drive test analysis (t mobile)

8/12/2019 Drive Test Analysis (T Mobile)

1/60

1 2005 Nokia 3GRANOP_Module5/v2/Sep05/Nokia OSP

3G RANOP

3G Radio Optimisation

Module 4Drive Test Analysis


2/60


3G RAN Optimisation

RF Optimisation

and Neighbour

Planning

RF optimisation

New Site Integration

Neighbour plan

optimisation

Signalling

Flows

RRC Establishment

RAB Establishment

SHO

ISHO

Drive Test

Analysis

Drive Survey Analysis

System Performance

(RRC and RAB phases)

Cluster

Preparation

Cluster health checks

Parameter consistency

check

Neighbour list verification Uplink interference as a

problem indicator

Inter-System

Working and

Optimisation

3G2G Cell reselection

Neighbour Planning

Handover Process and

compressed mode

3G ISHO service analysis(AMR and PS)

GSM ISHO Optimisation

Parametric

Optimisatio

n

Use of Parameters to optimise

network performance

Network

Statistics

Cell Resources

RRC/RAB Performance

Handovers Abnormal Release


3/60


Module 4Drive Test Analysis

Objectives

After this module the delegate shall be able to:-

Understand the different elements required for an effective drive

test program

Understand how all aspects of drive data can be used to obtain a

view of network performance Differentiate between genuine (RF) and non-genuine (system)

failures

Understand the KPIs that can be obtained


4/60


Drive Test Process

Cluster

Preparation Define Cluster

Define Drive Route

Data Analysis

Levels ofReporting

Failure Type

Breakdown

Post Processing

functionality

KPI Gap

Analysis

Data Preparation

and Collection Services to test

KPI definitions

Equipment

Exclusions

Call Patterns

OSS Alarms

Network Stats

Trouble

Shooting Root Cause

Analysis

Corrective

Action

Further data

logging (maybe)

New Site Integration

RF Tuning Network Optimisation

Network Benchmarking (Golden Routes)

Why Drive the network?


5/605 2005 Nokia 3GRANOP_Module5/v2/Sep05/Nokia OSP

Drive Test AnalysisTest Equipment

SwissQual 7.5, Nokia 6650 trace UEs

Tri-band scanner

WDMA/GSM/DCS

SwissQual 7.5

Unit

GPS Laptop

Log Files

Land UnitNQMP

Log Files

FTP

Server

Important to drive with Call logging equipmentand 3G and 2G scanner in the same vehicle


6/60


Drive Test AnalysisCall Patterns

Mobile Originated Calls (MOC)

2 min calls

30 sec idle

UE in Dual mode (2G/3G)

AMR Call PS Call

Mobile Terminated Calls (MTC)

2 min calls

30 sec idle


Enough call samples have to be made to make the measurement statistically valid.

In a 50 call sample one dropped call will cause a change in performance of -2%

In a 500 call sample one dropped call will cause a change in performance of -0.2%

Call length should be defined at the beginning

We can use different call testing patterns for different optimisation techniques

Short Calls (for Calls setup performance and delay)

Long calls (for Drop call performance and SHO performance)

GPRS Attach,

PDP Context Activation

FTP Download (1MB file)/FTP Upload (500 KB file)

PDP Context Deactivation

GPRS Detach

Alternate download and upload with 30 sec idletime

Session is upload or download



7/60


Drive Test AnalysisDefining KPIsAMR Statistics

Threshold KPIs

MOC Setup time 5 sec

MOC CCR 99 %

RAW END USER

Event Count Rat io Count Ratio

Call Attempts 132 122

Call Setup Success Rate 108 81.8% 108 88.5%

Call Setup Failure Rate 24 18.2% 14 11.5%

Failures due to Tool (TSF) 10 41.7%

Failures due to Core Problem 10 41.7% 10 71.4%

Failure ASU (Sync) Problem 2 8.3% 2 14.3%

Failure due to Low Coverage Levels 2 8.3% 2 14.3%

Call Setup Success and Setup Time > 5s 7 6.5% 7 6.5%

Long Setup due to slow cell reselection 0.0% 0 0.0%

Long Setup due to clash with InterRAT reselection 0.0% 0 0.0%

Long Setup due to Unknown (suspect UE) 0.0% 0 0.0%

Long Setup due to Unknown 0.0% 0 0.0%

Average Call Setup Time 3.66 3.66

Call Completetion Rate 105 97.2% 105 97.2%

Call Drop Rate 3 2.8% 3 2.8%

Call Drop Poor 3G Coverage 1 33.3% 1 33.3%

Call Drop on GSM due to Interference 2 66.7% 2 66.7%

Overall Call Completion Rate 105 79.5% 105 86.1%

ISHO Attempt 14 14

ISHO Success 14 100.0% 14 100.0%

ISHO Failed 0 0.0% 0 0.0%

ISHO Failed cause physical channel failure 0 N/A 0 N/A

PS Data KPI Report

KPI Thresholds Value Unit

Attach Time 4 sec

PDP Activation Time 2 sec

FTP Download Throughput 110 kbit/s

FTP Upload Throughput 55 kbits

Signalling Statisti cs Count Success rate

Attach Attempt 155

Attach Success 140 90.32%

Attach Time more than threshold 5 3.57%

Attach Time less than threshold 135 96.43%

Attach Failed 15 9.68%

Average Attach Setup Time 1.36

Activate PDP Context Attempt 124

Activate PDP Context Success 124 100.00%

Activation Time more than threshold 2 1.60%

Activation Time less than threshold 123 98.40%

Activate PDP Context Failed 0 0.00%

Average PDP Context Activation Time 0.96

FTP Download Attempts 51

FTP Download Success 48 94.12%

FTP Down load t hroughpu t more than t hresho ld 25 52.08%

FTP Down load th roughpu t l ess t han th resho ld 23 47.92%

Average FTP Download Throughput 107.02

FTP Upload Attempts 32

FTP Upload Success 30 93.75%

FTP Upload throughput more than threshold 20 66.67%

FTP Upload throughput less than threshold 10 33.33%

Average FTP Upload Throughput 55.53

Data Transfer Cut-o ff Ratio 6.02%

PDP Context Dropped 4 3.23%

Deactivate PDP Context Request 121

Deactivate PDP Context Accept 121 100.00%

Deactivate PDP Context Failure 0 0.00%

Detach Request 281

Detach Accept 129 45.91%

Overall Data Session Complet ion Rate 78 62.90%

RAU Statistics Count Success rate

RAU Attempt 22

RAU Success 13 59.09%

RAU Failed 9 40.91%

Cell Reselection Statist ics Count Success rate

Cell Reselection from UMTS to GSM Attempts 2

Cell Reselection f rom UMTS to GSM Success 1 50.00%

Cell Reselection f rom UMTS to GSM Delay E2E 15.27

Cel l Reselection from UMTS to GSM Delay Signal ling N/A

Cell Reselection from GSM to UMTS Attempts 1

Cell Reselection f rom GSM to UMTS Success 0 0.00%

Cell Reselection from GSM to UMTS Delay E2E N/A

Time in System Seconds Ratio

GSM 171 1.02%

UMTS 16559 98.98%

Need to agree

What raw figures will contain

What End User will contain

Other cuts of Data


8/60


Need to Define the KPI measurement (from Drive test)

Call Setup Success (voice, circuit switched data) Successful call setup means that DL/UL Direct Transfer (CC: Alerting) message is received by

UE.

Session Setup Success (packet switched) This is related to PDP context activation.Successfully activated PDP context means that

activate PDP context accept message has been sent from RNC to UE (RRC:downlink directtransfer (SM:activate PDP context Accept)).

Call Setup Time (voice, circuit switched) Call setup delay is measured from L3 messages, starting from RRC Connection Setup

message to DL Direct Transfer (CC: Alerting) message.

Session Setup Time(packet switched) The session setup time is the delay between the time the UE sends the data session activation

request until GPRS attach and PDP context activation has been successfully completed.

Call Drop (voice, circuit switched) A dropped call occurs. The call will be dropped in case RRC connection release (not normal

release) message has been send from RNC to UE.

Session Drop (packet switched) Session drop rate can be defined as the number of successful PDP deactivations against

number of successful PDP activations.


9/60


Definition of Call Set-Up Success Rate (CSSR)

UERRC: Connection Request

RRC Connection Setup phaseResource Reservation in RNC, BTS, Transmission

RRC: RRC Connection Request Setup

RRC Connection Access phaseRNC waits reply from UE

RRC: RRC Connection Completed

RRC: Initial Direct Transfer cm service request

RANAP: Initial UE MessageDIRECT TRANSFER (Call

Proceeding)

RANAP: RAB AssignmentRequest

RRC: Radio Bearer Set-up

RRC: Radio Bearer SetupComplete

RAB Connection Setup phaseResource Reservation in RNC, BTS, Transmission

RANAP: RAB Assignment

ResponseDIRECT TRANSFER (Alerting)

BTS RNCCN

DIRECT TRANSFER (Connect)DIRECT TRANSFER (Connect

Acknowledge)

RAB Connection Access phaseRNC waits reply from UE

Call Set-upSuccess

Rate

Call Set-upTime


10/60


Definition of the Call Completion Rate (CCR)

UE RNC MGWNode B

Call Established

Iu Release Command

Iu Release Complete

RRC Connection Release

RRC Connection Release CompleteRRC Connection Release Complete

RRC Connection Release Complete

Radio Link Deletion Request

Radio Link Deletion Response

ALCAP: Release Request

ALCAP: Release Response

ALCAP: Release Request

ALCAP: Release Response

Call Released

Direct Transfer (Disconnect)

Direct Transfer (Release)

Direct Transfer (Release Complete)

DIRECT TRANSFER (Alerting)

DIRECT TRANSFER (Connect)DIRECT TRANSFER (Connect

Acknowledge)

Call DropRate

CallDuration


11/60


Definition of Session Setup TimeUE

CNRNCWBTS

INITIAL DIRECT TRANSFER (Attach Request)

Downlink Direct Transfer (Authentication & Ciphering Request)

UE already has an RRC connection

SCCP: Connection Request

SCCP: Connection Confirm

RANAP: Authentication & Ciphering Request

Security Mode Command

Uplink Direct Transfer (Authentication & Ciphering Response) RANAP: Authentication & Ciphering Response

RANAP: Security Mode Command

Security Mode Command RANAP: Security Mode Command

RANAP: Common ID

Downlink Direct Transfer: Identity Request RANAP: Identity Request

Uplink Direct Transfer: Identity Response RANAP: Identity Response

Downlink Direct Transfer: Attach Accept Direct Transfer: Attach Accept

Uplink Direct Transfer: Attach Complete Direct Transfer: Attach Complete

INITIAL DIRECT TRANSFER (Active PDP Context Request) DIRECT TRANSFER (Active PDP Context Request)

DIRECT TRANSFER (Active PDP context Accept)

RANAP: RAB ASSIGNMENTREQUESTRRC: Radio Bearer Set-up

RRC: Radio Bearer Set-up CompleteRANAP: RAB ASSIGNMENT

RESPONSERRC: Measurement Control

INITIAL UE MESSAGE (GPRS Attach)

SessionSet-upTime


12/60


Failure Breakdown

Non-genuine failures

Measurement system fault (CollectionTool or Analysis)

Genuine failures

RF issue (Coverage / Interference /

Poor dominance)

Missing neighbour

System issue Node B System issue RNC

Core network issue

System

(Unknown )

WBTS

RNC Core NW

UE

Iub Iu

It is beneficial tocategorise callfailures during theanalysis andreporting


13/60


Failure Breakdown

The KPI measurement conditions should be used to define exclusion areas

during drive test for acceptance of a cluster.

All failures happening in those area, that do not respect the coverage

requirements should be discarded.

Signal

aboveRSCP

threshold

SignalbelowRSCP

threshold

Signal aboveEc/Nothreshold

SignalbelowEc/No

threshold-110dBm

- -95dBm

-80dBm

Time

RSCP

CallOK

CallOK

CallOK Call

NOK

CallNOK

-12dB

-5dB

-20dB

Ec/No

Threshold

Example of Call Success Criteria

Discard sample

Call-(A)

Call-(B)

-110dBm

-

-80dBm

Time

RSCP

CallOK

CallOK

CallOK Call

NOK

CallNOK

-

-5dB

-20dB

Ec/No

Threshold


Discard sample

Call-(A)

-110dBm

-

-80dBm

Time

RSCP

CallOK

CallOK

CallOK Call

NOK

CallNOK

-

-5dB

-20dB

Ec/No

Threshold


Discard sample

-110dBm

-

-80dBm

Time

RSCP

CallOK

CallOK

CallOK Call

NOK

CallNOK

-

-5dB

-20dB

Ec/No

Threshold


Discard sample

Call-(A)

Call-(B)


14/60


Failure Breakdown

Call Set-up Failures Breakdown - Benchmark Drive

5%

20%

0%

5%

0%

0%

10%

5%

35%

15%

0%5% Equipment

Registration Clash

Core Network

Fail in 2G

RAN (fixed in next release)

Site maintenance (TMUK)

RAN (Other)

Missing neighbours

3G RF

slow cell Reselection

site configuration & maintenance(Nokia)

Other

Call Set-up Failures

Failure Type total %

Equipment 0 0.0

Registration Clash 0 0.0

Core Network 0 0.0

Fail in 2G 6 19.4

RAN (fixed in next release) 0 0.0

Site maintenance (TMUK) 16 51.6

RAN (Other) 0 0.0Missing neighbours 0 0.0

3G RF 3 9.7

Slow cell reselection 0 0.0

site configuration & maintenance (Nokia) 0 0.0

Other 6 19.4

Call Setup Failure Breakdown - Final Drive

0%

0%

0%

19%

0%

0%

0%

10%

0%

0%

19%

52%

Equipment

Registration Clash

Core Network

Fail in 2G

RAN (fixed in next release)

Site maintenance (TMUK)

RAN (Other)

Missing neighbours

3G RF

Slow cell reselection

site configuration & maintenance

(Nokia)Other

Call Set-up Failures

Failure Type total %

Equipment 1 5.0

Registration Clash 4 20.0

Core Network 0 0.0

Fail in 2G 1 5.0

RAN (fixed in next release) 0 0.0

Site maintenance (TMUK) 0 0.0

RAN (Other) 2 10.0Missing neighbours 1 5.0

3G RF 7 35.0

slow cell Reselection 3 15.0

site configuration & maintenance (Nokia) 0 0.0

Other 1 5.0

AMR Call Setup Failures


15/60


Non-Genuine Call Setup Failure Scenarios

Examples of non-genuine failures seen:

Uplink: CM Service Abortwithin milliseconds from CM Service Request

Call attempt during Location Area update (LA clash)

User initiated UL CC Disconnect

Location Area update interpreted as call setup failure

Cell reselection back to 3G from 2G interpreted as call setup failure

Measurement systems are often not perfect and may introduce errors

in data collection or analysis


16/60


Non Genuine Call Setup Failures

Measurement system failures by drive test tool

CM Service Abort within milliseconds from CM Service Request No time for response from NW


17/60



Measurement system failures

by drive test tool

Call attempt during LocationArea update (LA update clash)

LA Update

Request

Call attempt

RRC

Release


18/60



Measurement system failures by Actix workbook

Successful or failed Location Area update interpreted as call

setup failure

RRCConnection forInter-RAT cell

reselection

LA UpdateRequest


19/60


Non-Genuine Drop Call Scenarios

Measurement system failure examples:

Drive test tool User initiated UL CC Disconnect

Analysis Workbook

Inter-Rat cell reselection from 2G to 3G interpreted as drop call

Complete (e.g 90 seconds) call on either 3G or 2G

No drop in the log file / same drop listed twice


20/60


Genuine Call Setup Failure Scenarios

RF issue

Interference / Dominance / Coverage

Missing neighbour

System Issue - NodeB

No response to RRC Connection Request

RRC Connection Reject to RRC Connection Request

System issue - RNC CC Disconnect after Call Proceedingdue to DL RRC Connection Release

Core NW

CM Service Abort after CM Service Request

System issue (test number)

CC Disconnect after CC Progress


21/60


22/60


Drive Survey Analysis Process Summary Diagram


23/60


Failure Location

Analyse the

signalling flowto find the

location of

failure and

potential

cause

UE log may

only capture

some of the

messages


24/60


Start

Best serversRSCP > -102dBm

Best serversEc/No > -12dB

Coverage Optimisation

Dominance Optimisation

AICH(ACK) received?RACH failure

Message sent?

UL coverage & RACHparam. Opt(changing serving cell)

Check system message

Report & Finish

(FACH) RRC ConnectionSetup received?

Report & Finish(Check failure cause)

(DCH) RRC Connection setupCompleted sent from UE?

Report & Finish(Reason of problem:

L1 sync fail)

Radio Bearer setupfailureReceived?

Report & Finish(Check failure cause)

RRC setup rejectreceived?

AC optimisation(check PrxNoise

& interferer around BTS)

Report & FinishCheck failure cause

(Not radio problem/cell update)

Yes

No

Yes

No

Yes

No

No

Yes

No

Yes

Yes

No

Yes

No

No

Report & Finish

Yes

A

B

C

D

E

NeighbourlistOptimisation

MissingNeighbour ?

Yes

No

Call Setup Failure Analysis Process

A


25/60


Call setup failuresRF issue

RF issue? Coverage / Interference / Dominance

A

See the example in Module 3RF Optimisation

A


26/60


Call setup failuresMissing Neighbour

Missing neighbour analysis over the whole route (3G-3G, 3G-2G)

Search for failures due to missing 3G-3G neighbours Search for failures due to missing 3G2G neighbours

It is suggested to place 2G scanner to the test vehicle

A

B


27/60


Call Setup Failure Analysis- Block B -

The purpose of this activity is to check the Random Access Process is working

adequately by investigating whether AI (Acquisition Indicator) has been received

through DL AICH.

If AICH was not received by UE, the cause of the problem can be classified into:

Inadequate RAN parameter related to Random Access: RAN parameter settings for

pre-amble transmission or open loop power control information is not correct.

UL Coverage limit: UL coverage of UE is smaller compared to serving cells DL

coverage so that UEs Tx power cannot reach serving cell.

The Basic theory for RACH setup procedure and planning parameters can be

found in Module 7Parameter Optimisation

B

C ll S t F il A l i Bl k B

B


28/60


Call Setup Failure Analysis- Block B -

UE WBTS RNC

Preamble/RACH

Acquisition Indicator/AICH

RRC: RRC Connection Request/PRACH

NBAP: RADIO LINK SETUP REQUEST

RRC: RRC CONNECTION SETUP/FACH

L1 Synchronisation

NBAP: SYNCHRONISATION INDICATOR

RRC: RRC CONNECTION SETUP COMPLETE/DCH

UE in CELL_DCH state

NBAP: RADIO LINK SETUP RESPONSE

B

B


29/60


RACH Process

Downlink

BS

L1 ACK / AICH

Uplink

MS Preamble1

Not detected

Message partPreamble2

PRACH_preamble_retrans# PRACH preambles transmitted during one PRACH cycle without receiving AICH response

UEtxPowerMaxPRACH

RACH_tx_Max# preamble power ramping cycles that can be done before RACH transmission failure is reported

PowerRampStepPRACHpreamble

PowerOffsetLastPreamblePRACHmessage

Initial preample power:Ptx = CPICHtransmissionPower-RSCP(CPICH) +RSSI(BS) +

PRACHRequiredReceivedCI

B

C ll S t F il A l i Bl k B B


30/60


Call Setup Failure Analysis- Block B-

Solutions for RACH optimisation

Max UE Tx power hitthe UE_P_MAX(24dBm)?

To increase PRACH_Preamble_retraOr PowerRampStepPRACHPreambl

No

Yes

Is UL Interferenceabnormally HIGH?

Yes

No

Report there might be an interferingsource Nearby the serving cell

Change the Serving cell to cover the problem Area

=> UE is too far to reach the serving cell

B

C ll S t F il A l i Bl k B B


31/60


Call Setup Failure Analysis- Block B

Open Loop Power Controlparameters from RACHInfo message

B

Call setup failures System issue Node B C


32/60


Call setup failuresSystem issue Node B


Good RF conditions

Wrong MHA settings or cable loss settings can cause the site not to hear the UE

PrxNoise statistics, receive link parameters and HW units to be checked (faulty

MHA, wrong MHA parameters, wrong cable / feeder loss parameters, faulty units)

C

Call setup failures System issue NodeB C


33/60


Call setup failuresSystem issue NodeB

RRC Connection Reject after RRC Connection Request

Good RF conditions

Admission Control can reject too many (or admit too many) connection requests due

to wrong PrxNoise measurements.

PrxNoise statistics, receive link parameters and HW units to be checked

C

Call Setup Failure Analysis C


34/60


Call Setup Failure Analysis

UE has the appropriate DL/UL coverage but if RNC does not allow to set up the

RRC connection of the requested RAB (Radio Access Bearer), Call setup will fail.

Admission Control (AC) is involved in RRC connection setup

PREVENTATIVE STATE:

If measured UL (PrxTotal) or DL (PtxTotal) load exceeds target

thresholds (PrxTarget and PtxTarget) AC can still admit new RAB to the

cell if a new non-controllable load keeps below target thresholds (inpractice this means that AC can admit only new controllable load RABs

i.e. NRT RABs)

OVERLOAD STATE:

If measured UL (PrxTotal) or DL (PtxTotal) load exceeds overload

thresholds (PrxTarget + PrxOffset and PtxTarget + PtxOffset) then ACcan't admit more RABs to the cell

C

Call Setup Failure Analysis C


35/60



During the pre-optimisation phase it is unlikely that AC will stop an RRCconnection setup during the drive testing because there are normally very

few UEs in the network. (Traffic loading is trivial) However, it should be checked that measured PtxTotal and PrxTotal are

less than PtxTarget (e.g. 40dBm) and PrxTarget (e.g. 4dB, 60% loading)respectively.

If DL AC does not allow RRC setup check the Tx power of WBTS, # ofchannels transmitted, Signaling messages.

If UL AC does not allow RRC setup: Check out if there is an interferingsource nearby the serving cell.

C

Call Setup Failure Analysis D


36/60



To check if Layer 1 Synchronization (slot/frame sync) has failed

If RRC Connection Setup was received by UE but UE does not send RRC

Connection Setup Completed, we will report L1 synchronization failure and have to

check L1 system messages.

D

Call setup failures System issue RNC E


37/60


Call setup failuresSystem issue RNC

CC Disconnect after Call

Proceeding

Good RF conditions

Failures in RAB setup

occur between the RAB

Assignment Request being

received from Core

Network and the RANsending out Radio Bearer

Setup. Therefore the failure

is between NodeB and

Core Network.

E


38/60

Call setup failures Core NW E


39/60


Call setup failures Core NW

Security Mode CommandCommon ID

UE RNC MGWNode B

RRC Connection Establishment

Initial Direct Transfer (CM Service Request) SCCP: Connection Request

SCCP: Connection Confirm

Location Reporting Control

RRC: Initial Direct Transfermessage is sent using acknowledged mode RLC to the CS core

domain. Routing is to be based upon the local P-TMSI

The NAS message is not read by the RNC but is forwarded to the multimedia gateway. The NASmessage includes the IMSI as a UE identity

The SCCP: Connection Requestmessage establishes the connection orientated signalling link inthe same way as it was for the RRC connection phase.This does not reserve any resources for the

AMR call itself.

The Connection Confirm message identifies the RNC with a destination local reference which is thesame as the source reference within the Connection Requestmessage

The Connection Confirm message identifies the CS core with a source local reference

The CS core sends a RANAP: Location Reporting Controlmessage to the RNC requesting

information regarding the location of a particular UE

The RANAP: Common ID message specifies the IMSI belonging to the UE

The Security Mode Commandmessage triggers the start or stop of ciphering and integrity

protection.

CM Service Abort after

CM Service Request

Good RF conditions

Security Mode Command-

message not received by

UE, thus the failure is

believed to be at Core

Network.

E

Call setup failures System Issue (test number) E


40/60


Call setup failures System Issue (test number)

CC Disconnect after CC Progress

Cause: recovery on timer expiry

The call goes via IN SCP to arecording.

A static test was done by NokiaCustomer Care and in few instancesthe call dropped after 30 seconds ofrecording passed. Hence the

problem is associated with the testnumber not the RAN 30sec

Cause: recoveryon timer expiry

E

Call Drop Failure Analysis Process


41/60


Start

Best serversRSCP > -102dBm

Best serversEc/No > -12dB

Coverage Optimisation

Dominance Optimisation

Yes

YesYes

Neighbour listOptimisation

MissingNeighbour

Yes

Call Drop Failure Analysis Process

SHO Failed

Investigatepossible

Node B orRNC problem

No

ISHO Failed

No

ISHO FailureAnalysis

B

Yes

SHO FailureAnalysis

No

A

Call Drop Failure Analysis Process (SHO Analysis)


42/60


Call Drop Failure Analysis Process (SHO Analysis)

DL Active Set Updatereceived

Yes

SC Clash

UE Tx Power Max

Fix SC Clash

CPICH Optimisation

Uplink InterferenceLoad

Optimisation/ExternalInterferer

Link Unbalanced

Yes

Yes

Yes

Yes

No

No

No

Yes

Inter RNC HOCheck Iur

Yes

Congestion on target cellLoad

Optimisation

No

Yes

NoCheck neighbour definition parameters

Check RF Levels

NoDL Tx Power Max

No

Yes

Start

C

D

Drop call failuresRF issue A


43/60


p

RF drops mostly due to poor dominance or

interference

Poor coverage could lead to ISHO,although poor dominance or interference

can cause ISHO to fail.

Rapid field drop can cause drop due to

coverage

Poor dominance or interference can cause

Compressed Mode (CM) to start even if

RSCP is still good.

In CM UE transmits with higher power

(more interference) and spends less time

on 3G (less accurate measurement

reporting)

Poor dominance or interference can lead

to Active Set update failures andeventually to drop call. Poor dominancecauses Active Setupdate failures

A



44/60


p

DL synchronisation is lost ->

UE has stopped transmitting

TrChAgg and DL

DPCCH BER high

A



45/60


p

Transport ChannelBER. Btw UERNC (MAC layer)

Sometimes DPCCH BER (btw UENodeB) can be a better indicator of

what's happening to the dedicatedchannel than the CPICH EcNo, inparticular in the case that power controlmay not be tracking well.

Fairly goodCPICH PilotEcNo

A

Drop call failuresSystem issue NodeB B


46/60


p y

Sudden drop to idle, no disconnect messaging

Site malfunctions to be checked

In the example below site had faulty unit (WTR)

Drop to IDLE

B

Drop call failuresSystem issue RNC B


47/60


Sudden RRCConnection Release

DPCCH BER CC Disconnect due to

DL RRC Connection

Release No response to UL

Measurement Reports

In the example site had no

alarms, good RF & BER

Not able to add SC265 to

Active Set, next call on thesame cell => no failure.

Difficult to troubleshoot if

the failure does not

happen systematically =>

follow up in the next weeks

drive / do a separate drivetest in the area

Drop call failures (SC conflict) C


48/60


Sudden drop to idle mode

(no disconnect

messaging) Cause of the failure:

overshooting site and SC

reuse

Short term solution to add

overshooting neighbour in

ADJS definitions

Cell ABC, SC258

Transportchannel BLER

100%

C

Drop Call - Uplink Interference D


49/60


UL interference from the SIB7message

D

Drop CallLink Balance D


50/60


UL & DL Power Control commands can help

indicating problems in link balance.

PC frequency is 1500 Hz, thus ideally the sum of

PC commands to increase or decrease power is1500

E.g. if the sum of UL PC commands is < 1500,

this would indicate UE is starting to loose

synchronization

in Compressed Mode there is less PC

commands, UE spends time on 2G

UE RX power control

message: DL reception

weak -> UE is ordering

WBTS to increase power.

Sum of UL PC commands

< 1500, UE not receiving

all the PC commands.

Drop call failuresSystem issue RNC or Node B ?


51/60


CC Disconnect due to DL RRC Connection Release is just aconsequence of failure which can be due to different reasons

From UE point of view L3-messaging does not identify the point of failuredistinctly

Node B or RNC failure? => Suspect Node B first, then RNC

Rule out Node B failures Check the site performance from OMC counters (Iub, Servlev, SHO, etc) and that site iscarrying traffic

PrxNoise, receive link parameters, alarms

SCreuse

UE performance ?

Identified causes for Active Set Update failure

Deaf sites (PrxNoise)

Faulty HW

SC-reuse

Drive Test AnalysisReporting Levels


52/60


Optimiser

Very High Level KPIs that give ausers perception of the network(Network KPI)

KPIs that provide an Engineeringview of network performance e.gCSSR, CDR, OCSR, SHOperformance. (KPIs required foreach optimisers area)

Highly detailed KPIs that give adetailed picture of networkperformance at an Engineering

level and allow root cause analysis

Regional OptimisationManager

Senior

Management

Processing Drive Data to provide the information required at thebottom level means that the higher level information can be easilyextracted

The different reporting levels may want to see KPIs based ondifferent cuts of the data (e.g. raw or end user)

KPI reporting


53/60


Non-genuine failures to be removed from the raw KPIs

Call Completion

Call SetUp Success Rate 97.5% 97.9%

Call Drop Rate 1.3% 0.3%

Overall Call Success Rate 96.2% 97.6%Call Connection time


54/60


Weekly KPI trends (non-genuine failures should be excluded)

All Routes

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

wk4

1

wk42

wk43

wk4

4

wk45

wk46

wk47

wk48

wk49

wk50

wk5

1

wk52

wk02

0

100

200

300

400

500

600

700

800

Call SetUp Success RateCall Drop Rate

Overall Call Success Rate

Time on 3G

Time on 2G

Call Attempts

KPI reportingN d B f il h t ( ll t f il & d )


55/60


Node B failure chart (call setup failure & drops)

Cumulative number of failures that occurred per site over time

If the UE is spending only a small percentage of time on 3G problems may not

be identified.

CELL_C

Cell_ACell_D

CELL_B

Node B failure examples: CELL_A


56/60


Long history of failures (over weeks 46, 47, 02)

Call Setup failure scenarios:

CC Disconnect after CC Call Proceeding

CM Service Abort after CM service Request

3rdsector showing low average PrxNoise108 dBm Commissioning data

(feeder loss) was found incorrect.

After this site was still failing, not carrying traffic.

Alarm 7750 failure in WCDMA BTS O&M Connection. COCO rebuilt (27.1.05)

NodeB failure examples: CELL_B


57/60


Failures only on week 49


No alarms

At WBTS: MHA parameters ok

At RNC: MHA=0, cable loss = 3 dB (DPCCH init pwr)

PrxNoise checked OK, OMC statistics showed the site carried traffic during the

drive. No failures in the following weeks drives

NodeB failure examples: CELL_C


58/60


Failures over weeks 44, 45, 49, 50

No response to RRC Connection Request most frequent failure, also one caseof sudden drop to idle.

Test calls were made, the counters were not incremented during the test.

Protocol analyser proved no activity in Iub. The counters were incremented only

after site reset.

Alarm WSMA RR-bus error The site had faulty WTR, incorrect feeder loss in the commissioning file.


59/60


60/60

drive test analysis (t mobile)

Documents