This document discusses various types of transmission media used for wireless networks. It defines transmission media as materials that can propagate energy waves and notes that while material is not strictly required for electromagnetic waves, they are usually affected by the media they pass through. It then categorizes transmission media as either wired/guided, using conductors like wires, or wireless/unguided, using radio waves without a physical connection. Examples of wireless media discussed include terrestrial microwave using high-mounted dishes, satellite microwave for long-distance communication, broadcast radio, and infrared for line-of-sight transmission over short distances.

1. Unguided
Network
A WIRELESS APPROACH TO INTERNET..
This Photo by Unknown Author is licensed under CC BY-NC-SA

2. Transmission
Medium
 A transmission medium is a material substance (solid, liquid, gas, or
plasma) that can propagate energy waves. For example, the transmission
medium for sounds is usually a gas, but solids and liquids may also act as
a transmission medium for sound.
 The absence of a material medium in vacuum may also constitute a
transmission medium for electromagnetic waves such as light and radio
waves. While material substance is not required for electromagnetic waves
to propagate, such waves are usually affected by the transmission media
they pass through, for instance by absorption or by reflection or refraction
at the interfaces between media.
 The term transmission medium also refers to a technical device that
employs the material substance to transmit or guide waves. Thus, an
optical fiber or a copper cable is a transmission medium. Not only this but
also is able to guide the transmission of networks.
 Electromagnetic radiation can be transmitted through an optical medium,
such as optical fiber, or through twisted pair wires, coaxial cable, or
dielectric-slab waveguides. It may also pass through any physical material
that is transparent to the specific wavelength, such as water, air, glass, or
concrete. Sound is, by definition, the vibration of matter, so it requires a
physical medium for transmission, as do other kinds of mechanical waves
and heat energy.

3. Transmission and
Telecommunication
 A physical medium in data communications is the transmission
path over which a signal propagates.
 Many transmission media are used as communications channel.
 For telecommunications purposes in the United States,
transmission media are classified as one of the following:
1. Wired (or guided)—waves are guided along a solid
medium such as a transmission line.
2. Wireless (or unguided)—transmission and reception are
achieved by means of an antenna.

4. Classes of
Transmission Media
 Wired or guided media
 Use a conductor such as a wire or a fiber optic cable to
move the signal from sender to receiver.
 Examples include telephone networks, cable television
or internet access, and fiber-optic communication.
 Wireless or unguided media
 Use radio waves of different frequencies and do not
need a wire or cable conductor to transmit signals.
 Examples of applications of radio wireless technology
include GPS units, garage door openers, wireless
computer mice, keyboards and headsets, headphones,
radio receivers, satellite television, broadcast television
and cordless telephones.

5. Unguided or Wireless
Transmission Media
 Transmission and reception are achieved by
means of an antenna
 Directional
 Transmitting antenna puts out focused beam
 Transmitter and receiver must be aligned
 Omni-Directional
 Signal spreads out in all directions
 Can be received by many antennas
 Wireless Examples :
 Terrestrial Microwave
 Satellite Microwave
 Broadcast Radio
 Infrared

6. Terrestrial
Microwave
 Used for long-distance telephone
service
 Uses radio frequency spectrum, from 2
to 40 Ghz.
 Parabolic dish transmitter, mounted
high
 Used by common carriers as well as
private networks
 Requires unobstructed line of sight
between source and receiver
 Curvature of the earth requires stations
(repeaters) ~30 miles apart

7. Satellite Microwave
 Television distribution
 Long-distance telephone transmission
 Private business networks
 Satellite Microwave Transmission
 A microwave relay station in space
 Can relay signals over long distances
 Geostationary Satellites
 Remain above the equator at a height of 22,300 miles
(geosynchronous orbit)
 T0ravel around the earth in exactly the time the earth takes to
rotate
 Satellite Transmission Works
 Earth stations communicate by sending signals to the satellite on an
uplink
 The satellite then repeats those signals on a downlink
 The broadcast nature of the downlink makes it attractive for services
such as the distribution of television programming

8. Radio
 Radio is omnidirectional and
microwave is directional.
 Radio is a general term often
used to encompass frequencies
in the range 3 kHz to 300 GHz.
 Mobile telephony occupies
several frequency bands just
under 1 GHz.
 Repeaters need to be placed
after few miles.

9. Infrared
 Uses transmitters/receivers
(transceivers) that modulate
noncoherent infrared light.
 Transceivers must be within
line of sight of each other
(directly or via reflection ).
 Unlike microwaves, infrared
does not penetrate walls.

10. Thank You
Presented By: Hemant Sarthak