization with the first contention resolution message; and transmitting, by the user equipment, an acknowledgement (ACK) signal to the base station.