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ECE 5221 Personal Communication Systems Prepared by:

Dr. Ivica Kostanic

Lecture 7: Example of link budgets and coverage planning

Spring 2011

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Balanced pathNominal cell radius calculationTypical link budget matrixExample of a coverage designCross band coverage planningExamples

Outline

Important note: Slides present summary of the results. Detailed derivations are given in notes.

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Balanced path

Forward and reverse link need to be balanced

Links are balanced if the maximum sustainable losses are the same

Base station has much more power than the mobile

Usually power from the base station needs to be reduced

Other ways to balance the linko Use different gain antennas for

forward an reverse linko Use tower top mounted

amplifierso Use higher sensitivity receivers

at the base station

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Example of unbalanced links. To achieve balance power on the forward

link need to be reduced by 4dB

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Nominal cell radius

Radius that corresponds to maximum sustainable path loss

Determined using link budget analysis and appropriate propagation model

Used for nominal budget estimation Dependant on the required reliability

o More reliable coverage results in smaller nominal radii

o Typically design is done to 90% area reliability

Nominal call radius is a principal input into budgetary planning of the deployment

Practical experience – Nominal planning determines cell count within 10-15% margin

Example. Link budget evaluation in suburban area determined maximum allowable path loss of 128dB. The operating frequency is 850MHz. Using Lee model determine the nominal cell radius. If the size of the suburban area is 400 square miles, determine the number of required cells. Assume 20% cell overlap.

Answers:

a) Nominal radius: 3.12 miles

b) Area of the cell: 30.6 miles

c) Cell count: 17 cells

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Link budget matrix – coverage design

In basic nominal design o four environments: dense urban,

urban, suburban, ruralo three design goals: in-building, in-

vehicle, street level RSLT – threshold is always the same Each combination (environment, design

goal) has its on RSLP threshold Each RSLP value can be translated

into corresponding nominal cell radius Knowing nominal cell radii, for different

environments one may estimate required cell count

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Nominal design flow

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Clutter maps (land classification maps)

Maps with land use classification Available from USGS or commercial

companies Usually 12 standard categories Each category may have its own

propagation parameters Each category may have its own

design goals In a nominal design phase – use

nominal propagation parameters In later phases of the design – more

sophisticated propagation modeling is used

o Models obtained through propagation modeling studies

o The models are obtained through measured versus predicted analysis

o Typically 5-10 representative sites for each morphological type are surveyed

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Example of a land classification map for Chicago area

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Example of coverage designConsider a system with following parameters:

Environment: one mile intercept: 109dB, slope: 38.4dB, StDev: 8dB

Rx Sensitivity: Bandwidth: 30KHz, noise figure: 8dB, S/N min: 17dB

In-building coverage: area reliability: 90%, building losses: 15dB, StDev: 6dB

In-vehicle coverage: area reliability: 90%, vehicle losses: 8dB, StDev: 3dB

Street level coverage: area reliability: 90%

MS parameters: antenna gain 0dB, body loss 3dB

BS parameters: ERP 47dBm

Determine:

a) Rx Sensitivity A: -104.2dBm

b) RSLp for in-building coverage A: -79dBm

c) RSLp for in-vehicle coverage A: -87.5 dBm

d) RSLp for street level A: -95dBm

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Link budget evaluation

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Link Budget

Morphology Data Urban Suburban Rural Mobile Station ParametersBuilding/Vehicle Penetration Loss 18 dB 15 dB 8 dB Transmit Power 2 w

Penetration Loss Std Deviation 6 dB 6 dB 3 dB 33.0 dBmBody/Head Loss 2 dB 2 dB 2 dB Antenna Gain 0 dBi

% Area Coverage Reliability 90.0 % 90.0 % 90.0 % Minimum Reciever Sensitivity -102.0 dBm

Fade Margin 6.5 dB 7.4 dB 6.4 dB Base Station Parameters1 mile Intercept -75 dBm -73 dBm -71 dBm BS Tx Power 28 W

Slope (dB / decade) 47 dB/dec 38 dB/dec 31 dB/dec 44.5 dBmPropagation Model Std Deviation 8 dB 8 dB 8 dB Minimum Receiver Sensitivity -108.0 dBm

Diversity Gain 3 dBAntenna Centerline 120 ft 150 ft 200 ft LNA-fixed gain 0.0 dB

36.59 m 45.73 m 60.98 mNumber of Transmit Antenna 3 3 2

Antenna Gain 15.4 dBd 15.4 dBd 16.6 dBdCoax & Connector Loss 3.0 dB 3.0 dB 3.0 dB

BS Jumper Loss 1.0 dB 1.0 dB 1.0 dBBS Duplexer Loss 0.5 dB 0.5 dB 0.5 dBBS TX Filter Loss 0.0 dB 0.0 dB 0.0 dB

Combiner Insertion Loss 0.0 dB 0.0 dB 0.0 dB

Urban Suburban Rural Lee Cell Radius 0.99 mi 1.4 mi 3.9 mi

TX Power ERP (dBm) 53.0 dBm 52.9 dBm 54.1 dBmTX Power ERP (watts) 197.3 W 195.4 W 257.6 W

Required BS TX Power 15.9 W 15.9 W 15.9 W

Display BandsRSL at Cell Edge -75.5 dBm -77.6 dBm -85.6 dBm

Examine attached link budget

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Coverage planning across multiple bands Different frequencies – different propagation Majority of networks operate in multiple frequency bands Examples:

o In US the networks may operate between: 850MHz and 1900MHz

o In Europe the networks may operate between 900MHz, 1800MHz and 2100MHz

Additional challenge – balance the coverage between bands

o Use higher antenna gaino Power down lower frequency sites o “one to one” collocation between the bands

Deploy mobiles with dual band capabilitieso All technologies support multiband operation

Handoff and mobility management

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Frequency allocation for different countries may be found @

http://www.worldtimezone.com/gsm.html

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Coverage maps

Provided on websites of every cellular provider

Three shades for three coverage criteria

Plots are usually generated for 90% reliability

One can easily see correspondence between signal level and population centers

Remember: objective is not to cover everything, but to cover more of relevant areas than the competition

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Example – ATT coverage map (2011)

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Homework assignment

Homework 2

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