Tools for Optimization GSM

8/14/2019 Tools for Optimization GSM

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Main Tools for Radio Network

Optimization GSMStatistic Handling Tool

OSS Recording Tool

Cell Data Design Tools

Field Measurement

Cell Planning Tool

Field Measurement Analysis

NWS (C); SPOS&Turle, Statics (I)

PMR, RNO package (C)

CNA (C); IPOS, BSSTool (I)

TEMS only!!!

TEMS Cellplanner (C); MCOM (I)

TEMS, MapInfo (C); MCOM (I)

Model Tuning

Network Integration Test

Design & Rollout

Initial Tuning

Training

Operation & Improvement

Verification of Network Changes

Network Feature Optimization

Traditional Optimization

GPRS PerformanceVerification

Where does TEMSINVESTIGATION fit in

Network Integration Test

When a site is integrated to BSC it is tested

• Call set up test• Timeslot test, forced call test

DESIGN & ROLLOUT PHASE

* TEMS Pocket is the preferred tool for Network Integration Test

Initial Tuning

• Produce Coverage Plot

• Identify Coverage Holes• Identify Interference Area

• Optimize Neighbor Relations

• Find Hardware/Installation Problems

• Verify Parameter Setting

DESIGN & ROLLOUT PHASE

GPRS Performance VerificationDESIGN & ROLLOUT PHASE• Application Performance Test

• WWW, FTP, WAP etc.• Mobility Test

• Cell Reselection, RA Update

Traditional Optimization

• Investigate & Trouble-shooting Specific Areas

• Neighbor Relation Optimization• Coverage Issues

OPERATION & IMPROVEMENT

Network Feature Optimization

Parameter Settings:

• MS, BTS Power Control• HCS

• Idle Mode Behavior

• Locating Algorithm

• Frequency Hopping

• Intra-cell Handover

Verification of Network Changes

Did a certain change in the network give desired results?

• New coverage area?• Less interference?

• Better speech quality?

• Is handover possible?

Clear objective

Why should thismeasurement bedone

Preparations Collect Data Analyze

Check equipment

Get input files

Prepare route

External Antenna?

Save logfile

Take notes

Monitor

Find problemareas

Find solutions

What should bechanged?

Report

Give answerto objective

Changes inNetwork

TEMS Measurement & Analyzing

Process

Clear objective

Why should thismeasurement bedone

Preparations

Check equipment

Get input files

Prepare route

External antenna?

Possible Objectives

• Coverage analysis• Trouble shooting• Scanning• Verify network changes

Measurement Will Depend onObjective

Drive Test

• Large areas

• Specific areasWalk Test

Scanning

Performing Measurements withTEMS

Plots & Report

- Signal Strength

- Quality

Trouble Report /

Area for furtherinvestigation

Acceptance

New sites on air

Frequency Re-plan

BSC Re-homing

OUTPUTINPUT MEASUREMENT

Drive definedroute/area

Record Logfile

Long / Short calls

Assure no data loss

Drive Test

- Large area

Manipulate

- Forced handover

- Lock on to Frequency

- Layer 3 messages

Analysis on-spot

Rectify & Verify on-spot

OUTPUTINPUT Measurement

Statistics

Customer complain

Large area drive testTrouble Report

Trouble Report

- Identified problem

- Solution

Drive Test

- Specific area

Statistics

Customer complain

Micro cell planning

Indoor cell planning

Add file marks (GPS)

Scanning

Trouble Report

Planning Report

- Antenna location

- Frequency

- HCS setting

Walk Test

* TEMS Light is the preferred tool for indoor cell planning

Finding a newfrequency

Area Network

Scanning

Received SS ondifferent ARFCNplot

New frequency

TEMS INV inscanning mode

Set ARFCN to scan

Scanning

Analyzing Measurements

Post-Processing TEMS LogfilesTEMS

Log files

StatisticsReport

GeographicalPresentation

Analysis

Low Signal Strength• Interference• Handover• Call Setup Failure• Dropped Call•

Problem Cases

Signal Strength CaseINPUT

Large area DT

Specific area DT

Post-Processing

Analysis

TEMSLogfiles

• Identify areas with low signal strength e.g. SS < -100dBm (outdoor)

• Look at RxLev distribution (for acceptance)

• Compare with design level or new requirements

• Shadowed Antenna

• Antenna Direction

Antenna Height / down tilt• Output Power

• Missing Neighbor Relation

Site Location• Faulty Hardware e.g. antenna & TMA

• Cell is down

Signal Strength Case –

Possible Reasons

Shadowed Antenna Faulty Hardware

Height/down Tilt

Output Power

Visit site

Check antenna installation

Is there a better antennaposition at same site?

Add reduce down tilt?

Can antenna be placedlower or higher to givebetter coverage?

Check output power

ParametersBSPWRT - NON BCCH FREQ

BSPWRB - BCCH FREQ

Site Location

Possible to move site?

New antenna location atsame site? Is it necessaryto expand and build a newsite?

Check alarm & BTS Error

logVisit site

Analysis

Missing Neighbor

Is the call dragged?

Is low SS due to missingneighbor relations

• Change parameter BSPWR , BSPWRT.

• Add neighbor relation.

• Physical changes:• Antenna direction

• Antenna height, tilt or position

• New site as last option.

Possible Solutions

Large area DT

Identify areas with Rxqual > 5

Identify source using Map and STS

New drive test around problem area?

Specific area DT

Post-Processing

Analysis

Interference Case

TEMSLogfiles

From logfile & map :

What channel group suffer from interference? HOP or Non HOP?

• Check Current channel information in TEMS INV, hoppingchannel and hopping frequency.

Where does the interference come from? Cell name?

• Study map and logfile, look for co-channel or adjacent channelinterference.

Does the interference lead to lower SQI?

• Look at SQI measurement during high RxQual.

Use STS & RNO to assist analysis.

Interference Case –

Logfile analysis

BCCH 590 BCCH 590

High site

BCCH 590

BCCH 595

BCCH 600 CASE 1

CASE 2

Types of Interference • Co - Channel interference• Adjacent Interference

• Poor frequency plan• No dominant cell --> low C/I ---> increased Rxqual• Frequency Hopping is off• External interference e.g. jammer

Example of high Rxqualdue to low Signal Strength

Interference Case – Possible Reasons

Interference Case –

Possible solutions• Enable Frequency Hopping or add frequencies to

Hopping group.

• Enable BTS Power Control, MS power control andmake it less aggressive.

• Change frequency of interferer or interfered cell: – Possible to find new frequency by using TEMS

Scanning.

• Down tilt or change antenna of interferer.

Large area DT

Specific area DT

Post-Processing

Analysis

Look for:

Repeated handover (Ping Pong)

Repeated Intra-cell handover

Handover failure,

Unrealistic handover

Handover Case

Repeated Handover (Ping Pong) - Examples

Repeated Handover (Ping Pong)

- Possible Reason 1

Merry-go-round Handover, Offset >Hysterisis

- Possible Reason 2 • Offset only in one direction e.g A-B for Inter

BSC relation

CELL A CELL B

A -> B OFFSET = -5dB

BSC 2BSC 1

No B -> A OFFSET

No dominant Server

Repeated Handover (Ping Pong) –

Other Possible Reasons• No dominant server• Locating penalty settings

e.g. PSSBQ, PTIMBQ• Too small hysterisis

setting

Antenna direction

Antenna Tilts

Plan for new site

Change Locating Parameter e.g.KHYST or LHYST

Repeated Handover (Ping Pong) – Possible Solutions

Change Parameter, KHYST or LHYST

Hysterisis CELL A CELL B

HandoverFrom A to B

– Possible Solution

Check layer 3 message

Handover command BSC correct?

Check reason for handover SS, RXQUAL

Target cell?

Handover Case –

Handover Reversion

Duplicates of BSIC BCCH combinations in neighboring list

610_31 610_31

610_12

606_33

608_32

Serving cell Neighbor cell 1

Neighbor cell 2

Handover command?

Handover Reversion

– Common Reason

Uplink interference in target cell

Downlink interference at MS

Solutions

Interference Investigation

• MRR

• Statistics

• Scanning

Handover Reversion

– Other Reasons

Possible Reasons

Wrong intra-cell handover settings

External Uplink Interference

Possible Solutions

Consider to change parameters:

• SSOFFSETUL, SSOFFSETDL

• QOFFSETUL, QOFFSETDL

A wrong setting of parameters will cause “unnecessary” IHO

Turn off Intra-cell Handover?

Handover Case – Repeated Intra-cell Handover

Handover Case – Unrealistic Handover

Possible Reasons

Wrong locating settings, in Serving or Target cell

Note: Could be on purpose e.g. Dual Band network with HCS

Solution

• Fix locating settings e.g. MSRXSUFF, BSRXSUFF

Unrealistic Handover – Reason & Solution

Call Setup Failure

Call Setup Failure –

Input Activities, Initial TuningActivities

Initial Tuning(Acceptance Test)

Troubleshooting

(Customercomplaint etc.)

Measurement Type•Large Area Drive Test•Short Call Sequences

Post-Processing Output

•Statistics Report•Geographical Reportshowing failure positions

Call Setup Failure –

Input Activities, TroubleshootingInput Activities

Initial Tuning(Acceptance Test)

Troubleshooting

(Customercomplaint etc.)

Measurement Type•Small Area Drive Test

•Lock on problem cell’s BCCH •Force handover to the cell

Post-Processing Output

•Geographical Report (ifnecessary)

Call Setup Failure Analysis- Initial Tuning Scenario

• Check the TEMS statistics report (Blocked Call)if there is Call Setup Failure.

• If yes, identify the problem cells and whichlogfile from geographical report.

Replay the logfile and jump to the Blocked Callevent.• Check if there is any successful call setup to the

problem cell.

Call Setup Failure Analysis

- Initial Tuning Scenario cont.• Review the layer 3 messages to check at which

sequence the failure occur (random access,SDCCH, TCH assignment etc.).

• Check STS report on the problem cell. Is thereany traffic (SDCCH & TCH) in the cell, SDCCH& TCH seizures, congestion etc.

• Check fault report & CDD configuration.

Call Setup Failure Analysis- Possible reasons with ranking

• Low Signal Strength• Interference• High Congestion on SDCCH• High Congestion on TCH• Transmission Fault• Faulty TRU/Hardware•

Central Processor Overload• Software File Congestion

• Cell is not defined in MSC .

Call Setup Failure Analysis- Possible solutions

• Low signal strength Signal strength analysis.• Interference Interference analysis.• High Congestion on SDCCH:

Define more SDCCHs.Activate adaptive configuration of logical channel

feature and immediate assignment to TCH.• High Congestion on TCH:

Add capacity/Tune coverage array.

Activate assignment to worse cell.

Failed Call Setup (Blocked Call)

Example

Multiple Channel Requests.

Successful Random Access after thethird try.

Congestion in SDCCH.

Dropped Call Case

- Input• Statistics Report• Note from drive test.

Dropped Call Case

- Analysis• From plot, identify which & where in logfile

the dropped call occurs.• In the log file, Jump the drop call event.• Check if there is a disrupt in the recording. If

yes could be a false drop due to TEMSmobile disconnection during recording!!!

Dropped Call Case- Analysis (cont)

• Check the Radio environment just before drop: – If High Rxqual for a longer period of time and RLINKT expire

Interference problem. – If Low SS DL, SS DL < MS SENS ( -104dBm) low signal strength problem. – If TA > 63 too far from the cell.

• If DL radio is good, check the TX power. If there is MS powerdown regulation when the MS is close to the cell. If full power

suspect uplink interference or antenna, TMA problem.• Verify or isolate the problem using STS (Drop call and reasons).

From TEMS Logfile

• Good Signal strength DL, Good Rxqual DL

• No call set up possible unless very close to site = high SS

• Dropped call when SS < approx. -75dBmAnalysis

• Since DL SS & Rxqual is good

Suspect UL problems e.g. external uplink interference

Conclusion

TMA power turned off

Miscellaneous Case 1

From TEMS Logfile

• TCH has lower Signal strength than BCCH (Own BCCH included inBA-list )

• BTS power control = OFF

CHG0 B C C H

S D C C H \ 8

CHG1 T C H

Configuration/cellSEKTOR A

SEKTOR B

SEKTOR C

Conclusion

Antenna cable for TCH is swapped between sectors (CDU-A)

From TEMS Logfile

• Fail to perform Call Setup

Analysis

• Check if any success call setup to the same cell No

• Check if handover is possible Yes

• Suspected wrong cell definition in MSC but Cell is properlydefined in MCS and LA

Conclusion

• Corrupted block in MSC

GPRS Measurement Activities• GPRS Performance Prediction• GPRS Field Measurement

GPRS Performance Prediction- Overview• GPRS RNAP Service uses TEMS Inv to predict

following performance: – Throughput – Cell Reselection & Routing Area Update

GPRS Throughput Prediction• Perform Throughput prediction for each

coding scheme

Cell Reselection Prediction• Dedicated mode drivetest

Cell Reselection Prediction• BCCH Scanning• Simulate the cell update with different CRH

valuesCRH = 4 dB CRH = 8 dB

CRH # HO

10 147

12 138

14 130

GPRS Field Measurement- Procedure

Set up files Cell definitionsPreparations

TEMS,IP Sniffers

Dig maps

Mapinfo

Graphical

presentation of route

Charts / Tables

Report

GPRS Field Measurement- Application Performance Test

• Attached performance – Attached Time = Attach Complete msg – Attach

Request msg – Attach Success Rate

• PDP context activation performance – PDP context activation = Activate PDP Context

Accept msg – Activate PDP context request• Throughput on RLC level• Dela

GPRS Application Test Tools

• General – Windump, Commview, Ethereal, Protocol Analyser

for Gb• PING

– MS DOS ping command• WWW

– IE, Netscape• FTP

– DOS FTP, WS_FTP, TEMS built in sequence

GPRS Field Measurement- Mobility Performance

Investigation• Number of Cell Reselection & RA Update• TCP Outage Time•

Cell Reselection Failure

Mobility test CRH = 4, CRO = 4

Cell Reselection Sample ReportRouting Area Time Cell Target

CellReselection

timeResult Comments

BSC1 16:30:42 D0241A D0241C 2 s OK NABSC1 16:33:18 D0241B D0242A 2 s OK NABSC1 16:35:04 D0242A D0248C 21 s OK This cell reselection was

made to a cell located quitefar away (not the closest),

thus the RxLev was quitebad!BSC1 16:37:44 D0244B D0248C -- NA No throughput before or

after the cell reselection.This is due to that the cellDF0242B were halted by

some reason!BSC1 16:38:11 D0248C D0244B -- Failed The through put was never

resumed and the FTP

connection was aborted bythe ftp-server!

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