Operation with various timers in a wireless communication system

1. A method for a user equipment (UE) operating in a wireless communication system, the method comprising:

receiving, by the UE, values for each of a plurality of timers related with a discontinuous reception (DRX) operation from a network;

monitoring, by the UE, a physical downlink control channel (PDCCH) from subframe n+1 to subframe n+X based on a first timer among the plurality of timers, when a first event for starting the first timer occurs at subframe n and a value for the first timer among the received values is X; and

monitoring, by the UE, the PDCCH from the subframe n to the subframe n+X−1 based on a second timer among the plurality of timers, when a second event for starting the second timer occurs at the subframe n and a value for the second timer among the received values is X, wherein X is greater than zero.

2. The method of claim 1 , wherein the first event comprises receiving a PDCCH indicating a new transmission, and

wherein the first timer comprises a DRX inactivity timer.

3. The method of claim 1 , wherein the first event comprises transmitting a message 3 of a random access procedure, and

wherein the first timer comprises a medium access control (MAC) contention resolution timer.

4. The method of claim 1 , wherein the second event comprises a case when a hybrid automatic repeat request (HARQ) retransmission timer (RTT) expires at the subframe n and data of a corresponding HARQ process was not successfully decoded, and

wherein the second timer comprises a DRX retransmission timer.

5. The method of claim 1 , wherein the second event comprises a case when system frame number meets a predetermined condition with regards to a DRX cycle, and

wherein the second timer comprises an on duration timer.

6. The method of claim 5 , wherein the DRX cycle is based on either a long DRX cycle or a short DRX cycle, and

wherein, if the received value for a DRX short cycle timer is X, the UE uses the short DRX cycle during a period starting from the subframe n and ending on the subframe n+X−1, and starts to use the long DRX cycle on the subframe n+X, when a DRX inactivity timer expires or a DRX command medium access control (MAC) control element is received on the subframe n.

7. The method of claim 1 , further comprising:

monitoring the PDCCH from the subframe n+1 to subframe n+Y based on the first timer, when the first event for starting the first timer occurs at the subframe n and if the wireless communication system operates in a time divisional duplex (TDD) mode; and

monitoring the PDCCH from the subframe n to subframe n+Y−1 based on the second timer, when the second event for starting the second timer occurs at the subframe n and if the wireless communication system operates in the TDD mode,

wherein Y corresponds to a minimum number of subframes so that X subframes having a physical downlink control channel (PDCCH) are included within a first period starting from the subframe n+1 and ending on the subframe n+Y or within a second period starting from the subframe n and ending on the subframe n+Y−1, respectively.

8. A user equipment (UE) for operating in a wireless communication system, the UE comprising:

a transceiver configured to transmit or receive signals over the air;

a microprocessor electrically connected to the transceiver and configured to control the transceiver to:

monitor a physical downlink control channel (PDDCH) from subframe n+1 to subframe n+X based on a first timer among timers related with a discontinuous reception (DRX) operation, when a first event for starting the first timer occurs at the subframe n and a value received from a network for the first timer is X; and

monitor the PDCCH from subframe n to subframe n+X−1 based on a second timer among said timers, when a second event for starting the second timer occurs at the subframe n and a value received from the network for the second timer is X, wherein X is greater than zero.

9. The UE of claim 8 , wherein the first event comprises receiving a PDCCH indicating a new transmission, and

wherein the first timer comprises a DRX inactivity timer.

10. The UE of claim 8 , wherein the first event comprises transmitting a message 3 of a random access procedure, and

wherein the first timer comprises a medium access control (MAC) contention resolution timer.

11. The UE of claim 8 , wherein the second event comprises a case when a hybrid automatic repeat request (HARQ) retransmission timer (RTT) expires at the subframe n and data of a corresponding HARQ process was not successfully decoded, and

wherein the second timer comprises a DRX retransmission timer.

12. The UE of claim 8 , wherein the second event comprises a case when system frame number meets a predetermined condition with regards to a DRX cycle, and

wherein the second timer comprises an on duration timer.

13. The UE of claim 12 , wherein the DRX cycle is based on either a long DRX cycle or a short DRX cycle, and

wherein, if the received value for a DRX short cycle timer is X, the microprocessor uses the short DRX cycle during a period starting from the subframe n and ending on the subframe n+X−1, and starts to use the long DRX cycle on the subframe n+X, when a DRX inactivity timer expires or a DRX command medium access control (MAC) control element is received on the subframe n.

14. The UE of claim 8 , wherein the microprocessor is further configured to:

monitor the PDCCH from the subframe n+1 to subframe n+Y based on the first timer, when the first event for starting the first timer occurs at the subframe n and if the wireless communication system operates in a time divisional duplex (TDD) mode; and

monitor the PDCCH from the subframe n to subframe n+Y−1 based on the second timer, when the second event for starting the second timer occurs at the subframe n and if the wireless communication system operates in the TDD mode,

wherein Y corresponds a minimum number of subframes so that X subframes having a physical downlink control channel (PDCCH) are included within a first period starting from the subframe n+1 and ending on the subframe n+Y or within a second period starting from the subframe n and ending on the subframe n+Y−1, respectively.