Fresh Field Mtc 004 Section 1

8/9/2019 Fresh Field Mtc 004 Section 1

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GSM SystemOptimisationSection One

Overview


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2001 Freshfield Communications Limited.Company Confidential Slide 2

Optimisation StrategyOptimisation Strategy Principal Network Data SourcesPrincipal Network Data Sources

Principal Network MetricsPrincipal Network Metrics

Typical Network Problems ListTypical Network Problems List

SummarySummary

Presentation OutlinePresentation Outline


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At the end of this course, attendees will:At the end of this course, attendees will: Have an appreciation of optimisation responsibilitiesHave an appreciation of optimisation responsibilities

Understand the network data sources availableUnderstand the network data sources available

Identify a strategy for optimisationIdentify a strategy for optimisation

ObjectivesObjectives


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Optimisation Team ResponsibilitiesOptimisation Team Responsibilities

Planning & DesignPlanning & Design Generate final cell planGenerate final cell plan

Operations & MaintenanceOperations & Maintenance Build sites and integrateBuild sites and integrate

Network SwitchingNetwork Switching Manage network switching subManage network switching sub--systemsystem

OptimisationOptimisation Ensure that network works!Ensure that network works!


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OptimisationOptimisation

Good signal

level (No

coverage

deficiency)

Customer has

network

access

(No blocking

or dropped

calls)

Reduced

signalling

(SDCCH) load

Good speech

quality

Be aware of

new cell sitetraffic

forecasting

Be aware of

seasonal

changes onRF hardware

Be aware ofeffects of

seasonal

changes on

traffic

Be aware of

specialmarketing

promotions

No delayedsetups

Be aware of

the

competition

Be aware of

every point in

GSM

architecture

where faults

can arise

Be aware of

new network

features


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Optimisation makesOptimisation makessuggestions andsuggestions and

recommendationsrecommendations

onon

BSS Database

Parameters for

RF

Environment

Radio

Frequency

Assignments

BTS-BSC

Connectivity

New sites for

coverage and

traffic

BTS hardware

Antenna

downtilting,

re-orientations

and heights


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Optimisation mustOptimisation mustcollate and managecollate and manage

the followingthe following

informationinformation

OMC Statistics

Customer

complaints

RF Frequency

plan and site

locations

SC and MSC

site parenting

information

Typical TS

hardware and

software

problems

ST

exchange

locations and

parented

numbers

GSM 04.06,

04.08, 05.02,

05.08

specifications


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2001 Freshfield Communications Limited.Company Confidential

Slide 8

Identify objectiveIdentify objective Identify objective such as dropped calls, SDCCH congestion,Identify objective such as dropped calls, SDCCH congestion,

high handover count, etc., and document ithigh handover count, etc., and document it

Remove variablesRemove variables

Isolate objective from other possible problems which may ariseIsolate objective from other possible problems which may arise Isolate system componentsIsolate system components

Identify what aspect of the system you are trying to work on suchIdentify what aspect of the system you are trying to work on such

as MSC, BSC, BTS Hardware, BTSas MSC, BSC, BTS Hardware, BTS--BSC link, mobile or RFBSC link, mobile or RF

environmentenvironment

Test planTest plan

Establish battle plan and write down what you want toEstablish battle plan and write down what you want to

accomplish, how you will accomplish it and the expected resultsaccomplish, how you will accomplish it and the expected results

Optimisation StrategyOptimisation Strategy


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Slide 9

CommunicateCommunicate

Inform your line manager and other colleagues about what youInform your line manager and other colleagues about what you

intend to do and whyintend to do and why

Take actionTake action

Conduct the work or trouble shooting that is identified in yourConduct the work or trouble shooting that is identified in your

test plantest plan

Conduct postConduct post--analysisanalysis

Issue a closing document either supporting or refuting yourIssue a closing document either supporting or refuting your

initial conclusions and identifying the next actionable itemsinitial conclusions and identifying the next actionable items

Update TroubleUpdate Trouble--shooting manualshooting manual Provide a brief description and solution to a problem which canProvide a brief description and solution to a problem which can

then be used by other colleaguesthen be used by other colleagues

Optimisation StrategyOptimisation Strategy


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Slide 10

Principal regular sources of dataPrincipal regular sources of data

DriveDrive--test mobile surveystest mobile surveys

OMC OMC--R statistics and alarmsR statistics and alarms

Customer complaints and troubleCustomer complaints and trouble--ticketstickets

Interference islands identified by radio planning toolInterference islands identified by radio planning tool

Other less regular but important sourcesOther less regular but important sources

A/Abis data collectionA/Abis data collection

Pre Pre--retune / site activation RF frequency scanningretune / site activation RF frequency scanning

CW measurements and model calibrationCW measurements and model calibration

Actual speech generation and listening testsActual speech generation and listening tests

Post Post--retune / site activation interference measurementretune / site activation interference measurement

Competing network benchCompeting network bench--markingmarking

Principal Network Data SourcesPrincipal Network Data Sources


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Slide 11

Metrics available from OMCMetrics available from OMC--RR

Call volume per cell and BSCCall volume per cell and BSC

Call success rate per cell and BSCCall success rate per cell and BSC

Assignment success or failure rate per cell and BSCAssignment success or failure rate per cell and BSC

SDCCH congestion rate per cellSDCCH congestion rate per cell

TCH congestion rate per cellTCH congestion rate per cell

Maximum Busy TCH slots per cellMaximum Busy TCH slots per cell

Handover success or failure rate per cell and BSCHandover success or failure rate per cell and BSC



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Slide 12

Metrics available from OMCMetrics available from OMC--RR

Setup congestion rate per cellSetup congestion rate per cell

Dropped call rate per cell and BSCDropped call rate per cell and BSC

FR / HR / EFR usage ratioFR / HR / EFR usage ratio

Dual Dual--band / singleband / single--band usage ratioband usage ratio

Failed hardware as reported by alarms (hardware could includeFailed hardware as reported by alarms (hardware could include

RF equipment, A/C equipment, BTSRF equipment, A/C equipment, BTS--BSC link equipment)BSC link equipment)



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Slide 13

Metrics available from driveMetrics available from drive--test mobile surveystest mobile surveys

Dropped calls by geographical areaDropped calls by geographical area

Blocked calls by geographical areaBlocked calls by geographical area

Failed assignments by geographical areaFailed assignments by geographical area

Coverage area deficiency (low RXLEV) by geographical areaCoverage area deficiency (low RXLEV) by geographical area

Poor quality (bad RXQUAL and FER) by geographical areaPoor quality (bad RXQUAL and FER) by geographical area

Poor uplink quality (cyclic MS TX Pwr at fixed location)Poor uplink quality (cyclic MS TX Pwr at fixed location)

Handover quantities (high or low) by geographical areaHandover quantities (high or low) by geographical area

Handover pingHandover ping--pong by geographical areapong by geographical area

Over Over--reaching cells (high timing advance) by geographical areareaching cells (high timing advance) by geographical area Poor speech quality by geographical areaPoor speech quality by geographical area

Inadequate neighbours in OMC databaseInadequate neighbours in OMC database



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Slide 14

Metrics available from driveMetrics available from drive--test mobile surveystest mobile surveys


Failed

Handover /

Assignments


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Slide 15

Metrics available from customer complaintsMetrics available from customer complaints

Dropped calls by geographical areaDropped calls by geographical area

Dropped calls by handset manufacturer and model numberDropped calls by handset manufacturer and model number

Bad speech quality by geographical areaBad speech quality by geographical area

Cell link imbalance ( I can hear him but he cant hear me)Cell link imbalance (I can hear him but he cant hear me)

Low signal level (I am not getting five bars)Low signal level (I am not getting five bars)

Congestion (I cannot make a call even after several retries)Congestion (I cannot make a call even after several retries)

Poor SMS retry settings (It takes hours to receive SMSs)Poor SMS retry settings (It takes hours to receive SMSs)

High interference at high elevation (I get good signal levels inHigh interference at high elevation (I get good signal levels in

my penthouse, but I cannot make a call)my penthouse, but I cannot make a call) Low inLow in--building penetration (I cannot make calls in mybuilding penetration (I cannot make calls in my

basement or living room)basement or living room)



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Slide 17

For example, identifying interference locations andFor example, identifying interference locations and

improving through automatic frequency planningimproving through automatic frequency planning

Red areas have C/I < 12 dBRed areas have C/I < 12 dB

East=Mountains, West=OceanEast=Mountains, West=Ocean


Before adjustments

from automatic

frequency planning

After adjustments

from automatic

frequency planning


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Slide 18

Metrics available from A/Abis DataMetrics available from A/Abis Data

Uplink signal level (RXLEV) per callUplink signal level (RXLEV) per call

Uplink quality (RXQUAL not FER) per callUplink quality (RXQUAL not FER) per call

Dropped calls by handset manufacturer and model numberDropped calls by handset manufacturer and model number

Identification of cells with poor competitor coverage fromIdentification of cells with poor competitor coverage from

location update rejectslocation update rejects Traffic hotspots by examining number of normal location updatesTraffic hotspots by examining number of normal location updates

Identification of hardware failureIdentification of hardware failure

Identification of major causes of problems which are switch andIdentification of major causes of problems which are switch and

not radio resource relatednot radio resource related



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Slide 19

Metrics available from A/Abis DataMetrics available from A/Abis Data


A interface

Abis interface


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Slide 20


A/Abis Data Collection possible fault identification areasA/Abis Data Collection possible fault identification areas


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Slide 21

Metrics available from preMetrics available from pre--retune/site activation RFretune/site activation RF

scanningscanning

Bad frequency selection by RF planning if measured signal levelBad frequency selection by RF planning if measured signal level

is high with interference source due to own channels or externalis high with interference source due to own channels or external

interference (e.g. MTC ETACS network interfering with GSM)interference (e.g. MTC ETACS network interfering with GSM)

Metrics available from CW measurements and modelMetrics available from CW measurements and modelcalibrationcalibration

Inaccuracy in any existing propagation models and thereforeInaccuracy in any existing propagation models and therefore

better coverage predictionbetter coverage prediction

Coverage inadequaciesCoverage inadequacies Potential poor interference locationsPotential poor interference locations



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Slide 22

Metrics available from preMetrics available from pre--retune/site activation RFretune/site activation RF

scanningscanning



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Slide 23

Utilising a CW measurement system, data is collated andUtilising a CW measurement system, data is collated and

used in a modelling tool to generate a propagation modelused in a modelling tool to generate a propagation model



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Slide 24

Metrics available from actual speech generation andMetrics available from actual speech generation and

listening testslistening tests

Exact uplink speech quality as perceived by subscribersExact uplink speech quality as perceived by subscribers

Exact downlink speech quality as perceived by subscribersExact downlink speech quality as perceived by subscribers

Exact uplink music quality as perceived by subscribersExact uplink music quality as perceived by subscribers

Exact downlink music quality as perceived by subscribersExact downlink music quality as perceived by subscribers

Calibration of vendor supplied speech quality index for KuwaitCalibration of vendor supplied speech quality index for Kuwait



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Slide 25

Metrics available from postMetrics available from post--retune / site activationretune / site activation

interference measurementsinterference measurements

Quality (RXQUAL/FER) performance of new frequency planQuality (RXQUAL/FER) performance of new frequency plan

Signal level (RXLEV) performance of new frequency planSignal level (RXLEV) performance of new frequency plan

Suitability of power control, handover and congestion reliefSuitability of power control, handover and congestion relief

thresholds for new planthresholds for new plan

Metrics available from competing network benchmarkingMetrics available from competing network benchmarking

Cell count comparisonCell count comparison

Quality (RXQUAL/FER) comparisonQuality (RXQUAL/FER) comparison

Signal level (RXLEV) comparisonSignal level (RXLEV) comparison Site proximity (comparison of timing advance figures)Site proximity (comparison of timing advance figures)

Competitors technologyCompetitors technology

Is SFH in use? Is DL PC in use? Is DTX in use?Is SFH in use? Is DL PC in use? Is DTX in use?



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2001 Freshfield Communications Limited.

Company Confidential

Slide 27

Dropped callsDropped calls

SymptomsSymptoms: High TCH RF loss, High SDCCH RF loss at OMC;: High TCH RF loss, High SDCCH RF loss at OMC;

dropped call statistics from drivedropped call statistics from drive--tests, customertests, customer--reportedreported

dropped callsdropped calls

Too many handovers:Too many handovers:

SymptomsSymptoms: Several handovers per call: Several handovers per call --> high signalling load in> high signalling load innetworknetwork --> if SDCCH is used for handover, SDCCH congestion> if SDCCH is used for handover, SDCCH congestion -->>

long call setup timeslong call setup times

Why Why:: hhreqtreqt,, hhreqavereqaveset incorrectly; powerset incorrectly; power--budget / pathloss basedbudget / pathloss based

handover instead of quality; N and P parameters set incorrectlyhandover instead of quality; N and P parameters set incorrectly



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Slide 28

Too few handovers:Too few handovers:

SymptomsSymptoms: Too few handovers per call: Too few handovers per call --> possible cell dragging> possible cell dragging

since handovers do not take place quickly enoughsince handovers do not take place quickly enough --> interference> interference

to other cells.to other cells.

SymptomsSymptoms: Too few handovers: Too few handovers-->dropped calls>dropped calls

Large handover failuresLarge handover failures If a high number of handover failures are due to radio interfaceIf a high number of handover failures are due to radio interface

loss, then coverage deficiency is the problemloss, then coverage deficiency is the problem

Failures may also occur due to inadequate circuits/channels atFailures may also occur due to inadequate circuits/channels at

the target cellthe target cell

If the handover failure rate between 2 cells is 100%, then theIf the handover failure rate between 2 cells is 100%, then the

source cell is missing in the OMC database for the target cellsource cell is missing in the OMC database for the target cell



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Slide 29

CoCo-- / adjacent/ adjacent--channel interference:channel interference:

SymptomsSymptoms: Poor FER / RXQUAL measured in drive: Poor FER / RXQUAL measured in drive--test even iftest even if

RXLEV is highRXLEV is high-->dropped calls.>dropped calls.

Why: Bad frequency planning e.g. assignment of coWhy: Bad frequency planning e.g. assignment of co--channelschannels

and adjacent channels to neighbouring cellsand adjacent channels to neighbouring cells

BTS Connectivity Problems:BTS Connectivity Problems: Failure of microwave radios, failure of other types of BTSFailure of microwave radios, failure of other types of BTS--BSCBSC

links such as laserlinks such as laser--based links, failure of PSTN links; Symptomsbased links, failure of PSTN links; Symptoms

include zero call volume, 100 % handover failure from other sitesinclude zero call volume, 100 % handover failure from other sites



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Slide 30

Overshooting coverageOvershooting coverage

Symptoms: Cell dragging, leading to possible dropped calls.Symptoms: Cell dragging, leading to possible dropped calls.

Remedied by effecting antenna downtilts or reRemedied by effecting antenna downtilts or re--orientationorientation

Cell congestionCell congestion

Symptoms: TCH Congestion. Remedied by introducing additionalSymptoms: TCH Congestion. Remedied by introducing additional

sites or transceivers.sites or transceivers.



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Slide 31

Peculiar Problems:Peculiar Problems:

Poor dropped call rates on a network could even be due toPoor dropped call rates on a network could even be due to

problems such as calling an engineering number linked to failedproblems such as calling an engineering number linked to failed

interactive voice response systeminteractive voice response system

In indoor locations, if the indoor antenna is placed too low and inIn indoor locations, if the indoor antenna is placed too low and in

close proximity to mobiles, some mobiles will not be able toclose proximity to mobiles, some mobiles will not be able tomake calls because the transmitter in the indoor BTS may bemake calls because the transmitter in the indoor BTS may be

swamping the receiver.swamping the receiver.

Incorrectly supplied transceiver hardware for example, incorrectIncorrectly supplied transceiver hardware for example, incorrect

encryption algorithm.encryption algorithm.



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Slide 32

Network optimisation is the most challenging aspect ofNetwork optimisation is the most challenging aspect of

the operating a networkthe operating a network

Several data sources are available including OMCSeveral data sources are available including OMC--R,R,

drivedrive--test, A/Abis data, etc.test, A/Abis data, etc.

Several performance metrics are also availableSeveral performance metrics are also available

The optimisation engineers task is to ensure that theseThe optimisation engineers task is to ensure that these

metrics are examined and processed daily to find faultsmetrics are examined and processed daily to find faults

and solve problems.and solve problems.

SummarySummary

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Fresh Field Mtc 004 Section 1

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