Connected Mode DRX:
- DRX in connected mode is a power-saving method.
- DRX is a method by which the UE can switch off its receiver for a period of time.
- Applicable when UE is in RRC_CONNECTED state.
- When UE is in RRC Connected state UE may be configured with a UE specific DRX.
- if DRX is configured, the UE is allowed to monitor the PDCCH discontinuously in RRC Connected state.
- Controls the UE’s PDCCH monitoring activity for the UE’s C-RNTI, TPC-PUCCH-RNTI, TPC-PUSCH-RNTI and Semi-Persistent Scheduling C-RNTI (if configured).
- In the RRC_CONNECTED state DRX mode is enabled during the idle periods during the
packet arrival process,when there are no outstanding/new packets to be transmitted/received, eNB/UE may initiate the DRX mode.
- If the UE is configured with DRX, the UE may delay the measurement reporting for event triggered and periodical triggered measurements until the Active Time.
- cqi-Mask - Limits CQI/PMI/PTI/RI reports to the on-duration period of the DRX cycle.
DRX Cycle :
-On
Duration followed by a possible period of inactivity.
DRX Configuration:
onDurationTimer :
- The duration of 'ON time' within one DRX cycle.
- The
number of consecutive PDCCH-subframe(s) UE monitors at the beginning of a DRX Cycle.
- If both Long DRX and Short DRX is configured for a particular UE, onDurationTimer i.e. on duration time during Short DRX cycle or Long DRX cycle should be same.
- When to onDurationTimer should be started depends on :
- If (Short DRX Cycle) && If ([(SFN * 10) + subframe number] modulo (shortDRX-Cycle) == (drxStartOffset) modulo (shortDRX-Cycle))
or
- If (Long DRX Cycle) && If ([(SFN * 10) + subframe number] modulo (longDRX-Cycle) == drxStartOffset)
- start
onDurationTimer.
drx-InactivityTimer :
- During Active time if UE receives PDCCH
indicates a new transmission (DL or UL) drx-InactivityTimer started or restarted.
- Determines the number of consecutive PDCCH-subframe(s) UE monitors before going to sleep, after
successfully decoding a PDCCH during active time.
- Value in number of PDCCH sub-frames.
drx-RetransmissionTimer :
- PDCCH subframe(s) the UE should remain active as soon as a DL
re-transmission is expected by the UE.
- Value in number of PDCCH sub-frames.
longDRX-Cycle :
- Once drxShortCycleTimer expires Long
DRX cycle starts.
- longDRX-Cycle and drxStartOffset . The value of longDRX-Cycle is in number of sub-frames.
- If shortDRX-Cycle is configured,the value of longDRX-Cycle shall be a multiple of the shortDRX-Cycle value.
- The value of drxStartOffset value is in number of sub-frames.
shortDRX-Cycle :
- It is a optional one.
- If Short DRX is configured, if drx-InactivityTimer expires or a DRX Command MAC
control element is received, drxShortCycleTimer is started and short DRX cycle is used.
drxShortCycleTimer :
- Specifies
the number of time(s) the UE shall follow the Short DRX cycle.
- Value in multiples of shortDRX-Cycle. A value of 1 corresponds to shortDRX-Cycle, a
value of 2 corresponds to 2 * shortDRX-Cycle and so on.
Active Time:
- Time when UE continuously monitors PDCCH.
- Includes when onDurationTimer or drx-InactivityTimer or drx-RetransmissionTimer or mac-ContentionResolutionTimer is running.
- SR is sent on PUCCH and is pending.
- Uplink grant for a pending HARQ re-transmission can occur, and there is data in the corresponding HARQ buffer.
- A PDCCH indicating a new transmission addressed to the C-RNTI of the UE has not been received after successful reception of a RAR for the preamble not selected by the UE i.e. Dedicated RACH.
DRX
Command MAC Control Element :
- DRX
Command MAC control element is identified by a MAC PDU subheader with LCID (11110).
- It has a fixed
size of zero bits.
