Optimization

WCDMA Network Optimisation

Company Confidential

1 © Nokia Siemens Networks WCDMA Network Optimisation / June2007

Presenter :- Varun Sood

What Is optimization?????

• Optimization is an effort to improve the Quality of Service in the network and thereby make optimum use of network capacity deployed to carry more traffic on the same network.

• Optimization is the exercise done in the network to Bridge any planning and implementation gaps.

• Optimizers correct planning mistakes/Gaps.


2 © Nokia Siemens Networks WCDMA Network Optimisation / June 2007

Contents

• Optimization Procedure

• Types of Optimization

• Identifying problem Area

• Recommended Solutions



Optimisation Process

Drive-Test

(1st Round)

Analysis of Drive-Test Logs

Site Status Verification

Changes

Implemented?

Site Status Verification

Drive-Test

Recommendation for changes and

implementation (if needed)

No

Yes

No

Start the KPI Drive



Drive-Test Logs

Drive-Test Report (1st

Round)

Recommendation for changes and implementation

Drive-Test

(2nd Round)

Analysis of Drive-Test Logs

Drive-Test Report (2nd

Round)

KPI met?

Final Report

No

Yes

Presentation of Results

KPI should be met after 2 rounds of

DT

Possibility of Delays

3G Network optimization is divided into

1. Pre-launch optimization (without traffic, No OSS KPIs related to traffic)

2. Continuous optimization (with traffic, KPIs used)

3G Network optimization could be splitted into

A. Cluster optimization:• Mainly concentrates on the detail network optimization

for each individual sub-cluster area• Cluster optimization work start when all the sites in the

3G Network pre Optimization vs. Optimization

Cluster

Area



• Cluster optimization work start when all the sites in the Sub-cluster have been implemented and integrated into the Network

• 10-12 cells form one clusterB. Area optimization:

• takes broader approach by focusing the network performance over the whole area

• Will begin after a number of clusters have finished implemented & optimised

Pre-launch Optimization Process

ClusterPreparation

ClusterTuning

ClusterOptimizatio

n

NetworkVerification



n

Scanner Measurements

for RF Optimization

Service Performance measurements

for RF verification

Service Performance verification

Configuration & Health check

(RF +TRS Alarm

check)

• Cluster Identification

• Site locations, major roads, RNC borders, other geographical aspects, e.g. rivers

• Interference analysis to minimise the amount of external interference to a cluster from neighbouring clusters

• MapInfo plot illustrating sites within cluster, cluster borders etc.

• Site information spreadsheet (cluster id, priority etc.)

• Site Integration percentage criteria check

• Drive route planning

• A good percentage of main roads, motorways

• Different clutter types, where applicable

• Areas of special interest, e.g. airport routes, corporate routes

Cluster Preparation – basic information



• Areas of special interest, e.g. airport routes, corporate routes

• Drive test equipment check

• Site Verification (crossed feeders etc.)

• Find out bad planning (coverage holes etc.)

• Collect planning tool data

• Dominance plot

• CPICH coverage plot

• Best server Ec/Io plot

• RSCP plot

• SHO plot

• Configuration data (scrambling codes, tilts & bearing, data build)


ClusterPreparation

ClusterTuning

ClusterOptimizatio

n

NetworkVerification



n


RF Optimization


for RF verification



(RF +TRS Alarm

check)

Cluster Tuning – basic information

• Make RF Optimization in areas having poor dominance or weak dominance

• physical change of antenna tilt, azimuth, type and height) based on scanner data

• Make neighbours list (scrambling code) verification based on scanner data

• incl. GSM/EDGE neighbours

• Make Call Performance KPI Verification with logging tool

• AMR call setup success rate (CSSR)

• AMR call drop rate (DCR)

• Call setup Time (CST)




ClusterPreparation

ClusterTuning

ClusterOptimizatio

n

NetworkVerification



n


RF Optimization


for RF verification



(RF +TRS Alarm

check)

Cluster Optimization – basic information

• Make service measurements in given routes after RF tuning- > analyse the results

• Make Gap analyses –based on measured KPIs <-> target KPIs

• Investigate of bad quality related to radio interface

• Identify Coverage problems

• Look at Dominance

• Look at interference

• Look at Missing neighbours

• Make SomeTroubleshooting (call trace, counters.) in specific area (golden clusters) to find out if the



• Make SomeTroubleshooting (call trace, counters.) in specific area (golden clusters) to find out if the

problem is related to

• System

• Configuration

• Blocking

• UEs

• SHO Optimization

• Parameter Optimization

RF Optimization – Identifying Problem Areas

Drive Test Measurement

Coverage area optimisation

Dominance area optimisation

Best server’s CPICH RSCP>X dBm

# of pilots within

window from best

server >y

Yes

No

No

Coverage problem area

Dominance

problem area (Excessive # of pilots)

(C)

Yes

(A)

(B)



Dominance area optimisation

Complete

Measurement

Analysis

Best server’s

Ec/No<z dB

No

No

Yes

(C)

Dominance problem area (Low best server Ec/No)

RF Optimization

• RF optimization involved taking care of following areas –

- Coverage Related Problems [Poor RSCP]

- Quality Related Problems[ Poor EcIo]

- Lack of Dominance [ EcIo just ok but no single strong server]



Cell Overlaping

• Cell overlapping is needed to control the amount of interferences since the network

capacity is directly related to it. The little i value describes how much cells overlap:

• Some overlap is required to allow soft handover to occur

• Soft handover helps to reduce interference. (Soft HO Gain)

own

other

I

I i little =



• Soft handover helps to reduce interference. (Soft HO Gain)

• Typically soft HO should occur in 30-40% of connections, but in practice it could be as high as 60-80 %

• Too much overlap:

• Increases interference to other cells --> reduce capacity

• Increases Soft Handover overhead --> reduce capacity

Thresholds Definition

• Before starting the optimization, we have to define the thresholds for both RSCP and EcIo. That

Means what kind of coverage [RSCP] you are expecting from the network and second what kind of

quality [EcIo] is expected.

• These thresholds then should be compared with the measured logs and try to achieve those defined

KPIs.



Distribution Of Best Server CPICH RSCP and Ec/No

-Loaded and Un-loaded Network-

Network A- With Traffic Network B- No Traffic



• The Overall Io in Network Increased when the Traffic getting higer

• Measurement Result clearly show the Ec/Io in the loaded Network is lower

RF Optimization



Quadrant

• Measured data can be distributed in the previous slide.

• Quadrant A - This region contains all the samples which have both RSCP and EcIo above the required thresholds. We can call it the “Optimum Area”.

• Quadrant B - This region contain samples which have RSCP above the required threshold but EcIo below the threshold set. We can call it the “Pilot Pollution Area”.

• Quadrant C – This region has samples that have both RSCP and EcIo below the thresholds. We can call it “Low Coverage” area.



• Quadrant D – This region although has RSCP below the threshold but EcIo is still better then the set thresholds. We can call it “Low Coverage” area. This mostly happens in the edge of the network where although the coverage is bad but there is only one server present and hence better EcIo performance.

Initial Optimization

• Second step is to take actions to improve the radio conditions to reach the agreed RF targets:

•Down-tilting of interfering cells’ antenna, which generate pilot pollution•Change antenna bearing angles of cells

• Up-tilting of serving cell’s antenna to extend coverage radius and to improve coverage area

Tuning methods for Coverage Problem Area

Tuning methods for EcIo Problem AreaHigh PriorityHigh Priority



•Change antenna bearing angles of cells involved in pilot pollution•Change antenna patterns of cells involved in pilot pollution. Smaller gains for interfering cells and higher gain for victim cell•Decrease antenna height of interfering cells and increase antenna height of victim cell with adequate tilting angle

area•Change Antenna Bearing Angle: Focus the main beam of antenna to coverage holes and low RSCP area• Change Antenna Pattern: Displace with higher gain antenna with adequate antenna tilting•Increase serving cell antenna height to get higher effective antenna gain but there is risk to make undesirable inter-cell interference to adjacent cells

In Call Performance Analysis

• In call analysis is carried out to collect following information –

- Call setup success/failure rate for different services

- Cause of setup failures for different services

- Call completion success/drop rate

- Cause of call drops

- Soft/Hard handover performance

- Identifying any abnormal behavior from Network/UE side

- Verification of results from post processing tool.



- Verification of results from post processing tool.

UERRC: Connection Request

RRC Connection Setup phaseResource Reservation in RNC, BTS, Transmission

RRC: RRC Connection Request Setup

RRC Connection Access phase RNC waits reply from UE

RRC: RRC Connection Completed

RRC: Initial Direct Transfer cm service request

RANAP: Initial UE MessageDIRECT TRANSFER (Call

BTS RNC CN

Call Set-up

Definition of Call Set-Up Success Rate (CSSR)



DIRECT TRANSFER (Call Proceeding)

RANAP: RAB Assignment Request

RRC: Radio Bearer Set-up

RRC: Radio Bearer Setup Complete

RAB Connection Setup phaseResource Reservation in RNC, BTS, Transmission

RANAP: RAB Assignment ResponseDIRECT TRANSFER (Alerting)

DIRECT TRANSFER (Connect)DIRECT TRANSFER (Connect

Acknowledge)

RAB Connection Access phase RNC waits reply from UE

Call Set-up Success

Rate

Call Set-up Time

Typical failures/Drops ( From Drive Test Tool)

• Missing message (e.g. no L3 messages)

• RRC Setup Failures due to AC

• Cell reserved (Not seen for a while – but it is an easy check)

• Collision between LAC update/Registration and Call attempt

• Call failures because of ‘user busy’ (MOC)

• Calls disconnected by measurements system

• Calls disconnected by the network

• Radio Bearer setup failure due to AC and LC.



• Radio Bearer setup failure due to AC and LC.

• Missing adjacencies leading to a call failure or a dropped call

• Poor coverage/quality

• Coverage related (poor RSCP/EcN0)

• Quality related (poor EcN0/good RSCP)

• Cells covering ‘unwanted’ areas

• Overshooting cells

• Large back loops for some cells

Parameter Optimization

• Normally parameter optimization is undertaken on network level to resolve issues affecting the

performance of various services, following actions are taken during the process –

- Observe and monitor the Key performance Indicators of network

- Check for any degradation of services

- Identify the root cause of degradation and conclude if it is a cell/connection specific or network wide

issue.

- Recommend necessary solutions to resolve the issue

- Implement and verify the performance after changes are implemented



- Implement and verify the performance after changes are implemented

- Continue with performance monitoring of the network.

Parameter Optimization

New Network Parameter Changes required

Confirm parameters are applicable in existing network

releases

Is param

Fall back to original param set

no

no

Test param in Test Bed*, results ok?

Troubleshoot parameter Troubleshoot parameter set.set.

* Whenever applicable



Pre-Test Drive Test

yes

Load into Test Cluster

Post-Test Drive test

Analysis

Is param performing as

expect?

Implement to network

Cont’ to monitor network perf. thru routine drive tests

yes

Analysis - Neighbour List VerificationNeighbour definitions required for cell re-selection and handover

Soft handovers are based upon intra-frequency neighbour list

Hard handovers are based upon either intra-frequency, inter-frequency or inter-system neighbour lists

Intra-Frequency Neighbors

Cell a

Inter-Frequency Neighbors

Cell k

(32

/ca

rrier)

Inter-System Neighbors

Cell r

The critical objective of neighbour list verification is to -

Ensure that sufficient neighbours are present to achieve the desired coverage performance



Each neighbour has a set of associated parameters e.g. CPICH measurement offset

Actix Analyzer is able to suggest appropriate neighbour lists

Strategy for initial system deployment is to place the emphasis upon adding neighbours rather than removing them

Cell a

Cell b

Cell c

Cell d

Cell e

Ma

x. 3

1

Cell k

Cell l

Cell m

Cell n

Cell o

Ma

x. 4

8

(32

/ca

rrier)

Cell r

Cell s

Cell t

Cell u

Cell v

Ma

x. 3

2

coverage performance

Future objective – Ensure lists aren’t excessively large

Network Performance Measurements

UE RNC

RRC: Connect ion Request

Correctly Received messageRRC Connect ion Setup StartsTriggers: 1001C0 RRC Connection At tempt

BTS


RRC: RRC Connect ion Request Setup

RRC Connect ion setup completedTriggers: 1001C1 RRC Con Setup Compl

Failure Case:RRC Connect ion Setup failsDue to Triggers: 1001C2 Handover control1001C3 Admission control1001C4 BTS1001C5 Transmission network1001C6 RNC internal reason1001C7 Frozen BTS


Failure Case:RRC Connect ion Access failsDue to Triggers: 1001C9 L1 synchronization in BTS1001C10 UU interface1001C11 RNC internal reason

RRC: RRC Connect ion Completed

RRC: Initial Direct Transfer

CN

RANAP: Init ial UE Message

RRC Connect ion Access completedTriggers: 1001C8 RRC Con Acc Comp

RRC Connection Active phaseUE-CN Signaling

Failure Case:RRC Connect ion Active failsDue to Triggers: 1001C15 Iu interface 1001C16 Radio interface1001C17 BTS1001C18 Iur interface1001C19 Ciphering failure1001C20 Integri ty check1001C21 RNC internal reason

RANAP: Iu Release Command

RRC Connect ion Active completedTriggers: 1001C12 RRC Con Active Comp

Special Reason: RRC Connect ion Active Release Due to Triggers:

UEUE RNCRNC

RRC: Connect ion RequestRRC: Connect ion Request

Correctly Received messageRRC Connect ion Setup StartsTriggers: 1001C0 RRC Connection At tempt

BTSBTS


RRC: RRC Connect ion Request SetupRRC: RRC Connect ion Request Setup

RRC Connect ion setup completedTriggers: 1001C1 RRC Con Setup Compl






RRC: RRC Connect ion CompletedRRC: RRC Connect ion Completed

RRC: Initial Direct TransferRRC: Initial Direct Transfer

CNCN

RANAP: Init ial UE MessageRANAP: Init ial UE Message

RRC Connect ion Access completedTriggers: 1001C8 RRC Con Acc Comp

RRC Connection Active phaseUE-CN Signaling



RANAP: Iu Release CommandRANAP: Iu Release Command

RRC Connect ion Active completedTriggers: 1001C12 RRC Con Active Comp



• Currently, Nokia RAN able to provide a lot of network measurements data for network

optimization:

1. Cell resource

2. Service level

3. Traffic

4. RRC signalling

5. L3 signalling at Iub

6. L3 signalling at Iu

7. L3 signalling at Iur



1001C12 RRC Con Active Comp Triggers: 1001C13 SRNC Relocat ion 1001C14 Pre-emption

1001C12 RRC Con Active Comp Triggers: 1001C13 SRNC Relocat ion 1001C14 Pre-emption

Triggers: 1001C13 SRNC Relocat ion 1001C14 Pre-emption

7. L3 signalling at Iur

8. L3 relocation signaling measurement

9. Soft handover

10. Intra-system hard handover

11. Inter-system hard handover

• Totally more than 1,000 counters can be

triggered and monitors as network

performance KPIs

Performance Monitoring – Common Statistics




ClusterPreparation

ClusterTuning

ClusterOptimizatio

n

NetworkVerification



n


RF Optimization


for RF verification



(RF +TRS Alarm

check)

Network Verification

• Make Service verification in the whole optimisation area for performance acceptance

• Make sure that KPIs are measured in areas of ”acceptable” coverage is achieved

• It is recommended that the Minimum RF conditions for field measurements for all KPIs is as

described below:

• Best server CPICH RSCP > -100 dBm

• Best server CPICH EcNo > -11 dBm

• CPICH EcNo of the 4th strongest cell > 6dB below best server (= below drop window)

• KPI target examples for AMR



• KPI target examples for AMR

• Call setup success rate, 98 %

• Call drop rate, 2 %

• Overall call success rate, 96 %

• Call connection time <8 s, 98 %

Optimization Tools


30 © Nokia Siemens Networks WCDMA Network Optimisation / June2007

NetAct Tools

• Radio Network (RNW) Object Browser- part of NetAct

• WCDMA parameter changing and checking (RNC,WBTS,WCEL,ADJS (ADJI,

ADJG),HOPS (HOPI, HOPG),FMCS (FMCI, FMCG))

• RNW Online Management tool

• Cell level load monitoring with graphical user interface (Ptx/PrxTotal, Ptx/PrxTarget,

PrxNoise)



PrxNoise)

Online Monitoring- GUI



14 X PS 64K

Field Measurement Tools

• Field Measurement tools

• Scanner (Agilent, DTI, Anritsu for example) could be used for Coverage and Scrambling code

analysis

• Logging tools are available from a many manufacturers, those typically used by Nokia are Nemo

• Nemo Technologies – Layer 1 & 3 trace capability



Preparation for Drive test

• Connection configuration of equipments

RX - AntennaGPS -Antenna

GPS

DC / AC Inverter

Socket

To Battery1m over



GND

DC-12v In

RS232C Cable

RS232C Cable

ML8720B

Pulse In

RF -In

COM-2 Port

COM-1 Port

Gyro Unit

GPS

Receiver

Serial Port NOKIA

software

Socket

( Min DIN 8P )( D-sub 9P )

PC-Card

Analysis Tools

• Data processing and Analysis tools

• Actix: NOKIA's preferred supplier for post processing tools used for generating tuning

report automatically.

• PM data: NetAct Reporter, EOSFlex, TANO

• NQDI: SwissQual proprietary tool used for producing KPI report automatically

• RANOPT – Post processing tool from Aircom integrated with Planning tool.



Tom Kit

SwissQual+ scanner

Actix

NQDI

Tuning Report

KPI Report

Mass Modification with CM Tools

CM Provisoner to provide the actual parameter values from the network

CM Editor

• Create a new plan

• Copy objects from actual configuration and paste to plan

• Specify the new parameters

• Customised templates for mass modifications can be used!

CM Editor -plan modifications

CM Provisioner-upload actual configurations

CM Plan Manager



modifications can be used!

CM Plan Manager to prepare the plan

CM Provisioner to activate the plan

Element Manager to check if changes are correctly done

CM Provisioner-activate planned configurations

CM Plan Manager-plan creation

Element Manager-control the changes

Optimization strategy after pre-optimization

1. Network Monitoring • Key KPIs definition• Performance Tools (PM tools, tracing tools)

2. Problem Solving

Maintain & control Initial performance

0. Network audit & health check• Network element audit• Configuration audit

Optional if network is well-known



2. Problem Solving • Actions plan ready for each typical problem• Measures to avoid blocking (upgrade, parameter change)

performance

3. Parameter Optimization• Implement Nokia recommended RAN parameter set• Testing & statistical analysis to tune network/area/cell specific

4. System level optimization• Bearer specific optimization • Service-based & end-to-end performance optimization

Increase & optimizePerformance

KPI Types

• Service Access - If the customer wants to use a service, the network operator should provide

access to the service as fast as possible. The service accessibility is defined as the probability that a

service can be obtained within specified tolerances and other given operating conditions when

requested by the user.

• Service Retainability - Service Retainability describes the termination of services (in

accordance with or against the will of the user). The service Retainability is defined as the probability

that a service, once obtained, will continue to be provided under given conditions for a given time

duration.



duration.

• Service Integrity - describes the Quality of Service during service use. The service integrity

performance is defined as the degree to which a service is provided without excessive impairments,

once obtained.

KPIs - Service Types

• Circuit Switched – MOC, MTC and Video calls will fall in this category.

• Packet Switched – PS downloads and video streaming will fall in this category.



Common Global KPIs for Prelaunch OptimisationCriteria Success rate

1. Voice Call Setup Success Rate 98 %

2. VT Call Setup Success Rate 97 %

3. PS Call Setup Success Rate 98 %

4. Voice Call Termination Success Rate 98 %

5. VT Call Termination Success Rate 97 %

6. PS Call Termination Success Rate 98 %

7. Voice Long Call Duration 30 min



8. VT Long Call Duration 15 min

9. Average throughput for PS 300 kbps

10. Voice Call Setup Time 7 Sec

11. VT Call Setup Time 7 Sec

12 PS call setup Time 6 Sec

13. SHO Success Rate 98%

14. ISHO Success Rate 95%

Optimization

Documents

site status

service performance

launch optimization

parameter

rf verification

interfering

rf optimization

coverage holes