CHAPTER CHAPTER Communication MediaCommunication Media

Chapter Objectives

• Present the functions and features of leading transmission media, both guided and open media

• Guided media– Twisted pair, coaxial cable, optical

fiber and mixed cabling• Open media (space)

– RF, Ultraviolet, Microwave and satellite

Chapter Modules

• Twisted Pair • Coaxial Cable • Optical Fiber • Mixed Cabling • Wireless • Microwave • Satellite Communication

MODULE

Twisted Pair Wire

Questions• What are the two different types of twisted

pair wires that are in use?• Why are the wires twisted?• Name the categories of wires and their

respective uses• What is the role played by bandwidth in the

quality of the wires?• What is a Plenum wire? Where is it used?• Name the types of twisted pair wires that

could be used in high speed LANs such as the Gigabit Ethernet LAN

• Describe the properties of the newer categories of twisted pair wires

Terminology to Remember

• Shielding (Conductive material)• Insulation (Non-conductive

material)– Casing (Plastic material)

Types and Purpose of Twisting

• Types– Unshielded twisted pair (UTP)– Shielded twisted pair (STP)

• Twisting– Minimizes the effect of electromagnetic

interference– The electromagnetic field from one wire

counterbalances the field from the other wire

Shielding and Insulation

• The cables are shielded from electro magnetic interference– In both directions, from outside as

well as inside

• The plastic casing is not to be considered as shielding– It is an insulation against electric

shock

Twisted Pair Cable Illustration

Source: Black Box

Characteristics• Cheap• Easy to install• Generally speaking, different frequencies

may not be assigned to carry different channels on the same twisted pair wire

• Compared to coaxial cables, twisted pair wires have a lower bandwidth– But, recent improvements have contributed

to an increase in bandwidth– Speed is proportional to bandwidth

Quality and Categorization

of the Wires • Twisted pair wires are categorized

according to their quality• Category 3 wires are of the lower

quality• Category 5, 5e, 6 etc. wires are of

higher quality– Partly achieved by having a larger number

of twists in the cable

• Higher category wires such as Cat 6 etc. are now available

Areas of Application

• Phone lines• Used extensively in

telecommunications• LANs

Typical Twisted Pair Connection

Hub/Switch

Twisted Pair Wire

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Reasons for its Increasing Popularity

• Better quality UTP is being produced• Ease of installation superseding its

other limitations• A LAN to be configured with twisted

pair wires requires a hub– A hub based implementation is

preferred because it is easy to install and manage

Gigabit Ethernet Medium

• IEEE 802.3ab Twisted Pair– Cat 5e (350 MHz/ 1Gbps)

• IEEE 802.3z Fiber Optics

LAN Speed

• The following questions apply to the LAN shown in the next slide

• What is the speed of the network?• How could it be upgraded to a

higher speed?

Source: Black Box

Important Areas of Application for Twisted

Pair Wires• LAN

– RJ 45• 10baseT LANs operating at 10 Mbps • 100baseTX LANs operating at 100 Mbps• 1000baseT LANs operating at 1 Gbps • 8 wires

• Telephone wiring connections– RJ 11 (4 wires)– RJ 14 (6 wires)

Wiring a Building or Home

Questions• What are the two different types of twisted

pair wires that are in use?• Why are the wires twisted?• Name the categories of wires and their

respective uses• What is the role played by bandwidth in the

quality of the wires• What is a Plenum wire? Where is it used?• Name the types of twisted pair wires that

could be used in high speed LANs such as the Gigabit Ethernet LAN

• Describe the properties of the newer categories of twisted pair wires

END OF MODULEEND OF MODULE

MODULE

Coaxial Cable

Questions

• Name the two types of coaxial cables– Name different use for each type of cable

• Are they shielded?• What is the difference between

shielding and insulation? • Explain the current replacements for

coaxial cables both at the lower and higher end of the coaxial cable

Questions

• List the uses for thin and thick coaxial cables

• Name the types of LANs that use coaxial cables

A Description of the Coaxial Cable

Copper conductor

InsulatorShielding

Outer casing

Types of Coaxial Cables

• Thin coaxial – Lighter version– Thin Ethernet cable

• Thick coaxial– Original version– Standard Ethernet cable

Thin Coaxial Cable

• Higher bandwidth than twisted pair wires

• Lower bandwidth compared with the thick coaxial able

• More flexible compared to thick coaxial cable

• Cheaper

Type of Thin Coaxial Cable

Used in LAN

• Standardized• 10Base2 cable

– 10M bps– Ethernet– Thin coaxial cable– Bus topology

Thick Coaxial Cable

• Compared to thin coaxial cable– Higher bandwidth – Less maneuverable – More expensive

Thick Coaxial Cables Used in Networks

• Standardized• 10Base5

– 10M bps– Ethernet– Thick coaxial cable – Bus topology

Overall Characteristics of the Coaxial Cables

• Relatively cheap compared to fiber-optic cables

• Wider bandwidth compared to twisted pair wires

• Good transmission characteristics • Used in high-speed synchronous

transmission• Supports broadband communication• Can be tapped for multi-drop

connection

A Typical Coaxial Connection

Bus LAN

Coaxial Cable

A multi-drop connection

Components Used in Connecting a Computer to

a Coaxial Cable

Thin coaxial cable

T connector

Terminator

NetworkInterface

Card

An Example of the Use of Thick Coaxial Cables

Router

Backbone

Coaxial CableSwitch

Thick coaxial cable

Areas of Application for Coaxial Cables

• Ethernet bus LANs• Telephone trunks• Mainframe networks • Cable TVs

Future of Coaxial Cables• Overall use is on the decline• LANs (Lower End)

– Replaced by newer and better twisted pair wires

• Telephone trunks (Higher End)– Fiber cables are replacing coaxial

cables• Mainframes of yesterday or perhaps

today as well – Connected to peripheral devices over

larger networks built on fiber-optic cables and twisted pair wires

Questions

• Name the two types of coaxial cables– Name different use for each type of cable

• Are they shielded?• Are they insulated?• Explain the current replacements for coaxial

cables both at the lower and higher end of the coaxial cable

• List the uses for thin and thick coaxial cables• Name the types of LANs that use coaxial

cables

END OF MODULEEND OF MODULE

MODULE

Fiber Cables

Questions• How does light travel in a fiber cable?

– Name the different types of optical transmission methods

• What is the most appealing aspect of fiber cables?– What are their consequences?

• What are the two different types of fiber cable connections used in practice?

• What are the two different materials that could be used in the production of fiber cables?

• Where are fiber cables used mostly in a LAN?

Fiber Optics Transmission

• Light travels along the path of the fiber by bouncing around its edges

• Propagation methods– Multi-mode step index– Multi-mode graded index– Single mode

IncreasingSpeed

Characteristics

• Very broad bandwidth• Higher transmission speeds are

possible• Signals travel a longer distance• No Electro-magnetic field

– No interference– Signals are difficult to tap

• Smaller size– Multiple fiber strands can be included in

a cable of very small diameter

Fiber-Optic Cable Bandwidth

FiberOptics

Part Of Ultraviolet

Visible

Part Of Infra-red ?

The laser beam could also travel along a fiber optic cable

Fiber Cables

Usage of Fiber Optic Cables

• Long distance telephone cabling (trunks)

• LANs– Used in large networks as the

backbone• An example is the FDDI backbone used in

a number of campuses

– Used for extending cable limitations applicable to networking and other computing devices

A Simple Fiber LAN

Source: Black Box

Types and Cost• Types

– Regular glass fibers– Plastic fibers

• Purer the fibers the better the transmission characteristics

• Cost– Fiber cables are costlier than twisted pair

wires and coaxial cables– The cost has declined over a period of

time– Plastic fiber cables are cheaper than glass

fiber cables

Fiber Usage

• Network backbones• Extending distance between

network connections• Connecting high speed switches

Web Research

• Visit the following link at Corning for a tutorial on fiber optic technology http://www.corning.com/prod_svcs/index.html

• http://www.corningfiber.com/library/lib_premises.htm

Questions• How does light travel in a fiber cable?

– Name the different types of optical transmission methods

• What is the most appealing aspect of fiber cables?– What are their implications?

• What are the two different types of fiber cable connections used in practice?

• What are the two different materials that could be used in the production of fiber cables?

• Where are fiber cables used in the implementation of a LAN?

END OF MODULEEND OF MODULE

MODULE

Mixed Cabling

Questions

• Name a few different types of cable conversions that could be performed using a media converter

Mixed Cabling

• LANs may be constructed with different segments having different cable types

• Devices are available for interfacing the different media

• Optical fiber is often used for high speed links within a LAN of mixed speed ratings

Media Interface

A Mixed Media LAN

Source: Black Box

Identify the components and relate to the previous slide.

Listing of Media and Communication Network

Services

Web Research: Find the meaning of the above terms

Web Research

• Obtain information on twisted pair wires that are of a higher quality than category 5

• Visit www.corning.com to get more information on fiber cables

END OF MODULEEND OF MODULE

MODULE

Microwave

Frequency Range and Propagation

• Microwave frequency range – 10e8 to 10e11– Bandwidth is nearly 10e11 Hz

• Propagation– Over space– Requires line-of-sight

• At higher frequencies the waves tend to behave like light waves

Line-of-Sight Requirement

3o miles limit to offsetEarth’s curvature.

Line of sight isrequired.

Characteristics

• Advantage– Cable laying is not required

• Disadvantage– Can easily be tapped– Encryption is one way of securing the

data from eavesdropping

Applications Areas• Telecommunications

– Used extensively

• LAN – Used for wireless connections

• WANs benefit from microwave• Usage on the increase

– LANs and WANs area– Fueled by FCC's reassignment of part of the

microwave bandwidth from military to civilian use

END OF MODULEEND OF MODULE

MODULE

Satellite Communication

Types

• Geosynchronous Earth Orbit (GEO)• Medium Earth Orbit (MEO)• Low Earth Orbit (LEO)

Geosynchronous Earth Orbit (GEO)

• First satellites to be launched• Remain stationary with respect to

the position of the earth at a high altitude– Balance between the gravity of the

moon and the earth

• Appear to be stationary with respect to a position on earth

Medium Earth Orbit

• Fall to earth after a certain number of years of service

Low Earth Orbit

• Today’s focus – Touted to play an important role in global

communications

• Several being launched under the Iridium project– Usher a new era in global communications– Support computer systems and personal

communicant devices in communicating with one another

Propagation• Requires line-of-sight • Frequencies in use are higher than

those used in microwave– Upload 12 GHz– Download 16 GHz

• GEO– At least 3 satellites are required to

provide total global coverage

Total Global Coverage Using GEO Satellites

I

IIIII

12 GHZ16GHZUpload

Down load

3 satellites are required to cover the earth

Salient Features of Satellite Communications • Uploading and downloading

– Uploading at 12 GHz– Downloading at 16 GHz

• Basic function– Receive the signals from an earth

station, amplify them and then transmit them back to another earth station

Applications• Telecommunications

– Especially for inter-continental communication

• TV broadcast– Usage is increasing

• Navigation and other similar local applications– GPS

Factors Contributing to Expansion of Satellite

Communication

• Reassignment of military frequencies to civilian use

• Anticipated progress in the Iridium project

END OF MODULEEND OF MODULE

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