Introduction to Wireless Communication

1. EC6801
WIRELESS COMMUNICATION
Mrs.R.Ramalakshmi
Assistant Professor
Department of ECE
Ramco Institute of Technology
Rajapalayam

2. Introduction
• Communication is defined as the process of
transferring or exchanging the information from
one place to other place.
• Communication channel is a connection between
transmitter and receiver through which Data can
be transmitted.
• Communication channel also called as
communication media or transmission media

3. Communication Model
Transmitter
Communication
channel
Receiver

4. Types of Communication Channel

5. • Communication channel is essential for
communication systems.
• The transmission characteristics are important
in selecting channel because they directly
affect the communication quality.
• Different types of communication channels
have different transmission characteristics and
costs, they are used in different applications.

6. Twisted-pair cable
 One of the wires carries signal, the other is
used only as a ground reference.
 Number of twists per unit length determines
the quality of the cable.

7. Coaxial cable
• Used for both analog and digital signals
• Effectively used at higher data rate and higher
bandwidth
• For analog signals need amplifiers every few
km
• For digital signals requires repeater every 1km

8. Optical Fiber

9. Terrestrial Microwave
 Requires fewer repeaters
 Use a parabolic dish to focus a narrow beam.
 1-40GHz frequencies

10. Satellite Communication
 Receives on one frequency, and transmits on another frequency
 eg. uplink 5.925-6.425 GHz & downlink 3.7-4.2 GHz
• Height 35,784km

11. Broadcast Radio
• Radio frequency range is 3kHz to 300GHz
• Use broadcast radio of 30MHz - 1GHz, for:
– FM radio
– UHF and VHF television
• Is unidirectional
• Suffers from multipath interference
• Reflections from land, water, other objects
• Are used for multicasts communications, such as radio and
television, and paging system.

12. Wireless Communication
• Transmitting voice and data using
electromagnetic waves in open space.

13. Need for Wireless Communication
Freedom from wires
• No cost of installing the wires, No bunches of
wires.
• Running around e.g. Bluetooth , Wi-Fi

14. Global coverage
where wired communication is not feasible or
costly.
e.g. rural areas, battle field and outer space.
Stay Connected
Any where any time
Flexibility
Connect to multiple devices simultaneously

15. Electromagnetic Spectrum

16. CELLULAR SYSTEMS-BASIC CONCEPTS
• Cellular system solves the problem of spectral congestion.
• Offers high capacity in limited spectrum.
• High capacity is achieved by limiting the coverage area of
each BS to a small geographical area called cell.
• Replaces high powered transmitter with several low power
transmitters.
• Additional radio capacity is achieved.

17. FREQUENCY REUSE
• Used by service providers to improve the efficiency of a
cellular network and to serve millions of subscribers using a
limited radio spectrum
• After covering a certain distance a radio wave gets
attenuated and the signal falls below a point where it can no
longer be used or cause any interference
• A transmitter transmitting in a specific frequency range will
have only a limited coverage area

18. • Beyond this coverage area, that frequency can
be reused by another transmitter.
• The entire network coverage area is divided
into cells based on the principle of frequency
reuse
• A cell is the basic geographical unit of a
cellular network; is the area around an antenna
where a specific frequency range is used.

19. • When a subscriber moves to another cell, the antenna
of the new cell takes over the signal transmission
• A cluster is a group of adjacent cells, usually 7 cells; no
frequency reuse is done within a cluster
• The frequency spectrum is divided into sub-bands and
each sub-band is used within one cell of the cluster
• In heavy traffic zones cells are smaller, while in isolated
zones cells are larger
• The design process of selecting and allocating channel
groups for all of the cellular base stations within a
system is called frequency reuse or frequency planning.

20. • Cell labelled with same letter use the same set
of frequencies.
• Cell Shapes: Circle, Square, Triangle and
Hexagon.

21. FREQUENCY REUSE CONCEPT