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•When both schedulers indicate “inactivity” on DL as well as on UL (based on DRB data availability) the UE inactivity detection algorithm indicates UE combined activity state “inactivity” to UE State Handling (UE-SH). Following this indication UE combined activity state is reset to “activity” again such that as soon as the above conditions are met again another indication of UE “inactivity” to UE state handling is performed.

•Schedulers are also indicating a UE being “active” again to UE inactivity detection algorithm such that always the correct state of UL and DL activity is reflected in DRX/DTX-ALG. Once of the transmission directions becoming “active” again is not explicitly reported to UE state handling.

•The inactivity timer applied by the schedulers is O&M configurable T_INACTIVE

•The effect of an UE inactivity indication to UE state handling is not reported back to DRX-DTX-ALG. If the UE is removed from RRC_CONNECTED state this will be visible via release of all RBs of a UE from RAC.

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DRX is not disabled for Release 9 UEs that do not benefit from battery consumption optimization. DRX is disabled in this case if:

The parameter drxApplyDeviceType is set to True (This parameter determines whether the device type noBenFromBatConsumpOpt of the UE is considered for DRX configuration. Such an UE does not foresee to particularly benefit from NW-based battery consumption optimization)

The UE capabilities for E-UTRA contain the device type noBenFromBatConsumpOpt

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Note: If UE hasn’t been scheduled in On Duration and the UE doesn’t get DRX Active again later in this cycle (e.g. by sending a SR), there is no possibility to start the DRX Inactivity timer for the rest of the DRX cycle! In this case no transmission will take place in this DRX cycle.

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Starting of the DRX Inactivity Timer

DRX Inactivity Timer will be started if the PDCCH indicated a new UL or DL transmission and if the UE is DRX Active at that time

Restarting of the DRX Inactivity Timer

DRX Inactivity Timer Window will be moved with every grant indicating a new transmission in UL or DL. This can only happen when such a grant will be received when UE is DRX active

Continuously grants to UE, DRX Inactivity Timer Window will be moved beyond the end of the DRX cycle

–If no further grants to UE during DRX Active time frame

▪ The DRX Inactivity Timer will exceed and UE stops being DRX Active (not listening to PDCCH any more)

▪ Cannot receive further grants, until it awakes again e.g. at the the beginning of the next DRX cycle when the On Duration Timer will be started.

The parameter provides a means for the network to keep a user “alive” when there is a sudden need to largely schedule the UE. Hence the mechanism allows for large power saving while facilitating high QoS for bursty traffic types. Setting is a trade-off between scheduler freedom and power saving as UE is forced to continuous monitor for PDCCH whenever scheduled

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Note that HARQ retransmissions are planned outside of the DRX cycle to allow for a tighter DRX optimization without having to plan for the worst case retransmission.

The DRX retransmission timer is defined so that the UE does not have to wait for a full DRX cycle for an expected retransmission that has been lost due to either ACK/NACK misinterpretation or PDCCH failed detection

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Extended settings for the long DRX cycle require UL out-of-synch handling UEs can’t be kept time aligned any more

TA estimation is based on periodic CQI reporting if there is no UL traffic;

For long DRX cycle settings and during phases of data transmission, UE has to be kept in active time continuously, realized by restricting the DRX Inactivity timer accordingly

If phase of data transmission ends, TA to UE is stopped, and UE goes UL out-of-sync UE releases dedicated resources on PUCCH and for SRS

Re-synchronization via RA procedure due to UL or DL data arrival and re-configuration of dedicated resources must be supported.

Transition to uplink In-Sync

DL data transmission trigger

The eNodeB initiates a random access procedure for UEs which are in uplink Out-of-Sync and have data for downlink transmission. The eNodeB provides in this case the RACH parameters via the PDCCH order to the UE.

UL data transmission trigger

During the UL Out-of-Sync state, UE may start a contention based random access procedure in order to transmit data on uplink

Following the transition to In-Sync, UEs are reconfigured with any resources released during UL Out-of-Sync transition (resources on PUCCH and for SRS, if applicable).

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Behavior depending on ‘short term inactivity detection’

As long as no short term inactivity has been detected (short term inactivity timer has not been expired) UE needs to be kept time aligned

Note: During DRX Active for UEs with extended settings of the long DRX cycle (with the extended settings of the long DRX cycle the DRX Inactivity Timer has to be set accordingly as to ensure UE being DRX Active until detection of short term inactivity in order to be able to keep UE UL in-sync.)

Short term inactivity has been detected

eNB stops sending timing alignment command to UE (although subsequent DRX On-Duration arrives and TAT has not expired -> UE goes UL out-of-sync when TAT expires)

In case traffic resumes before TAT expires, UE will be DRX active at least for a time period corresponding to DRX Inactivity Timer

If traffic resumes after TAT expires a RA procedure is required to recover UE UL synchronization.

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