Aster Rf Planning

8/2/2019 Aster Rf Planning

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Introduction to RF Planning

A good plan should address the following Issues :

Provision of required Capacity. Optimum usage of available frequency spectrum. Minimum number of sites.

Provision for easy and smooth expansion of theNetwork in future. Provision of adequate coverage.


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Introduction to RF Planning

In general a planning process starts with the inputs from the customer. Thecustomer inputs include customer requirements, business plans, systemcharacteristics, and any other constraints.

After the planned system is implemented, the assumptions made during

the planning process need to be validated and corrected wherevernecessary through an optimization process.

We can summarize the whole planning process under the 4 broad headings

Capacity planning Coverage planning Parameter planning Optimization


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CELLULAR ENGINERING OBJECTIVES

1) To provide adequate coverage- Contiguous coverage of the required areas withoutappreciable holes

- Adequate depth of coverage (i.e. outdoor or indoor , 2 Wor 1.2 W mobiles ) to meet the companys marketing plans.

2) To provide adequate network capacity- Accommodating traffic in the busiest hour with only a low

probability of blocking (congestion).3) To accommodate network growth

- Extension of coverage in new areas- Expanding the network capacity so that the quality of

service is maintained at all times.4) To achieve a cost effective design

- Lowest possible cost over the life of the network whilemeeting the quality targets.


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COST JUSTIFICATION OF CELLULAR RNPThe cellular mobile radio system design can be broken downin the following elements, which have a mutual relationship .

- Reuse of frequency channels- Co- channel interference reduction- A desired minimum carrier to interference ratio (C/I)- Handover mechanism- Cell Planning

Historical perspective- Wireless telephony network design is relatively new

business with a 10-15 year historyDuring this period many new tools and techniques havebeen developed:- More accurate radio coverage prediction

- More accurate facility network design- Enhanced field measurement analysis to improvenetwork performance.

- New technology applications ( microcells, repeaters,smart antennas systems. )

- Better tools and methods to evaluate and predict traffic

conditions


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COST JUSTIFICATION OF CELLULAR RNPThe challenge of accurate cellular network planning is still acomplex task.Potential cost of Opportunities Lost Due to Network Planningproblems Lost Subscribers

- Lost base subscriber fee revenues- Lost enhanced service fee revenue- Lost airtime revenues (local and long distance)- Damaged reputation will impact competitive strength

Cost Considerations That Include in the Design of a qualitynetwork

- Design optimal network : extensive modeling and numerousrevision of design.

- Acquire radio site candidates that meet the designcriterion.

- Manage delays in permitting / zoning of best candidates- Extensive testing of radio site performance (coverage )

before commissioning.

- Integration of field measurements in design.


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COST JUSTIFICATION OF CELLULAR RNP

Design Activity to compensate for Improperly designed orless than than optimal radio site in design.

- Modify cell operational parameters (eg. Handover valuesand location)

- Modify output power - Modify equipment (eg. Change antenna )- Move site location- Add new sites (micro or macro cells)


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COST JUSTIFICATION OF CELLULAR RNPAn equation for Costing Comparison of AccurateNetwork PlanningOption one : Poor design / no redesign

- Weak competitive position- Lost disgruntled subscribers- Earn a poor service reputation (Weak attraction for

new subscribers ).Option two : Quality network design

- Additional design cost (engineering and equipment ).- Teardown and reinstall cost.

Simple equation for characterizing cost /benefits- Quality network performances = ( Cost of engineering ,

equipment, installation ) (Lost revenues, cost ofengineering, equipment, installation )

- The benefits of quality design should farweigh lostrevenues particularly in the fact of competition fromnew wireless companies.


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DESIGN CONSTRAINTS

The objective of radio planning is a technicalrealization of the marketing requirements, taking

into account of the following constraints.- Technical requirements from the license conditions.- GSM system specific parameters (e.g. GSM recs 5.05

etc.)- Manufacturer specific features and parameters.- Radio communications principles and fundamentals.- Budgetary factors.


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LICENSE CONDITIONSAn example of technical requirements following from alicense . Coverage requirements.

- Class 2 or class 4 coverage of 60 % of the population 12months from commercial launch.

- Class 2 or class 4 coverage of 95 % of the population 36months from the commercial launch.

Quality of coverage

- Service to be available in 90 % of the declared area and for 90 % of the time.

Grade of Service- Endeavour to achieve 5 % or better

Frequency Allocation

- One of the major limitations in the GSM 900 system is thenumber of frequencies available to a GSM network operator. There is a relatively small bandwidth available thathas to be divided over all the licensed operators. Mostnetwork operators are limited to 30-60 frequencies for

handeling all traffic.- GSM 1800 offers 75 MHz bandwidth


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MANUFACTURER SPECIFIC PARAMETERS

- BTS Transmit power - Receiver sensitivity- Combiner performances- Cable loss- Antenna performance- Availability of frequency hopping and power control- Handover algorithm- Capacity number of TRX provided.


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RADIO COMMUNICATION FUNDAMENTALS

- Propagation loss- Shadowing- Multipath fading- Power link budgets- Interference effects- The (un)predictability of radio wave propagation


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QUALITY OF SERVICE SPECIFICATIONS

The service requirement from the marketing should includeinformation on which the technical plan can be based ,including :Coverage Quality : Defined as a part of optimizing the

business plan (indoor / outdoor coverae, handheld car,mobile set). Interference should be taken into account for coverage quality including margin of 12 dB) :Co channel C/IAdjacent channel C/I

Call completion and Dropped call Rates : Dictated by thelisence conditions and quality of the competingnetwork(includes Blocking rates 2% etc.)Service availibility


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QUALITY OF SERVICE SPECIFICATIONS

Traffic forecast :- Longterm forecast and trends for the network must be

developed by the marketing.- Traffic distributions for the existing coverage areas and

typical densities may be obtained from the network.

Spectral effeciencies : for demonstration within the context ofwinning maximum points for a mobile license. The spectralefficiency is determined by decisions taken in :

- Quality of coverage- Frequency Reuse plan

- Use of cell splitting- Design for traffic demend- Feedback into the business plan

Customer support measures


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DEFINITION OF COVERAGE QUALITY

Outdoor coverage :- Default definitions of coverage- Refers to 2 Watt class 4 mobiles in the street- Probability of coverage is 95 % averaged across the cell area.- Coverage probability at the edge of cells is less than this

value.In car coverage :

- A supplementary level of coverage for highways- Refers to a Class 4 mobile inside car or other vehicles.- Coverage probability is nominally 95% averaged- Coverage is critically dependent on the position of the

handheld mobile within the vehicle.8 Watt Coverage

- A Supplementary level of coverage for remote areas.- Refers to class 2 mobile or class 4 with an 8 watt booster and

external antenna


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DEFINITION OF COVERAGE QUALITY

Indoor coverage- Especially good coverage for city centers and stragetic

locations- Refers to a class 2 mobile indoors

- Building loss is very variables, so indoor coverages cannever be guaranteed

- Where indoor coverage is provided , outdoor coverage willbe nearly 100 %


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BLOCKING RATE ( Grade of Service, GOS )

GOS is defined as the probability that a call will be blocked or delayed due to unavailability of the radio resource. Examplefor license requirement

- 5 % Averaged over a defined sub-network (e.g. weightedaverage by traffic load over the worse 10 cells )

- No cell to be worse than 10%- By a particular date , 8 % of the cells permitted to be

between 2 % and 10 % GOS.- By a particular date , 5 % of the cells permitted to be

between 2 % and 10 % GOS.- Ultimate target is that no cells should be worse than 2 %

GOS.


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CALL SUCCESS RATECall failure may be due to :

- Coverage holes- Interference- Congestion- Problem in fixed network - Handover failures- Equipment failures

Call success rate is often expressed as the proportion of callsconnected and held for 2 min.

- Target is normally 90 % at launch of service- Mature networks achieve in excess of 98 %

- Only applies within a declared coverage area.

By a particular date , 95 % of the calls to the network boundary should be set up within four seconds and held for two min.


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RADIO PLANNING METHODOLOGYOverall pictureIt is important to create an overall picture of the network

before going into the detailed network planning. This is thefact the main objective of this presentation.

Coverage Capacity and QualityProviding coverage is usually considered as the mostimportant activity of a new cellular operator. For a while ,every network is indeed coverage driven. However thecoverage is not the only thing. It provides the means ofservice and should meet certain quality measures.

The starting point is a set of coverage qualityrequirements.

To guarantee a good quality in both uplink and downlink direction, the power levels of BTS and MS should bebalanced at the edge of the cell. Main output results ofthe power link budget are:

- Maximum path loss that can be tolerated between MSand the BTS.

- Maximum output power level of the BTS transmitter.


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Introduction to RF Planning A simple Planning Process Description

Business plan.No of Subs.Traffic per Subs.Subs distributionGrade of service.Available spectrum.Frequency Reuse.

Types of coverageRF ParametersField strength studiesAvailable sitesSite survey

CapacityStudies

Plan verificationQuality check Update documents

Coverage&C/I studySearch areas

ImplementPlan

MonitorNetwork

OptimizeNetwork

CustomerAcquires

sites

Capacity StudiesCoverage plan & Interference studiesFrequency plans and interference StudiesAntenna SystemsBSS parameter planningData base & documentation of approved sites

Expansion Plans.


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Introduction to RF PlanningData Acquisition

OMC Statistics

A Interface

Drive Test

Implemented

PlanningData

Data

Evaluation

Implemented

Recommendation

Recommendations :Change frequency plan

Change antenna orientation/Down tiltChange BSS ParametersDimension BSS EquipmentAdd new cells for coverageInterference reductionBlocking reduction

Augment E1 links from MSC to PSTN


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Cell Planning Aspects

At the end of it all, a good cell plan should have the followingcharacteristics :

Coverage as required as predicted.Co Channel and Adjacent Channel interference levels as predicted.Minimum antenna adjustments during the optimization process.Minimum changes to the BSS parameters/database during theoptimization phase.Should be well phased, requiring optimization only for short periods in

the initial commissioning phase and duringFacilitate easy expansion of the network with minimal changes in thesystem.


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Cell Planning Aspects

What is the area of coverage needed ?How many sites are required for this area ? ( cell radius of 1Km. Means an approximate coverage area of 3 sq. Kms. )Do we need so many sites ? Can some site be bigger ?Decide number of sites based on capacity and coverage

requirements.Divide city into clutter types such as .>Urban>Suburban>Quasi Open>Open>Water.Identify search areas covering all clutter types.Customer selects a few sample sites.


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Cell Planning AspectsSurvey sites with reference to :>Clutter heights>Vegetation levels.>Obstructions.>Sector orientations

>Building strengths and other civil requirementsPrepare Power Budgets.Conduct propagation testsCalculate Coverage probabilities based on the drive testresults.Verify Power budget sensitivityagainst drive test result ,

modify planning tools parameters.Prepare final coverage maps..


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A typical Power BudgetRF Link Budget UL DL

Transmitting End MS BTS

Tx Rf power output 33 dBm 43 dBm

Body Loss -3 dB 0 dB

Combiner Loss 0 dB 0 DbFeeder Loss(@2 Db/100M)

0 dB - 1.5 dB

Connector loss 0 dB - 2 Db

Tx antenna gain 0 dB 17.5 dB

EIRP 30 dBm 57 dBm

A t i l P B d t


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A typical Power BudgetRF Link Budget UL DL

Receiving End MS BTS

Rx sensitivity -107 dBm -102 dBm

Rx antenna gain 17.5 dBm 0 dB

Diversity gain 3 Db 0 dB

Connector Loss - 2 dB 0 dB

Feeder loss - 1.5 dB 0 dB

Interference degradation margin 3 dB 3 Db

Body loss 0 dB -3 dB

Duplexer loss 0 dB 0 dB

Rx Power -121 dBm -96 dBm

Fade margin 4 dB 4 Db

Reqd Isotropic Rx. Power -117 dBm -92 dBm

Maximum Permis. Path los 147 Db 149 dB


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Summary

A good RF Planning ensures that the mobiles receive certain minimum

signal strength for specified percentage of time over a specified area ofcoverage.

The MS receive signal strength depends on the path loss depends onthe path loss between the MS and the BTS.

The path loss in a mobile environment includes :

> Free space path loss>Additional Loss due to Topography of the site ( clutter Factor )>Confidence level required. (Probability of area coverage )

In general RF Planning means the understanding of :

> Propagation Models> Coverage aspects> Link Budgets ( Power Budgets)> Antenna considerations> Frequency planning and reuse aspects.


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Urban Propagation EnvironmentThis is the most common and yet unpredictable propagation environment for a mobilesystem.

Building Penetration:

Building are responsible for the reflection and shadowing of signals. Trees and foliagesalso contribute to shadowing as well as scattering of radio signals.

Attenuation of signals by building is measured by taking the difference between themedian signal level in front of the building and inside the bu9ilding. Obviously, thebuilding attenuation depends on the type of construction and the material used as wellas how big or small it is.

Typically the attenuation values may cause the signal levels to vary by 40 to +80 DbThe negative value implies that the signal is attenuated and the positive values impliesthat the increase in the signal level.

Windows and Doors in general give a good penetration of RF signals. Another important factor is the angle of arrival of RF signals in to the building. Generally, abuilding facing the BTS site has better penetration than the one that is side facing andwithout windows.

The furniture used in the building also contributes to attenuation. Typically a furnishedbuilding gives a loss of 2-3 dB more than an empty one.


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Propagation EnvironmentSome Typical values for Building Attenuation

Type of building Attenuationin dBs

Farms, Wooden houses, Sport halls 0-3

Small offices,Parking lots,Independent

houses,Small apartment blocks

4-7

Row Houses, offices in containers, Offices,Apartment blocks

8-11

Offices with large areas 12-15

Medium factories, workshops without roof topswindows

16-19

Halls of metal, without windows 20-23

Shopping malls, ware houses, buildings with

metals/glass

24-27

P ti M d l


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Propagation Models Classical Propagation models :-

Log Distance propagation model Longley Rice Model (Irregular terrain model ) Okumara

Hata Cost 231 Hata (Similar to Hata, for 1500-2000 MHz band Walfisch Ikegami Cost 231 Walfisch-Xia JTC

XLOS (Motorola proprietary Model ) Bullington Du path Loss Model Diffracting screens model

P ti M d l


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Propagation Models Important Propagation models :-

Okumara Hata model (urban / suburban areas )( GSM900 band )

Cost 231 Hata model (GSM 1800 band ) Walfisch Ikegami Model (Dense Urban / Microcell

areas ) XLOS (Motorola proprietary Model )

Ok H t M d l


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Okumara Hata ModelsIn the early 1960 , a Japanese scientist by name Okumara conducted

extensive propagation tests for mobile systems at different frequencies.The test were conducted at 200, 453, 922, 1310, 1430 and 1920 Mhz.

The test were also conducted for different BTS and mobile antennaheights, at each frequency, over varying distances between the BTSand the mobile.

The Okumara tests were valid for :

150-2000 Mhz. 1-100 Kms. BTS heights of 30-200 m. MS antenna height, typically 1.5 m. (1-10 m.)The results of Okumara tests were graphically represented and were not

easy for computer based analysis.Hata took Okumaras data and derived a set of empirical equations to

calculate the path loss in various environments. He also suggestedcorrection factors to be used in Quasi open and suburban areas.


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Hata Urban Propagation ModelThe general path loss equation is given as :-

Lp = Q1+Q2Log(f) 13.82 Log(Hbts) - a(Hm)+{44.9-6.55Log(Hbts)}Log(d)+Q0

Lp = L0 +10 r Log (d) path loss in dBF = frequency in Mhz.D = distance between BTS and the mobile (1-20 Kms.)Hbts = Base station height in metres ( 30 to 100 m )A(hm)={ 1.1log(f) - 0.7 } hm - {1.56log(f) - 0.8} for Urban areas and

= 3.2{log(11.75 hm) 2 - 4.97 for dense urban areas.Hm= mobile antenna height (1-10 m)Q1 = 69.55 for frequencies from 150 to 1000 MHz.

= 46.3 for frequencies from 1500 to 2000 MHz.

Q2 = 26.16 for frequencies from 150 to 1000 MHz.= 33.9 for frequencies from 1500 to 2000 MHz.

Q0 = 0 dB for Urban

= 3 dB for Dense Urban


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Path Loss & Attenuation SlopeThe path loss equation can be rewritten as :

Lp = L0 + { 44.9 6.55 + 26.16 log (f) 13.83 log (h BTS)-a(H m )Where L 0 is = [69.55 + 26.16 log (f) 13.82 log ( H BTS) A (Hm )Or more convenientlyLp = L0 + 10 log(d)

is the SLOPE and is = {44.9 6.55 log(h BTS)}/10Variation of base station height can be plotted as shown in the

diagram.We can say that Lp 10 log(d)

typically varies from 3.5 to 4 for urban environment.When the environment is different, then we have to choose

models fitting the environment and calculate the path lossslope. This will be discussed subsequently.


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Non line of Sight Propagation

Here we assume that the BTS antenna is above roof level for anybuilding within the cell and that there is no line of sight betweenthe BTS and the mobile

We define the following parameters with reference to the diagramshown in the next slide:

W the distance between street mobile and buildingHm mobile antenna heighthB BTS antenna height

Hr height of roof hB difference between BTS height and roof top.Hm difference between mobile height and the roof top.


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Non line of Sight Propagation The total path loss is given by:

Lp = L FS+L RFT +L MDB LFS= Free space loss = 32.44+20 log(f) + 20 log(d) Where, LFS = Free space loss.

LRFT = Rooptop diffraction loss. LMDB = Multiple diffraction due to surrounding buildings. LRFT = -16.9 10 log(w) +10log(f) +20log(^Hm)+L(0)Where

hm=hr-hmL( ) = Losses due to elevation angle.L( ) = -10 + 0.357 ( -00) for 0<


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Non line of Sight Propagation The losses due to multiple diffraction and scattering

components due to building are given by :

LMBD = k 0 + ka +kd.log(d) +kf.log(f) 9.log(w)WhereK0 = - 18 log (1+ h B)Ka = 54 0.8 ( h B)Kd = 18 15 ( h B /hr)Kf = - 4 +0.7 {f/925) 1 } for suburban areasKf = - 4 +1.5 {f/925) 1 } for urban areasW= street width

hB= h B hrFor simplified calculation we can assume ka = 54 and kd = 18


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Choice of Propagation ModelEnvironment Type Model

Dense UrbanStreet Canyon propagation Walfish Ikegami,LOS

Non LOS Conditions, Micro cells COST231

Macro cells,antenna above rooftop Okumara-Hata

UrbanUrban Areas Walch-ikegami

Mix of Buildings of varying heights, vegetation,and open areas.

Okumara-Hata

Sub urbanBusiness and residential,open areas. Okumara Hata

Rural

Large open areas,fields,difficult terrain with

obstacles.

Okumara-Hata


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Calculation of Mobile Sensitivity.

The Noise level at the Receiver side as follows:

NR = KTB Where, K is the Boltzmanns constant = 1.38x10 -20

(mW/Hz/ 0Kelvin)

T is the receiver noise temperature in 0Kelvin B is the receiver bandwidth in Hz.


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Signal Variations

Fade margin becomes necessary to account for theunpredictable changes in RF signal levels at the receiver.The mobile receive signal contains 2 components :

A fast fading signal (short term fading ) A slow fading signal (long term fading )


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Probability Density FunctionThe study of radio signals involve actual measurement of signal levels at

various points and applying statistical methods to the available data.

A typical multipath signal is obtained by plotting the RSS for a number of samples.

We divide the vertical scale in to 1 dB bin and count number of samples isplotted against RF level . This is how the probability density function for thereceive signal is obtained.

However, instead of such elaborate plotting we can use a statistical expressionfor the PDF of the RF signal given by :

P(y) = [1/2 ] e [ - ( - y m ) 2 / 2 ( ) 2

Where y is the random variable (the measured RSS in this case ), m is the meanvalue of the samples considered and y is the STANDARD DEVIATIONof the measured signal with reference to the mean .

The PDF obtained from the above is called a NORMAL curve or a GaussianDistribution. It is always symmetrical with reference to the mean level.


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Probability Density FunctionPlotting the PDF :

Plotting the PDF

-100

-80

-60

-40

-20

0

SAMPLES

R S S

RSS

A PLOT OF RSS FOR A NUMBER OFSAMPLES


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Probability Density FunctionPlotting the PDF :

Plotting the PDF

Bin Numbers

P ( x )

ni/N

NORMAL DISTRIBUTION

P(x) = ni/NNi = number of RSS within1 dB bin for a given level.


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Probability Density FunctionA PDF of random variable is given by :P(y) = [ ] e [ - (y-m) 2 / 2( ) 2 ]Where, y is the variable, m is the mean value and is the Standard

Deviation of the variable with reference to its mean value.The normal distribution (also called the Gaussian Distribution ) is

symmetrical about the mean value.A typical Gaussian PDF :


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Probability Density FunctionThe normal Distribution depends on the value of Standard

DeviationWe get a different curve for each value of The total area under the curve is UNITY


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Calculation of Standard DeviationIf the mean of n samples is m, then the standard deviation is

given by:

= Square root of [{(x1-m) 2 + ..+( xn -m) 2 }/(n-1)]

Where n is the number of samples and m is the mean.For our application we can re write the above equation as :

= Square root of [{RSS1-RSS MEAN )2+..+(RSSN -

RSS MEAN )2 /(N-1)}]


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Confidence IntervalsThe normal of the Gaussian distribution helps us to estimate the

accuracy with which we can say that a measured value of therandom variable would be within certain specified limits.

The total area under the Normal curve is treated as unity. Then forany value of the measured value of the variable, its probabilitycan be expressed as a percentage.

In general, if m is mean value of the random variable withinnormal distribution and is the Standard Deviation, then,The probability of occurrence of the sample within m and any

value of x of the variable is given by :P=

By setting (x-m)/ = z, we get,

P=


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Confidence IntervalsThe value of P is known as the Probability integral or the ERROR

FUNCTIONThe limits (m n )are called the confidence intervals.From the formula given above, the probability

P[(m- ) < z < (m+ )] = 68.26 % ; this means we are 68.34 % confident.P[(m- ) < z < (m+ )] = 95.44 % ; this means we are 95.44 % confidentP[(m- ) < z < (m+ )] = 99.72 % ; this means we are 99.72 % confident.

This is basically the area under the Normal Curve.


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The Concept of Normalized Standard DeviationThe probability that a particular sample lies within specified limits is given

by the equation :

P=

We define z = (x-m)/ as the Normalized Standard Deviation.

The probability P could be obtained from Standard Tables (available instandard books on statistics ).

A sample portion of the statistical table is presented in the next slide..

l l f d


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Calculation of Fade MarginTo calculate the fade margin we need to know :

Propagation constant>From formulae for the Model chosen>Or from the drive test plots

Area probability :>A design objective usually 90 %

Standard Deviation>Calculated from the drive test results using statistical formulae or>Assumed for different environments.

To use Jakes curves and tables.

l l f d b b l d d


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Calculation of Edge Probability and Fade MarginFrom the values of and we calculate :

Find edge probability from Jakes curves for a desired coverage probability,against the value of on the x axis.

Use Jakes table to find out the correlation factor required Look for the column that has value closest to the edge probability and read

the correlation factor across the corresponding row.

Multiply by the correction factor to get the Fade Margin.

Add Fade Margin to the RSS calculated from the power budget

Si ifi Of A d Ed P b bili i


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Significance Of Area and Edge Probabilities

Required RSS is 85 dBm.

Suppose the desired coverage probability is 90 % and the edge probabilityfrom the Jakes curves is 0,75

This means that the mobile would receive a signal that is better than 85dBm in 90 % of the area of the cell

At the edges of the cell, 75 % of the calls made would have this minimum

signal strength (RSS).

I B ildi C


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In Building CoverageRecalculate Fade Margin.

>Involves separate propagation tests in buildings.>Calculate and for the desired coverage ( say 75 % or 50% )>Use Jakes Curves and tables to calculate Fade Margin.>Often adequate data is not available for calculating the fade marginaccurately.

>Instead use typical values.Typical values for building penetration loss :

Area 75 % coverage 50 % coverageCentral business area < 20 dB < 15 dB

Residential area < 15 dB < 12 dB

Industrial area < 12 dB < 10 dB

In Car 6 to 8 dB

F M h d F L i


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Fuzzy Maths and Fuzzy LogicThe models that we studied so far are purely empirical.The formulas we used do not all take care of all the possible environments.

Fuzzy logic could be useful for experienced planners in making rightguesses.

We divide the environment into 5 categories viz., Free space, Rural,Suburban, urban, and dense urban.

We divide assign specific attenuation constant values to each categories ,say

Fuzzy logic helps us to guess the right value for , the attenuation constantfor an environment which is neither rural nor suburban nor urban but amixture, with a strong resemblance to one of the major categories.

The following simple rules can be used :Mixture of Free space and Rural :Mixture of Rural and Suburban :Mixture of Suburban and Urban :Mixture of Urban and Dense urban :


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Cell Planning and C/I IssuesThe 2 major sources of interference are: Co Channel Interference. Adjacent Channel Interference.The levels of these Interference are dependent on The cell radius The distance cells (D)The minimum reuse distance (D) is given by :

D = ( 3N ) R

Where N= Reuse pattern= i 2 + i j + j 2

Where I & j are integers.


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Cell Planning and C/I Issues

R

D


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Assuming the cells are of the same size .All cells reansmit the same power.The path loss is not free space and is governed by theattenuation constant .By geometry, for every cell there are 6 interfering cells in thefirst layer.The reuse distance Dand cell radius R are related to the c/I asgiven below

(D/R) = 6 (C/I)

The C/I is in absolute value.

C ll Pl i g d C/I I


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Co Channel Interference C/I for Omni Cells

D/R = 3NC/I = 10 Log [ 1/m (D/R ) ], where m is the number of interferers.M= 1 to 6 for the first layer of interfering cells.

Assuming = 3.5, m = 6 (worst case ), we calculate the theoreticalC/I available for various reuse plans as shown below :

N D/R = 3N C/I = 10 Log [ 1/6 (D/R) ]3 3 8.917 dB4 3.46 13.29 dB7 4.58 21.80 dB9 5.19 25.62 dB

12 6 29.99 dB

C ll Pl i g d C/I I


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Adjacent Channel Interference :

Adjacent Chl Interference = - 10 Log [1/m (D/R) ]+

Where is the isolation offered by post modulation filters

Minimum value of is 26 dB , as per EIA standards.If ( C/I ) for co channel interference is 10 dB, then for adjacentchannel interference it is 36 dB.

Freq enc Planning Aspects


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Frequency Planning Aspects

The primary objective of frequency planning is to ensure that,given the limited RF spectrum, we achieve the required capacity(traffic channels), keeping the interference within specified limits.

There are two types of frequency planning :>Frequency planning based on Reuse patterns (manual)>Frequency planning based on heuristic algorithm (automatic)

Manual planning is done by dividing the available frequencies into a number of frequency groups (as per a selected reuse pattern) and assigning frequencies to various sectors / cells.

Suppose we have n frequencies . For a 3 cell repeat pattern with3 sectors, we have 9 frequency groups, each group having n/9frequencies.The sectors are labeled A1,A2,A3,B1,B2,B3 and so on..Assuming that an operator has 32 frequencies, say, from ARFCN 63to 94, the frequencies could be grouped as shown in the tableopposite.



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Say, for 32 frequencies (ARFCN 63 94 ), for a 3*3 reusepattern, the frequencies are grouped as shown belowA1 A2 A3 B1 B2 B3 C1 C2 C363 64 65 66 67 68 69 70 7172 73 74 75 76 77 78 79 8081 82 83 84 85 86 87 88 8990 91 92 93 94

ORA1 B1 C1 A2 B2 C2 A3 B3 C363 64 65 66 67 68 69 70 71

72 73 74 75 76 77 78 79 8081 82 83 84 85 86 87 88 8990 91 92 93 94



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The Frequency reuse could be done in either of 2 waysmentioned in the tables in the previous slide :



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q y g pDirectional reuse :

In a sectorised site, a group of channels (ARFCN) istransmitted in the direction of antenna orientation , This is

based on tri cellular platform consisting of 3 identical cellsas shown in the diagram in the last slide.Every cell is considered as an omni logically. The cells

are excited from the corners, separated by 120 0The axes of the diagram represent the 3 directions of

reuse. These are designated as { f(00)}, {f(1200)} and{f(2400)}

Because we use directional antennas, the worst cochannel interference will be from only one interferingstation in the same direction



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q y g pWe form a generic combination of the tricell patternusing 7 such pattern, as shown in fig. Down. From thiswe can see that each of three axes has three parallel

layers.This result in a total of six or multiples of six frequencyGROUPS.While assigning frequencies to individual calls we haveto take the directions of reuse into account.


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Antenna Considerations

Uniform coverage in all cells

Alignment with hexagonal patternSpace availabilityConnectivity to BSC/MSC

Urban areas may have the following conditions :

Several sites may be needed.Frequency reuse is unavoidableIn building penetration is mustBuilding act as RF shield and contain coverage.Buildings reflect signals and provide coverage toareas where LOS would have failed.

Such additional paths improve in buildingpenetration.Antenna at a very high point may not meet inbuilding coverage requirements


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Tackling Multipath Fading

In general we have the following methods to combat Multipathfading:

In time domain Interleaving and codingIn Freq. Domain Frequency hoppingIn spatial domain Space diversityIn the polarization domain Polarization diversity

The last two are related to Antenna Systems.


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Diversity Antenna Systems

A diversity antenna System essentially has :

Two or more antennaA combiner circuitry.

Signals A and B should have minimum correlation between themtypically the correlation coefficient


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Antenna Spacings :Separation D/ 900 Mhz 1800MhzHorizontal 10 3.3 m 1.7 m

Vertical 17 5.7 m 2.8 m>Figures in the table are of minimum required separation>If space is not a constraint, larger separation is alwaysrecommended.>Horizontal separation is preferred because it provides lowcorrelation values.>However, horizontal separation suffers from angular dependence (demonstrated in the diagram, next page ).>Vertical separation does not suffer much from the angular dependence.

>It also requires minimum supporting fixtures and does notoccupy a lot of space.>But as the distance increases the correlation between the RFsignal at the antenna points increases rapidly, thereby negatingthe very advantage of space diversity.



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Space diversity can be achieved using:

3 antenna system2 antenna system

The 3 antenna system provides very good spatial separationbetween the two receive antenna and avoids the use of

duplexers. This reduces the risk of generating intermodulationproducts.

The 2 antenna system is preferred where the space for theantenna structure is limited or where the operators want to useless number o antenna.



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Advantages of dual polarization :

Reduced support structure for the antennaReduced weightSlim towers and hence quicker construction and low cost.Cost of one dual polarized antenna is generally lower than thecost of two space diversity antenna.

Choice of Dual Polarized typeH/V type :As most mobile are held at an angle 45 0, H/V is more likely tocause balanced signals at the two branches.The diversity performance is less dependent on the mobilelocation

Slant typeCorrelation between the two elements is angular dependent.Unbalanced signals at the two arms of the receive antenna, sinceone of the signal could be at the same angle as the mobile

General Antenna Specifications


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Typical parameters of importance :Polarization

Linear polarization :Evector contained in one plainHorizontal polarization :H Vector parallel to the horizontalplaneVertical Polarization : E Vector parallel to the vertical planeCircular / Elleptical Polarization

The extremity of the E or H field describes a circle or an ellipse inthe direction of propagation

Radiation patternThis is a plot of electric field intensity as a function of direction from

the antenna, measured at the fixed distance.

General Antenna Specifications


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When the main radiation lobe of the antenna is intentionallyadjusted above or below its plane of propagation, the result isknown as a beam tilt. When tilted downward, we get the Downtilt.

Down tilt can be done in two ways :Electrical down tiltMechanical down tilt

RADIO PLANNING METHODOLOGY


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RADIO PLANNING METHODOLOGYOverall pictureIt is important to create an overall picture of the network

before going into the detailed network planning. This is thefact the main objective of this presentation.

Coverage Capacity and QualityProviding coverage is usually considered as the mostimportant activity of a new cellular operator. For a while ,every network is indeed coverage driven. However thecoverage is not the only thing. It provides the means ofservice and should meet certain quality measures.

The starting point is a set of coverage qualityrequirements.

To guarantee a good quality in both uplink and downlink direction, the power levels of BTS and MS should bebalanced at the edge of the cell. Main output results ofthe power link budget are:

- Maximum path loss that can be tolerated between MSand the BTS.

- Maximum output power level of the BTS transmitter.



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RADIO PLANNING METHODOLOGYThese values are calculated as a result of designconstraints.

- BTS and MS receiver sensitivity.- MS output power level- Antenna Gain- Diversity reception- Losses in combiners, cables etc.

The cell ranges are derived with propagation lossformulas such as Okumara Hata or Walfisch Ikegami,which are simply to use . Given a maximum path loss,differences in the operating environment and the qualitytargets will result in different cell ranges.

The traffic capacity requirement have to be combinedwith the coverage requirements, by allocatingfrequencies. This also may have impact on the cellrange.

COVERAGE PLANNING STRATEGIES


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The selection of site configurations, antenna and cables inthe core of the coverage planning strategy. The rightchoice will provide cost saving and guarantees smooth

network evolution.

Some typical configurations are :- 3 sector site for (sub)urban areas- 2 sector site for road coverage.- Omni site for rural areas.

These are not the ultimate solutions, decisions should bebased on careful analysis.Cell Range and Coverage Area :For any site configurations, the cell ranges can bedetermined given the equipment losses and gains. The sitecoverage areas can be calculated then and these will leadto required number of sites for a given coverage region. Thismakes it possible to estimate the cost, eg. Per km 2, to beused for strategic decisions

After getting the overall picture, the actual detailed

radio network planning is done with a RNP tool.


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- Marketing specifications- Define design rules and parameters.- Set performance targets.

- Design nominal cell plan.- Implement cell plan.- Produce frequency plan.- Optimize network.- Monitor performances.

METHODOLOGY EXPLAINED


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Define design rules and parameters- Identify design rules to meet coverage and capacity targets

efficiently

- Acquire software tools and databases- Calibrate propagation models from measurements.Set performance targets

- Clear statement of coverage requirements (rollout andquality)

- Forecast traffic demand and distribution.- Test business plan for different roll out scenarios and quality

levels.Design nominal cell plan.

- Use computer tool to place sites to meet coverage an dcapacity targets.

- Verify feasibility of meeting service requirements- Ensure a frequency plan can be made for the design.- Estimate equipment requirement and cost.- Develop implementation and resource plans (including

personal requirements)

- Radio plan will provide input to fixed network planning.



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Implement Cell plan- Identify physical site locations near to nominal or theoretical locations, using search areas.

- Modify nominal design as theoretical sites are replacedwith physical sites

- Modify search areas in accordance with envolvingnetwork.

Produce Frequency Plan- Fixed Cluster configration, can be done manually.- Flexible, based on interference matrix using an automatic

tool.



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Optimize the network - Campaign of measurements- Analyze results- Adjust network parameters such as : antenna directions,

handover parameters, and frequencies.

Expand the network - In accordance with rollout requirements- In accordance with forecast traffic levels- To improve coverage quality.- To maintain blocking performances.

RF Planning Process


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1 Understand the Customers requirementsCoverage requirements

In building coverage experimentsInitial Roll out plansPre determined number of sites ?

2 SurveyTraffic Distribution and PatternGrowth areasHigh density business/ residential areasPropagation tests for in building coverage estimatesand model calibrations

3. Prepare Planning ToolGet Digitized mapsLoad maps in the planning tool.Use survey data and run the programme.

RF Planning Process


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RF Planning Process

4. Draft PlanDivide the city into number of regions-Busy business areasAreas that need excellent inbuilding coverage

areasUse appropriate model and link budgets tocalculate the number of sites required per region.

5. Fine Tune plan.Perform more with drive test, confirm plan

predictions.Review plan with customer and fine tune the plan.

RF Planning Process


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RF Planning ProcessUnderstanding Customer Requirements :

What are the boundaries for the network ?Are there any special pockets to be covered due toGovt. requirements ?What are the areas in which medium to average inbuilding coverage is acceptable ?

What are the areas where excellent in buildingcoverage is needed ?Areas with high growth potential

Need colonies under developmentHigh revenue areasShopping malls , offices complex, industrial estatesetc.

RF Planning Process


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RF Planning ProcessInitial Implementation Strategy :

High usage, high revenue users first ?High end residential and business areas ?Street coverage first ?Special areas like 5 star hotel, commercialbuilding with fine in building coverage ?High way coverage critical ?Total coverage on day one ?Number of sites more than the competition ?

Any Budget Limitations ?Give an ideal plan to start with.

Let the customer cut corners.Not an easy job !!

RF Planning Process


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RF Planning ProcessCity Surveys :

Basically a scouting exerciseLooking for :-

Major traffic routesMarketsBusiness CentresShopping malls

General customer behaviorsTelephone densityCongested areas with narrow lanesNarrow water canals/lakes/pondsGeneral city layoutPrestigious residential areas.VIP areasParks/ playground/open areas.General Building types.. Multistoried, Row houses,apartments, colonies etc.Airport coverage

RF Planning Surveys


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RF Planning SurveysIn building Coverage Surveys :

Classify Buildings-

Hotel/restaurantsCommercialIndustrialResidentialShopping malls/markets

Propagation tests in a number of buildings in each variety.Rf signal on road Vs. inside building gives building penetration loss.Repeat tests in as many buildings as possible to get an estimate ofbuilding loss for the area.In building coverage affected mostly in ground floor/basementTypical values (examples only) :

> Hotel restaurants 15 dB> Commercial buildings 20 dB> Shopping malls 15 dB> Industrial Estates 12-15 dB> Residential buildings 15-20 dB> Old/Historical buildings 25-30 dB

RF Propagation Test KitsB d T i 10 20 W f i


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Battery powered Transmitter. 10 or 20 Watts output : frequency inGSM 900/1800 Mhz.

Portable mast Adjustable upto 5 m. With 1 m

antenna on top, effective heightabove ground is 6 m.Transmit antenna High gain omni or directional antenna

as requiredReceiver TEMS mobile Hand held mobile phone with RS232

connection to a laptop. Or an

accurate portable RF sensitivity meter / CW receiver if model calibration isrequired.

Positioning system GPS system, with PCMCIA cardComputer Laptop PC with TEMS software and

GPS softwareCables accessories Calibrated cable lengths (10 m) of lowloss feeder with known attenuationvalues; 12 Volts battery withappropriate cable to connect totransmitter.

Power meter, VSWR meter.

RF Planning ToolPlanning Tool preparation and Model Calibration :


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Planning Tool preparation and Model Calibration :

There are many planning tool available toaday :PLANET (MSI)

Cell Cad (LCC)Odessy (Aethos)Asset (Aircom)NetPlan (Motorola)

A planning tool Should be :Easy to useCompatible with tools like TEMSMinimum hardware requirements.Economical.

Maps collected from authorized sources.1:50000 or 1:25000 scale50 m resolution for macroLess than 30 m resolution for Micro cell planning using Ray tracing Tool

Maps are digitized under 3 categories :LandUseDigital Terrain MapVectors (Roads, Railways, etc.)



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Most Planning tools use corrections for the land use or clutter.Propagation Model tuned by assigning the values to

Clutter factor (Gain or Loss due to clutter )Clutter Heights (for diffraction modeling)

Different types of clutter are defined in these models/ tools

1. Dense Urban2. Urban3. Suburban4. Suburban with Dense Vegetation5. Rural6. Industrial area7. Utilities (marshalling yards, docks, container depots etc. )8. Open area9. Quasi Open Area10. Forest11. Water

Too many clutter type definitation complicate planning process 10 to 15 istypical.



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DTMProvided by the map vendorProvides contour information as a digital map.

VectorsHighwaysMain RoadsRailwaysCanals / water ways.Coast lineRivers.

Each categories is digitized as different layer

Displayed separately if requiredMap information is set up in the planning tool.Model calibration carried out.

Model CalibrationAll tools have provision for manipulating clutter values.


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All tools have provision for manipulating clutter values.Different tools have different directory structures and means of handlinggeographical data.The procedure mainly talks about ensuring correct data header files toinclude.

BTS locationEIRP of BTSAntenna Type

BTS antenna heightDescription of surrounding area.

Procedure uses a general core model equation :

The equation has constant k 1 to k 6 and a constant of clutter, k clutter

Initial values for the constants are set as per the model chosen (sayOkumara Hata )PLANET programme is run repeatedly to make RMS error values forall data files ZERO or a minimum.For each run of the programme, the values of k 1 to k 6 are manipulated.

This completes model calibration.

Link Budget and other Steps


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Key Points To be Considered :

Coverage ProbabilityExpected inbuilding coverageEdge probabilityFade margin required

Maximum permissible path loss ( from the link Budget )What is the radius of the cell ?Number of sites required (from coverage point of view )Is the number of sites calculated as above adequate for capacity ?Decide on more sites for capacity.

Capacity Calculations


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Capacity Calculations

Capacity calculations :

Check if number of sites is enough to give capacity.

Depends onSpectrum available

This decides the site configuration.Availability of features like frequency hopping etc.

If Capacity is not met, add more sites.

If number of site is not OK with the customer, then :-

Recalculate site density, for 50 % in building coverage in placeof 75 %

Fine Tune The Plan


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Fine Tune The Plan

Use Planning tool to return Coverage predictionsIterate the process in consultation with the customer.Finalize Plan and document it.

Search Areas

Planner issues search areas for each site location with informationon :LocationLat/LongAntenna heightsSpecific target areas if any

Size of search areasSize acquisition team scouts for buildings.3-5 alternatives preferred.

Site Selection


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Site SelectionCentral Business area

Small Search areas (100 m)Avoid near field obstruction.Antenna at or slightly above the average clutter height.Orientation is critical.Try solid structure (lift room ) for antenna mounting.This helps reduce backlobe radiation problemsAvoid towers on building tops. This reduces interference to neighbouring cells.

Residential suburban areas :

Larger search areas (200 m)Location not very critical.Antenna 3-5 metres above average clutter height.Antenna orientation less critical.

Site Selection


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Site SelectionIndustrial area :

A suitable central location.Avoid proximity to electrical installations like towers, transformersetc.Towers are common

Quasi / open Highways

Larger search areas (500 m)Limited by terrain and not the clutter. Hilly areas need care.Highways need closer search areas along road.Tall sites give better coverage.

Extending Cell Range


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Extending Cell RangeExtended cell range reduces number of sites.

Cell range improvement achieved through :

BTS transmit power enhancementBTS sensitivity enhancementCombination of both



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Extending Cell RangeIncreasing BTS transmit EIRP:

To maximize BTS O/P power, single carrier cells can be used.This will avoid the combination losses of multiple carrier cells.The output power at the top of the cabinet could be set to 40 Watt, giving anincrease in signal strength of 3 Db.For cells with more than aone carrier, air combination can be implemented sothat the combination loss is minimized.

Another way to maximize Tx and Rx signals is to implement lowloss feedercable.A typical 7/8 Andrewscoaxial cable has an attenuation of 3.92 dB/100 m. If a 5/8 Andrews cable with an attenuation of 2.16 dB/100 m is used, then anincrease of 1.6 dB can be obtained per 100m.



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Extending Cell RangeImproving BTS receiver sensitivity :

Better devices in the BTS receiver.Using Mast Head amplifiers with very low noise figures.Better RF cables.



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Extending Cell RangeImprovement in the transmit side gives 2 dB advantage.MHAs extend the BTS receiver sensitivity to 110 dBm instead of the usual

107 dBm.Overall improvements result in 4-5 dB advantage in path loss, leading toextended coverage.This improves quality of coverage.Experiments with MHAs have shown improvements

In areas with 50 % probability to approximately 70 % probability.In areas with 70 % probability to approximately 85 % probability.In areas with 85 % probability to approximately 95 % probability.In areas with 95 % probability to approximately 98 % probability.

Documents

Aster Rf Planning