METHOD AND APPARATUS FOR PERFORMING RANDOM ACCESS PROCEDURE IN WIRELESS COMMUNICATION SYSTEM

The present invention relates to a method of performing a Random Access (RA) procedure by a user equipment (UE) in a wireless communication system. Especially, the method includes the steps of generating a data unit; transmitting a first MsgA and a second MsgA to a network, wherein the first MsgA includes a first RA preamble and the data unit, and wherein the second MsgA includes a second RA preamble and the data unit; starting a first window for monitoring a first MsgB for the first MsgA and a second window for monitoring a second MsgB for the second MsgA; and monitoring the first MsgB until the first window expires and a second MsgB until the second window expires, wherein, when one of the first MsgB and the second MsgB is detected and when the detected MsgB includes successRAR, both the first and second windows are stopped.