coverage verification

8/12/2019 coverage verification

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Simon CavenettSimon Cavenett

Telecom Wireless Solutions Inc.Telecom Wireless Solutions Inc.

1999 Wireless Engineering1999 Wireless Engineering ComforumComforum

Dallas, 1 Nov 1999Dallas, 1 Nov 1999


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Link BudgetsLink Budgets

A link budget is determined for anA link budget is determined for anisolated cellisolated cell

Based on assumptions and equipmentBased on assumptions and equipment

specificationsspecifications

Is used to derive a coverage designIs used to derive a coverage design

IsIs notnot a direct measure of systema direct measure of systemcoverage or qualitycoverage or quality


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Cell Edge ReliabilityCell Edge Reliability

Probability that the RF signal strengthProbability that the RF signal strengthmeasured on a circular contour at the cellmeasured on a circular contour at the cell

edge will meet or exceed a desirededge will meet or exceed a desired

thresholdthreshold


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Cell Area Reliability (Availability)Cell Area Reliability (Availability)

Probability that the RF signal will meetProbability that the RF signal will meetor exceed a threshold after integrating theor exceed a threshold after integrating the

contour probabilities over the entire areacontour probabilities over the entire area

of the cellof the cell


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Cell Area Reliability (Availability)Cell Area Reliability (Availability)

Area reliability determined from edge reliabilityArea reliability determined from edge reliability

70

75

80

85

90

95

100

105

50 55 60 65 70 75 80 85 90 95 100

% Cell Edge Reliability

%

CellAreaReliability

NOTE: This p lot is for a slope of 35 dB/decade

and standard deviation of 8 dB


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Cell Area Reliability (Availability)Cell Area Reliability (Availability) Area reliability determined from edge reliabilityArea reliability determined from edge reliability

10/B

0.6

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

0 1 2 3 4 5 6 7 8

ARE

A

RELIAB

ILITY

CELL EDGE

RELIABILTY

0.70

0.95

0.90

0.85

0.80

0.75

0.65

0.60

0.55

0.50

Decre

asingRadius,

R


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Cell Area Reliability (Availability)Cell Area Reliability (Availability) = standard deviation of lognormal shadowing (e.g., 8dB)= standard deviation of lognormal shadowing (e.g., 8dB)

B = path loss slope (e.g., 35db/decade)B = path loss slope (e.g., 35db/decade) From curves, 75% cell edge reliability corresponds to about 90%From curves, 75% cell edge reliability corresponds to about 90%

Area ReliabilityArea Reliability

Increasing required cell edge reliability forces increased fadeIncreasing required cell edge reliability forces increased fade

margin for link budgetmargin for link budget Forces decreased cell radius for designForces decreased cell radius for design

Reference:Reference: ReudinkReudink, D., Properties of Mobile Propagation above 400MHz, IEEE, D., Properties of Mobile Propagation above 400MHz, IEEETrans.Trans. VehVeh. Technology,. Technology, VolVol VTVT--23, pp. 14323, pp. 143--160, Nov. 1974160, Nov. 1974


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= FM=z

A

1 km R

MEAN

PATH

LOSS

FADE

MARGIN

log10 r

RSL(d

Bm)

CELL INTERIOR

CELL

RADIUS

y

y

xB=PTHRESH

x

-R +R

R = 10-(PTHRESH + FM-A)/B

Cell Radius =

Note that the Cell Radius is defined

explicitly in terms of the quality of

coverage Cell Edge Reliability, F(z)

1

2F(z)= e dt

-t2

2

-

z

Typical Fade Margins: =8 dB

0.675

for F(z)=75% => FM = 5.4 dB1.282for F(z)=90% => FM

= 10.2 dB


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100%

log10R

Fu

lo

g10

(CellR

adius)

Area Reliability

Rural

Dense Urban

Lower Margins


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QoSQoS ConsiderationsConsiderations

Link Budget is for isolated cellLink Budget is for isolated cell

Does not predict system performanceDoes not predict system performance Design ToolDesign Tool

QoSQoS determinants in link Budget do not matchdeterminants in link Budget do not matchmeasuredmeasured QoSQoS for a systemfor a system

System is typically cellularSystem is typically cellular

Multiple cells overlapping to form coverageMultiple cells overlapping to form coverage QoSQoS for single (isolated) cell is not objectivefor single (isolated) cell is not objective

However, system requiredHowever, system required QoSQoS thresholds arethresholds are

normally used for Link Budget purposes.normally used for Link Budget purposes.


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Early SystemsEarly Systems

Pre AMPSPre AMPS

Even early AMPS deploymentsEven early AMPS deployments Few sites or cellsFew sites or cells

Relative antenna height often > 100mRelative antenna height often > 100m

Interference & ReInterference & Re--Use Issues were lowerUse Issues were lowerprioritypriority

Knowing where cell edge lay was relativelyKnowing where cell edge lay was relativelyunimportant as long as target area was coveredunimportant as long as target area was covered

Generally, more coverage was a good thingGenerally, more coverage was a good thing


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2G Systems2G Systems

Multiple sites in cellular layoutMultiple sites in cellular layout

Relative antenna height usually < 100mRelative antenna height usually < 100m Interference and ReInterference and Re--Use importantUse important

Capacity requirementsCapacity requirements

Cell overlap required for handoffCell overlap required for handoff

Knowledge and control of cell edge importantKnowledge and control of cell edge important

Excessive overlap causes capacity tradeExcessive overlap causes capacity trade--offoffandand QoSQoS tradetrade--offsoffs


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Legacy 2G sites must be used where possibleLegacy 2G sites must be used where possible

Shifting trend to coShifting trend to co--location (common) siteslocation (common) sites Primarily for business purposesPrimarily for business purposes

Allows venture to focus on core competenciesAllows venture to focus on core competencies

Focus of investment funds toward maximizing deploymentFocus of investment funds toward maximizing deployment

Outsourcing of site ownership and managementOutsourcing of site ownership and management

American TowerAmerican Tower Crown CastleCrown Castle

Divine TowersDivine Towers

Relative antenna height


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Increasing demand forIncreasing demand for wirelinewireline--likelike

performanceperformance Wireless loop services (in lieu ofWireless loop services (in lieu of wirelinewireline))

90% area availability insufficient90% area availability insufficient

99% or better desired to be comparable99% or better desired to be comparable

Providing higher area reliabilitiesProviding higher area reliabilities(availabilities) is the biggest challenge(availabilities) is the biggest challenge

Coverage must be provided from at least oneCoverage must be provided from at least onesingle cell to anysingle cell to any indivudualindivudual target sampletarget sample Must be above minimum thresholdsMust be above minimum thresholds

Else optimization is of no assistanceElse optimization is of no assistance

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Designs for deploymentDesigns for deployment

Prior to system build, predictive models are assumption andPrior to system build, predictive models are assumption andestimate basedestimate based

Morphology classificationsMorphology classifications Clutter loss assumptionsClutter loss assumptions

Very simplistic gross assumptions usedVery simplistic gross assumptions used

Terrain data accuracyTerrain data accuracy

Land Use data accuracyLand Use data accuracy

Infrastructure specifications and assumptionsInfrastructure specifications and assumptions

Simple propagation model usually usedSimple propagation model usually used

CostCost--231231 OkumuraOkumura HataHata

For macro cells,For macro cells, multipathmultipath farfar--field model usedfield model used

Near field and high equalNear field and high equal mulipathmulipath environments may notenvironments may not

be wellbe well modelledmodelled (dense urban)(dense urban) Above clutter relative antenna height often assumedAbove clutter relative antenna height often assumed

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Designs for DeploymentDesigns for Deployment

Usually predictive model tuning is performedUsually predictive model tuning is performed

Not all sites may be testedNot all sites may be tested

Often a set of typical tuned models according to morphologyOften a set of typical tuned models according to morphology

are producedare produced

In error unless environment is similar for all as classifiedIn error unless environment is similar for all as classified

Accuracy of tuned models depends on amount and quality ofAccuracy of tuned models depends on amount and quality ofmeasured data collectedmeasured data collected

Project and real world constraints may limit the data setsProject and real world constraints may limit the data sets

Data collection methods may have been flawedData collection methods may have been flawed

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QoSQoS RequirementsRequirements

Verification is done on operational systemVerification is done on operational system

Predictive tools prior to deployment at best estimatePredictive tools prior to deployment at best estimatenot simulate resultant system performancenot simulate resultant system performance

Direct measurementsDirect measurements

FERFER

RSSIRSSI

RxQualRxQual

Interference Ratios (e.g.,Interference Ratios (e.g., EbEb/No)/No)

Link setup/access and dropsLink setup/access and drops

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Verification is done on operational systemVerification is done on operational system

Confirmation is necessary from both sidesConfirmation is necessary from both sides

System measurements via operational measurements andSystem measurements via operational measurements andmetricsmetrics

Field based performance from within the target coverageField based performance from within the target coverageareaarea

System only data can never truly represent coverageSystem only data can never truly represent coveragereliabilityreliability

NonNon--coverage spots are not representedcoverage spots are not represented

Events occurring outside target coverage boundaryEvents occurring outside target coverage boundary

(e.g., user experiences spot with no coverage(e.g., user experiences spot with no coveragesososystem cannot be aware of this)system cannot be aware of this)

included (e.g., link drop as user travels outsideincluded (e.g., link drop as user travels outsidecoverage area of system)coverage area of system)

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The QuandaryThe Quandary

Area Reliability requirements are normally specified forArea Reliability requirements are normally specified for

system widesystem wide

But for design purposes, this is applied to single cellBut for design purposes, this is applied to single cell

algorithmsalgorithms

In the real world, events happen in the user space not acrossIn the real world, events happen in the user space not acrossthe entire systemthe entire system

The user experiences performance in a very small sample ofThe user experiences performance in a very small sample of

the system areathe system area

An areaAn area--wide performance threshold, by definition, does notwide performance threshold, by definition, does notdirectly and equally apply to sample spacesdirectly and equally apply to sample spaces

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Area ReliabilityArea Reliability

90% area reliability threshold allows 10% area to be90% area reliability threshold allows 10% area to bebelow the thresholdbelow the threshold

This 10% vary in distribution across the targetThis 10% vary in distribution across the target

coverage areacoverage area An areaAn area--based quality requirement does not directlybased quality requirement does not directly

equal a timeequal a time--based quality requirementbased quality requirement

90% by area does not equal 90% of the time in90% by area does not equal 90% of the time inany one location in the area !any one location in the area !

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QoSQoS Impacts for 3GImpacts for 3G

Increasing demand for wireless systems to provideIncreasing demand for wireless systems to provide wirelinewirelinereliabilities and availabilitiesreliabilities and availabilities

WirelineWirelineperformance is normally specified as temporal notperformance is normally specified as temporal notspatialspatial

e.g., 99% availability of diale.g., 99% availability of dial--tone when offtone when off--hookhook

e.g., 99.995% availability of data routese.g., 99.995% availability of data routes

Wireless performance is normally specified as spatial notWireless performance is normally specified as spatial nottemporaltemporal

Mobility and WLL SystemsMobility and WLL Systems

e.g., 90% area reliability or bettere.g., 90% area reliability or better

e.g.. 2% FER average by areae.g.. 2% FER average by area

e.g., 2% link drop by areae.g., 2% link drop by area

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For 3G systems, focus shifts to packet data rather than voice.For 3G systems, focus shifts to packet data rather than voice.

Packet DataPacket Data

DifferentDifferent QoSQoS requirements according to data typerequirements according to data type

VoiceVoice

VideoVideo

Data (files, web pages, email)Data (files, web pages, email) LatencyLatency

Packet Errors / Discards / RePacket Errors / Discards / Re--transmitstransmits

Bandwidth / Data RatesBandwidth / Data Rates Dynamic rates and allocationsDynamic rates and allocations

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Area based reliabilityArea based reliability QoSQoS criteria fit less wellcriteria fit less well

More temporalMore temporal--based criteria applybased criteria apply

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ConclusionsConclusions

Current 2GCurrent 2G QoSQoS Criteria and Measurement Methods insufficientCriteria and Measurement Methods insufficient

Voice no longer the primary information transmittedVoice no longer the primary information transmitted

Data Types and dynamic rates require a set ofData Types and dynamic rates require a set of QoSQoS criteria rathercriteria ratherthan a one size fits allthan a one size fits all

AreaArea--based criteria have less relevance to actual performancebased criteria have less relevance to actual performance

TimeTime--based criteria more relevance to actual performancebased criteria more relevance to actual performance

Ubiquitous coverage across entire target coverage area isUbiquitous coverage across entire target coverage area isdemandeddemanded

Push forPush for wirelinewirelineperformance equivalenceperformance equivalenceexpect more blurringexpect more blurringof distinctions and expectationsof distinctions and expectations

Transmission technology required to be more transparent to theTransmission technology required to be more transparent to theend user and applications.end user and applications.

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coverage verification