Guided and Unguided Media.

2.  MEANING:
 Communication: Transmission
 Channel: Passage
 DEFINITION:
 A path through which a information is transmitted from one
place to other is called Communication Channel.
It is also known as communication medium(transmission
tools).

3.  In data Communication channel, data is transmitted in the form
of signals(analog signal)
 The data is measured in bandwidth.
 BANDWIDTH: The amount of data that can be carried
through communication medium, in a unit time is called
Bandwidth . It means number of signals transmitted per
second. It is often expressed in hertz (Hz).
 For Digital signals, It is represented in Bits per second(bps).
 Different transmission media have different bandwidths. The
higher the band width of transmission media , the more
information can be transmitted.

4. TYPES
 There are two types of communication channel. i.e.
 Guided Media .
 Unguided Media .
 Guided media Unguided media

5. FLOW CHART

6. GUIDED MEDIA
 The type of media in which communication devices
are directly linked with each other via cable or
physical media , called guided media.
 It is also called physical transmission media.
 The data signals are bounded to cabling media .
Therefore it is also called bounded media.
 It is mostly used in LAN(Local Area Network)*.
 * A computer network that links devices within a building or
group of adjacent buildings, especially one with a radius of
less than 1 km.

7. EXAMPLES OF GUIDED MEDIA
Twisted pair
or wire pair
cable.
Coaxial
Cable.
Fiber
Optic
cable.
Following are some examples of guided media:

8. TWISTED –PAIR OR WIRE PAIR CABLE
 Twisted pair cable is one of the most commonly used communication media.
 It consist of pair of copper wires . These wire consist of insulating material (such
as plastic).These wires are twisted around each other. Twisting of wires protect
them from interference by external electromagnetic waves.
 It is used for short distance digital data transmission
 Speed: 9600 bps in a distance of 100 meter .
 It is commonly used in (LAN).
 It is used in telephone lines to carry data signals.

9. TYPES OF TWISTED-PAIR CABLE
 There are two types of twisted-pair cable:
 Shielded Twisted-Pair(STP): The word shielded means protected . This
type of cable is surrounded by a protecting material to reduce
electromagnetic interference.
 Unshielded Twisted-Pair(UTP): This type of cable is not surrounded by a
protecting material . It is mostly use in LAN and Telephone. It is used in
security camera.
 DIFFERENCE:
 STP is faster than UTP.
 STP is more expensive than UTP.

10. FIGURE

11. COAXIAL CABLE
 It is also called COAX (to get something).
 It carries signals of higher frequency ranges than twisted
–pair cable.
 It consist of solid copper wire called inner conductor .
Usually inner conductor is surrounded by three layers:
 Inner Insulating Layer: It covers the inner conductor.
 Copper Mesh: Mesh means net. It servers as a ground.
It reduces electromagnetic interference.
 Outer insulating Layer: It covers the copper mesh.
 The whole cable is protected by plastic cover .

12. FIGURE

13.  Coaxial cables are mostly used for long distances.
 These cables are used for cable TV ,telephone and
LAN.
 It provide very high quality data without distortion or
loss of data.
 It can transfer data with very high frequency.
 Its bandwidth is 80 times greater than twisted pair
media .
 It can transmit data with 10(Mbps).
 It is more expensive than twisted wire pair.
USES OF COAXIAL CABLE
BUT

14. FIBER OPTIC CABLE
STRUCTURE:
 It is very fast communication media. It consist of
hundreds of thousands of thin strands(threats) of glass
or plastic . Each strand is called Optical Fiber or
Core. It is as thin as human hair. Each fiber optic is
surrounded by a glass layer called Cladding. The
cladding is protected by plastic coating called Jacket .
An important characteristic of fiber optic is
Refraction*.
 *Refraction is the characteristic of material to either pass of reflect .
 Refraction is the bending of a light wave when it enters a different medium
from the previous one. The change in the speed of light when it crosses one.

15. FIGURE

16. WORKING
 The fiber optic transmit data in the form of light wave. In fiber
optic communication, converters are used on both sides. The
converter at transmitter side converts data from digital signal
to light* waves and transmit over the fiber optics. The
converter at receiver side receives data in the form of light
waves and converts back into the digital form.
 A single fiber optic cable may consist of 50,000 channels.
 *Light wave are electromagnetic waves having frequency from 4×1014 Hz
to 8×1014.

17. CONVERTER

18. ADVANTAGES:
 Fiber Optic cable provides high quality transmission at very high speed.
 Data transfer rate is up to billion bits per second ( usually 1Gbps to
2Gbps).
 Its transmission is not affected by electromagnetic waves.
 Both analog and digital signals can be transmitted.
 It is more reliable.
 It has low data transmission errors.
DISADVANTAGES:
 It is costly.
 It is difficult to install.
USES:
 Today, many telephone and cable TV companies are using fiber optic cables.
 In the near future, all communication system will use fiber optic cables.

19. UNGUIDED MEDIA
 The type of communication in which communication devices
sends and receives data signals through air or space is called
Unguided Media. It is also called wireless transmission media.
 In this type of communication media data is communicated
between communication device in the form of wave.
 Unguided media provides means to transmit data signals but
does not guide a specific path. The data signals are not
bounded to cabling media. Therefore, it is also called
unbounded media.
 This transmission medium is used when it is impossible to
install the cables. The data can be transferred through all over
the world through this medium.

20. EXAMPLES OF UNGUIDED
MEDIA
Microwaves.
Communication Satellites.
Radio Broadcast.
Cellular Radio.
Infrared.
Following are some examples of unguided media:

21. MICROWAVES
 Microwaves are the radio waves.
 It provide very high speed transmission.
 In microwaves data is transmitted through air or space
(like radio signals), instead of through wires or cables.
 It is often called Fixed Wireless.
 It uses line-of-sight transmission*.
 *Line of sight is a type of propagation that can transmit and receive data
only where transmit and receive stations are in view of each other without
any sort of an obstacle between them. FM radio, microwave and satellite
transmission are examples of line-of-sight communication.
 *Line of sight means data signals can only travel in straight lines and can
not bend.

22. WORKING:
 In microwave system data is transmitted or received through
microwave station. These stations are also called relay station
or Booster.
 It is an earth-based reflective dish that contains an antenna,
receiver, and other equipments that are necessary for
transmission.
 Microwave stations are installed on high towers or buildings
usually 40-50 feet above earth.
 They are placed with in 20-30 miles with each other.
 There may be many boosters between sender and receiver.
 Each booster receives data signals from previous microwave
station , amplifies these data signals and retransmits to the next
station.
 In this way data is transmitted over large distances.

23. FIGURE

24. LINE OF SIGHT
TRANSMISSION
MICROWAVE COMMUNICATION

25. ADVANTAGES:
 Data Transmission is up to 150Mbps.
 It is used in environments where installing physical
transmission media is impossible, and line of sight
transmission is available.
USES:
 It is used in wide open areas.
 It is used in telephone companies, cable television
provider, universities etc.

26. COMMUNICATION SATELLITES
 A communication satellite* is a space station.
 It receives microwave signals(or message) from earth-based
station. Satellite transmission station can send and receive
messages is known as earth station. The earth station are often
microwave stations.
 Satellites rotate approximately 22,300 miles above the earth in
precise(specific , exact) location.
 Other devices such as smart phones and GPS receivers, also
can function as earth base station.
 * A satellite placed in orbit round the earth in order to relay television,
radio, and telephone signals.

27. FIGURE

28. DESCRIPTION
 The communication satellite consist of solar powered ,
transceiver , that receives and send signals. Signals are
transmitted from earth station to the satellite . The satellite
receives and amplifies the signals and sends them to another
earth station . The entire process takes only a few seconds. In
this way , data or messages are transferred from one place to
another . Transmitting a signal from ground or earth station to
a satellite station in space is called up-linking and the reverse is
called down-linking .

29. USES:
 Different communication satellites are used to carry different
kinds of information such as telephone calls , television
transmissions , military communication , weather data , or even
radio stations use them for broadcasting.
 The global positioning systems and internet also use the
communication satellites.

30.  ADVANTAGES:
 The data transmission speed of communication satellite is very
high such as up to1Gbps.
 A large amount of data can be transferred from one country to
another.
DISADVANTAGES:
 Bad weather can affect the quality of transmission.
 It has serious security problems, because it is easy to catch the
transmission as it travel through the air.

31. BROADCAST RADIO
 Broadcast radio is the wireless transmission medium.
 It is used to communicate information through radio
signals in air , over long and distances such as between
cities, countries, within office or an home.
 WORKING:
 In this medium a transmitter is required to send
messages( signals) and receiver is required to receive
them.

32.  To receive the radio signal, the receiver has an antenna that is
located in the range of signal.
 Some networks use a specific device called Transceiver that
can both send and receive messages in the form of radio
signals.
TRANSCEIVER

33. EXAMPLE:
 Bluetooth is an example of short range broadcast radio
communication.
 It uses short-range radio waves to transmit data among
Bluetooth-enabled devices.
 Bluetooth is used in personal computers and in mobile devices.
 It can transmit data at the rate of 1Mbps.

34. CELLULAR RADIO
 Cellular radio is a form of radio broadcast that is used for
mobile communications such as cell phones and wireless
modems.
 A cell phone is a telephone device that uses high
frequency radio waves to transmit voice and digital
messages.
 USES:
 Some mobile computers connect their laptop or other
mobile devices to a cell phone to access the web, send
and receive e-mails.
 Other watch mobile TV, which is service that provides
television programs over cellular network.

35. FIGURE

36. INFRARED
 Infrared is a wireless transmission medium. It send
signals using infrared light waves*.
 It requires line of sight transmission.
WORKING:
 The wireless devices are connected to a IrDA(Infrared
Data Administration) port. This port enables the transfer
of data from one device to another without any cables
using infrared light waves.
 *Infrared light is one type of light that is invisible to us.

37.  EXAMPLES:
 Data transfer among computer and wireless key board.
 Data transfer among computer and wireless mouse.
 FIGURE: