User equipment and discontinuous reception control method in mobile communication system

User equipment capable of communicating by using N component carriers (CCs) through carrier aggregation, the user equipment comprising:

• N communication units configured to execute radio communication with a base station by using each of the N CCs;
• a controller configured to individually control an operation mode of each of the N communication units;
• and
• a plurality of timers, each configured to report to the controller that a constant time period has elapsed without receiving a further control signal, after receiving, by a communication unit of the N communication units, a control signal from the base station,
• wherein N is greater than or equal to 2,
• wherein, in response to detecting that a report from a first timer of the plurality of timers is received for a first communication unit of the N communication units, the controller is configured to control the operation mode of the first communication unit such that the first communication unit transitions to discontinuous reception mode, and
• wherein a specific plurality of communication units belonging to the N communication units, the specific plurality of communication units not including the first communication unit, is grouped such that operation modes of the specific plurality of communication units simultaneously transition to discontinuous reception modes, in response to detecting that a report from a second timer of the plurality of timers, the second timer being different from the first timer, is received for one of the specific plurality of communication units.