Wcdma Mobility Optimization And Casesharing.pdf

Wcdma kpi OPTIMIZATION- case studies

agenda ❖ DAY 1 WCDMA KPI OPTIMIZATION – ACCESSIBILITY CS/PS – RETAINABILITY CS/PS – CASE STUDIES

❖ DAY 2 WCDMA KPI OPTIMIZATION – MOBILITY – INTEGRITY – CASE STUDIES

COVERED YESTERDAY

❖MOBILITY

Handover in WCDMA ▪

Mobility/Handover is defined as the ability of a user to move between neighboring UMTS and GSM Cells and retain its requested service (CS or PS) once connected. ▪ ▪ ▪

Soft/Softer Handover Inter-Frequency Handover Inter-Radio Access Technology (Inter-RAT) Handover

Soft Handover In Soft Handover, the UE connection consists of at least two radio links established with cells belonging to different Node-B. In Softer handover, the UE connection consists of at least two radio links established with cells belonging to the same Node-B. Soft Handover is controlled through the events 1a, 1b, 1c & 1d: ▪ 1a: A new candidate for the active set enters reporting range ▪ 1b: A cell in the active set leaves the reporting range ▪ 1c: A cell not in active set becomes stronger than a cell in the active set ▪ 1d: Any cell becomes better than the best cell in the active set Majority of the SOFT/SOFTER Handover failures include: ▪ Failures due to interference, poor areas of dominance ▪ Primary Scrambling Code collision ▪ Missing neighbors ▪ Neighboring sites Hardware issues

I RAT Handover IRAT handover process includes the following two sub-processes: • Relocation preparation • Handover implementation Relocation preparation Failures are mainly due to following reasons: • The 2G resources are not enough. • The CN parameters are not configured reasonably. • The configurations of GSM neighboring cells are not consistent with actual parameters. Handover implementation failures are mainly due to following reasons: • Incorrect parameter configuration of neighboring 2G cells • There exists side-channel interference in 2G cells • Improper setting of neighboring threshold

INTER FREQUENCY Handover Inter-Frequency Handover allows continuation on dedicated channels when the UE is moving out of coverage of one WCDMA RAN frequency to an area where coverage on another WCDMA RAN frequency exists. IFHO can also be triggered when performing cell selection for a packet connection. IF Hanover has following events : Event 2a: Change of best frequency Event 2b: The estimated quality of the currently used frequency is below a certain threshold and the estimated quality of a non-used frequency is above a certain threshold. Event 2c:The estimated quality of a non-used frequency is above a certain threshold Event 2d: The estimated quality of the currently used frequency is below a certain threshold (It is based upon Ec/No measurements and RSCP measurement) i.e. start of compression mode Event 2e:The estimated quality of a non-used frequency is below a certain threshold Event 2f: The estimated quality of the currently used frequency is above a certain threshold. i.e. stop of compression mode Handover failures are mainly due to following reasons: • Incorrect parameter configuration of neighboring 3G cells • Hardware issue on neighboring cells. • Improper setting of neighboring threshold

Troubleshooting Possible Reasons for 3G-3G HO Failures • Interference • Pilot Pollution • Overshooting of nearby cells • Low coverage area • External Interference • PSC Collision • Two or more nearby Cells having same PSC • Missing Neighbour Definition • Improper cell relations resulting into failed HO • Neighbouring Site E1/Hardware Issue • Attempts to nearby site failing due to E1/Hardware issue • Improper Definitions • Improper External Definitions in RNC/MSS • Congestion on neighboring site • Limited resource neighboring site will lead to failures • On Utran Cell Locked, Channels Unlocked • Attempts to the cell will take place based on unlocked cell, but will not succeed as cell is locked

Possible Causes & Counters

CS IRAT HO Failure

Preparation Failure

Preparation failures pmNoFailOutIratHoSp eechGsmFail

Execution Failure

Physical Channel Failure pmNoFailOutIrat HoSpeechReturn OldChPhyChFai

not due to Physical Channel Failure pmNoFailOutIratHo SpeechReturnOldCh NotPhyChFail

Failure due to UE rejection pmNoFailOutIrat HoSpeechUeReje ction

IRAT Check Checklist

Definition Check

Hardware Check

• • • •

External Cell Definition – Cell defined in RNC/BSC Outer Definition – Cell defined in MSS/MSC SGSN Definitions – LAC/RAC Def RNC/MSS Definitions – Correct RNC/MSS(for new nodes)

• • • •

Blocking Hardware Failure Poor GSM BCCH Channel quality E1 Issues

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BaSIC mobility parameter check PARAMETER NAME

Object

Default

Recommended

Value Range

fddGsmHOSupp

RNC

TRUE

TRUE

0,1

hoType

Utrancell

GSM_PREFERRED

GSM_PREFERRED

0,1,2,

usedFreqThresh2dEcno

Utrancell

-12

-15

-24..0

usedFreqThresh2dRscp

Utrancell

-100

-105

-115..-25

gsmThresh3a

RNC

-95

-92

-115..0

COEXUMTS

BSC

1 (ON)

1 (ON)

0,1

gsmAmountPropRepeat

RNC

4

1

0..25

gsmPropRepeatInterval

RNC

5

15

0..25

tmStopGsmMeas

RNC

20

20

1..60

ifhoAmountPropRepeat

RNC

4

4

0..25

ifhoPropRepeatInterval

RNC

5

5

0..25

fddIfhoSupp

RNC

1

1

0,1

serviceOffset2dEcno

RNC

0

0

-20..20

utranRelThresh3aEcno

RNC

-1

0

-10..10

timeToTrigger3a

RNC

6

6

0..15

CASE STUDIES

Case study- parameter gsmAmountPropRepeat 1.- DESCRIPTION It is max number of repeated proposals (not including the first proposal) of GSM cell(s) for handover based on the same measurement report. If the proposal was rejected with cause "Relocation Preparation Failure" or with cause "Handover/CellChange from Utran Failure" and if no event 3a is buffered, then the GSM HO attempts shall be repeated. The number of repeated attempts, not including the first attempt, is set by the parameter gsmHoAmountPropRepeat. 2.- SCOPE: To apply and trial in one RNC in TIGO Bolivia Network & then whole network 3.- KPI TO EVALUATE: IRAT HO Relocation Preparation Success Rate, 4.- EXPECTED BENEFITS: Improvement in IRAT Preparation phase & Execution phase.. 5.- DETAILS: –Changing “gsmAmountPropRepeat” from 4 to 1, which will reduce the number of an IRAT attempts

Case study- parameter gsmAmountPropRepeat

gsmAmountPropRepeat

gsmAmountPropRepeat 4 -> 2

IRAT HO Preparation success rate improved for RNCSCZ3

2 -> 1

Case study- parameter gsmAmountPropRepeat gsmAmountPropRepeat 4 -> 2

gsmAmountPropRepeat 2 -> 1

IRAT HO Speech success rate improved for RNCSCZ3

Case study- parameter gsmPropRepeatInterval 1.- DESCRIPTION It is the minimum time interval between proposals of the same GSM cell for handover based on the same measurement report. If the proposal was rejected with cause "Relocation Preparation Failure" or with cause "Handover/CellChange from Utran Failure" and if no event 3a is buffered, then the GSM HO attempts shall be repeated after time specified by this parameter.. 2.- SCOPE: To apply and trial in one RNC in TIGO Bolivia Network & then whole network 3.- KPI TO EVALUATE: IRAT HO Relocation Preparation Success Rate, 4.- EXPECTED BENEFITS: Improvement in IRAT Preparation phase & Execution phase.. 5.- DETAILS: –Changing “gsmPropRepeatInterval” from 5(1sec) to 15(3sec), which will reduce the number of an IRAT attempts

Case study gsmPropRepeatInterval

IRAT HO Preparation success rate improved for RNCSCZ5

Case study gsmPropRepeatInterval

IRAT HO Speech success rate improved for RNCSCZ5

Case study-gsmThresh3a trial

1.- DESCRIPTION An Event 3a message is triggered when the estimated quality of the current UMTS frequency is below a certain threshold and the estimated quality of the other system (GSM) is above a certain threshold (gsmThresh3a). Event 3a is triggered when the estimated quality of the WCDMA RAN used frequency is below the threshold (usedFreqThresh2dEcno+ serviceOffset2dEcno+ utranRelThresh3aEcno) and the measured GSM carrier RSSI of a GSM cell is above the absolute threshold gsmThresh3a, during a time at least equal to timeToTrigger3a

2.- KPI TO EVALUATE: IRAT HO Success Rate, 3.- EXPECTED BENEFITS: Improvement in IRAT Success Rate. 4.- DETAILS: –Changing gsmThresh3a from -95 to -92

Case study-gsmThresh3a trial

gsmThresh3a from -95 to -92

Introduction ❖ Service Integrity represents the quality experienced by the user during A call or session. ❖ HSDPA & EUL throughput ARE used as MAIN Indicators FOR SERVICE INTEGRITY. ❖ THROUGHPUT PERFORMANCE OF A NETWORK DEPENDS ON THE SPEEDS IN EITHER DOWNLINK AND/OR UPLINK, EXPERIENCED BY THE END USER ❖ LOW THROUGHPUT IS ONE OF THE MOST COMMON ISSUES OBSERVED IN THE NETWORK

WCDMA Optimization Concept(OJT) | Ericsson Internal | SHRIKANT | 2015-07-29 | Page 21

troubleshooting flow chart

Low Throughput

Lack of Resources

Power

Code

CE

High Iub Limiting Ratio

Incorrect Parameter Settings

Poor Radio Conditions

Congestion

Poor Coverage/ Quality

Over shooting

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Pilot Pollution

Low CQI

Higher Order Modulation License

Alarms & Outages

Transmission Errors

BaSIC intigrity parameter check MO

Parameter

MO

Parameter

max Hsrate

codeThresholdPdu656 NumHspdschcodes 16 QAM

hsMeasurementPowerOffset

64 QAM HSDPA Dyanmic Code Allocation

Hsdsch

HSDPA flexischedular

Site Configuration

numHsPdschCodes numHsScchCodes

Eul2msTti

eulMaxTargetRtwp

CQI Hspower margin

queueSelectAlgorithm

numEagchCodes

Eul numEhichErgchCodes

eulmaxshorate

maxTransmissionPower eulMaxOwnUuLoad

eulMaxRotCoverage

UtranCell eulServingCellUsersAdm

CASE STUDIES

Case study- cqi ImprovementhsMeasurementPowerOffset 1.- DESCRIPTION Offset relative to the P-CPICH that the UE shall use when calculating the assumed HS-PDSCH power in the CQI estimation – Range: (0.. 200) – Default: 0 [0 dB] / 0.1 dB – Recommended: 80 [8 dB]

.The new recommended value is intended to shift the distribution of reported CQI away from the lower edge, since CQI=0 will result in no scheduling and reduced throughput. Tuning of the parameter might still be needed (considering the observed CQI distribution), but the recommended value is a better starting point for this tuning than the current default value. •

The channel quality indicator is used by the UE to signal to the RBS it’s current radio conditions. In fact it sends the RBS a number relating to the biggest transport block that the UE thinks it can successfully decode under the current conditions.

•

The UE reports a number between 1 and 30 and this indicates a maximum transport block size depending on the UE category

2.- EXPECTED BENEFITS: User and reported CQI. 3.- DETAILS: –Changing “hsMeasurementPowerOffset” from less than 80 to default value 80.

Case study- cqi ImprovementhsMeasurementPowerOffset

Case study- cqi Adjustment/ queUEselectalgorithm 1.- DESCRIPTION •

Channel quality knowledge at UE needed in the RBS – Link adaptation – Scheduling – Power control of HS-SCCH

•

CQI – UE measures and reports a recommended transport format to the RBS – Accounts for channel conditions and UE receiver performance

2.- EXPECTED BENEFITS: Improvement in reported and used CQI, HSDPA user throughput 3.- DETAILS:

–cqiAdjustmentOn & queueSelectAlgorithm enabled.

CQI Adjustment High number of NACKs

RBS throughput?

XXXXXX X High CQI reporting UE

√

= 10%

High retransmission rate cqiAdjustmentOn = TRUE => low throughput High number of ACKs

√√√√√√ Low CQI reporting UE

Low utilization => low throughput

Since the accuracy of the CQI reporting depends on the UE vendor and model, it is recommended to enable the CQI adjustment feature so that both cell and user throughput are maximized. This is particularly important when proportional fair or Max CQI is selected as scheduling algorithm.

WCDMA Optimization Concept(OJT) | Ericsson Internal | SHRIKANT | 2015-07-29 | Page 28

Case study- cqi Adjustment/ queUEselectalgorithm

- Changes done on 21st July when cqiAdjustmentOn was enabled and queueSelectAlgorithm was set to Proportional Fair Medium on site 3ETR. - Good Improvement observed in Used CQI after changes.

WCDMA Optimization Concept(OJT) | Ericsson Internal | SHRIKANT | 2015-07-29 | Page 29

Case study- cqi Adjustment/ queUEselectalgorithm

- Significant improvement observed in HSDPA User Throughput after changes. WCDMA Optimization Concept(OJT) | Ericsson Internal | SHRIKANT | 2015-07-29 | Page 30

Case study- cqi Adjustment/ queUEselectalgorithm

- Changes done on 21st July when cqiAdjustmentOn was enabled and queueSelectAlgorithm was set to Proportional Fair Medium on site 3GRA. WCDMA Optimization Concept(OJT) | Ericsson Internal | SHRIKANT | 2015-07-29 | Page 31

Case study- cqi Adjustment/ queUEselectalgorithm

- Significant improvement observed in HSDPA User Throughput after changes. WCDMA Optimization Concept(OJT) | Ericsson Internal | SHRIKANT | 2015-07-29 | Page 32

Case STUDY - ECiO IMPROVEMENT BY HSPOWERMARGIN 1.- DESCRIPTION In determining how much power can be allocated to HS-PDSCH, the total transmit power (including all common channels, dedicated channels, HS-SCCH, HS-PDSCH and the Enhanced Uplink downlink control channels) is limited to the maximum downlink transmission power for the cell signaled from the RNC, minus the hsPowerMargin back off. P HS = P max - P non-HS - hsPowerMargin [dB],

2.- KPI TO EVALUATE: HS Throughput. 3.- EXPECTED BENEFITS: EcIo. 4.- DETAILS: –Changing hsPowerMargin 02

Case STUDY - ECiO IMPROVEMENT BY HSPOWERMARGIN

hsPowerMargin 02

WCDMA Optimization Concept(OJT) | Ericsson Internal | SHRIKANT | 2015-07-29 | Page 34

Case STUDY - ECiO IMPROVEMENT BY HSPOWERMARGIN PRE EcIo

POST EcIo

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Case STUDY –Eul thput improvment

1.- DESCRIPTION • The maximum total interference tolerated is set by the parameter eulMaxRotCoverage. A high value of this parameter limits the cell coverage but increases EUL capacity. A low value increases coverage at the expense of cell capacity. The purpose of this estimate is to dynamically allow as much EUL throughput as possible without compromising the planned cell coverage. 2.- KPI TO EVALUATE: Eul Througput,RSSI 3.- EXPECTED BENEFITS: Eul Throughput . 4.- DETAILS: – Changing eulMaxRotCoverage 100 to 300

Case STUDY – Eul throughput improvement

WCDMA Optimization Concept(OJT) | Ericsson Internal | SHRIKANT | 2015-07-29 | Page 37

Case STUDY – Eul throughput improvement

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