LAB 1: Intro To RF Path Loss & Propagation

LAB 1: Intro To RF Path Loss & Propagation Joshua White SUNYIT Telecommunications 1/30/07

TEL 590 / 400 Labs

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)D^2

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) Pr=sAr 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 Lambda=c/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 7

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 8

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 Don’t: 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 We’ll 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 OS’s Linux (With Wine Support) Uses Terrain Elevation For The Calculation Of Coverage Indicating Received Signal Strength At Various Points Along The Path. 15

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 @ .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 18

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 20

Next Week Fresnel’s 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/wirelesspropagation_bib liog.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/lectures/trivino/ Radio_Mobil.ppt 22