Telecomm Handbook

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Telecommunications Handbookfor Transportation ProfessionalsThe Basics of Telecommunications

Final Report

September, 2004


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Notice

This document is disseminated under the sponsorshipof the Department of Transportation in the interest of

information exchange.

The United States Government assumes no liability for its contents or use thereof.


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Technical Report Documentation Page 1. Report No.

FHWA-HOP-04-034

2. Government Accession No. 3. Recipient's Catalog No.

5. Report DateAugust, 2004

4. Title and SubtitleTelecommunications Handbook for Transportation ProfessionalsThe Basics of Telecommunications

6. Performing Organization Code

7. Author(s)Sheldon Leader

8. Performing Organization Report No.

10. Work Unit No. (TRAIS)9. Performing Organization Name and Address

11. Contract or Grant No.

13. Type of Report and Period Covered12. Sponsoring Agency Name and Address

14. Sponsoring Agency Code

15. Supplementary Notes

16. Abstract

This handbook was created to provide individuals responsible for managing and implementing TrafficSignal, and Freeway Management programs with an understand of the basic technologies oftelecommunications. The handbook provides a brief look at the history of telecommunications so thatits readers may gain an understanding of why various processes exist, and how the technologiesevolved. The handbook is not designed to be used as a specification for telecommunication systems.

The technologies associated with telecommunications are in a constant state of change. This handbook

was written over a two year period between August, 2002 and June 2004. During this time, a number ofemerging technologies began to reach maturity. The most significant of these, wireless internet access,and voice over IP have caused the major carriers (telephone companies) to announce the construction ofnew facilities to provide Internet Telephony services.

Readers of this handbook should gain an understanding of the basic technologies underlying mosttelecommunications systems designed to transmit both voice and data information.

17. Key Word

Telecommunications18. Distribution Statement

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages287

22. Price


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5

FOREWORD

This handbook was crea ted to provide ind iv iduals respons ib le formanaging and implement ing Traff ic S ignal , and Freeway

Management programs wi th an unders tanding of the bas ictechnologies of t e lecommunicat ions . The handbook provides abr ief look a t the h i s tory of t e lecommunicat ions so tha t i t sreaders may gain an unders tanding of why var ious processesexis t , and how the technologies evolved . The handbook i s no tdes igned to be used as a speci f ica t ion for t e lecommunicat ionsys tems .The technologies associa ted wi th te lecommunicat ions are in acons tan t s ta te of change. This handbook was wr i t t en over a two

year pe ri od betw een Augus t , 2002 and June 2004 . Du ring th i st ime, a number of emerging technologies began to reach matur i ty.The most s ign i f icant of these , wi re less in ternet access , and voiceover IP have caused the major car r iers ( t e lephone companies ) toannounce the cons t ruct ion of new fac i l i t i es to provide In ternetTelephony serv ices . This cons t ruct ion i s to s tar t in 2004.

Welcome to the fu tu re !


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6

ACKNOWLEDGEMENTS

The au thor would l ike to acknowledge the invaluable cont r ibu t ionsof the fo l lowing ind iv iduals for vo lunteer ing the i r t ime to rev iew

this document : Karen Jehanian , KMJ Consul t ing , Haverford , P A Jambala (Jay) Rui t , Edwards and Kelcey, Inc . , Wes t Ches ter,

PA Jeffery Purdy, Edwards and Kelcey, Inc . , Wes t Ches ter, PA Richard Eas ley, E2 Engineer ing , Ashburn , VA Ray Cauduro , GDI Sys tems, LLC, Newpor t , OR

The fo l lowing ind iv iduals suppor ted the overa l l development ofth i s document :

Paul Olson , FHWA, San Francisco , CA Bil l Jones , FHWA, Washington , D.C. Lou Neudorf , S iemens ITS, New York , N Y Rober t Reiss , Dunn Engineer ing Associa tes , Wes thampton

Beach , NY Rober t Gordon, Dunn Engineer ing Associa tes , Wes thampton

Beach , NY Warren Tighe , S iemens ITS, Concord , CA


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7

TABLE OF CONTENTS

1. Chapter One - Telecommunication Basics....................................................................................................

Introduction........................................................................................................................................................Purpose ...............................................................................................................................................................Relationship to National Architecture ..............................................................................................................1Open System Interconnection Model (OSI) ...................................................................................................16Telecommunications History .............................................................................................................................Handbook Organization.....................................................................................................................................

2. Chapter Two Fundamentals of telecommunications..............................................................................23Introduction........................................................................................................................................................Transmission Media...........................................................................................................................................

Media Consideration Factors .........................................................................................................................Wireline Media ..............................................................................................................................................

Transmission Signaling Interfaces....................................................................................................................5Data & Voice Signaling - Basics ....................................................................................................................Electro-Mechanical Signal Interfaces ........................................................................................................54Video Transmission........................................................................................................................................Video Compression........................................................................................................................................Video CODECS.............................................................................................................................................Video Compression........................................................................................................................................Streaming Video.............................................................................................................................................

Basic Telephone Service.....................................................................................................................................Multiplexing.......................................................................................................................................................

Time Division Multiplexing ...........................................................................................................................

Packet Division Multiplexing........................................................................................................................T-1 Communication Systems.........................................................................................................................Transporting Digital Communications via an Analog Network...............................................................68

High Capacity Broadband Transmission ...........................................................................................................T-1/DS-1 & T-3/DS-3 ....................................................................................................................................DSL ................................................................................................................................................................SONET...........................................................................................................................................................ATM...............................................................................................................................................................FDM ...............................................................................................................................................................WDM CWDM & DWDM..........................................................................................................................Ethernet..........................................................................................................................................................

Conclusions........................................................................................................................................................3. Chapter Three Telecommunications & The National ITS Architecture ........................................83Introduction........................................................................................................................................................Overview The National ITS Architecture ...................................................................................................84

Vehicle-to-Vehicle (VtV) ...............................................................................................................................National ITS Architecture Flows & Telecommunications...........................................................................89

Market Packages............................................................................................................................................Example Illustration .......................................................................................................................................

Application of Telecommunications Using the National Architecture Flows ........................................94


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Comparison of Rural and Urban Telecommunications Requirements Using the NationalArchitecture Flows .............................................................................................................................................

Rural Systems................................................................................................................................................National Transportation Communication for Intelligent Transportation Systems Protocol (NTCIP)............................................................................................................................................................................Conclusion..........................................................................................................................................................

4. Chapter Four Developing the Telecommunication System................................................................ 106Introduction........................................................................................................................................................Selecting the Consultant ....................................................................................................................................

Theres no substitute for experience........................................................................................................ 107Different Telecommunication Design Specialties..................................................................................108Types of Telecommunications Experience................................................................................................10Knowledge of Telecommunications Systems Relationships.................................................................. 109Educational Qualifications .............................................................................................................................

Requirements Analysis ......................................................................................................................................The Gee-Whiz Factor .................................................................................................................................Keep expectations realistic ask questions .............................................................................................115

A Systematic Engineering Approach to the Requirements Analysis ......................................................116Key points to consider:...................................................................................................................................Ask The Questions.........................................................................................................................................

Creating The Requirements Document............................................................................................................1Three Basic Systems Types:........................................................................................................................ 1Developing a Budget......................................................................................................................................

Conclusion..........................................................................................................................................................A few simple guidelines to follow: .............................................................................................................. 1

5. Chapter Five Telecommunications for Field Devices .........................................................................124Basic Communication Circuits for Field Devices.......................................................................................... 12

Basic Circuit Types.........................................................................................................................................The Design Process............................................................................................................................................

Traffic Control Device Circuits...................................................................................................................1Traffic Control System ................................................................................................................................. 1

Basic Data Circuit Types ....................................................................................................................................Basic Traffic Device Type Communication Circuits...............................................................................138Basic Video Communication Circuits............................................................................................................Video-over-IP (VIP) .......................................................................................................................................

Basic Traffic and Freeway Management Networks.....................................................................................151Basic Device Networks..................................................................................................................................

Complex Communication Networks ..................................................................................................................

Summary........................................................................................................................................................Network Topology .............................................................................................................................................Point-To-Point Networks ...............................................................................................................................Star Networks.................................................................................................................................................Ring Networks ...............................................................................................................................................Mesh Networks ..............................................................................................................................................Network Redundancy .....................................................................................................................................

Conclusion..........................................................................................................................................................6. Chapter Six Maintenance & Warranties ................................................................................................168


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Introduction........................................................................................................................................................Why create a Maintenance Budget? ............................................................................................................... 16Creating the Maintenance Budget ................................................................................................................... 1Warranties, Extended Warranties & Service Plans................................................................................... 177

Warranties ......................................................................................................................................................Extended Warranties..................................................................................................................................... 1Relationship of Warranties to System Specifications..........................................................................181Service Plans..................................................................................................................................................

Conclusions........................................................................................................................................................7. Chapter Seven System Examples.............................................................................................................18

Introduction........................................................................................................................................................Utah DOT System..............................................................................................................................................

Background ....................................................................................................................................................The System - Existing....................................................................................................................................The System - New..........................................................................................................................................

City of Irving Texas ...........................................................................................................................................Background ....................................................................................................................................................Proposed Update............................................................................................................................................5.8 GHz Attributes.........................................................................................................................................Theory of Operation.......................................................................................................................................The Irving Proposal........................................................................................................................................Tie-in To Main Communication Network....................................................................................................2

Conclusion..........................................................................................................................................................8. Chapter Eight Construction.......................................................................................................................2

Introduction........................................................................................................................................................Handling and Installation of Fiber Optic (and Copper) Communications Cable ..................................205

Receiving and inspecting fiber optic cable...............................................................................................206Unloading, moving and storing cable...........................................................................................................2Testing the cables...........................................................................................................................................Documentation and record maintenance...................................................................................................21

General Cable, Installation and Design Guidelines.......................................................................................21Cable Pull-box/Splice-box Placement .........................................................................................................2Cable Installation and Pulling Guidelines...................................................................................................2

General Cable Construction Guidelines...........................................................................................................2Aerial Construction ........................................................................................................................................Direct Burial Construction ............................................................................................................................ 2Conduit Construction .....................................................................................................................................

Wireless Systems Construction.......................................................................................................................22

Planning for Wireless Systems....................................................................................................................2A Word About Antennas ...............................................................................................................................2Guidelines for Handling & Installation of Wireless Antenna and Transmission Cable................224

Conclusion..........................................................................................................................................................Resources:......................................................................................................................................................

9. Chapter Nine The internet ........................................................................................................................22Introduction........................................................................................................................................................

What is the Internet? ...................................................................................................................................22History of the Internet ................................................................................................................................22


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The Internet and the World-Wide-Web ......................................................................................................229How Does the Internet Work?.........................................................................................................................23

Addressing Formats.....................................................................................................................................Types of Internet Networks .......................................................................................................................23

Role of the Internet for Traffic, ITS, Freeway Management & Traveler Information.................239Use of the Internet for Center-to-Center Communications ..............................................................241

Conclusions........................................................................................................................................................10. Chapter Ten The Future........................................................................................................................2

Introduction........................................................................................................................................................Circuit Switched Vs. Packet Switched ......................................................................................................247

Trends for Transportation ................................................................................................................................24High Speed Ethernet......................................................................................................................................Resilient Packet Ring (RPR)..........................................................................................................................Broadband Wireless........................................................................................................................................Radio Frequency Identification (RFID) ....................................................................................................253

Conclusions........................................................................................................................................................11. Appendix...................................................................................................................................................

IEEE 802 Standards & Working Groups........................................................................................................25Comparison Analog Voice & VoIP.....................................................................................................................Calculating Fiber Optic Loss Budget...............................................................................................................2

Criteria & Calculation Factors......................................................................................................................2Calculating a Loss Budget..........................................................................................................................

Rural Telecommunications Requirements Testimony..................................................................................262Steve Albert Senate hearing....................................................................................................................26

About the Author ....................................................................................................................................................Glossary..................................................................................................................................................................


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L IST OF TABLES Table 1-1: OSI Protocol Stack ............................................................................................................................................... Table 2-1: Twisted-Pair Communication Cable Category Ratings........ .............. .............. .............. ............. ............. ........... 3 Table 2-2: Fiber Optic Cable Classifications.......................................................................................................................... Table 2-3: Fiber Cable Color Identification Chart ............. .............. ............... .............. .............. ............ .............. ............. ..3 Table 2-4: Fiber Optic Cable Buffer Types............................................................................................................................ Table 2-5: Comparison Single Mode Fiber & Multimode Fiber...........................................................................................4 Table 2-6: Frequencies for Unlicensed Radio Systems ............. .............. .............. .............. .............. ............ ............. .........49 Table 2-7: CEA Estimates of the Number of Low Power Radio Devices.........................................................................50 Table 2-8: Comparison of TDM & PDM............................................................................................................................... Table 3-1: DSRC Vehicle-Roadside Relationships................................................................................................................ Table 3-2: Communication Needs & Requirements............................................................................................................... Table 3-3: NTCIP Device Management Protocol List .............. .............. .............. .............. ............... ............ ............. ......... 1 Table 3-4: NTCIP List of Systems Management Protocols..............................................................................................104 Table 5-1: Location of Field Controllers .............. .............. .............. ............. .............. .............. .............. ............. ............. ..... Table 5-2: Location & Data Requirements Table..................................................................................................................1 Table 5-3: DB-25 Connector Cable....................................................................................................................................... Table 5-4: Voice, Video & Text Transmission Requirements............................................................................................143 Table 5-5: Field Device Location ............. .............. .............. .............. .............. .............. ............. ............. .............. ............. .. Table 6-1: Example Communication Device Inventory List.................................................................................................1 Table 6-2: Technician Experience Classification.................................................................................................................17 Table 7-1: Deployment Cost Estimates .............. .............. .............. .............. .............. .............. ............ ............. .............. ...... Table 8-1: Example of Manufacturer Recommended Span Lengths for Areial Cable Segments.............................216 Table 9-1: Internet Communication Elements ............. .............. .............. .............. .............. ............. ............. .............. ........ 2 Table 10-1: Comparison Traditional CCTV vs. VIP Systems Requirements ............. ............. .............. ............. ............. 250 Table 11-1: IEEE 802 Standards List .................................................................................................................................... Table 11-2: Fiber Loss Budget Calculation...... ............. .............. ............. .............. .............. ............. ............. ............. ...........


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L IST OF F IGURES Figure 1-1: Diagram - NTCIP Standards Framework............................................................................................................ Figure 1-2: Telecommunication Timeline.............................................................................................................................. Figure 2-1: RJ45 Connector ............. .............. ............. .............. .............. .............. .............. ........... .............. ............. ............ Figure 2-2: Twisted Pair Cable.............................................................................................................................................. Figure 2-3: Co-Axial Cable Illustration................................................................................................................................. Figure 2-4: Basic Fiber Optic Strand Construction..............................................................................................................3 Figure 2-5: Fiber Optic Cable Illustration.............................................................................................................................. Figure 2-6: Diagram of Basic Connector Wiring................................................................................................................... Figure 2-7: Illustration of Basic Telephone Call Process....................................................................................................62 Figure 2-8: TDM Process Flow Chart.................................................................................................................................... Figure 2-9: Flow Chart - PDM Process ............. .............. .............. .............. .............. .............. ............ .............. ............. ....... Figure 2-10: Diagram of Computer Digital Output Converted to Analog using a MODEM..........................................67 Figure 2-11: Diagram of Analog Inputs to T-1 Mux............................................................................................................... Figure 2-13: DWDM Channels............................................................................................................................................. Figure 2-14: Diagram - Typical Office LAN.......................................................................................................................... Figure 2-15: Diagram - Metro Area Network (MAN) ........................................................................................................... Figure 3-1: National ITS Architecture Communications Sausage Diagram....................................................................83 Figure 3-2: Diagram - Mobile 2-Way Radio Network...........................................................................................................8 Figure 3-3: National Architecture EM-4 Market Package..................................................................................................90 Figure 3-4: EM-4 Market Package with Telecommunications Flows.................................................................................92 Figure 3-5: EM-4 Market Package with "Sausage Diagram" Elements ............. .............. ............... .............. ............ ........93 Figure 3-6: TMC Area of Responsibility ............ .............. .............. .............. ............. .............. ............. .............. ............. ...... Figure 3-7: Diagram - TMC to EMA Link .............. .............. ............. .............. .............. ............. .............. ............. .............. . Figure 3-8: Diagram - TMC to EMA with Fiber Communication Link................................................................................9 Figure 3-9: Diagram - TMC to EMA Comm Link Rural Setting........................................................................................... Figure 3-10: Diagram - TMC to EMA Rural using Leased Telephone Lines .............. .............. .............. .............. ............. 98 Figure 3-11: NTCIP Standards Framework........................................................................................................................... Figure 4-1: Field Devices Communication Link Requirements ............. .............. ............. .............. .............. ............ ............1

Figure 4-2: Chart Relationship Communication to Overall System..................................................................................114 Figure 5-1: Diagram - Technology Flow ............ .............. .............. .............. .............. ............. ............. .............. ............. ...... Figure 5-2: Diagram - 3 Types of Communication Circuits................................................................................................12 Figure 5-3: Napkin Sketch of Communication System.......................................................................................................12 Figure 5-4: Location Map..................................................................................................................................................... Figure 5-5: System Schematic............................................................................................................................................... Figure 5-6: DB-25 Connector................................................................................................................................................ Figure 5-7: DB-9 Connector.................................................................................................................................................. Figure 5-8: Modem Block Diagram....................................................................................................................................... Figure 5-9: CCTV Circuit Diagram...................................................................................................................................... Figure 5-11: Diagram Field Controller to Host Computer..................................................................................................13 Figure 5-12: Diagram - Point-to-Multipoint..........................................................................................................................

Figure 5-13: Diagram - Multidrop System............................................................................................................................ Figure 5-14: Diagram - FDM Hub Circuit............................................................................................................................. Figure 5-15: Diagram - CCTV with CODEC ............ ............. .............. ............. ............. .............. .............. ............. ............. . Figure 5-16: Diagram - Typical CODEC Communication Circuit - 1990's Deployment................................................147 Figure 5-17: VIP Basic Camera System................................................................................................................................ Figure 5-18: Diagram - Add-on Conversion to VIP ............. .............. .............. .............. .............. ............ ............. ............. ... Figure 5-19: Diagram - Basic Traffic Device Communication Circuit ............. ............. ............. ............. .............. ............151 Figure 5-20: Diagram of described system ............. .............. .............. .............. .............. .............. ............ ............. ............. .1 Figure 5-21: Diagram STSS Communication System .............. .............. .............. .............. .............. ........... .............. ........... 1 Figure 5-22: Diagram UTSS Communication System .............. .............. .............. .............. .............. ............. ............. ......... 1


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Figure 5-23: Straight Line Diagram....................................................................................................................................... Figure 5-24: Diagram - Site Equipment .............. ............. .............. .............. ............. .............. ............. .............. .............. ..... Figure 5-25: System Block Diagram ..................................................................................................................................... Figure 5-26: Diagram - Point-to-Point Network .............. .............. .............. .............. .............. ............. ............. ............. .....1 Figure 5-27: Diagram - Star Network.................................................................................................................................... Figure 5-28: Diagram - Ring Network ..................................................................................................................................

Figure 5-29: Diagram - Mesh Network .............. .............. .............. .............. .............. .............. ............ .............. ............. ...... Figure 6-1: Photograph of a Fiber Optic Modem.................................................................................................................1 Figure 7-1: Diagram UDOT Current System......................................................................................................................... Figure 7-2: Graph - Comparison of Savings Realized by UDOT Converting to an IP Architecture.........................191 Figure 7-3: Diagram - Comparison Multi-Drop VS. Ethernet .............. .............. .............. .............. .............. ............ ......... 19 Figure 7-4: Diagram - Wireless Channel Alignment for 360 Degree Coverage .............. ............. .............. ............. .....195 Figure 7-5: Diagram - Channel Re-use Plan for Wide Area Coverage ............. .............. ............... .............. ........... ......... 197 Figure 7-6: Diagram - Proposed Channel Re-use Plan .............. .............. .............. .............. .............. ............. ............. ......... 1 Figure 7-7: Drawing - Typical CCTV Site............................................................................................................................. Figure 7-8: Typical CCTV Site Schematic .............. .............. .............. .............. ............. .............. ............. ............. ............. .. Figure 7-9: Map of Proposed Irving Texas System............................................................................................................20 Figure 7-10: Schematic - Microwave Backbone Configuration.............. .............. .............. .............. .............. ............ ...... 202

Figure 7-11: Diagram - Microwave Backbone ...................................................................................................................... Figure 8-1: Fiber Cable Route Construction Photograph Courtesy Adesta, LLC.......... ............. .............. .............. ... 204 Figure 8-2: Fiber Cable Route Construction Photograph Courtesy Adesta, LLC...... .............. .............. .............. ..... 204 Figure 8-3: Fusion Splicing Fiber Strands - Photograph Courtesy Adesta, LLC .............. .............. .............. ............. . 209 Figure 8-4: Aerial Fiber Optic Cable Splice Box - Photograph Courtesy Adesta, LLC..............................................212 Figure 8-5: Typical Telephone Pole ...................................................................................................................................... Figure 8-6: Installation of Wireless System - Photograph Courtesy GDI Systems, LLC.... .............. .............. ........ 220 Figure 8-7: Example of Antenna Coverage Pattern - Antenna Specialists Products.............. .............. .............. ....... 224 Figure 9-1: Actual Sketch of the Original Internet Concept......... .............. .............. .............. ............. ............. ............. 228 Figure 9-2: Map - Location of Major MCI Internet Nodes in United States............... .............. ............... ............ ..... 229 Figure 9-3: Diagram General Internet Architecture........................................................................................................ 232 Figure 9-4: Diagram - Traveler Information Provided via the Internet..... .............. .............. ............... ............ .......... 234 Figure 9-5: National ITS Architecture Sausage Diagram with Internet added .............. .............. .............. ............ . 240 Figure 9-6: Internet Elements Schematic ............... .............. .............. .............. .............. .............. ............ ............. ............. 24 Figure 9-7: Schematic - Multiple Agency Center-to-Center Links via the Internet ............. .............. .............. ....... 244 Figure 9-8:ITS Center-to-Center Communication Diagram........ .............. .............. .............. .............. ............ ............. .... 245


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1. CHAPTER O NE - TELECOMMUNICATIONBASICS

IntroductionThe Telecommunicat ions Handbook for Transpor ta t ionProfess ionals was or ig inal ly publ i shed in 1987 as theCommunicat ions Handbook for Traff ic Cont ro l Sys tems. Thef i rs t (and only) update was in i t i a ted in 1991, and publ i shed in1993. Given the s ign i f icant advances in the technology ofte lecommunicat ions , and the complexi t i es of Traff ic and ITSsys tems deployment i t s i s necessary to crea te a new ( ra ther thana rev is ion) handbook provid ing a broader v iew ofte lecommunicat ions technology as appl ied for t raff ic and

t ranspor ta t ion purposes . This handbook provides a broad overv iewof te lecommunicat ions technology and h i s tory.Purpose

The Telecommunicat ions Handbook for Transpor ta t ionProfess ionals i s in tended to provide an in t roduct ion tote lecommunicat ion technology and process for t ranspor ta t ionengineers and pro jec t managers involved in the des ign anddeployment of t raff ic s ignal and f reeway management sys tems .The handbook can be used as a resource tha t p rovides an overv iewof the var ious technica l i s sues associa ted wi th the p lanning ,des ign , opera t ion , and management of a communicat ions sys tem. I ti s in tended to provide the user wi th a be t ter unders tanding ofappl ied communicat ions technology and the cons idera t ions for usein f reeway and surface s t ree t ne tworks .The in tended audience i s t ranspor ta t ion profess ionals who may beinvolved wi th , o r respons ib le for any phase in the l i fe cycle of at raff ic s ignal or f reeway management cont ro l ne twork . Thisinc ludes a l l publ ic or pr iva te prac t i t ioners (e .g . , managers ,superv isors , engineers , p lanners , o r t echnic ians) involved wi th anyissue or deci s ion (e .g . , po l icy, p rogram, funding , or sys temimplementa t ion) and who may d i rec t ly or ind i rec t ly inf luence theperformance of t raff ic on local a r ter ies or f reeway fac i l i t i es .These ac t iv i t i es may inc lude , bu t no t be l imi ted to , p lanning anddes ign , opera t ional s t ra teg ies , p rograms, and serv ices tha tsuppor t cont inuous management of t ravel and cont ro l of t raff ic ,and the technology inf ras t ructure to provide these capabi l i t i es .


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Relationship to National ArchitectureTelecommunicat ions sys tems as par t o f the Nat ional ITSArchi tec ture are the connect ing pathways tha t b ind the var iouselements of t raff ic s ignal , f reeway management , andt ranspor ta t ion sys tems together. The Nat ional ITS Archi tec turesausage d iagram indica tes how these e lements are boundtogether, bu t does not speci fy the te lecommunicat ion sys tem. Thedevelopers of the Nat ional ITS Archi tec ture unders tood tha teach te lecommunicat ion sys tem would be uniquely des igned tomeet the needs of each pro jec t .The s igni f icant d ivers i ty of communicat ions technologies and theovera l l complexi ty of t raff ic s ignal , f reeway management , andt ranspor ta t ion sys tems have crea ted a need for t raff ic andt ranspor ta t ion profess ionals to implement the Sys temsEngineer ing Process (SEP) . This handbook provides a summary(Chapter 4) of how to apply an SEP to the development of ate lecommunicat ions sys tem, for t raff ic s ignal and f reewaymanagement sys tems development .

Open System Interconnection Model (OSI)The OSI model i s an In ternat ional S tandards Organiza t ion ( ISO)s tandard tha t def ines a f ramework for implement ingte lecommunicat ion and sof tware pro tocols . The OSI model i sorganized in to seven h ierarchal l ayers . Cont ro l i s passed f rom onelayer to the next s tar t ing a t the appl ica t ion layer and proceedingdown to each success ive layer and back as requi red for any g ivenprocess . Most of the funct ional i ty of the OSI model ex is t s in a l lcommunicat ions sys tems - however, two or th ree layers may becombined in to one . The most s ign i f icant ro le of the OSI model i sto serve as a reference for the development of o ther pro tocols tacks . A deta i led explanat ion of the OSI Model i s p rovided inthe Addendum sect ion of th i s handbook. Table 1-1 , p rovides a l i s tof the OSI Model Pro tocol S tack .


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Table 1-1: OSI Protocol Stack

O S I P r o t o c o l S t a c k

L a y e r # P r o t o c o l

7 A p p l i c a t i o n

6 P r e s e n t a t i o n

5 S e s s i o n

4 Tr a n s p o r t

3 N e t w o r k

2 D a t a L i n k1 P h y s i c a l

Telecommunicat ions hardware genera l ly u t i l i zes l ayers one andtwo of the pro tocol s tack . Modems, mul t ip lexers , b r idges ,routers , swi tches , media conver ters , codecs , e tc . a re examples ofthe types of devices tha t ex i s t a t the phys ica l and data l inklayers of the pro tocol s tack . Al l media and most of the pro tocolconver ters are cons idered as l ayer one i t ems . Somecommunicat ion hardware devices are des igned to opera te a th igher l ayers . A network router i s o f ten refer red to as a layer 3router . This i s one of the few examples of communicat ionhardware tha t i s des igned to funct ion above layer two. Mostcommunicat ion sys tems are not des igned us ing the OSI pro tocols tack . This i s because the hardware vendors have a l ready takenthe OSI model in to cons idera t ion for the des ign of the i rproducts . The RS232 and RJ45 connectors bu i l t in to the 2070t raff ic cont ro l ler a re a l ready layer one compl ian t . Serv ing as apro tocol s tack model , OSI i s used as the reference for thedevelopment of mos t o ther communicat ions pro tocols . TheNat ional Transpor ta t ion Cont ro l In ter face Pro tocol (NTCIP)

1

hasa specia l ly developed pro toco l s tack based on the OSI model .

1 http://www.ntcip.org


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Not ice ( f igure 1-1) tha t the NTCIP pro tocol s tack i s modeled onthe OSI s tack , and has embedded te lecommunicat ion s tandards .Communicat ion sys tem des igners would s imply use the pre-def inedte lecommunicat ion s tandards . However, developers of sof twarecont ro l sys tems must be acute ly aware of the NTCIP pro tocols tack . NTCIP and i t s ro le in the development of a communicat ionsys tem i s expla ined in Chapter 3 .

Telecommunications HistoryThe h i s tory of modern-day communicat ions technology can be sa idto have s tar ted when Samuel Morse invented the wi re l inete legraph in 1832. However, i t was Alexander Graham Bel l s

invent ion of the te lephone, in 1874, tha t l ed to the developmentof our present day communicat ions technology. Morse had s implycreated a way for humans to ex tend the i r ab i l i ty to t ransferinformat ion ins tan t ly over grea t d i s tances . Bel l gave us theabi l i ty to have the mos t in t imate form of communicat ion overd is tances the use of our vo ices .The concept of the te lephone ins t rument and the sys tem thata l lows i t to work was so s t rong tha t mos t communicat ion

F ig u re 1 -1 : D iag ram - N T C IP S tan d a rd s F ram ew o rk


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t echnology dur ing the pas t 125 years was developed to suppor t aneff ic ien t vo ice communicat ion network . I t wasnt un t i l 2004 tha tmajor t e lecommunicat ion car r iers announced the need to develop ,and suppor t , a ne twork des igned for the purpose of t ranspor t ingdig i ta l da ta .

The wi re less t e legraph (now refer red to as rad io) was invented byGui l lermo Marconi in 18962. When wi re less communicat ion wasf inal ly ab le to be used for vo ice t ransmiss ion , i t emula ted thete lephone sys tem.From 1874 to 1980, communicat ion networks around the wor ldwere cons t ructed to fac i l i t a te the eff ic ien t and economicalt ransmiss ion of vo ice conversa t ions . Mul t ip lex ing and d ig i ta lt ransmiss ion sys tems were developed to cram more voiceconversa t ions in to the ex is t ing copper wi re communicat ionfaci l i t i es .The In ternet , f i r s t developed in 1973 as a pro jec t for the U.S .Depar tment of Defense Advanced Research Pro jec t s Agency(ARPA), in i t i a ted a profound change in the fu ture development ofcommunicat ions networks and technologies . Or ig inal ly ca l led theArpanet l ink ing severa l Univers i t i es and research labora tor ies i t evolved in to the wor ld wide web (WWW). Dur ing th i s per iod ,there were a number of s ign i f icant t echnology advances andgovernment enforced corpora te reorganiza t ions tha t he lped tochange the d i rec t ion of communicat ions sys tems develop ment :

1 . Comput ing and communicat ions technologies were provided ab ig boos t by the invent ion of the in tegra ted c i rcu i t ( IC) in1959. The IC permi t ted development and manufacture ofsmal ler and more au tomated communicat ion devices a t a verylow cos t .

2 . The Car terphone Decis ion , by the U.S . Supreme Cour t , in1968, made i t poss ib le for the connect ion of non- te lephonecompany owned devices (unt i l th i s po in t , on ly devices ownedand opera ted by the te lephone companies were permi t ted) .

3 . In the 1970s , f iber s t rands were f i r s t used as acommunicat ion medium.4 . In 1983, the U.S . Supreme Cour t mandated reorganiza t ion

of AT&T was enforced .

2 Historically, Marconi is credited with the invention of the wireless telegraph, however, a landmark June 21, 1943 supreme court decision statedthat Marconi had violated Nikola Tesla's patents for wireless communications. See "United States Reports; Cases Adjudged in the SupremeCourt of the United States," Vol. 320; Marconi Wireless Telegraph Co. of America v. United States, pp. 1-80.


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New invent ions coupled wi th increas ing bus iness and consumerdemand for computer and data communicat ion serv ices forced achange in the nature of the development of communicat ionsnetworks . By 1995, mos t ins ta l la t ion of communicat ions networkswas devoted to the eff ic ien t t ransmiss ion of da ta genera ted by

computers . However, these networks were s t i l l based on a voice

communicat ion des ign .The development and in t roduct ion of broadband datacommunicat ions s tandards ( IEEE 802 Ser ies 3) he lped to crea te ademand for communicat ions networks des igned to suppor t da tacommunicat ions .By 2003, wi re less (ce l lu lar t e lephone) ne tworks were avai lab le toa lmos t every locat ion of the Uni ted S ta tes ( remote wi ldernessareas s t i l l l ack coverage) . Accord ing to the Cel lu larTelecommunicat ions & In ternet Associa t ion (CTIA) , there weremore than 148 mi l l ion wi re less subscr ibers , and 92% were us ing

dig i ta l serv ice .A t imel ine of the suppor t for t rad i t ional vo ice t ransmiss ionserv ices versus data t ransmiss ion serv ices might appear asfo l lows:By 2003, 63% of Americans use the in ternet , and 31% of homeusers have broadband access 4. In ear ly 2004, Ver izon , announceda major upgrade of i t s bas ic t e lephone network to suppor tIn ternet Telephony or Voice over In ternet Pro tocol (VoIP) 5.Southern Bel l Corpora t ion (SBC) a l so announced s imi lar upgradesfor i t s ne tworks .

Handbook OrganizationThe Telecommunicat ions Handbook for Transpor ta t ionProfess ionals i s o rganized to provide the reader wi th a log ica lf low of in format ion wi th a descr ip t ion of var ious communicat ion

3 http://www.ieee.org 4 Pew Trust Internet & American Life, December 2003. - http://www.pewtrusts.org 5 Ivan Seidenberg, CEO Verizon, at the Consumer Electronics Show, Jan 2004.

1876 Present1995

TelephoneInvented

VoiceNetwork

Dominance

DataNetwork

DominanceStarts

F ig u re 1 -2 : Te l eco m m u n ica t io n Tim e l in e


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t e rms and technologies tha t a re commonly used (or cons idered)for the deployment of Freeway Management and Traff ic S ignalsys tems . Technica l descr ip t ions are kept a t a min imumengineer ing level to provide non-communicat ion profess ionals wi tha bas ic unders tanding of the technologies .

Chapter Two Telecommunicat ions Fundamenta l s . Communicat iontechnology i s provided in a bas ic to complex order. The chapters tar t s wi th copper based t ransmiss ion media and s teps the readerthrough a progress ion of t e rminology tha t inc ludes : f iber op t ics ,wi re less , v ideo mul t ip lex ing and Ethern et sys tems .Chapter Three Telecommunicat ions & The Nat ional Archi tec ture .The chapter i s a genera l look a t the re la t ionship ofte lecommunicat ions sys tems des ign and the Nat ional ITSArchi tec ture and NTCIP. The reader wi l l be made aware of thefac t tha t NTCIP i s no t a s tandard , bu t a pro tocol tha t def inesthe re la t ionship of the many curren t (and developing)communicat ions s tandards for use in a t raff ic s ignal , f reewaymanagement , o r t ranspor ta t ion sys tem.Chapter Four Developing the Telecommunicat ion Sys tem. Thischapter provides the reader wi th a sys tem engineer ing approachto the des ign of a communicat ions sys tem that suppor t s t raff icand t ranspor ta t ion requi rements . The chapter provides a s tep-by-s tep process tha t should resu l t in a communicat ion sys temrequi rements analys i s and pre l iminary des ign . The pr imary ax iom

that dr ives the des ign of a communicat ions sys tem i s - there areno absolu tes ! For mos t communicat ion sys tems there are usual lysevera l ways to achieve the des i red resu l t s . A qual i f i edcommunicat ions sys tem des igner wi l l genera l ly present severa ld i fferen t approaches and ask the pro jec t manager to make adecis ion .Chapter F ive - Communicat ions for F ie ld Devices . The chapterprovides an in-depth look a t bas ic sys tem conf igura t ions for f i e lddevices used in t raff ic s ignal and f reeway management sys tems .Each f ie ld device has a speci f ic se t o f communicat ions

requi rements .Chapter S ix Communicat ion Sys tem Maintenance . Main tenance ofa te lecommunicat ion sys tem i s essent ia l . Opera tors of thesesys tems must provide for the care and feeding of the networksthat connect a l l f i e ld devices and opera t ional cen ters . Thechapter d i scusses the need to crea te a budget for main tenance ,the re la t ionship of manufacturer warran tees to main tenance , andtechnic ian qual i f i ca t ions .


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Chapter Seven Sys tem Examples . This chapter presents a lookat rea l -wor ld sys tems deployed by depar tments oft ranspor ta t ion . Two sys tems are descr ibed to show how s imi larproblems use d i fferen t approach es to a so lu t ion .Chapter Eight Ins ta l la t ion and Tes t ing . A major cos t e lement inthe deployment of a communicat ions sys tem i s ins ta l la t ion(cons t ruct ion) . Very of ten , p ro jec t managers assume that properins ta l la t ion procedures are be ing used by cont rac tors . Thischapter provides guidel ines for proper handl ing and ins ta l la t ionof communicat ions media . Wire l ine and wi re less media ared iscussed .Chapter Nine - The In ternet . F i rs t conceived and implementednear ly th i r ty years ago , has had a profound effec t on the wayindiv iduals , p r iva te companies and publ ic organiza t ionscommunicate on a day- to-day bas i s . The chapter in th i s documentwi l l p rovide the reader wi th a bas ic unders tanding of thecompos i t ion of the In ternet , the World Wide Web (WWW), how i tworks , and how i t can be used as par t o f an overa l lcommunicat ions and opera t ional s t ra tegy for Traff ic S ignal , FMS,and ITS sys tems .Chapter Ten - The Future . An a t tempt to provide some ins ight onthe genera l fu ture of communicat ions sys tems and the poss ib leimpl ica t ions for the deployment of t e lecommunicat ions sys tems tosuppor t Freeway Management and Traff ic S ignal sys tems .

Appendix A Conta ins addi t ional in format ion tha t readers of th i shandbook can use for inves t iga t ion of addi t ional resources . Thefo l lowing i t ems are inc luded in th i s appendix :

Lis t o f IEEE 802 s tandards and working groups Compar i son of analog voice and voice-over- IP (VoIP) How to ca lcu la te a f iber op t ic loss budget A discuss ion of rura l t e lecommunicat ions requi rements

Glossary Def in i t ions wi l l p rovide a l i s t ing of a l l t e rminology

used in th i s handbook.


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2. CHAPTER TWO FUNDAMENTALS OFTELECOMMUNICATIONS

IntroductionTransmi t ter, rece iver, t ransmiss ion medium - these are the bas ice lements tha t make up a communicat ion sys tem. Every humanbeing i s equipped wi th a bas ic communicat ion sys tem. The mouth(and vocal cords) i s the t ransmi t ter, ears are the receivers , andai r i s the t ransmiss ion medium over which sound t ravels be tweenmouth and ear. The t ransmi t ter and receiver e lements of a da tamodem (such as the type used in a t raff ic s ignal sys temcont ro l ler box) may not be readi ly v i s ib le . However, look a t a

schemat ic of i t s components , and you wi l l see e lements l abeled asXMTR and RCVR. The modems t ransmiss ion medium i s typ ica l lycopper wi re , f iber, o r rad io .Almost a l l communicat ions networks have as the i r bas i s the sameset of Telephony (TelephoNy) s tandards and prac t ices . Ma Bel l( the Bel l Telephone Sys tem andAmerican Telephone &Telegraph , and o thers ) spent

yea rs and b i l l ions of do l l a rscrea t ing , per fec t ing and

main ta in ing ate lecommunicat ions networkdedica ted to provid ing themost re l iab le voicecommunicat ion serv ice in thewor ld . Al l o ther communicat iontechnology and process evolved based on tha t communicat ionsnetwork . Engineers and sc ien t i s t s involved in the development ofnew communicat ion technologies and processes had to makecer ta in tha t the i r product could be used wi th in the ex is t ing

te lephone networks . And, the te lephone company requi redbackward compat ib i l i ty. Telephones manufactured in 1950 s t i l lwork in todays ne twork . Modems manufactured in 1980 s t i l l workin the curren t sys tem.As you read through th i s chapter, and the res t o f the handbook,p lease keep in mind tha t t e lecommunicat ion s tandards , p rac t ices ,and pro tocols were developed for the communicat ion indus t ry. Al l

Some communication transmissionprotocols were developed to workindependently of the Telephone System.Ethernet, for example was created tofacilitate data communication within aclosed system that was contained withinan office building. The Internet wascreated as a closed communicationnetwork.


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of these sys tems must be adapted for use in a t raff ic s ignal orf reeway management sys tem.Today, in Nor th America , Mexico , mos t of Europe and the Paci f icRim, voice serv ices are in fac t sen t as d ig i ta l s ignals andconver ted to analog jus t before leav ing (and ar r iv ing a t ) theserv ing cent ra l o ff ice , a t the end-user po in t s . The reader mightask : I f vo ice i s conver ted to d ig i ta l i snt tha t the same asdata? The answer i s no - d ig i ta l t ransmiss ion does notau tomat ica l ly infer da ta communicat ions compat ib i l i ty. Analogt ransmiss ion sys tems can , and do , car ry data . Inte lecommunicat ions , d ig i ta l and analog are d i s t inc t forms ofcommunicat ion t ransmiss ion . This chapter provides informat ionabout the bas ics of t e lecommunicat ions - the t ransmiss ion media

and t ransmiss ion sys tems , as wel l as an explanat ion of thedi fferences between analog and d ig i ta l t ransmiss ion . Transmiss ionmedia are those e lements tha t p rovide communicat ion sys temswi th a pa th on which to t ravel . Transmiss ion sys tems are thoseelements (hardware and sof tware) tha t p rovide management ofthe communicat ion process andthe use of the t ransmiss ion path .The te lecommunicat ions wor ldwould be very s imple i f thedis t inc t ion between t ransmiss ionmedia and sys tems (pro tocols )were eas i ly def ined . Of ten , aspeci f ic t ransmiss ion sys tem wi l lon ly work wi th in a speci f icmedium. Spread Spect rum Radiois one example . Radio (RF) i s thet ransmiss ion medium, and spreadspect rum i s the t ransmiss ion sys tem (pro tocol ) . Al though i t i sposs ib le to crea te a spread spect rum communicat ions s ignal overwire l ine , the process i s no t typ ica l ly used because there are

o ther more eff ic ien t methods of t ransmiss ion s ignal ing .Therefore , spread spect rum t ransmiss ion s ignal ing i s a lmos ta lways associa ted wi th RF. There i s a lways a poin t a t which theSpread Spect rum Radio sys tem must in ter face wi th anothert ransmiss ion medium, and/or sys tem. This i s accompl i shed byconver t ing f rom RF to a wi re l ine s ignal ing pro tocol . Thete lecommunicat ions process can be v iewed as an excel len t exampl eof mul t i -modal i sm.

F o r p u r p o s e s o f t h i s d i s c u s s i o n ,v o i c e i s a n y t r a n s m i s s i o n t h a tc a n b e s w i t c h e d t h r o u g h t h eC a r r i e r n e t w o r k s i n a n a n a l o g

f o r m a t . T h i s i n c l u d e s d a t at r a n s m i t t e d w i t h i n a v o i c ec h a n n e l u s i n g a m o d e m . D a t a i sa n y d i g i t a l t r a n s m i s s i o n t h a tc a n n o t b e s w i t c h e d t h r o u g h t h eC a r r i e r n e t w o r k s .


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The chapter i s d iv ided in to sec t ions tha t cover Transmiss ion Media Transmiss ion S ignal ing Basic Telephone Serv ice Mult ip lex ing High Capaci ty and Broadband Transmiss ion

Sub- topics in the sec t ions look a t : Media Cons idera t ion Factors (why use one over another) Differences between voice a nd data s ignal ing Video Transmiss ion (CODECS & Compress ion) T-1 Communicat ion SONET, WDM & Ethernet Wireless

Transmission MediaTransmiss ion media are the h ighways and ar ter ies tha t p rovide apath for t e lecommunicat ions devices . There i s a genera l t endencyto say tha t one t ransmiss ion medium i s be t ter than another. Infac t , each t ransmiss ion mediumhas i t s p lace in the des ign ofany communicat ion sys tem. Eachhas character i s t i cs which wi l lmake i t the ideal medium to usebased on a par t i cu lar se t o fc i rcumstances . I t i s impor tan tto recognize the advantages of each and develop a sys temaccord ingly.Transmiss ion eff ic iency i s genera l ly v iewed as the amount of

s ignal degradat ion crea ted by the use of a par t i cu lar t ransmiss ionmedium. The t ransmiss ion medium presents a barr ier to thecommunicat ion s ignal . The barr ier can be measured by manydi fferen t fac tors . However, one common ques t ion i s asked abouta l l communicat ion media . How far wi l l the communicat ion s ignalenergy t ravel before i t becomes too weak (or d i s tor ted) to becons idered unsable? There i s equipment avai lab le to ex tend thedis tance for t ransmi t t ing a s ignal , bu t tha t adds to the overa l lcos t and complexi ty of deployment .

Factors to consider whenchoosing t ransmiss ion mediainc lude : cos t , ease o f ins ta l la t ionand main tenance , ava i lab i l i ty, andmost impor tan t , e ff ic iency oft ransmiss ion .


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M EDIA C ONSIDERATION F ACTO RS

Ease of ins ta l la t ion of the communicat ion medium i s re la t ive lys imple to def ine . Genera l ly, a l l communicat ion media requi re carewhen being ins ta l led . The ins ta l la t ion should be accompl i shed byt ra ined and knowledgeable technic ians and managers . Forpurposes of th i s d i scuss ion , cons ider the re la t ive degree ofd i ff icu l ty for the p lacement of the t ransmiss ion medium. Cables( f iber or copper) requi re a suppor t ing inf ras t ructure , as doesrad io or in f rared . Cons ider the fo l lowing:I f you are p lanning to use f iber op t ic (or copper cable) and thesys tem plan ca l l s for cross ing the Delaware River, there wi l l bes igni f icant ins ta l la t ion (cons t ruct ion) chal lenges . Thecons t ruct ion may requi re a bore under the r iver, o r f ind ing asu i tab le br idge . Ei ther of these methods may add s igni f icant ly to

your budget . Wi re l es s mi gh t s eem l ike a good op t ion . I te l iminates the need to f ind a su i tab le cross ing locat ion for yourcable . However, you wi l l need to p lace the an tenna a t suff ic ien theight to c lear t rees bui ld ings and o ther ob jec t s , and account fo rter ra in d i fferences on both s ides of the r iver. Local res idents ofthe nearby Yacht Club condominiums may complain about the rad iotower spoi l ing the i r v iew of the sunset . Dont forget to add in thecos t of h i r ing a graphic ar t i s t to crea te a draw ing tha t shows howlovely the rays of the se t t ing sun are when ref lec ted off therad io tower.Some products may be morereadi ly avai lab le than o thers .For example , the mos tcommon type of f iber cableavai lab le i s ou ts ide p lan twi th armor sh ie ld ing , 96s t rands of s ing le mode f iberar rayed in loose buffer tubes , on 15 ,000 foot ree l s . Make cer ta inthat you a l low enough t ime for product to be manufactured ,especia l ly i f a specia l cab le or hardware conf igura t ion i srequi red . Avai lab i l i ty of product due to manufactur ing delays wi l limpact on overa l l p ro jec t schedule and may impact on overa l lpro jec t cos t s .Cables tha t conta in combinat ions of d i fferen t types of f ibers t rands such as s ing le mode and mul t imode f ibers , o r mix tures ofcopper and f iber, o r odd (d i fferen t f rom s tandard put -ups)

Put-ups the te rm cab lemanufac tu rers use to descr ibe theconf igura t ion o f a cab le . Theexpress ion i s o f ten used in thefo l lowing manner : The cab le i sava i lab le in 5000 foo t pu t -ups .


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numbers of f iber s t rands wi l l requi re more t ime to produce andcould add severa l months to the del ivery cycle .F iber, copper, rad io , in f rared a l l have d i fferen t t ransmiss ioncharacter i s t i cs . F iber i s cons idered to have the bes t overa l lcharac ter i s t i cs for t ransmiss ion eff ic iency. That i s , theeffec t ive loss of s ignal s t rength over d i s tance . Cable i s ra ted bythe manufacturer for s ignal loss . S ignal lo ss fac tors are s ta ted interms of dB per 1000 meters . Typica l s ing le mode f iber may havea s ignal a t t enuat ion fac tor of be tw een 0 .25 dB/km and 0 .5 dB/km.The cable manufacturer wi l l p rovide a speci f ica t ion descr ip t ionfor each product they offer. In theory, you can send a s ignalfur ther on f iber than v ia mos t o ther t ransmiss ion media .However, cons ider tha t rad io s ignals a t very low f requencies(below 500 k i loher tz) can t ravel for thousands of mi les . This typeof rad io s ignal can be used to car ry data , bu t very impract ica l foruse in t raff ic s ignal and f reeway management sys tems . VLF rad ios ignals are only capable of eff ic ien t ly car ry ing data a t very lowbi t ra tes . This type of sys tem was used by the Associa ted Pressorganiza t ion to t ransmi t news ar t i c les be tween Europe and Nor thAmerica , and i s a l so used by the Mi l i t a ry for very long d i s tancedata communicat ions .Main tenance and opera t ional cos t s are two o ther fac tors tha tshould be cons idered when compar ing t ransmiss ion media for anygiven appl ica t ion . F iber op t ic cable can be ins ta l led in condui t s ixfee t be low grade , and never touched for decades . Main tenance ofthe f iber cable i s min imal . Microwave sys tems may be cons t ructedin less t ime and a t a lower cos t than f iber cable p laced incondui t , bu t the tower s i t es requi re s ign i f icant ly moremain tenance , inc luding re-pain t ing the tower, and annualinspect ions for rus t .In summary, t ake a l l o f the a t t r ibu tes of the poten t ia l mediathat could be used for a speci f ic appl ica t ion and determine which

wi l l p rovide the mos t bang for the buck. This does not a lwaysmean most bandwidth , h ighes t t ransmiss ion speed , eas ies t toins ta l l , o r lowes t cos t - a l l fac tors tha t may inf luence your choiceof t ransmiss ion media . The bes t media are the ones tha t wi l lsuppor t as many of the sys tem requi rements as poss ib le and helpto assure sa t i s fac t ion wi th overa l l per formance.


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W IRELINE M EDIA

We begin wi th bas ic in format ion about the mos t common types oft ransmiss ion media used today:

Copper Wire Fiber Opt ics Radio Frequency (Wire less ) Free Space Opt ics

Many engineers wi l l a rgue tha t one t ransmiss ion medium i s thebes t , o r be t ter than some of the o thers . The reader should keepin mind tha t each medium has advantages and d i sadvantages .Which medium i s bes t depends upon the purpose of the

communicat ions sys tem and the des i red end resu l t s . In fac t , mos tsys tems are a hybr id . That i s , two or more media are combined toeffec t the mos t eff ic ien t communicat ion network inf ras t ructure .There are many t raff ic s ignal sys tems tha t combine a twis tedcopper pa i r in f ras t ructure wi th wi re less l inks to serve par t o fthe sys tem. The decis ion to crea te th i s type of sys tem may havebeen based on economics , bu t tha t i s cer ta in ly one of the reasonsto choose one medium over another, o r to combine the use ofsevera l .

Copper Media

The e lec t r ica l p roper t ies of copper wi re crea te res i s tance andin ter ference . The fur ther communicat ion s ignals t ravel the morethey are weakened by the e lec t r ica l p roper t ies associa ted wi ththe copper cable . E lec t r ica l , res i s tance wi th in the copper mediumslows down the s ignal or f low of curren t . The e lec t r ica lproper t ies of copper wi re are the key fac tors tha t l imi tcommunicat ion t ransmiss ion speed , and d i s tance . However, i t wasthose same proper t ies together wi th cos t , ease of manufacture ,ab i l i ty to be drawn in to very th in s t rands , and o thers tha t madecopper a log ica l choice for i t s se lec t ion as a communicat iont ransmiss ion medium, and a conductor of e lec t r ic i ty. Aluminumand gold are a l so used for communicat ion purposes , bu t go ld ( themost eff ic ien t ) i s too expens ive to use for th i s purpose andaluminum is no t an eff ic ien t conductor for communicat ionpurposes .There are two pr imary types of cables conta in ing copper wi reused for communicat ion :


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Twis ted Pai r Coaxia l

Twis ted Pa i r

Communicat ion s ignals sen t over copper wi re are pr imar i ly d i rec te lec t r ica l curren t (DC) which i s modula ted to represent af requency. Any o ther e lec t r ica l curren t near the communicat ionwire ( inc luding o ther communicat ion s ignals ) can in t roducein ter ference and noise . Mul t ip le communicat ion wi res wi th in acable bundle can induce in ter fer ing e lec t ro-magnet ic curren ts , o rcross - ta lk . This happens when one s ignal wi th in the cable i s sos t rong tha t i t in t roduces a magnet ic f i e ld in to an ad jacent wi re ,or communicat ion pai r. Energy sources such as power t ransmiss ion

l ines , o r f luorescent l igh t ing f ix tures can cause e lec t romagnet icin ter ference . This in ter ference can be minimized by twis t ing apai r o f wi res around a common axis , o r by the use of meta l l i csh ie ld ing , or bo th . The twis t ing effec t ive ly crea tes a magnet icsh ie ld tha t he lps to minimize cross ta lk .Twis ted pai r i s the ord inary copper wi re tha t p rovides bas icte lephone serv ices to the home and many bus i nesses . In fac t , i t i srefer red to as P la in Old Telephone Serv ice (POTS) . The twis tedpai r i s composed of two insu la ted copper wi res twis ted around oneanother. The twis t ing i s done to prevent oppos ing e lec t r ica l

curren ts t ravel ing a long the ind iv idual wi res f rom in ter fer ingwi th each o ther.Twis ted copper pa i r, i s what Alexander Bel l used to make thef i rs t t e lephone sys tem work and i s genera l ly the mos t common

t ransmiss ion medium used today.A broad genera l iza t ion i s tha ttwis ted copper pa i r i s in fac tthe bas i s for a l lt e lecommunicat ion technologyand serv ices today. Ethernet or ig inal ly developed to work overcoaxia l cab le - i s now as tandard based on twis ted pai r.By compar i son , a bas ic vo icete lephone conversa t ion uses one(1) twis ted pai r, where as anEthernet sess ion uses a t l eas ttwo (2) twis ted pai r (more about

F ig u re 2 -1 : R J -4 5 C o n n ec to r


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Ethernet l a ter in th i s chapter ) .Each connect ion on twis ted pai r requi res bo th wi res . S ince some t e lephone se t s or desk top locat ions requi re mul t ip le connect ions ,twis ted pai r i s somet imes ins ta l led in two or more pai rs , a l lwi th in a s ing le cable . For some bus iness locat ions , twis ted pai r i senclosed in a sh ie ld tha t funct ions as a ground. This i s known assh ie lded twis ted pai r (STP) . Ordinary wi re to the home i sunshie lded twis ted pai r (UTP) . Twis ted pai r i s now f requent lyins ta l led wi th two pai rs to the home, wi th the ex t ra pa i r makingi t poss ib le to add another l ine - perhaps for modem use .Twis ted pai r comes wi theach pai r un iquely co lorcoded when i t i s packagedin mul t ip le pa i rs .Di fferen t uses such asanalog , d ig i ta l , andEthernet requi red i fferen t pa i r mul t ip les . There i s an EIA/TIA s tandard for co lorcoding of wi res , wi re pa i rs , and wi re bundles . The co lor codingal lows technic ians to ins ta l l sys tem wir ing in a s tandard manner.A bas ic s ing le t e lephone l ine in a home wi l l use the red and greenwire . I f a second phone l ine i s p rovided , i t wi l l use the yel low andblack wi re . The most commoncause of t e lecommunicat ionsys tem problems i s incorrec twi r ing . This wi r ing pro tocol i sfor s tandard te lephone se t

jack con nect ions . D ata sys t emsuse d i fferen t ar rangementsand co lor codes . The most common i s the EIA/TIA s tandard .P lease note tha t NEMA and ICEA have co lor codes for e lec t r ica lwi re . Do not confuse these wi th te lecommunicat ion wi re co lorcoding s tandards .

Twis ted pai r i s ca tegor ized by thenumber of twis t s per meter. A grea ternumber of twis t s provides morepro tec t ion agains t c ross ta lk , and o therforms of in ter ference and resu l t s in abet ter qual i ty of t ransmiss ion . For da tat ransmiss ion , be t ter qual i ty equates to

fewer t ransmiss ion er rors . Later in th i s chapter, we l l look a t the

Cat 3 cab le i s considered to bethe s tandard fo r bas ic te lephoneand Etherne t se rv ices . However,CAT 5 i s be ing dep loyed as arep lacement and in a l l newinsta l la t ions .

EIA/TIA prov ides a co lo r code and wir ingstandard fo r RJ-45 Connectors . Thestandard i s EIA/TIA 568A/568B. Theses tandards u t i l ize 4 twis ted pa i r, becausethe RJ-45 connec tor has 8 te rmin a ls .

F ig u re 2 -2 : Tw is t ed P a i r C ab le


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effec t s of t ransmiss ion er rors as they impact on throughput anddelay t imes .There are two types of twis ted pai r cab les used for mos t in -bui ld ing s i tua t ions today - Category 3 UTP (CAT 3) and Category5 UTP (CAT 5) . However, as of the wr i t ing of th i s handbook, a l lnew and rep lacement ins ta l la t ions use CAT 5 . These cables havebeen developed based on a se t o f s tandards i s sued by theEIA/TIA (Elec t ronic Indus t ry Associa t ion /Telecommunicat ionsIndus t ry Associa t ion) . CAT 3 i s used pr imar i ly for t e lephonecabl ing and 10Base-T ins ta l la t ions , whi le CAT 5 i s used to suppor t10/100Base-T ins ta l la t ions . CAT 5 wi r ing can a l so be used forte lephone sy

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