Unit 1: Introduction and Physical Layer Topic 7: Unguided Media

1. SNS COLLEGE OF ENGINEERING
Kurumbapalayam(Po), Coimbatore – 641 107
Accredited by NAAC-UGC with ‘A’ Grade
Approved by AICTE, Recognized by UGC & Affiliated to Anna University, Chennai
Department of Information Technology
Course Name : CS8591 Computer Networks
III Year / V Sem
SNSCE / IT/ Sem V / S Rijutha / AP / IT
Unit 1: Introduction and Physical Layer
Topic 7: Unguided Media

2. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Recap - Guided Media
Transmission Media
Unguided Media
Guided Media
Twisted Pair
cable
Coaxial
Cable
Radio
Waves
Microwaves
Fibre Optic
Cable
Infrared
Waves
Shielded
Twisted Pair
cable
Unshielded
Twisted Pair
cable

3. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Unguided Media
⮚Surrounded with all kind of
electromagnetic waves
⮚Waves transmitted - Radio, TV
stations
⮚Generated from - Wifi, Phones,
ovens, computer, fire, radiator and sun
⮚Visible light
⮚Dizzy, lightheaded etc

4. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Unguided Media
➢ Transmits the electromagnetic waves without using any physical medium.
➢ Therefore it is also known as wireless transmission.
➢ Air is the media through which the electromagnetic energy can flow easily.
➢ Propagation methods
○ Ground Propagation - Waves travel through the lowest portion
○ Sky Propagation - High frequency waves radiate upward in ionosphere, reflected back to earth
○ Line of sight propagation - Very high frequency travel in straight lines (Antenna to Antenna)

5. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Electromagnetic
Spectrum
RADIO MICROWAVES INFRARED VISIBLE
LIGHT
ULTRA
VIOLET
X RAY GAMMA
RAYS

6. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Electromagnetic
Spectrum
Broadcast
Radio and
television
Cooking, radar,
telephone and
other signals
Transmit
heat from
sun, fire and
radiators
Able to see Absorbed
by skin,
fluorescent
tubes
View
inside of
body and
objects
Used in
medicine
for killing
cancer
cells
➢EM spectrum classified and arranged based on frequencies
➢Different bands with different name
➢From low frequencies to higher frequencies (1 Hz to 10^25 Hz)

7. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Radiowaves and Microwaves
⮚ Range from 3KHz to 300GHz
⮚ Radio waves - 3Hz to 1GHz
⮚ Microwaves - IGHz to 300GHz
⮚ Used for wireless communication

8. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Radiowaves and Microwaves
⮚Range from 30Hz to 300GHz
⮚Used for wireless communication
⮚Boundaries are not clearly cut, they are overlapping
⮚Wireless technologies are evolving
⮚Range 9KHz to 100KHz - Radio navigation, Marine or Aeronautical
⮚Given amount of power - travel greater distance with little interference
⮚AM radio - IMHz, Shortwave radio - 10MHz, FM Radio - 100MHz

9. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Radio Waves
⮚ Longest wavelengths in the electromagnetic spectrum.
⮚ Frequencies of radio waves is from 3KHz to 1 GHz.
⮚Omni directional, Propagated in all directions.
⮚Disadvantage, interference
⮚Low and medium frequency, can penetrate wall
⮚Disadvantage, AM radio - receive signals inside building
⮚Multicasting - one sender many receiver
⮚Ex: AM and FM radio, Television, Cordless phone, Paging

10. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Radio Waves

11. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Applications
⮚A Radio wave is useful for multicasting when there is one sender and many
receivers.
⮚An FM radio, television, cordless phones are examples of a radio wave.

12. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Advantages
⮚Radio transmission is mainly used for wide area networks and mobile cellular
phones.
⮚Radio waves cover a large area, and they can penetrate the walls.
⮚Radio transmission provides a higher transmission rate.

13. Microwaves Transmission
SNSCE / IT/ Sem V / S Rijutha / AP / IT
⮚Range from 1GHz to 300GHz
⮚Most relevant to wireless communication
⮚Range 300Mkz to 1GHz - Television
⮚Wifi, Wimax, Cell phone, GPS, Satellite
⮚Unidirectional, antenna aligned, no interference

14. What do Microwaves show us?
SNSCE / IT/ Sem V / S Rijutha / AP / IT
Penetrate haze, light rain and
snow, clouds and smoke, these
waves are good for viewing the
Earth from space.
The JERS satellite uses
wavelengths about 20 cm in
length (L-band). This is an image
of the Amazon River in Brazil.
This is a radar image acquired
from the Space Shuttle. Mountains
on the edge of Salt Lake City,
Utah.

15. Microwaves Transmission
SNSCE / IT/ Sem V / S Rijutha / AP / IT
⮚ Unidirectional, narrowly focused
⮚ Sending and receiving antenna, aligned
⮚ Microwaves are of two types:
➢ Terrestrial microwave
➢ Satellite microwave
⮚ Frequency between 1 and 300 GHZ
⮚ Unicast Communication

16. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Terrestrial Microwave Transmission
⮚ Line-of-sight wireless communication
⮚ High frequency beams
⮚ Used for long distance transmission
⮚ Parabolic dish transmitter
⮚ Used for voice and TV transmission

17. Satellite Microwave Transmission
SNSCE / IT/ Sem V / S Rijutha / AP / IT
⮚Microwave relay station
⮚Use to link two or more ground stations
⮚Receive and transmit using Transponder
⮚Cover large area
⮚Life time 10 to 15 years
⮚Launching satellite is costly

18. Satellite Microwave Transmission
SNSCE / IT/ Sem V / S Rijutha / AP / IT
⮚ Private business networks
⮚ Television distribution
⮚ Long distance telephone conversation
⮚ Global Positioning Service

19. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Advantages:
⮚ No cables needed.
⮚ Multiple channel available
⮚ Wide Bandwidth
Disadvantage:
⮚Line of sight requirement
⮚ Expensive towers and repeaters
⮚ Interference
Microwaves Transmission

20. Infrared Transmission
SNSCE / IT/ Sem V / S Rijutha / AP / IT
⮚Lie between the visible and microwave portions of the
electromagnetic spectrum.
⮚Light rays which are longer than light but shorter than
radio waves.
⮚The heat that we feel from sunlight, a fire, a radiator
⮚ Short range communication
⮚ Frequency from 300 GHz to 400THz
⮚ High frequency - cannot penetrate wall
⮚ Ex: Remote control, night vision goggles, infrared
thermometer etc.

21. How can we "see" using the Infrared?
SNSCE / IT/ Sem V / S Rijutha / AP / IT
Humans, at normal body
temperature, radiate
most strongly in the
infrared at a wavelength
of about 10 microns.
Cat in the infrared. The
orange areas are the
warmest and the white-
blue areas are the coldest
Special sensors, like those
aboard the Landsat 7
satellite, record data about
the amount of infrared light
reflected or emitted from
the Earth's surface.

22. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Advantages and Disadvantages
Advantages:
⮚ Secured communication
⮚ Battery - last for long duration due to lower
power consumption.
⮚ Detect motion in daytime and night time reliably.
⮚smaller in size and are more affordable.
Disadvantage:
⮚ It does not work through walls or door
⮚ High power can damage eyes
⮚ It can control only one device at one time
⮚ It supports shorter range
⮚ It performance degrades with longer
distances.

23. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Puzzle

24. SNSCE / IT/ Sem V / S Rijutha / AP / IT
Puzzle - Answer

25. THANK YOU !
SNSCE / IT/ Sem V / S Rijutha / AP / IT
SNSCE / IT/ Sem V / S Rijutha / AP / IT