Discontinuous reception (DRX) enhancements in LTE systems
Embodiments of a system and method for providing DRX enhancements in LTE systems are generally described herein. In some embodiments, a system control module is provided for controlling communications via a communications interface. A processor is coupled to the system control module and is arranged to implement an inactivity timer and an on-duration timer for determining an active time for monitoring subframes on the physical downlink control channel for control signals, the processor further monitoring subframes after the active time.
1. An apparatus for a user equipment (UE), the apparatus comprising:
a memory to store values of a plurality of timers; and
one or more processors configured to:
decode, from a base station, a Radio Resource Control (RRC) message comprising a discontinuous reception (DRX) configuration, the DRX configuration comprising:
the plurality of timers that indicate timing for the UE to monitor for a physical downlink control channel (PDCCH), timing before the UE enters an idle state, and timing for downlink retransmission, and
a long DRX cycle start offset that provides a timing to enable transmission of a Hybrid Automatic Repeat Request (HARQ) for Time Division Duplexing (TDD), wherein the long DRX cycle start offset is 70 ms; and
monitor, based on the timers in the DRX configuration, PDCCHs for a control signal that indicates transmission of user data for the UE.
2. The apparatus of claim 1 , wherein the timers comprise an on-duration timer, an inactivity timer, a retransmission timer, and a DRX short cycle timer, and wherein the one or more processors are configured to stop at least one of the timers in response to reception by the apparatus of a DRX Command Medium Access Control (MAC) control element.
3. The apparatus of claim 2 , wherein the one or more processors are further configured to, in response to expiration of the inactivity timer or reception of the DRX Command MAC control element, start or restart the DRX short cycle timer and use the short DRX cycle.
4. The apparatus of claim 2 , wherein reception of the DRX Command MAC control element stops the on duration timer and inactivity timer.
5. The apparatus of claim 1 , wherein the one or more processors are further configured to use the long DRX cycle after expiration of a DRX short cycle timer.
6. The apparatus of claim 1 , wherein the one or more processors are further configured to:
detect the control signal during a particular subframe in which the PDCCH is monitored;
decode the control signal;
determine whether the control signal has been decoded at an end of the particular subframe;
while the control signal is being decoded, continue to monitor at least one subframe to determine whether a user data transmission for the UE is received; and
initiate an inactivity timer of the plurality of timers after the control signal has been decoded.
7. The apparatus of claim 6 , wherein the control signal is received during one of a continuous reception mode, an on-duration period of a short DRX cycle, or an on-duration period of the long DRX cycle.
8. The apparatus of claim 1 , wherein the one or more processors are further configured to restart an inactivity timer of the plurality of timers following successful decoding of a PDCCH for a first transmission of data and not for a retransmission of the data.
9. The apparatus of claim 1 , wherein the PDCCH is an enhanced PDCCH (ePDCCH), and wherein the one or more processors are further configured to monitor the ePDCCH in subframes after an active time for a number of the subframes determined based on ePDCCH processing time of the one or more processors.
10. A method for a user equipment (UE) to communicate with a base station, the method comprising:
receiving, from the base station, a Radio Resource Control (RRC) message comprising a discontinuous reception (DRX) configuration, the DRX configuration comprising:
a plurality of timers that indicate timing for the UE to monitor for a physical downlink control channel (PDCCH), timing before the UE enters an idle state, and timing for downlink retransmission, and
a long DRX cycle start offset that provides a timing to enable transmission of a Hybrid Automatic Repeat Request (HARQ) for Time Division Duplexing (TDD), wherein the long DRX cycle start offset is 70 ms; and
monitoring, based on the timers in the DRX configuration, PDCCHs for a control signal that indicates transmission of user data for the UE.
11. The method of claim 10 , further comprising:
detecting the control signal during a particular subframe in which the PDCCH is monitored;
receiving the control signal;
determining whether the control signal has been decoded at an end of the particular subframe;
while the control signal is being decoded, continuing to monitor at least one subframe to determine whether a user data transmission for the IE is received; and
initiating an inactivity timer of the plurality of timers after the control signal has been decoded.
12. The method of claim 11 , further comprising initiating the inactivity timer after the control signal has been decoded.
13. The method of claim 10 , wherein the control signal is received during one of a continuous reception mode, an on-duration period of a short DRX cycle, or an on-duration period of a long DRX cycle.
14. The method of claim 10 , further comprising restarting an inactivity timer of the plurality of timers following successful decoding of a PDCCH for a first transmission of data and not for a retransmission of the data.
15. The method of claim 10 , wherein the PDCCH is an enhanced PDCCH (ePDCCH), and wherein the method further comprises monitoring the ePDCCH in subframes after an active time for a number of the subframes determined based on ePDCCH processing time of the UE.
16. A non-transitory computer-readable medium that stores instructions for execution by one or more processors of a user equipment (UE) to communicate with a base station, the one or more processors to configure the UE to:
receive, from the base station, a Radio Resource Control (RRC) message comprising a discontinuous reception (DRX) configuration, the DRX configuration comprising:
a plurality of timers that indicate timing for the UE to monitor for a physical downlink control channel (PDCCH), timing before the UE enters an idle state, and timing for downlink retransmission, and
a long DRX cycle start offset that provides a timing to enable transmission of a Hybrid Automatic Repeat Request (HARQ) for Time Division Duplexing (TDD), wherein the long DRX cycle start offset is 70 ms; and
monitor, based on the timers in the DRX configuration, PDCCHs for a control signal that indicates transmission of user data for the UE.
17. The non-transitory computer-readable medium of claim 16 , wherein the instructions further configure the one or more processors to:
detect the control signal during a particular subframe in which the PDCCH is monitored;
receive the control signal;
determine whether the control signal has been decoded at an end of the particular subframe;
while the control signal is being decoded, continue to monitor at least one subframe to determine whether a user data transmission for the IE is received; and
initiate an inactivity timer of the plurality of timers after the control signal has been decoded.
18. The non-transitory computer-readable medium of claim 17 , wherein the instructions further configure the one or more processors to initiate the inactivity timer after the control signal has been decoded.
19. The non-transitory computer-readable medium of claim 16 , wherein the control signal is received during one of a continuous reception mode, an on-duration period of a short DRX cycle, or an on-duration period of a long DRX cycle.