2. COMMUNICATION
 Communication is a process whereby
information is enclosed in a package and is
channeled and imparted by a sender to a
receiver via some medium.
 Sender: The One who sends the message
idea or concept
 Receiver: The one for whom the message is
made or to one the message is delivered

3.  A Communication channels is a path way
over which information can be conveyed
 It may be defined a physical wire that
connects communication devices

5. Features of Communication
 Four things required
 Sender, receiver, medium, and message
 Types of messages
 File
 Request
 Response
 Status
 Control
 Correspondence
 Understandability
 Error Detection

7. Data
Communication
 Is the process of transmitting data from
one computer to another
 Focus is on transmission medium,
different signal levels and data coding

8. Information Transmission
 Data are entities that convey information and are
being exchanged
 A signal is an encoded form of data using a
physical mean.
E.g. voltage.
 Two domain of signal
Time
Frequency

9. Transmission Medium
 Provides the path for data
communication
 Allows a bit stream to be transported
from one machine to another
 Can be categorized as
○ Guided media
○ Unguided media

10. Guided Media
 Copper Wires
Twisted Pair
○ UTP
○ STP
Coaxial Cable
 Fiber Optics

11. Twisted Pair
 Consist of two insulated copper wires.
 Wires are twisted together each other.
 Commonly used in Telephone lines.
 Can run several meters without amplification.
 For longer distances Repeaters are used.
 Used for analog and Digital transmission.
 Cat-3, cat-5 and cat-6 used in computer
Networks.
 Commonly referred as UTP.

12. Types of Twisted Pair
 Twisted pair
Unshielded twisted pair
○ each wire is insulated with plastic wrap, but
the pair is encased in an outer covering

13. Benefits of UTP
 Inexpensive and readily available
 Flexible and light weight
 Easy to work with and install

14. Disadvantages of UTP
 Susceptibility to interference and noise
 Attenuation problem
For analog, repeaters needed every 5-6km
For digital, repeaters needed every 2-3km
 Relatively low bandwidth (3000Hz)

15. Unshielded Twisted Pair
Connector
 The standard connector for unshielded
twisted pair cabling is an RJ-45 connector.
This is a plastic connector that looks like a
large telephone-style connector. A slot
allows the RJ-45 to be inserted only one
way. RJ stands for Registered Jack,
implying that the connector follows a
standard borrowed from the telephone
industry. This standard designates which
wire goes with each pin inside the
connector.

16. The RJ-45 Connector

17. Shielded Twisted Pair (STP) Cable
 A disadvantage of UTP is that it may be
susceptible to radio and electrical frequency
interference (RFI, EFI).
 Shielded twisted pair (STP) is suitable for
environments with electrical interference; however,
the extra shielding can make the cables quite
bulky.
 Shielded twisted pair is often used on networks
using Token Ring topology.
 More expensive, harder to work with.

19. Baseband Coaxial Cable
 Commonly known as “coax”.
 More fast than Twisted pair
and span longer distance
due to better shielding.
 Consist of Copper wire
surrounded by Insulating
material which is covered by
a mesh of conductor and
which is covered by Plastic
sheath.
 Two types, 50 ohms and 75
ohms.
 Used in Cable TV and LANs.

20. Broadband Coaxial Cable
 Used for Analog transmission.
 Can run 300 MHz for long distances.
 Analog signaling has better S/N than digital
signaling.
 Interfaces must convert digital signals to
analog and vice versa.
 Designed for long distances - can use
amplifiers.
 Commonly used for Cable TVs.

21.  Better shielding
More resistance to noise and cross talk
Longer distances and higher speeds

22. Fiber Optics
 Consist of glass core surrounded by
cladding of Glass, covered by a thin
plastic Jacket.
 Typically grouped together in bundles,
protected by an outer sheath.

23. Types of Fiber Optic
 There are two types of Fiber Optic
cable.
Multimode
Single-mode fiber
 Single-mode fibers are more fast and
expensive than Multi-mode because of
covering long distance i.e. 50 Gbps for
100km without amplification.

24. Diameter = 50 microns
Diameter = 8 microns

25. Unguided Media

26. Radio Transmission
 Radio waves have certain advantage over other
Wireless medias.
 Travel long distance.
 Obstacles do not effect.
 Omni-directional
 The disadvantages are the Interference among
users, interference of Motors and Electrical
equipments.
 VLF, LF and MF bands are not used for Data
communication due to their low bandwidth.
 HF and VHF bands are used for communication.

27. Wireless LAN Technologies
 Infrared (IR)
 Microwave Transmission
 Satellite Communications

28. Infrared (IR)
 Used for short range communication.
 Remote controls of devices use Infrared.
 Directional, Cheap and easy to build.
 Can not pass through Solid objects.
 No problem of interference between two
Infrared waves.

29. Microwave Transmission
 Travels in straight line.
 Parabolic antennas are used.
 Problem of Multi-path fading can occur.
 Antennas at transmitter and receiver must
be aligned (Line of Sight)
 Long distance links must have repeaters
 Used commonly in Telecommunication,
Mobiles, TV distribution,

30. Often the microwave antennas are on towers and
buildings.

31. Why we require Satellites
Due to curvature of earth, signal can not be sent
directly between two stations.
dish
dish
uplink station downlink station
satellite
transponder

32. Solution: Satellites
 Simply works as a Relay Station /
Repeater.
Earth
Satellite
Ground station /
Antenna
Ground station /
Antenna

33. Important Terms
 Uplink: earth->satellite.
 Downlink: satellite->earth.
 Transponder: satellite
electronics converting uplink
signal to downlink.

34. Properties of Satellites
 There are several Transponders in
the Satellites, which are listening a
signal on certain frequency and
forwarding on a certain frequency
 Satellites have to take care of the Van
Allen belts as well, which are actually
highly Charged Particles (Magnetic
field)

35. Types of Satellites
 There are three categories of Satellites.
 GEO satellites (Geo-stationary)
 MEO Satellites (Medium Earth Orbit)
 LEO Satellites (Lower Earth Orbit)