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Chapter 3 11

Transmission Media

Chapter 3

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Chapter 3 2

Chapter Objectives

Discuss characteristics of cables

List the various types of copper wired cables

Discuss fiber optic cables

List the various types of wireless transmission media

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Chapter 3 3

Recall - I

Topology is a pattern of computer devices anddescribes the way in which these devices are

connected

The disadvantages of bus topology are:

Entire network gets affected if main cable breaks

Terminators are required at both ends of backbone

cable

Difficult to detect the faulty device Limited number of devices can be attached

Heavy traffic degrades performance

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Chapter 3 4

Recall - II

The advantages of ring topology are:

Easier to mange as compared to Bus network

Handles large volume of traffic

Very reliable and offers great speed

Provides a good communication over a long distance

No terminators are required

Types of mesh topology are:

Full mesh topology Partial mesh topology

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Chapter 3 5

Characteristics of Cables

Segment Length

Length of single wire Attenuation Indicates loss of signal

Bandwidth Amount of data carried by cable

Number of Segments Maximum number of

segments in network

Cost Copper cables are cheapest, fiber optic

cables are expensive

Interference susceptibility and crosstalk

Definesconcept of electronic interference on cables

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Chapter 3 6

Types of cables

Copper medium is the cheapest mode of data transfer

Types of cables

Coaxial cable Twisted pair cables

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Chapter 3 7

Coaxial cable

Consist of a solid copper core surrounded by aninsulator mainly made up of Poly Vinyl Chloride(PVC) or Teflon

Coaxial cables are less prone to interference (bothinternal and external)

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Chapter 3 8

Types of Coaxial cable

Coaxial cables are mainly divided into fourcategories

Types of

Coaxial cables

RG58 RG8 RG6 RG59

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Chapter 3 9

RG58

Maximum segment length is 200 meters

Interference protection is better than twisted pair

cables

Offers resistance of 50 ohms BNC-T connector is used to connect this cable

Used in thinnet (10BASE2) network

Mostly used in changing environments

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Chapter 3 10

RG8

Maximum segment length is 500 meters

Interference protection is good compared to any

copper cable

Offers resistance of 50 ohms BNC-T or Vampire Tap connector is used to connect

this cable

Used in 10BASE5 network

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Chapter 3 11

RG6

Broadband quad-shielded

cable that offers an

impedance of 75 ohms

Provides lower attenuationcharacteristics

Useful in cable TV, CCTV

and satellite dish antenna

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Chapter 3 12

RG59

Solid conductor is

surrounded by a foam

polyethylene dielectric

Offers impedance of 75ohm

Useful in security

camera, cable TV and

home theatre

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Chapter 3 13

Twisted Pair Cables

A pair of cables twisted around each other forms a twistedpair cable.

Twisted Pair cables

UnshieldedTwisted Pair

ShieldedTwisted pair

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Chapter 3 14

UTP Cables

Pair of unshielded wires

wound around each other

Easily gets affected by

EMI, RFI and crosstalk Cable offers resistance of

50 ohms

Maximum segment length

is 100 meters

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Chapter 3 15

UTP Cable Types

Cat 7

Cat 6

Cat 5eCat 5

Cat 4

Cat 3

Cat 2

Cat 1

UTP

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Chapter 3 16

STP Cables

Pair of wires wound

around each other is

placed inside shield

Better protection fromEMI, RFI and crosstalk

as compared to UTP

Offers resistance of 50

ohms Maximum segment

length of 100 meters

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Chapter 3 17

Case Study 1

The Mumbai branch of MoneyMaker bank has

multiple departments, which are on different floors in

the same building. Each department is

interconnected using UTP cables. John, the networkadministrator has set up a client server environment

and has used a star topology. The employees of the

bank are unable to transmit data and information

from one department to another in an efficientmanner

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Chapter 3 18

Problem

Data and information cannot be transmitted betweenthe departments efficiently

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Chapter 3 19

Suggested Solution

The problem is caused due to EMI emitted by the

electrical transformers. John should use STP cables

to interconnect the different departments located oneach floor as STP provides better protection from

EMI. The computers inside each department can be

interconnected using UTP cables.

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Chapter 3 20

Fiber Optic Medium

Consists of centre glass core surrounded by cladding Electrical signals are converted into light signals

A phenomenon called as total internal reflection is

used for transmission

LED or laser is used to transmit signal

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Chapter 3 21

Fiber Optic Cable Characteristics

Bandwidth Carries large amount of data ranging

from 100 Mbps to 1 Gbps

Segment Length Transmits data signals over

larger distance Interference No electric signals pass through

these types of cables thus providing security

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Chapter 3 22

Fiber Optic Cable Types

Fiber optic cables can carry signals in a singledirection.

Fiber Optic Cable

Types

Single Mode Multi mode

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Chapter 3 23

Single Mode Fiber Optic cable

A type of cable that has only a single strandof glass fiber with a thin diameter.

Fiber optic cables that use lasers are knownas single mode cable.

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Chapter 3 24

Multi Mode Fiber Optic cable

A type of cable that contains a glass fiber with alarger diameter.

It is a 62.5/125 micrometer fiber cable.

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Chapter 3 25

Fiber Optic Cable Connectors

Straight Tip (ST) Joins individual fibers to optical

devices

Subscriber Connector (SC) Attaches two fibers to

send and receive signals Medium Interface Connector (MIC) Joins fiber to

FDDI controller

Sub Miniature Type A (SMA) Uses individual

connectors for each fiber stand Fiber Jack Attaches two fibers in snap lock

connector

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Chapter 3 26

Case Study 2

The Chennai branch of MoneyMaker bank has a

database server. All departments are connected to

this server using coaxial cables. These departmentsare unable to retrieve and update information from

the server spontaneously. It takes a lot of time to get

updated information.

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Chapter 3 27

Problem

The employees of the bank are unable to retrieve

information from the database quickly.

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Chapter 3 28

Suggested Solution

The problem is caused due to the lower transmissionspeeds provided by the coaxial cables. These cables

provide a maximum transfer rate of 10 Mbps. Thus, if

all departments of the bank try to access the

information from the server, the speed slows down.To increase the data transfer rate, the network

administrator should use UTP Cat 6 twisted pair

cables. This cable provides higher bandwidth and

higher data transfer rate as compared to coaxialcables.

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Chapter 3 29

Wireless Medium

Unguided form of transmission medium

Transmitters and receivers are used to send and

receive signals

Involves use of electromagnetic waves such asmicrowave, infrared, radio waves etc.

Wireless medium is useful in connecting large

geographical areas

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Radio Waves

Line of sight between devices is not required

Frequencies used are VLF, LF, MF, HF, VHF, UHF,

SHF and EHF

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Chapter 3 31

Microwave

High frequency EM wave that is used for point to point

communication

Microwave Categories:

Terrestrial

Relay towers are used to transmitradio signals between earth stations

Satellite Radio signals are transmitted between

different base stations using satellites

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Chapter 3 32

Infrared Transmission

Uses Infrared lights for transmission and receptionof signals

Line of sight must be maintained between the

devices

Mainly used in LAN environments

LEDs or Injection Laser Diode (ILD) is used to

transmit information and photodiodes are used to

receive the signals

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Chapter 3 33

Case Study - 3

Money Maker Bank plans to link all its branches

located across India to a centralized server

located in Mumbai. As all the branches are

located at various geographical locations, thebank plans to maintain an account of all the

transactions of each and every branch. The

overhead cost of the current network is too

high. So the network administrator wants to use

a cost effective way.

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Chapter 3 34

Problem

Identify the type of setup required to connect

various branches to the central server in a costeffective manner.

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Chapter 3 35

Suggested Solution

The bank should establish a wireless network

from all the branches to the central server. This

will reduce the cost of installing cables for

interconnecting the branches. This will alsoreduce the overhead cost of maintenance of

cables, as it is costlier to connect all the

branches, which are spread in India, using

cables.

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Chapter 3 36

Media Comparison

Characteristics UTP STP Coaxial Cables Fiber Optic Cables

Bandwidth 10 Mbps100 Mbps 10 Mbps100 Mbps 10 Mbps 100 Mbps - 1 Gbps

Maximum cable segment 100 meters 100 meters 200500 meters 2 k.m.100 k.m.

Interference rating Poor Better than UTP Better than twisted pairwires

Very good as comparedto any other cable

Installation cost Cheap Costly than UTP Costly than twisted pair

wires

Most costly to install

Bend radius 360 degrees / feet 360 degrees / feet 360 degrees / feet or 30

degrees / feet

30 degrees / feet

Security Low Low Low High

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Chapter 3 37

SummaryI

Networking hardware involves all peripheral devices,interface cards and other components such as cablesand wires that are used to establish network connection

All cables have certain characteristics such as segmentlength, bandwidth, crosstalk, attenuation, interferencesusceptibility, cost and number of segments

Different types of medium are available for transmittingdata over the network such as copper medium, fiber

optic medium and wireless medium Copper medium includes coaxial cables and twisted pair

cables

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Chapter 3 38

SummaryII

Twisted pair cable consists of a pair of cables that is

twisted around each other

Two types twisted pair cable are STP and UTP

Crosstalk is a phenomenon in which signals of one wireinterfere with the signals transmitted over the other wire

To avoid crosstalk, a pair of wires wound around each

other and each pair is placed inside a protective foil wrap

Types of UTP cables are Cat 1, Cat 2, Cat 3, Cat 4, Cat5, Cat 5e, Cat 6 and Cat 7

STP cable types include Cat 5e and 150 ohm shielded

cable

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Chapter 3 39

SummaryIII

Coaxial cables consist of a solid copper core that issurrounded by an insulator which is again covered by amesh like ground wire and an outer cover known as asheath

Thinwire or RG-58 cable is approximately 0.64 cm indiameter and is used in constantly changingenvironments

BNC connector is used to connect devices to the thinnet

coaxial cable network RG-8 cable is approximately 1 cm in diameter and used

as a backbone cable

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Chapter 3 40

SummaryIV

For RG-6 cable, the center conductor is 1.05 mm in

diameter and for RG-59 cable is 0.86 mm

A fiber optic cable consists of a centre glass core that is

surrounded by a glass cladding, Kevlar fibers and anouter sheath material

LEDs and lasers are used to transmit light signals

through the fiber optic cables

There are two types of fiber optic cables availablenamely single mode and multi mode

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SummaryV

The primary types of connectors used to connect fiber

cables are ST, SC, SMA, Fiber Jack and MIC

In wireless medium, signals are transmitted through air

and space using radio and satellite networks High frequency radio waves used for point to point

communication of audio, data and video signals are

called as microwaves

Infrared wireless transmission networks use Infraredlights to send and receive signals