Method and apparatus for monitoring a downlink control channel in a wireless communication system supporting multiple carriers

A user equipment that supports carrier aggregation performing communication using a plurality of component carriers, the user equipment comprising:

• a radio resource control (RRC) layer module performing a discontinuous reception (DRX) function;
• a plurality of HARQ (Hybrid Automatic Repeat Request) entities respectively corresponding to the plurality of component carriers;
• a MAC layer module performing an operation based on the DRX function of the RRC layer module;
• and
• a physical layer module mapping a transport channel received from the HARQ entities into an uplink physical channel and transmitting the mapped data to a network, and receiving a downlink control channel from the network,
• wherein the MAC layer module receives configuration information on a specific one of the plurality of component carriers from the network, and starts a timer configured by the RRC layer module if the physical layer module receives a control signal from the network through the downlink control channel, and the physical layer module monitors the downlink control channel through the specific component carrier if the timer expires and deactivates the other component carriers of the plurality of component carriers.