Fundamentals Of Telecommunication

What is Communication ??

Exchange Of Information

What is Communication??

Exchange Of Information

I get it !!!!!!!!!!!! My Information.

Audio Video Data Signal

Free Space Copper Fiber Optic

Source

Destination

Transfer of information from one place to another

Transmission Medium

How to transfer information??

Some carrier is required to carry information over long distances….

Why???

Through Some Carrier

Limitation: Information cannot go beyond certain distance without the aid of a carrier

Carrier

•Should be capable of carrying information •Can take it through long distance•Should have good speed

•Which is the most suitable carrier??

Electromagnetic Wave

•Highest Known speed 3x108m/s

• Can carry any information through modulation

•Energetic - Can go through long distance

•Supports multiple media Eg: Free space/Copper/Fiber etc..

Electromagnetic Wave

In electromagnetic wave electrical and magnetic fields vary harmonically

Harmonic oscillations at atomic level gives oscillating electric field

Electromagnetic wave generation

(Figure)

Relation between electric and magnetic field

Changing electric field gives rise to changing magnetic field & vise versa

(Perpendicular)

So in electromagnetic wave electric and magnetic fields oscillate perpendicular to each other and

electromagnetic energy transmits perpendicular to both

Figure of a wave

Wavelength = distance travelled in one cycle()

Frequency = Number of cycles per second()

Velocity(v) = x

Velocity of all the electromagnetic wave is same, 3 x 108m/s

Electro Magnetic Spectrum

Block Diagram of a Telecommunication System

What is the other thing required apart from carrier for transmitting signals over longer distances??

Some medium for carrying signals from transmitter to the receiver

Media…..

Different types of media used for transmitting signals….

•Wired : Twisted Pair Co-axial cable Optical fiber

•Wireless(Free space/air):Microwave Satellite

Rx

MEDIA

TxCarrier

Twisted Pair

Twisted pair is made of two copper wires which are covered by plastics or materials that are similar

The insulated wires are twisted to form the communication line,the purpose of twisting the wires is to avoid electrical interference

Twisted pair can be combined into a cable that may consist of two,four,fifty or hundreds of pairs

Twisted pair is the basis of transmission media(Telephone)

Twisted Pair

Coaxial Cable

Coaxial cable contains two conductors which are insulated from one another

The inner conductor is covered by the dielectric and the outer conductor is covered by a shield

Coaxial cable has many applications,for instance cable TV,local networks,short run computer system links and long distance telephone transmission

In local network coaxial cable can support different type of traffic and data

By using FDM,it can carry more than 10,000 channels at a time

Coaxial Cable

Optic Fiber

Optic Fiber(Physical Appearance)

Optic fiber is made up of 3 parts : Core,Cladding and jacket

The inner most part is the core which contains one or more thin fibers that are made up of plastic or glass

Each of the fiber in the core is covered by a cladding which has different optical properties from the core

The outer most part of the optical fiber is made up of plastic or other materials ,which is called the jacket

Optic Fiber

Because of greater performance and higher data rate,the application of optic fiber has dramatically increased in long distance communication and military applications

Optic Fiber

Microwave

Microwave

In terrestrial microwave transmission a pair of towers mounted on top of the towers will transmit signals through air

Microwave antennas are equipped in higher place in order to achieve better transmission effect

Voice transmission,television transmission and the short point to point links will be the major application of microwave transmission

Satellite Communication

Satellite

A satellite consists of several transponders which receive signal from one frequency band,this action is called uplink

The satellite will amplify or repeat the signal to other frequency band,this action is called downlink

A satellite link is called a microwave link

The most application of satellite communication will be long distance telephone transmission

Private business networks and television distribution

Comparison of Twisted Pair,Coaxial Cable and Optic fiber

Twisted Pair Coaxial Cable Optic Fiber

Data Rate/Bandwidth

4Mbps 500Mbps Upto100Gbps

Repeater Spacing 1-10Km 1-10Km 10-100Km

Electromagnetism Affected Affected Not affected

Comparison of Satellite and Optic Fiber

Optic Fiber Satellite

Reconfiguration Not possible Possible

Bandwidth Practically upto10 GHz

36-72MHz

Weather Condition Affected by storm Not affected bystorm

ElectromagneticInterference

Not affected Affected