Drive Test Measurement and Analysis Using TEMS 4

Network Monitoring and Optimization

Rajendra

Radio Network Design

Rajendra@xl.co.id

02-03 September 2004 Network Optimization

1. RF Optimization2. Network KPIs Overview3. Optimization Flow4. Tems Investigation 4.15. Drive Test Measurement and Analysis6. Optimization Expert (RNO)7. Reporting

Agenda

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RF OPTIMIZATION

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RF Optimization

What is it ..?the fine-tuning of all system parameters and antenna configurations to attainoptimum quality in the built network.

How to achieve..?By carrying out drive tests and other RF measurements to determine optimal settings for system parameters whilst meeting network specification

What the Output’s are ..?• Report containing the final parameter setting• History of changes• Final site configuration data along with graphical plot showing the actual measurement report

RF OPTIMIZATION

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Optimization Tasks include :

1. Reviewing any site and network design object set2. Discussing the routes that will be using for performing drive test3. Determining the setting default network parameter4. Identifying the neighboring of each cell5. Reviewing the frequency planning6. Completing site audit to ensure that all RF equipment has been correctly

installed and located7. Executing test to verify the correct operation of all air interface parameter8. Carriout baseline drive test9. Analyse and identify problem from drive test data10. Investigate and analyse each problem area ( interference and cell coverage)

Note : Every change should be test individually and noted to ensure there is no degradation on the surrounding network

Network KPI’s Overview

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Input for the RF Optimization :

1. Key Performance Statistic such as Dropped call, Handover failure and Blocking

2. Customer Complain

1. Accessibility Random Access ( > 99.6% Good)SDCCH Drop ( < 0.8 % Good)TCH Assignment ( > 99.8% Good)SDCCH Congestion TCH Congestion

2. RetainabilityCall Drop ( < 1.3 % Good)Call Minutes Per Call Drop ( > 106.9 Second Good)

3. IntegrityHandover ( > 97.2% Good)

Network KPI’s Overview

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Optimization Flow

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Daily Brief KPIanalysis

Is TCHAssignment

<x%?

Perform TCHAssignment

analysis

Is CellCongestion

>x%?Yes Yes

Is DroppedCalls >x%

No

Yes

End

Is SDCCH/TCHcongestion

<x%

Is HO <x%Goto HOanalysis

GotoCongestion

analysis

No

No

Yes

Yes

GotoCongestion

analysis

Has Siteperformanceimproved?

Clear off TroubleTickets

Yes

No

Some processhere to catch the

rest

No

PerformDropped Call

analysis

No

Network KPI’s Overview

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Drop Call Problem

Cause :

1. Coverage2. Handover3. Interference4. Uplink and Downlink Unbalance cause by antenna and feeder system5. Transmission Failure6. Unreasonable Parameter setting7. Equipment Failure

Network KPI’s Overview

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Dropped Calls on TCHDropped Calls on TCH

Bad LocatingParameterSetting?

Is PowerRegulation

used properly?

Is the PowerBalanced?

Is DTXused?

Is FrequencyHopping Used?

Check Output Power

Check Dropped call reason

BadQuality?

Low SignalStrength?

B

TimingAdvance?

SuddenDrop?

Other?

No

Yes

Yes

Yes

Yes

No

No

No

No

No

Correct ParameterSetting

Correct powerregulation

parameters

Adjust outputpower

Introduce DTX

ActivateFrequencyHopping

PerformInterference

Analysis

Perform lowSignal

Strengthanalysis

Check sitelocation &

TALIM

Yes

No

No

No

No

Yes

Yes

Yes

End

B

Check Lost Handover

Most droppedcalls duringhandover?

Check site position

Dragon site?

Check BTS Error log

HW fault?

Check link quality& synchronisation

Transmissionfault?

Best serverexists?

Check MS problem

Perform drive test

Perform CTR recordings

Perform site survey

Check antenna installation

Performhandoveranalysis

Remove site orchange frequency

Swap & repair HW

Perform linkinvestigation

Add site

No

No

No

No

Yes

No

Yes

Yes

Yes

Yes

Check reason forsudden loss

Investigatepossible Hardware

fault

Drop Call Flow Analysis

Network KPI’s Overview

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Handover Problem

Cause :

1. Improper antenna installation2. Interference 3. CO BCCH and CO BSIC4. Unreasonable parameter setting5. Congestion on the destination cell6. Equipment failure ( TRX` Performance Deterioration)7. Uplink and Downlink Unbalance

Network KPI’s Overview

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Handover Analysis

Handover analysis

Check successfulhandovers per Cell

Is success <x%?

Check handoveractivity

More than yhandoverspeformed?

Check site location,site to site distance,

co-sited?

Priority Cell?high traffic

Checkhandover flow

Unevenflow?

Difference inperformance in out-

and incoming?

Focus on baddirection

A

A

External?Start Inter BSC/MSC analysis

High ratio ofurgency

handovers?

High ratio of losthandovers?

High ratio ofreversion?

End

No

Yes

No

No

No

Yes

Yes

Yes

No

Yes

No

Yes

No

Yes

NoNo

No

InterferenceAnalysis

Does up or down linkinterference exist?

Yes

Does co-channel exist?

Handover relatedparameters such as

relations, missing relations,BA-List, BSIC, hystersis,offsets, etc set correctly?

Ping PongHandovers?

Correct parametersettings

Ping ponganalysis

No

Does cell havehardware problem?

Is Target Cellcongested?

Fix faulty hardware

Congestionanalysis

No

Yes

Yes

Yes

Yes

No

ChangeFrequency

Yes

Select worstrelation

Handover Flow Analysis

Tems Investigation 4.1

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Key Feature in Tems Investigation

1. C/I and C/A Measurement2. In Building Positioning3. Identification Interference source 4. Channel Verification Tool for testing traffic channel5. Frequency Scanning6. Decoding and Modification of layer 3 Signaling7. Cell Reselection and handover behavior8. Logging and Export9. Summary of Logfile in .HTML

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Workspace and Worksheets

Toolbars

Status Bar

Menu bar

Navigator

Interference MeasurementCarrier to Interference (C/I) Measurement

- In Idle and dedicated mode- In hopping and non hopping networks- Per used TS

Carrier to Adjacent (C/A)- In Idle and dedicated mode- On frequency hopping with 2 MS’s

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The C/I parameter enables the identification offrequency exposed to particular high level interference

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FER, RXQUAL and DTX Measurement

RxQual is a value between 0-7 where each value corresponds to an estimated number of bit error in number of burts

RxQual Bit Error Rate, BER

0 BER < 0.2 %

1 0.2% < BER < 0.4%

2 0.4%< BER < 0.8%

3 0.8%< BER < 1.6%

4 1.6%< BER < 3.2%

5 3.2%< BER < 6.4%

6 6.4%< BER <12.8%

7 12.8%< BER

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DTX DL Rate indicate in percent how many TCH frames that were not sent to the mobile station during the last SACCH multi frameDTX DL Rate varies from 0 to 96% ( never reach 100%)

DTX DL Rate (%)=(number of silent blocks/total number of blocks)*100

*Total number of blocks = 24

DTX DL Rate information element can be used to investigate “silent call” problem in the network.

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FULL and SUB Values

The FULL values are based on upon all frames on the SACCH multiframe whether they have been transmitted from the base station or not.

The SUB values are based on the mandatory frames on the SACCH multiframe i.e frames that always must be transmitted

If DTX DL is used in the network, the SUB set must be usedIf DTX DL is not used in the network , the FULL values are preferred

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Frame Erasure Rate (FER)

FER rate is a value between 0 and 100% and is calculated and presented in TEMS once each SACCH Multiframe (Synchronous with the RxQual values) and calculated on the TCH and SACCH Blocks

FER FULL% = (Number of blocks with incorrect CRC/25)*100

Total number of blocks on a full rate TCH channel is 24 TCH +1SACCH =25 FER SUB % = (Number of blocks with incorrect CRC/2 )*100

Total number of blocks on a full rate TCH channel is 2 TCH +1 SACCH =2

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BER/Timeslot ( %)

BER parameter gives the bit error rate for each used timeslot that calculated by summing the number of bit errors for each of the 24 blocks included in the BER the dividing the sum by the total number of bits in the 24 blocks.

BER % = (total number of bits error in 24 blocks/total number of bits in 24 blocks) * 100

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Quality Identification

RxQual : transforming the bit error rate (BER) into a scale from 0 to 7 (see GSM 05.08). Acceptable RxQual range is 0-3 ( basic measurement)RxQual : doesn’t reflect to speech quality

SQI : can produce unbiased prediction of the speech quality, independently of channel conditions

Computation of SQI involves :-Bit Error Rate-Frame Error Rate-Data on handover events-Statistic on distribution of these parameters

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Interference Identification

Co-Channel Interference is usually by far the most common type of interference encountered in a GSM network

SQI Level decreased suddenlyC/I Level decreased suddenlyRxQual increased until 6-7

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Interference Source Identification 1

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Interference Source Identification

Traditional Of Methods of tracing co-Channel Interference-Temporarily shutdown base station -Repeatedly modifying the frequency planning

Effect :-Disturb network traffic-Cause inconvenience to subscribers New feature in TEMS Investigation 4.1 offer a way to spot interferes -without resorting to such heavy handed and costly methods-Without any performance loss

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Interference Identification

HOW IT WORKS…?

Main task Interference identification :

-To determine the base station color code ( BCC) = TSC ( Training Sequence Code) that is found in the middle of GSM Burst.

-Do Interference Scan

-Knowing The BCC/TSC reduce the number of possible interferers by factor 8

-Many proposed cell as candidates can be rule out simply ( too far from disturbed cell, and topology features of the area).

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Interference Identification

Outcome of Interference Scan

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Interference Identification

Eliminating Remote Candidates

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Troubleshooting :• BCCH Scanning on the problem area• Replace interfered BCCH with low interference BCCH channel as temporary•Lock the interfered BCCH to get the interfered cell or do scanning on the interfered BCCH including with BSIC decoding

Display on the map :- Co-Channel - Adjacent Channel- Scan Channel including BSIC Scanning

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Interference Identification

Problem area with measurement statistic

• High RxQual• Low SQI• High BER• High Signal Strength

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Interference Source Identification 2

Co-Channel might come from : 12912

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Channel Verification* Allow to check the availability a set of traffic channel.

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Channel Verification Properties

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Improved Site Presentation on the map

- Show neighbor cells - Show serving cell - Show to neighbor lines

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Cell Definition File in *.cel format

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Frequency Scanning and Neighbor List Scanning

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CW ScanningAdjacent Scan Bar Chart

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Logfile Summary and Analysis

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Logfile Statistics

Standard Drive Test Report

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Table of Drive Test Report

1 Executive summary2 Test conditions2.1 Purpose of the drive test2.2 Site Data2.3 Drive route3 Test results3.1 Reference to attached plots3.2 Reference to attached listings of statistics collected during the drive test4 OSs Statistics4.1 Daily reports from NMC4.2 SRP reports5 Performance and optimisation summary6 action points6.1 Change Requests6.2 Other actions7 Conclusions8 References

RNO

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Radio Network Optimization

RNO is a collection of several radio network optimization applications in OSS

•FAS Frequency Allocation Support•FOXFrequency Optimization eXpert•NCSNeighbouring Cell Support•NOXNeighbouring cell list Optimization eXpert•MRRMeasurement Result Recording

RNO

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Radio Optimization Expert (RNO-MRR)

a tool for measuring the radio characteristics of the connections between MSs and the network. MRR records information on the radio characteristics of the dedicated channels and calculates statistics on the data recorded

•Supervision of the network performance •Troubleshooting of the network •Comparison of the network performance before and after a change is made to the network

RNO

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Radio Optimization Expert (RNO-FAS)

FAS is an optional feature that helps the operator achieve good frequency allocations and minimize the interference levels in the radio network with a minimum of effort.

RNO

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Radio Optimization Expert (RNO-FAS)

FAS is an optional feature that helps the operator achieve good frequency allocations and minimize the interference levels in the radio network with a minimum of effort. • To find frequencies in

order to add or expand a cell (frequency planning).

• To improve the cell plan and/or frequency plan due to capacity and/or quality problems (optimization).

• To supervise the interference level in a certain area (supervision).

• To verify improvement after a frequency change (verification).

RNO

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NCS (Neighbouring Cell Support) is a tool that helps users to specify adequate neighbouring cell relations for each cell in the radio network

•to find neighbouring cell relations to a new cell (network planning) •to find missing neighbouring cell relations in the active BA-List (network optimization) •to find neighbouring cell relations to be removed from the active BA-List (network optimizati on) • to evaluate neighbouring cell relations (network supervision).

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THE END

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