A method for performing PDCCH monitoring of component carriers (CCs) in a carrier aggregation scheme that aggregates a first CC and a second CC. In some embodiments, the method includes: calculating a first monitoring occasion start time for a monitoring occasion of the first CC, wherein the first monitoring occasion start time is expressed as a first symbol-index value; calculating a second monitoring occasion start time for a monitoring occasion of the second CC, wherein the second monitoring occasion start time is expressed as a second symbol-index value; and generating a schedule for the monitoring occasion of the first CC and the monitoring occasion of the second CC based on an ascending order of the first monitoring occasion start time and the second monitoring occasion start time.