L115203 Load Based Idle Mode Mobility_FinalVersion

COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.


L115203 – Load Based Idle Mode Mobility

Gianina TATAR - Network Engineering & Assurance/ Wireless Features



STANDARD CONTENTS

1 | FEATURE DESCRIPTION

3 | FEATURE ACTIVATION STRATEGY

4 | PERFORMANCE EVALUATION

5 | CONCLUSION

2 | UPGRADE RULES

2



Feature Overview

1 3


Feature Overview

Feature Description:

• Automatically adapt SIB3 cell reselection parameters based on serving cell load;

• Used to favor idle UEs cell reselection to less loaded neighbour cells, when serving cell is heavily loaded;

• PRB consumption is used as cell load criteria. Operator can configure a separate weight factor for DL and UL.

Feature Value:

• This feature provides the capability to adjust cell selection settings according to cell load, thus helping to balance traffic and load among cells;

• Can be used to impact intra-freq, inter-freq and/or IRAT reselection

4



Overview on idle mode load balancing principles 1/2

Serving cell (loaded)

Inter-freq neighbor

(not loaded)

Intra-freq neighbor

(not loaded)

Intra-freq neighbor

(loaded)

Favours inter-freq reselection

QhystDelta up & sNonIntraSearchDelta up

Favours intra-freq reselection

QhystDelta up on serving cell

Equal priority for reselection

QhystDelta up on both cells

Lower band (e.g. 800 MHz)

Higher band (e.g. 2600 MHz)

Help to balance traffic among cells on same frequency

Help to balance traffic between co-located cells with equal priority,

using different bands



Overview on idle mode load balancing principles 2/2

Serving cell (loaded)

Inter-freq neighbor

(not loaded)

Intra-freq neighbor

(not loaded)

Intra-freq neighbor

(loaded)

Favours inter-freq reselection

threshServingLowDelta up &

sNonIntraSearchDelta up

Lower band (e.g. 800 MHz)

Low priority

Higher band (e.g. 2600 MHz)

High priority

Help to balance traffic between co-located cells with different priority,

using different bands

No intra-frequency load balancing, QhystDelta equal to zero



Delta Parameter Selection 1/2

• This feature supports up to three instances of CellReselectionAdaptation

objects, each instance includes the following parameters:

lowerBound

upperBound

qHystDelta

threshServingLowDelta

threshServingLowQDelta

sNonIntraSearchDelta

sNonIntraSearchPDelta

sNonIntraSearchQDelta

7



• When the traffic of the cell is lower than lowerBound parameter, the reselection parameters remain unchanged.

• When the traffic of the cell increases and becomes between lowerBound and upperBound parameters, the reselection parameters are updated accordingly:

qHyst qHyst + qHystDelta

threshServingLow threshServingLow + threshServingLowDelta

threshServingLowQ threshServingLowQ + threshServingLowQDelta

sNonIntraSearch sNonIntraSearch + sNonIntraSearchDelta

sNonIntraSearchP sNonIntraSearchP + sNonIntraSearchPDelta

sNonIntraSearchQ sNonIntraSearchQ + sNonIntraSearchQDelta

* threshXHigh parameter is not adjusted by this feature, so reselection towards the higher priority cell is not impacted by idle Load balancing

Delta Parameter Selection 2/2

8



Impact of qHystDelta to Cell Reselection

• For intra-frequency and equal priority inter-frequency cell reselection, serving cell and neighbor cells are ranked as:

Rs = Qmeas,s + (qHyst + qHystDelta)

Rn = Qmeas,n – Qoffset

Where:

Qmeas,s = RSRP of serving cell

Qmeas,n = RSRP of neighbor cell

• Intra-frequency and equal priority inter-frequency cell reselection occurs when a neighbor cell is better ranked than the serving cell:

Rn > Rs

9

qHyst prevents some UEs at CE from reselection to a neighbor

qHyst some UEs at CE reselect to a neighbor earlier



• A UE shall perform measurements of equal / lower priority inter-frequency cells if:

Srxlev <= sNonIntraSearch + sNonIntraSearchDelta for R8 UE

Srxlev <= sNonIntraSearchP + sNonIntraSearchPDelta

and/or for R9 UE

Squal <= sNonIntraSearchQ + sNonIntraSearchQDelta

sNonIntraSearchDelta &

sNonIntraSearchPDelta &

sNonIntraSearchQDelta

Impact of sNonIntraSearch to Cell Reselection

some UEs to reselect a neighbor earlier

10



• A UE will reselect to a lower priority inter-frequency or inter-RAT cell if:

Srxlev < threshServingLow + thresholdServingLowDelta

& for R8 UE

Srxlev > ThreshXLow

Squal < threshServingLowQ + threshServingLowQDelta

&

Squal > threshXLowQ (inter-frequency or UTRAN FDD) for R9 UE

or

Srxlev > threshXLowP (GERAN or CDMA2000)

threshServingLowDelta &

threshServingLowQDelta

Impact of threshServingLow to Cell Reselection

some UEs to reselect a neighbor earlier

11



RSRP • 2600 MHz cell, high priority

• 800 MHz cell, low priority

distance

qRxLevMin +

threshXLow

Lower priority cell is reselected

qRxLevMin +

sNonIntraSearch

UE starts measuring

qRxLevMin +

threshServingLow

Idle mode procedure IF 1/2 Reselection: higher priority cell lower priority cell (2.6 800)

12

2.6 800



RSRP

distance

qRxLevMin +

threshXHigh

Higher priority cell is reselected

Idle mode procedure IF 2/2 Reselection: lower priority cell higher priority cell (800 2.6)

13

• 2600 MHz cell, high priority

• 800 MHz cell, low priority

800 2.6



• Up to 4 levels (Default + 3 levels of Cell Reselection Adaptation) of loading

can be created in order to impact UEs reselection differently;

• The neighbor load is not considered in this feature and there is no communication to inform the neighbor of a parameter adjustment

• Up to four types of PRB consumption measurements are available in eNB with measurement interval determined by RadioCacCell::periodMeasforPRBConsumption:

DL PRB consumption per cell

UL PRB consumption per cell

DL PRB consumption per band per eNB

UL PRB consumption per band per eNB

Loading Level 1/3

available if isUnlimitedPRBLicenseAllowed is set to “False” (only with bCEM)

14



15

Loading Level 2/3 - RAN Data Model



The load level is derived from the latest UL / DL PRB consumption reported:

• An individual weighting factor can be applied for each of the 4 components of PRB consumption using MIM parameters:

weightDlPrbCell

weightUlPrbCell

weightDlPrbEnb

weightUlPrbEnb

• At the interval defined by autoReselectMinInterval, the system will apply the weighting factors as following:

bEnbweightUlPrbEnbweightDlPrbCellweightUlPrbCellweightDlPr

%bEnbweightUlPr%bEnbweightDlPr

%bCellweightUlPr%bCellweightDlPr

%eNBeNB

CellCell

ionRBconsumptaverageULPionRBconsumptaverageDLP

ionRBconsumptaverageULPionRBconsumptaverageDLP

nConsumptioCell

Loading Level 3/3

available if isUnlimitedPRBLicenseAllowed is set to “False” (only with bCEM)

16



Feature Dependencies or Interactions 1/2

• L115223 – Inter frequency Load Balancing: complementary features, related as one offloads the idle UEs and the other one the connected UEs recommended to be activated

together to maintain a consistent strategy for idle and active users.

• L115616 - Support for dual-band eNodeB with two modems: This feature supports multiple LTE carriers in different bands. Each carrier advertises its own SIB3 parameters. There is an interaction in the sense that, when applying the PRB per band per eNB criteria, L115203 needs to consider all the PRB usage in the correct band.

17



Feature Dependencies or Interactions 2/2

• L115616 - Support for dual-band eNodeB with two modems: on each modem we

could configure one band with one carrier and one bandwidth.

• This feature enables operators to collocate different carriers on different LTE bands within a

single eNB, when spectrum available in one band is not sufficient.

6 – antennas

6 – sectors

6 – cells

800 MHz

2600 MHz

18



2 Upgrade Rules



First Upgrade Using the Feature

• To ensure the same level of functionality and performance after the upgrade than before (ISO-functionality, feature disabled), the following flags should be set:

isSIB3ReselectionAutomationEnabled = FALSE

20



3 Feature Activation Strategy



• Load based idle mode mobility is activated through dedicated activation flag:

isSIB3ReselectionAutomationEnabled = TRUE Intra-LTE inter-frequency cell reselection is activated when: isInterFreqEutraSameFrameStructureMobilityAllowed = TRUE

• This feature also includes:

parameter autoReselectValueTagChange to allow operator to determine whether the systemInformationValueTag broadcast in SIB1 will be modified when load based adjustments are made to the reselection parameters. Recommended value: TRUE

parameter autoReselectMinInterval that specifies the minimum interval that the function that automatically adjusts cell reselection parameters must maintain between 2 successive adjustments.

Recommended value: 60 seconds

Activation Strategy

22



23

Activation Strategy Parameters used to load the cell

Parameter Object Value

dlMinBitRateForBE RadioCacCell 30

weightDlPrbCell CellSelectionReselectionConf 1

weightDlPrbEnb CellSelectionReselectionConf 1

ulMinBitRateForBE RadioCacCell 30

weightUlPrbCell CellSelectionReselectionConf 1

weightUlPrbEnb CellSelectionReselectionConf 1

Parameters weightDlPrbCell / weightUlPrbCell indicates the weighting factor of %

of cell DL / UL PRB consumption contributing to the calculation of cell load (cell PRB consumption). Parameters dlMinBitRateForBE / ulMinBitRateForBE define the DL and UL bit rates

that assumed for a Best Effort (i.e. non-GBR) radio bearer.



24

800 MHz vs. 2600 MHz Comparison • Pathloss on 800 band is ~10dB higher than pathloss on 2600 band if the two

bands are defined to have same priorities, the UE in idle mode will never select 2.6 cell first • qHyst parameter has an effect on both intra-freq reselection and inter-freq reselection when the bands have equal priorities, so we cannot adjust this parameter for inter-freq without affecting also intra-freq reselection • Considering all this, the two bands are defined to have different priorities:

CellReselectionPriority_800 = 4 CellReselectionPriority_2600 = 5

• Setting a higher priority to 2.6 in idle mode, UE will always select 2.6 band first

and further we’ll use LoB to balance the bands • In the following slides, it’s described the procedure for reselection when going from the higher priority cell towards the lower priority cell (from 2.6 800), as

threshXHigh parameter is not adjusted by idle load balancing • In this case, configuration rules:

qHystDelta = 0 keep at least 4 dB offset between threshXHigh & threshServingLow parameters in order to avoid ping-pong



Non load balancing case (NO LoB) Parameter Object Value

qRxLevMin CellSelectionReselectionConf -126 dBm

sNonIntraSearch CellSelectionReselectionConf 10 dBm

threshServingLow CellSelectionReselectionConf 10 dB

threshXHigh CellSelectionReselectionConfLte 18 dB

threshXLow CellSelectionReselectionConfLte 16 dB

• UE will start measuring for inter-freq neighbors when RSRP of the serving cell reaches: qRxLevMin + sNonIntraSearch = -126 + 10 = -116 dBm • UE will perform a reselection from 2.6 to 800 cell when RSRP of 2.6 gets worse than: qRxLevMin + threshServingLow = -126 + 10 = - 116 dBm and RSRP of 800 gets better than: qRxLevMin + threshXLow = -126 + 16 = - 110 dBm • UE will perform a reselection from 800 to 2.6 cell when RSRP of 2.6 gets better than: qRxLevMin + threshXHigh = -126 + 18 = - 108 dBm

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26

Object 1 – load balancing case (60-80% load)

Parameter Object Value

lowerBound CellReselectionAdaptation 60%

upperBound CellReselectionAdaptation 80%

sNonIntraSearchDelta CellReselectionAdaptation 2

threshServingLowDelta CellReselectionAdaptation 2



• threshServingLowDelta = 2

• sNonIntraSearchDelta = 2

threshServingLow = 12 dB sNonIntraSearch = 12 dB




27

Object 2 – load balancing case (80-100%) Parameter Object Value

lowerBound CellReselectionAdaptation 80%

upperBound CellReselectionAdaptation 100%

sNonIntraSearchDelta CellReselectionAdaptation 4

threshServingLowDelta CellReselectionAdaptation 4



• threshServingLowDelta = 4

• sNonIntraSearchDelta = 4

threshServingLow = 14 dB sNonIntraSearch = 14 dB




4 Performance Evaluation



4. Performance Evaluation

• The KPIs to be measured are:

Traffic per cell/carrier

Throughput per cell/carrier (average and distribution)

RRC Connections per cell/carrier

RSRP distribution per cell

PRB consumption per cell

Connection setup failure rate

Call drop rate

Number of HOs

29



4. Performance Evaluation • Counters:

Counter Name Counter

ID

Counter Description

X2 received throughput 12909 This counter provides the throughput received on the X2 interfaces of the

eNodeB equipment (including Ethernet headers).

X2 received packets 12910 This counter provides the total number of packets received on the X2

interfaces of the eNodeB equipment.

X2 sent throughput 12911 This counter provides the throughput sent on the X2 interfaces of the

eNodeB equipment (including Ethernet headers).

X2 sent packets 12912 This counter provides the total number of packets sent on the X2

interfaces of the eNodeB equipment.

Downlink PRB used 12032 This counter provides the average, maximum and minimum number of

downlink PRBs that have been assigned by the downlink scheduler in the

cell.

Downlink total PRB usage 12029 This counter provides percentage of DL Physical Resource Block usage.

Downlink PRB allocated 12037 This counter provides the average, maximum and minimum number of

downlink PRBs that have been allocated by the PRB allocator to the cell.

Uplink PRB used 12033 This counter provides the average, maximum and minimum number of

uplink PRBs that have been assigned by the uplink scheduler in the cell.

Uplink total PRB usage 12028 This counter provides percentage of UL Physical Resource Block usage.

Uplink PRB allocated 12038 This counter provides the average, maximum and minimum number of

uplink PRBs that have been allocated by the PRB allocator to the cell.

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4. Performance Evaluation • Counters 2/2:

Counter Name Counter

ID

Counter Description

Downlink PRB usage 12035 Downlink PRB usage other GBR, non-GBR

Uplink PRB usage 12034 Uplink PRB usage other GBR, non-GBR

User distribution 13247 This counter allows to have a distribution of the number of UE that are in

or transitioning into RRC_CONNECTED state in the cell for the concerned

PLMN.

Number of UEs in or transitioning into

RRC_CONNECTED state

13201 This counter allows to have the averaged (by dividing the cumulated value

by the elapsed time), maximum and minimum number of UE that are in or

transitioning into RRC_CONNECTED state in the cell for the concerned

PLMN.

RRC connection request 12311 This counter provides the number for RRC connection requests received

from UE in the cell.

Total RRC connection success 12302 This counter provides the number for RRC connection procedures

successfully completed.

Total RRC connection failure 12303 This counter provides the number for RRC connection procedures that

have been failed.

Total initial context setup failed 12502

12503

This counter provides the number of Initial Context Setup procedures that

have been failed.

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Conclusion

5



Conclusion

• Feature is recommended for initial deployment as it decreases probable additional loading of idle UE on loaded cell.

• Offloading idle UEs earlier due to loading will decrease the coverage of the loaded cell.

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L115203 Load Based Idle Mode Mobility_FinalVersion

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