WPO-30 WCDMA Drive Test Data Analysis_PPT-72

7/27/2019 WPO-30 WCDMA Drive Test Data Analysis_PPT-72

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WCDMA Drive Test Data Analysis

ZTE University


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Overview of Network Optimization Process

Coverage-related Data Analysis

Service-related Data Analysis

Case Study

Content


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Engineering Optimization Phase

Single-site Optimization

zSingle-site optimization test

zSite rectification

zSingle-site acceptance

Base station Cluster

Optimization

z Cluster optimization test

z Cluster optimization data analysis and

optimization plan draft

z Cluster optimization plan implementation

z Cluster optimization acceptance

Entire Network

OptimizationzCluster boundary optimization

zCluster optimization

zEntire network optimization and

acceptance

Ensure that network can run normally and reach preset network performance KPIs


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NO YES

Network performance

monitoring

Network performance

monitoring

Data analysisData analysis

Optimization plan draftOptimization plan draft

ImplementationImplementation

TestTest

DT, CQT

OMC Complain

O&M Optimization Phase

Improve network quality and customer satisfaction


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Tool Preparation

F852 (mobile)

z Supports HSDPA/UMTS

z Supports EDGE/GPRS/GSM

z Supports HSDPA 3.6 Mbps downlinkz Supports R99 PS 384 kbps downlink

MF632 (Data card)

z Supports HSUPA/HSDPA/UMTS

z Supports EDGE/GPRS/GSM

z Supports HSDPA 7.2 Mbps downlink

z Supports HSUPA 2 Mbps uplink

z Supports receive diversity


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Tool Preparation

CPICH RSCP

CPICH Ec/Io

Pilot Path Count

PDU

BLER

Tx power

Neighbours

CRC

Throughput

Log

CPICH RSCP

CPICH EC/Io

Coverage analysis

Overshooting analysis

Pilot pollution analysis

Neighbor cell analysis

Call drop analysis

Delay analysis

Signaling process

Network KPIs

Coverage analysis

Overshooting analysis

Pilot pollution analysis


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Drive Test (DT)

A drive test (DT) is to collect signal coverage data ofa single site, cluster or even the entire network aswell as to collect KPIs about CS and PS services.

The data to be collected include signal strengthindicator Ec, signal quality indicator Ec/Io, serviceestablishment success rate, handover success rate,handover percentage, call drop rate, averageuplink/downlink throughput, delay occurred duringservice establishment. All of these data helps toassess outdoor signal coverage quality. Besides,

based on these data, engineers can find out whethera single site runs normally and locate faults thatcause network KPIs deteriorate, such as devicefaults, pilot pollution, cell faults, improper settings of

system parameters, and so on.


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Call Quality Test (CQT)

A call quality test (CQT) is a test towards a fixedpoint. Its purpose is to collect indoor and outdoorsignal strength data as well as to collect data about

service establishment and maintaining. A fixed point test is to check signal quality of a local

area. KPIs of service establishment and maintaining

are useful for analyzing network problems occur atthe fixed point, especially problems likeindoor/outdoor signal optimization, repeaterinterference, complexity of radio propagation

environment, and so on. Key KPIs that the test focuses include link signal

quality, multipath impact, service establishment

status, cell throughput, and so on. compared to DT,it does not care about KPIs about handover.


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Case Study

Content


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Pilot Pollution

Cell pilot signals received at a test point have no difference insignal strength (either strong or weak), but no dominant pilot isreceived.

The symptom is that the received pilot power is good but Ec/Ioof each cell is weak.

At present, most WCDMA equiment supports up to three activesets. If the number of similar Ec/Io values of different cells is

more than three, it can be regarded as a kind interferencetowards three radio links in the active sets.

The causes of signal distortion include, overshooting of sites athigher places, ring deployment, streect effect, strong reflectors,and so on.

Pilot pollution algorithm

z Algorithm1: Ec/Io > Ec/Io_for_BestServingCell - the numberof 8dB cells is more than 3

z

Algorithm2: Ec/Io > Ec/Io> Ec/Io_for_BestServingCell - thenumber of Window_add cells is more than Active Size


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Pilot Pollution

Pilots in Scanner, rscp>Trscp & ecio > Tecio

Check for pilot pollution via the test data of ScannerCheck for pilot pollut ion via the test data of Scanner


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Pilot Pollution

Check for pilot pollution via the test data of UE-method 1Check for pilot pollut ion via the test data of UE-method 1


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Pilot Pollution

Check for pilot pollut ion via the test data of UE-method 2Check for pilot pollution via the test data of UE-method 2


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Neighbor Cells without Configuration

A neighbor cell may has been added to an active set. It may be

involved in cell re-selection or handover with other cells.

When a mobile is in the idle and FACH state, the mobile readsthe neighbor cell information from system messages, and

measures these neighbor cells when conditions are met. If a

neighbor cell fails to be set, cell re-selection cannot be

complete timely which further cause call establishment failure.

When the mobile is in the DCH state, RNC sends out neighbor

cell information through measurement control command to askthe mobile to measure all neighbor cells where handover may

occur. In this case, if a neighbor cell fails to be set, handover

failures may occur and further cause call drops.


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Compare Ec/Io results obtained by the mobi le and that obtained by Scanner to see whether acell is set or not

Compare Ec/Io results obtained by the mobi le and that obtained by Scanner to see whether acell is set or not

Ec/Io results obtained by UE are poor while that obtained by Scanner are good.

Scanner recorded that Best Server scramble did not appear in the Measurementcontrol signaling sent out by RNC.


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Judge whether a cell is set or not via the active set and monitor set measured by the mobileJudge whether a cell is set or not via the active set and monitor set measured by the mobile

There are cells whose signal is strong in the monitor set, but

they are not added to the active set.


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Unreasonable Handover Area

Typical handover process: measure control> measure report>

handover dicision> handover implementation> new measurement

control.

Unreasonable handover area may cause that signals jitter to fast and

have not enough time to complete handover which further causes call

drops.

Corners and street crossroads


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Unreasonable Handover AreaCompare Ec/Io results obtained by the mobile and that obtained by Scanner to see

whether a cell is set or not

Compare Ec/Io results obtained by the mobile and that obtained by Scanner to see

whether a cell is set or not

Ec/Io results obtained by UE are poor while that obtained by Scanner are good.

Scanner recorded that Best Server scramble did appear in the Measurement controlsignaling.


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Pilot Pollution

The core to solve pilot pollution is to form dominant pilot at theplace where pilot pollution occurs.

Optimization methods include:

Adjust antenna engineering parameters, like azimuth, downtilt

angle, installation position (install antenna at a higher place) Adjust cell pilot transmission power, including increasing

transmission power of a certain cell and decreasing that ofother cells

Adjust base station layout, and add signal sources in pilotpollution areas to introduce a strong primary signal

Adjust cell selection and re-selection parameters whennecessary to imrpove call access success rate

SolutionsSolutions


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Overshooting Pilot signals in some area are too strong and cover the areas beyond their planned

coverage range. This leads to the formation of discontinuous dominant areas in the

coverage range of other cells.

The places where bases stations are deployed are too high; antenna engineering

parameters are not reasonable; street effects; and so on.

Use Best SC to check for

overshooting

Use Best SC to check for

overshooting


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OvershootingUse Over Shoot to check for

overshooting

Use Over Shoot to check for

overshooting


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Overshooting

Use Over Shoot to check for overshootingUse Over Shoot to check for overshooting

Global sample points: RSCP > -105dBm & Ec/Io >-15dB

Overshooting sample points:

z Distance from a sample point to a cell > Geographical threshold (Distance)

z RSCP > RSCP.Threshold & Ec/Io > Ec/Io.Threshold

If number of global sample points >M & number of overshooting sample points >N &

number of global sample points / number of overshooting sample points > Propotion,

then it indicates that there are overshooting problems.

Measure of severity

z Measure of distance: W1=distance from a sample point to a cell / geographical

threshold

z Measure of severity:

W2=W21, indicates that ecio of an overshooting sample point is strongest

W2=W22, indicates that ecio of an overshooting sample point is the secondstrongest

W2=W23, others

z Overshooting degree: W=W1*W2


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Case Study

Content


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RRC Connection Establishment Success Rate

RRC connection establishment success rate (service-related)

Number of RRC connection establishment success times (service-related)/Number of RRC connection establishment attempts (service-related)100%


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RRC Connection Establishment Success Rate

RRC connection establishedRRC connection established

AuthenticationAuthentication

EncryptionEncryption

NAS connection establishedNAS connection established

ConversationConversation

Release of the called partyRelease of the called party

RRC connection releasedRRC connection released

Call establishedCall established

RB establishedRB established


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Call Access Success Rate

Call access establishment success rate

Number of RB establishment success times /Number of RRC connection establishment attempt times 100%


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Call access establishment success rate











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Call establishment success rate











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PDP Context Activation Success Rate

PDP context activation success rate

Number of PDP context activation success times /Number of PDP context activation attempt times100%


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PDP Context Activation Success Rate






PDP deactivatedPDP deactivated





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Average Access Delay

Average access delay

{ Time that UE receives RRC Connection Setup-Time UE sends RRC Connection Request}/

Number of RRC connection establishment attempt times


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Average access delay










Ch l S h i ti D l


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Channel Synchronization Delay

Channel synchronization delay

{ Time UE sends RRC Connection Setup Complete-Time UE sends RRC Connection Request}/

Number of RRC connection establishment attempt times

Ch l h i ti d l


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Channel synchronization delay


Authent icationAuthentication








C ll A D l


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Call Access Delay

Call access delay

{ Time the call ing UE sends Radio Bearer Setup Complete-Time the call ing UE sends RRC Connection Request}/

Number of call attempt times

C ll d l


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Call access delay










Call Establishment Delay


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Call Establishment delay

{ Time calling UE receives Alerting-Time the call ing UE sends RRC Connection Request}/

Number of call attempt times



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AuthenticationAuthent ication








PDP Context Activation Delay


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PDP context activation delay

{ Time UEA receives Active PDP Context Accept-Time calling UE sends Active PDP Context Request}/

Number of PDP activation attempt times



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PDP deactivatedPDP deactivated




Content


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Case Study

Content

Locating Area Where Call Drop Occurs


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Use Marker Setting to locate the areaUse Marker Setting to locate the area

Select calling events like RRC Connect Fail, Call Drop, RB setup Failure.

Then the system displays the area where call drop occurs in the Map window.



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Check if the signaling is complete to locate the areaCheck if the signaling is complete to locate the area

Select calling events like RRC Connect Fail, Call Drop, RB setup Failure.

Then the system displays the area where call drop occurs in the Map window.



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Check if the signaling is complete to locate the areaCheck if the signaling is complete to locate the area

Broadcasting messages are received suddenly; call re-establishment fails.



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Locating Area Where Call Drop OccursCheck if the signaling is

complete to locate the area

Check if the signaling is

complete to locate the area

Broadcasting messages are received suddenly; call re-establishment

succeeded without call drops.

Radio quality

deteriorates;

UE initiates cell update

process and waits for

call re-establishment

The network re-configure

the transmission channel

for the UE throughCellupdate Confirm to

re-synchronize radio

links;

Call re-established

successfully.


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Poor RSCP

Before Optimization


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The signal is blocked by buildings.

Optimization Plan


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p

Analyze the si te survey photos, and then

Change antenna direction of SC283 from 160 to 140 degree.

Change antenna downtilt of SC283 from 7 to 2 degree.

After Optimization


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Optimization result: coverage is improved to some extent.


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Before Optimization


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Problem: some Ec/Io in the red circle is poor below -10dB, RSCP is normal around -85dBm

505

p

Optimization Plan


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The red circle area, which is in the middle of several NodeBs, has no primary server cell for

coverage. In order to improve Ec/Io, it is necessary to select a cell, SC505 in the case, as primary

server cell.


Change antenna downtilt of SC505 from 6 to 4 degree.

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After Optimization


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Optimization result: The primary server cell is more outstanding, and Ec/Io is improved

obviously.


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Problem: low HSDPA download rate

Before Optimization


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Problem: The red circ le area, active set has three cells Ec/Io all below -10dB, RSCP is around -85dBm, causing HSDPA download rate lower than 1Mbps.

1820

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Optimization Plan


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The main idea is to make primary server cell outstanding. After analysis on the basis of fieldenvironment, consider SC18 to cover the red ci rcle area. And decrease the effect of SC20 and

SC13, making them not cover the area.



Change antenna downtilt of SC20 two degree more.


Pilot Pollution


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Results to network:

decreasing the CSSR (Call Setup Success Rate)

decreasing the SHO rate

decreasing the system capacity

Trouble shooting

Generating a dominating cell in the pilot pollutionarea

After Optimization


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Optimization result: primary server cell S18 is outstanding. Ec/Io is improved obviously andHSDPA download rate increase to normal above 2Mbps.

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Optimization Issues


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The hill blocking signal causes call drop

Overshooting at Sofitel Beach

No Throughput Round SWHT Site for R99 Ftp

Download

Issue1: The hill block signal cause call drop


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site cell signal are blocked by a

mountain, UE lock in 3G cause

call drop in the back of

mountain.

Before Optimization


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Problem: The signal of this is area quite poor because the mountain blocked signal from

site, SC27 cell RSCP


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Change 2d event threshold (compress mode) of SC27 cell from -95dBm to -92dBm.

Change 3a event threshold (inter-RAT handover) of SC27 from -95dBm to -92dBm.

Change 3a time to trigger of SC27 from 100ms to 80ms.

Purpose: Let UE handover to 2G more faster in order to avoid call drop.

After Optimization


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Optimization result: UE can success to handover from 3G to 2G if mobile choices auto

mode , the result show no call drop.


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Before Optimization


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Problem: There are overshooting signal of SC11(KHTK1) and SC17(HNSS2) in the Sofitel

Beach. Distances to sites are over warn distance, customer can not share 3G service,

including CS and PS.

11

17

20


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After Optimization


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Optimization result: SC20(SWHT2) is primary service cell at mostly area in the beach. Thoughsignals of SC 17(SNSS2) and SC11(KHTK1) stil l exist in the beach, all service (CS and PS) are

normal.

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Issue3:No throughput Round SWHT Site for

R99 Ftp Download


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Soft handover failure cause low

throughput for R99 service.

Before Optimization


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Problem: Signal quality of SC28(SWHT3) is better than signal quality of SC12(SWHT1), but UE cannot report 1A event, SC28 cell can not update to active set , so result in R99 throughput is low.

Optimization plan: First step check whether NodeB has alarm , the second check RNC parameterabout intra and find that intra parameters set isnt correct set, so change back to correct

parameters set and resolve problem.

After Optimization


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Optimization result: SC28(SWHT3) can be added into active set, soft handover is success and

R99 throughput is normal.


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WPO-30 WCDMA Drive Test Data Analysis_PPT-72

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