LAB 1: Intro To RF Path Loss

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LAB 1 Intro To RF Path Loss Propagation
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Lecture Outline

• Part 1 Introduction To Path Loss
• Path Loss Of Line Of Site Links
• Free Space Propagation Equation In Two Forms
• Example Solution
• LOS Obstacles In Brief
• Part 2 Introduction To Propagation
  Modeling/Studies
• Part 3 Introduction To Radio Mobile
• Laboratory Exercise 1
• 802.11g Point-To-Point Link Model Using Radio
  Mobile
• Summary Of Laboratory Writeup
• Next Week

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Part 1 Introduction To Path Loss
1

• Goal Of A Radio Link Is To Deliver Enough Signal
  Power
• Enough To Be Within The Rx Threshold
• This Function Is Based On BER
• Which Is Based On SNR
• Limiting Factors Include
• Noise
• Interfering Signals
• Multipath Interference

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Path Loss Of Line Of Site LOS Links

• Benchmark Measurement For Transmission Link Is
  Loss In Free Space
• Loss Occurring In A Region Where No Objects Will
• Absorb RF Energy
• Reflect RF Energy
• This Is Ideal But Not Always Feasible

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Free Space Propagation Equation

• Consider A Tx With A Power
• Pt
• Coupled To An Antenna
• Which Radiates Equally in Every Direction
• (Isotropic) Not A Real Antenna
• At A Distance From The Rx
• D
• The Radiated Power Is Spread Equally Over An Area
• 4(pi)D2
• Defining A Power Flux Density of

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Free Space Propagation Equation Cont.

• Transmission Loss Depends On How Much Power The
  Rx Antenna Can Capture
• The Effective Area Of Rx Antenna
• Ar
• Power Which Can Reach The Rx (Excluding Line
  Loss)
• PrsAr
• Assuming Previous Perfect Isotropic Antenna

• With Derivation We Get

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Free Space Propagation Equation Fin.

• The Previous Equation Is In Units Of Meters
  (Wavelength)
• We Deal In Frequency When Discussing RF
• Lambdac/f
• Lambda Is Wavelength
• C Is The Speed Of Light
• F Is Frequency
• With Substitution Our Equation Becomes

• This Give Us Classic Square-Law
• The Dependence Of A Signal Versus Distance

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Actual System Free Space Loss Calculation

• Real Systems Have
• Antenna Gain
• Cable Connector Losses
• Free Space Path Loss Expressed Logarithmically
• Lp 32.4 log f 20 log D (dB)
• f is Frequency in Mhz
• d is Distance in Miles
• This Shows The Relationship Between Path Loss And
  Distance
• Double The Distance, Lose 6 More dB of Signal
• Taking Additional (Real System) Losses Into
  Account
• Pr Pt Lp Gt Gr Lt Lr
• Gt And Gr Gain Of The Tx and Rx, Respectively
• Lt And Lr Tx And Rx Line Loss, Respectively

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Example Problem
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Example Problem

• Total Free Space Path Loss Is Calculated At
• 111.48dB
• Pr Pt Lp Gt Gr Lt Lr
• Pr 26.53 111.48 10 10 2 2 -68.95

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LOS Obstacles In Brief

• Refraction
• Earths Atmosphere
• Ionization In Different Layers
• Dependent On Day And Night
• Diffraction (Of Objects In The Near Path)
• Earths Curvature
• Objects Within Path
• Leaves
• Larger Objects
• Reflections (Of Objects In The Near Or Far Path)
• Buildings
• Mountains

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Part 2 Introduction To Propagation
Modeling/Studies 2

• Mathematical Simulations Of Radio Wave
  Propagation As A Function Of
• Frequency
• Distance
• Elevation
• Environment
• Location
• And Much More
• Designed To Estimate
• Path Loss
• Effective Area Of A Tx Site

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Introduction To Propagation Modeling/Studies Cont.

• Propagation Studies Are Imperial In Nature
• They
• Using Large Datasets Collected From Various
  Sources To Estimate Link Scenarios
• The More Data The More Accurate The Model
• Sources Include
• Satellite Imagery
• Infrared Ground Coverage
• Topological Data
• Various Other Databases
• They Dont
• Provide An Exact Reproduction Of What Will Really
  Happen

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Propagation Model Types

• Indoor Models
• ITU Model For Indoor Attenuation
• Log Distance Path Loss Model
• Outdoor Models
• Well Focus On These
• Environmental Attenuation Models
• Point To Point Models
• Terrain Models
• City Models
• Sky Wave Models
• Ground Wave Models
• Each Of These Model Types Have Many Variations

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Part 3 Introduction To Radio Mobile
3,4

• Radio Mobile
• Is a tool For The Design And Simulation Of
  Wireless Systems.
• Predicts The Performance Of A Radio Link.
• Uses Digital Maps And GIS Systems
• Is Public Domain
• Not Supported For Commercial Use
• Runs On
• All Current Windows OSs
• Linux (With Wine Support)
• Uses Terrain Elevation For The Calculation Of
  Coverage
• Indicating Received Signal Strength At Various
  Points Along The Path.

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Introduction To Radio Mobile Cont.

• Radio Mobile Software
• Models 20 KHz to 200 GHz.
• Calculates
• Line Of Sight.
• Path loss
• Free Space
• A Coverage Area Of The Base Station
• (Only For Point To Multipoint Systems)
• Used To Create Networks From Different Topologies
  (Net Master/Slave, PTP and PMP

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Radio Mobile Getting It Up And Running

• Download Radio Mobile From
• http//www.cplus.org/rmw/english1.html
• Download Elevation Data From
• Various Sources Including NASA
• For A Complete List Visit
• http//www.cplus.org/rmw/dataen.html
• Various Tutorials Can Be Found Here
• http//www.cplus.org/rmw/howto.html

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Lab 1 802.11 P2P Link Study With Radio Mobile

• Design A Network Based On
• The Previous Link Conditions
• 900 Mhz
• Tx Power 450 mW
• Cable Type Cat5e Aerial _at_ .02 dB / ft Loss
• The Real World Conditions Of
• The Utica Wireless Network Backbone Connection
• Tx and Rx Antenna Gains 19 dBi
• Antenna Types Corner
• Tower On Top Of The Utica Hotel (N43.102469 x
  W-75.231408)
• Antenna Mount Hight 60 ft
• 100 ft (30m) Of Cable
• Tower On Dutch Hill (N43 00 10 65 x  W-75 08 42
  86)
• Antenna Mount Hight 80 ft
• 100 ft (30m) Of Cable

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Laboratory Write Up Points

• Include
• Screen Shots Of Your Propagation Model Using
  Radio Mobile
• Including An Elevation View and Top Down View
• Answer The Following Questions Which May Require
  Additional Research
• (Short Answers, No Essays!)
• What Is The Significance Of Doing A Propagation
  Study?
• Why Are There So Many Different Types Of Models
  That Can Be Used?
• What Is The Inverse Square Law As It Applies To
  RF Propagation?

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Laboratory Write Up Points Cont.

• Include A Cover Page With The Following Format
• Lab 1 Radio Path Loss and Propagation
• Name
• Date
• Course Tel 400 Wireless Communications
• Telecommunications
• Department Of ISET
• State University Of New York Institute of
  Technology
• Include An Index Page With Table Of Figures
• Include A Citations Page

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Next Week

• Fresnels Zone
• Means Of Measurements
• Quality Of Service Calculations

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Citations

• 1 VHF/UHF/Microwave Radio Propagation A Primer
  For Digital Experiments, Barry McLarnon, VE3JF
• 2 NIST, Wireless Propagation,
  http//w3.antd.nist.gov/wctg/manet/wirelesspropaga
  tion_bibliog.html
• 3 Radio Mobile, V7.8.6, http//www.cplus.org/rmw
  /english1.html
• 4 ICTP Trieste Wireless School,
  http//wireless.ictp.trieste.it/school_2002/lectur
  es/trivino/Radio_Mobil.ppt