Efficient DRXDTX for Connected UE.pdf

Efficient DRX/DTX for Connected UE

USER DESCRIPTION

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Copyright

© Ericsson AB 2011. All rights reserved. No part of this document may bereproduced in any form without the written permission of the copyright owner.

Disclaimer

The contents of this document are subject to revision without notice due tocontinued progress in methodology, design and manufacturing. Ericsson shallhave no liability for any error or damage of any kind resulting from the useof this document.

Trademark List

All trademarks mentioned herein are the property of their respective owners.These are shown in the document Trademark Information.

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Contents

Contents

1 Introduction 1

1.1 Basic Characteristics 1

1.2 Benefits 1

1.3 Additional Information 1

2 Feature Operation 3

2.1 Network Requirements 3

2.2 Feature Operation Sequence Diagram 3

2.3 Process Steps 3

3 Parameters 7

3.1 Introduced Parameters 7

3.2 Affected Parameters 7

4 Network Impact 9

5 Associated Features and Affected Functions 11

5.1 Prerequisite Features 11

5.2 Affected Features 11

5.3 Related Features 11

5.4 Affected System Functions 11

6 Performance 13

6.1 KPIs 13

6.2 Counters and Events 13

6.3 Events 14

7 O&M Information 15

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Introduction

1 Introduction

This document describes the Efficient Discontinuous Reception(DRX)/Discontinuous Transmission (DTX) for Connected UE feature and itsmain benefits and impacts in the LTE RAN.

The Efficient DRX)/DTX for Connected UE feature is configured separatelyfor UE in RRC_IDLE and RRC_CONNECTED mode respectively. DRX inRRC_CONNECTED mode is provided as a licensed feature and makes it possibleto have DRX for UE in RRC_CONNECTED mode.

1.1 Basic Characteristics

This section describes the basic characteristics of the feature.

Feature identity:FAJ 221 0801, Efficient DRX/DTX for Connected UE

Replaces: N/A

Dependencies

This feature has no prerequisite features.

This feature affects no other features.

1.2 Benefits

The Efficient DRX/DTX for Connected UE feature allows the UEs to stopmonitoring the PDCCH during certain time periods. This makes it possible tosave UE battery during periods when the UE is in RRC_CONNECTED mode.The saving in terms of battery time depends on the type of traffic and howthe function is configured. Web-browsing type of traffic typically has moresignificant saving potential than voice type of traffic.

1.3 Additional Information

• 3GPP TS 36.331

• 3GPP TS 36.321

• 3GPP TS 36.133

• Automated Neighbor Relations

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Feature Operation

2 Feature Operation

This section describes the Efficient DRX/DTX for Connected UE feature in moredetail, including network configuration requirements and operation flows.

2.1 Network Requirements

The following must be fulfilled at feature activation:

• The Efficient DRX/DTX for Connected UE feature is a licensed feature ofLTE RAN. A license is needed to activate the feature.

• According to 3GPP, this feature is UE capability dependent. UE is capableof DRX function is prerequisite.

2.2 Feature Operation Sequence Diagram

The DRX cycle begins with an On Duration time during which the UE is awake,followed by a period with Opportunity for DRX. The UE is asleep duringOpportunity for DRX if no timer is forcing it to be awake as shown in Figure 1.There are two DRX states possible for a specific UE. Either it is active (awake)or inactive (asleep). The active time is defined as the time during which the UEmonitors the PDCCH for a PDCCH subframe. Further information can be foundin 3GPP TS 36.321.

L0000426A

UE shall monitor PDCCH

On duration Opportunity for DRX

DRX cycle

Figure 1 DRX Cycle Principle

2.3 Process Steps

This section describes the main process steps for the feature flow.

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2.3.1 DRX Configuration

There are three levels of UE capability for DRX:

• No DRX support

• Partial DRX support (no support for short cycles)

• Full DRX support (support for both short and long cycles)

The UE capability support is translated into a DRX parameter configuration inthe eNodeB.

Table 1 shows parameters with fixed values in the current release of LTE.

Table 1 DRX Configuration Parameters

Parameter Value Description

onDurationTimer 2 ms Specifies the number of consecutive PDCCH subframesat the beginning of a DRX Cycle

drxInactivityTimer

100 ms Specifies the number of consecutive PDCCH subframesafter successfully decoding a PDCCH indicating an initialUL or DL user data transmission for this UE, in 100 ms

drxRetransmissionTimer

2 ms Specifies the maximum number of consecutive PDCCHsubframes for as soon as a DL retransmission isexpected by the UE

longDrxCycle 40 ms Specifies the periodic repetition of active time resultingfrom a started On Duration Timer followed by a possibleperiod of inactivity

The parameter is applied when the UE follows the longDRX cycle.

shortDrxCycle 20 ms Specifies the periodic repetition of active time resultingfrom a started On Duration Timer followed by a possibleperiod of inactivity

The parameter is applied when the UE follows the longDRX cycle.

drxShortCycleTimer

20 ms Specifies the number of consecutive subframes the UEmust follow the short DRX cycle after the DRX InactivityTimer has expired

There is a UE individual time offset for when the DRX pattern should be started.The purpose is to enable a load balancing on the air interface with respect tothe on duration periods of the DRX pattern.

More information about these DRX parameters can be found in 3GPP TS36.321.

2.3.2 DRX Control in UL and DL

The DRX state controls the UE PDCCH monitoring activity. To avoidtransmissions to or from the UE during its DRX sleep periods, the eNodeBstops scheduling to the UE during the UE DRX sleep periods.

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Feature Operation

2.3.3 DRX Activation

The activation of DRX in the UE takes place when setting up the first DataRadio Bear (DRB). By then the UE capability for DRX is known and correctDRX setting can be applied. Figure 2 shows the RRC sequence for the fist DRBsetup and DRX impact on the sequence.

L0000425A

UE

RRC signal sequence DRX

RBSRRC connection request

RRC connection setup

RRC connection setup complete

UE capability inquiry

UE capability information

RRC connection reconfiguration

RRC connection reconfiguration complete

SRB1

DRX parameters issent to UE dependingon capabilities whenthe first DRB is set up

Three types of UEs:

1. Can not handle DRX2. Can handle DRX but not short cycles3. Can handle DRX including short cycles

Corresponds to DRXconfiguration parameters

DRB1

UE may be in DRX mode I

Figure 2 DRX Activation in RRC

2.3.4 Handover Behavior

DRX is a cell based feature. During handover, the Handover RequestAcknowledge message from the target eNodeB provides DRX settinginformation to the source eNodeB as shown in Figure 3.

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L00004

UE SourceRBS

TargetRBS

RRC Measurement report(intra-frequency measurement results)

RRC: RRC connection reconfiguration“HO command”

RRC: RRC connection reconfiguration complete

RRC: RRC connection reconfiguration

X2 AP handover request(”HO preparation info”)

X2 AP handover requestaknowledge (”Handovercommand” RRC reconfig

including target DRX setting)

Must contain the DRX settingsfrom target

Containsthe DRX settingsfrom target

X2 AP: UE context release

RRC: RRC connection reconfiguration complete

“HO” decision

A second reconfiguration is sometimes performed from target to keep the RRC reconfig time during HO short

Figure 3 Handover with DRX

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Parameters

3 Parameters

This section describes the parameters introduced by the Efficient DRX/DTX forConnected UE feature and parameters affected by activating the feature.

3.1 Introduced Parameters

This section provides a brief description of the parameters introduced by theEfficient DRX/DTX for Connected UE feature. Further details relating to all ofthese parameters can be found in Managed Object Model RBS. ManagedObjects (MOs) hold the parameters.

Table 2 describes the parameters introduced by the feature.

Table 2 Introduced Parameters

Parameter Description

drxActive Determines whether the DRX functionality of the cell is activated

MO: EUtranCellFDD

featureStateDrx Indicates whether the licensed feature DRX is ACTIVATED orDEACTIVATED

MO: Drx

keyIdDrx The license key ID for the Efficient DRX/DTX for Connected UEfeature

MO: Drx

licenseStateDrx Indicates whether the licensed state of the Efficient DRX/DTX forConnected UE feature is ENABLED or DISABLED, and whether avalid license key is installed for the feature

MO: Drx

serviceStateDrx Indicates if the feature DRX is operable or inoperable

MO: Drx

DrxId Value component of the RDN(1)

MO: Drx

(1) Relative Distinguished Name

3.2 Affected Parameters

The implementation of this feature affects no parameters.

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Network Impact

4 Network Impact

The implementation of this feature has no impact on the network.

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Associated Features and Affected Functions

5 Associated Features and AffectedFunctions

This section describes how the Efficient DRX/DTX for Connected UE featureaffects other features and functions.

5.1 Prerequisite Features

This feature has no prerequisite features.

5.2 Affected Features

This feature affects no other feature.

5.3 Related Features

Table 3 lists features that are related to the Efficient DRX/DTX for ConnectedUE feature.

Table 3 Related Features

Feature Description

Coverage-Triggered CDMA-eHRPDSession Continuity

Measurement Gap is placed before the UE CQI measurement,to avoid a collision with CQI measurement and reporting and toallow for extended DRX Active right after the DRX On period

The periodicity of Measurement Gap is the same as DRX andCQI report, which is 40 ms.

Automated Neighbor Relations To perform the CGI measurement for the ANR function, theDRX cycle is temporary changed to a long enough period forthe CGI measurement, both in UE and eNodeB. Once the CGImeasurement of the candidate neighboring cell is completed, itis sent in a measurement report to the eNodeB. The eNodeBthen changes the DRX back to its ‘‘normal’’ value both in UEand eNodeB.

5.4 Affected System Functions

This feature affects no system functions.

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Performance

6 Performance

This section describes performance indicators, counters, and events associatedwith the Efficient DRX/DTX for Connected UE feature.

6.1 KPIs

This feature has no associated Key Performance Indicators (KPIs).

6.2 Counters and Events

Table 4 lists the counters associated with the Efficient DRX/DTX for ConnectedUE feature.

Table 4 Counters

Counter Description

pmDrxTotalTime DRX total time in number of subframes for all UE in the cell

pmDrxSleepTime DRX sleep time in number of subframes for all UE in thecell

pmPdcpLatTimeDlDrxSync Aggregated DL latency for a measurement period

The effective DL Latency time comprises the time fromfirst data entering the send buffer until the first data hasbeen transmitted to the UE. Samples that are the firstin the target cell during a handover are excluded sincethey will show impact of the packet forwarding bufferingalthough they are not a performance degrading action.The filters are that DRX is active and the UE has ULsynchronization status ‘‘synchronized’’.

pmPdcpLatPktTransDlDrxSync Number of samples for latency measurements duringmeasurement period

The filters are that DRX is active and the UE has ULsynchronization status ‘‘synchronized’’.

pmPdcpLatTimeDlNoDrxSync Aggregated DL latency for a measurement period

The effective DL Latency time comprises the time fromfirst data entering the send buffer until the first data hasbeen transmitted to the UE. Samples that are the firstin the target cell during a Handover are excluded sincethey will show impact of the packet forwarding bufferingalthough they are not a performance degrading action.The filters are that DRX is not active and the UE has ULsynchronization status ‘‘synchronized’’.

pmPdcpLatPktTransDlNoDrxSync Number of samples for latency measurements duringmeasurement period

The filters are that DRX is not active and the UE has ULsynchronization status ‘‘synchronized’’.

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6.3 Events

This feature has no associated events.

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O&M Information

7 O&M Information

Activating the Efficient DRX/DTX for Connected UE feature requires that thecorresponding license is installed. For more information on handling licenses,see the document License Management

The feature is activated by setting the drxActive parameter to TRUE. Theoperator can configure this feature on or off on cell level either directly in theRBS or from OSS-RC. The operational state of this feature can be checked withthe parameter featureStateDrx.

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Efficient DRXDTX for Connected UE.pdf

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