1. A method for a base station in a wireless access system, the method comprising:selecting a first component carrier (CC) included in a set of CCs, wherein the CCs are configured in an unlicensed band;
performing a first channel access procedure (CAP) on the first CC;
transmitting, based on the first CAP, a first transmission burst on the first CC after the first CC is determined to be idle and after a random number decrements to 0 based on decrementing the random number by 1 for each slot duration related to the first CC determined to be idle, wherein the random number is randomly obtained among a value included in a contention window;
performing a second CAP on a second CC included in the set of CCs for a predetermined time duration immediately before the transmission of the first transmission burst on the first CC, wherein the second CC is different from the first CC; and
transmitting, based on the second CAP, a second transmission burst on the second CC after the second CC is determined to be idle for the predetermined time duration.