unguided & guided media

1. Lecture#06
Computer Communications
& Networks CS-576

2. Unguided Media
 Unguided Media or Wireless
Communication transport Electromagnetic
waves without a physical conductor.
 signals are normally broadcast through air
and are available to anyone who has a
receiver capable of receiving them.

3. Unguided Media
 Electromagnetic spectrum for
wireless communication

4. Propagation of Radio Waves
 Radio Wave transmission utilizes s different
types of propagation.
• Ground Propagation
• Sky Propagation
• Line-of-sight Propagation

5. Ground Propagation
 In surface propagation, radio waves travel
through the lowest layer of the atmosphere,
hugging the earth.
 At the lowest frequencies signal emanate in all
direction from
the transmitting antenna and follow the curvature
of the planet.
 Distance depends on the amount of power in the
signal

6. Sky Propagation
 Higher frequency radio waves are radiated
towards the ionosphere(the layer of
atmosphere where particles exist as ions)
where they are reflected back to earth.
 This type of transmission allows for greater
distances with lower output.

7. Line-of-sight propagation
 Very high frequencies signals are transmitted in
straight line from antenna to antenna.
 Antennas must be directional facing each other or
either tall enough or close enough to each other
to avoid earth’s curvature .
 Radio waves can reflect of the objects in the
middle and can reach late to the receiver. These
late signals distort signal.

9. Bands

10. Unguided Media
Wireless transmission waves

11. Radio Waves
 Omni directional Antenna
 Frequencies between 3 KHz and 1 GHz.
 Radio waves are used for multicast
communications, such as radio and television,
and paging systems.

12. Microwaves
 Frequencies between 1 and 300 GHz.
 Microwaves are used for unicast
communication such as cellular telephones,
satellite networks, and wireless LANs.

13. Infrared
 Infrared signals can be used for short-range
communication in a closed area using line-of-
sight propagation
 Frequency range from 300GHz to 400THz.