Method and apparatus for controlling discontinuous reception in a wireless communication system
A method and apparatus for controlling Discontinuous Reception (DRX) by a User Equipment (UE) in a wireless communication system is provided. The UE receives a DRX configuration parameter from an evolved Node B (eNB), and determines whether to start an on-duration timer based on the DRX configuration parameter, after a change in DRX cycle is completed in a subframe, thereby preventing system performance degradation caused by transmission mismatch between the eNB and the UE.
1. A method for controlling Discontinuous Reception (DRX) by a User Equipment (UE) in a wireless communication system, the method comprising:
receiving a DRX configuration from an evolved Node B (eNB); and
after a DRX cycle is changed from a short DRX cycle to a long DRX cycle in a subframe or a DRX cycle is changed from a long DRX cycle to a short DRX cycle in a subframe, determining whether to start an on-duration timer based on the DRX configuration.
2. The method of claim 1 , wherein the on-duration timer indicates a time for which the UE monitors a control channel in each DRX cycle.
3. The method of claim 1 , wherein the the DRX cycle is changed in the subframe when a DRX inactivity timer and a short DRX cycle timer both expire in the subframe.
4. The method of claim 3 , wherein the DRX inactivity timer is considered to expire before the short DRX cycle timer.
5. The method of claim 1 , wherein the DRX configuration comprises at least one of an expiration time of an on-duration timer ‘onDurationTimer’, an expiration time of a DRX inactivity timer ‘drx-InactivityTimer’, the long DRX cycle ‘longDRX-Cycle’, a DRX start offset ‘drxStartOffset’, an expiration time of a short DRX cycle timer ‘drxShortCycleTimer’, and the short DRX cycle ‘shortDRX-Cycle’.
6. The method of claim 1 , wherein the determining of whether to start an on-duration timer comprises starting an on-duration timer ‘onDurationTimer’, if the short DRX cycle ‘shortDRX-Cycle’ is used and a remainder obtained by dividing [(System Frame Number (SFN)*10)+subframe number] by the short DRX cycle ‘shortDRX-Cycle’ is equal to a remainder obtained by dividing a DRX start offset ‘drxStartOffset’ by the short DRX cycle ‘shortDRX-Cycle’.
7. The method of claim 1 , wherein the determining of whether to start an on-duration timer comprises starting an on-duration timer ‘onDurationTimer’, if the long DRX cycle ‘longDRX-Cycle’ is used and a remainder obtained by dividing [(SFN*10)+subframe number] by the long DRX cycle ‘longDRX-Cycle’ is equal to a DRX start offset ‘drxStartOffset’.
8. The method of claim 4 , further comprising:
restarting the short DRX cycle timer according to expiration of the short DRX cycle timer in the subframe.
9. The method of claim 1 , wherein the determining of whether to start the on-duration timer comprises:
determining whether to start the on-duration timer after a predetermined number of DRX cycle changes occur in a current subframe.
10. The method of claim 1 , wherein the determining of whether to start the on-duration timer comprises:
determining whether to start the on-duration timer after the DRX cycle fully changes.
11. The method of claim 1 , further comprising:
maintaining a current DRX cycle when the short DRX cycle is scheduled to expire and restart in a subframe following a current subframe.
12. A User Equipment (UE) for controlling Discontinuous Reception (DRX) in a wireless communication system, the UE comprising:
a receiver for receiving a DRX configuration from an evolved Node B (eNB); and
a controller for determining whether to start an on-duration timer based on the DRX configuration, after a DRX cycle is changed from a short DRX cycle to a long DRX cycle in a subframe or a DRX cycle is changed from a long DRX cycle to a short DRX cycle in a subframe.
13. The UE of claim 12 , wherein the on-duration timer indicates a time for which the UE monitors a control channel in each DRX cycle.
14. The UE of claim 12 , wherein the controller determines that the DRX cycle is changed in the subframe when a DRX inactivity timer and a short DRX cycle timer both expire in the subframe.
15. The UE of claim 14 , wherein the controller considers the DRX inactivity timer to expire before the short DRX cycle timer.
16. The UE of claim 12 , wherein the DRX configuration comprises at least one of an expiration time of an on-duration timer ‘onDurationTimer’, an expire time of a DRX inactivity timer ‘drx-InactivityTimer’, the long DRX cycle ‘longDRX-Cycle’, a DRX start offset ‘drxStartOffset’, an expiration time of a short DRX cycle timer ‘drxShortCycleTimer’, and the short DRX cycle ‘shortDRX-Cycle’.
17. The UE of claim 12 , wherein the controller determines to start the on-duration timer ‘onDurationTimer’, if the short DRX cycle ‘shortDRX-Cycle’ is used and a remainder obtained by dividing [(System Frame Number (SFN)*10)+subframe number] by the short DRX cycle ‘shortDRX-Cycle’ is equal to a remainder obtained by dividing a DRX start offset ‘drxStartOffset’ by the short DRX cycle ‘shortDRX-Cycle’.
18. The UE of claim 12 , wherein the controller determines to start the on-duration timer ‘onDurationTimer’, if the long DRX cycle ‘longDRX-Cycle’ is used and a remainder obtained by dividing [(SFN*10)+subframe number] by the long DRX cycle ‘longDRX-Cycle’ is equal to a DRX start offset ‘drxStartOffset’.
19. The UE of claim 15 , wherein the controller further controls to restart the short DRX cycle timer according to expiration of the short DRX cycle timer in the subframe.