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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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2001 Freshfield Communications Limited.Company Confidential Slide 5
Optimisation Team ResponsibilitiesOptimisation Team Responsibilities
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 Team ResponsibilitiesOptimisation Team Responsibilities
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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2001 Freshfield Communications Limited.Company Confidential Slide 7
Optimisation Team ResponsibilitiesOptimisation Team Responsibilities
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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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
Principal Network MetricsPrincipal Network Metrics
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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)
Principal Network MetricsPrincipal Network Metrics
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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
Principal Network MetricsPrincipal Network Metrics
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Slide 14
Metrics available from driveMetrics available from drive--test mobile surveystest mobile surveys
Principal Network MetricsPrincipal Network Metrics
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)
Principal Network MetricsPrincipal Network Metrics
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2001 Freshfield Communications Limited.Company Confidential
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
Principal Network MetricsPrincipal Network Metrics
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
Principal Network MetricsPrincipal Network Metrics
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Slide 19
Metrics available from A/Abis DataMetrics available from A/Abis Data
Principal Network MetricsPrincipal Network Metrics
A interface
Abis interface
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Slide 20
Principal Network MetricsPrincipal Network Metrics
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
Principal Network MetricsPrincipal Network Metrics
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Slide 22
Metrics available from preMetrics available from pre--retune/site activation RFretune/site activation RF
scanningscanning
Principal Network MetricsPrincipal Network Metrics
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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
Principal Network MetricsPrincipal Network Metrics
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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
Principal Network MetricsPrincipal Network Metrics
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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?
Principal Network MetricsPrincipal Network Metrics
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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
Typical Network Problems ListTypical Network Problems List
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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
Typical Network Problems ListTypical Network Problems List
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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
Typical Network Problems ListTypical Network Problems List
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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.
Typical Network Problems ListTypical Network Problems List
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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.
Typical Network Problems ListTypical Network Problems List
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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