Introduction to Cognitive Radio Networks

1. Mrs.G.Gnana Priya
Assistant Professor(Sr.Gr.)/ECE
Ramco Institute of Technology
Introduction to
Cognitive Radios

2. What is communication?

3. • Communication is the process of establishing connection
between two points for information exchange
(i.e)
Basic process of exchanging information from one
location (source) to another location (destination).
3
Introduction to Communication
Systems
Source Destination
Information

4. 4
Elements of a Communication
System
• Basic block diagram of a communication system:
Information
Source
Transmitter
Channel
(Transmission
Medium)
Noise &
Distortion
Receiver Destination

5. Electronic Communication Systems
Direction of
Communication
Nature of Information
Signal
Half Duplex
Full Duplex
Analog Digital
Unidirectional Bidirectional
Simplex
Techniques of
Transmission
Baseband
Transmission
Communication
using
Modulation
Classification of Electronic Communication Systems

6. Advantages and disadvantages of wireless
communication
• Advantages:
– Mobility
– A wireless communication network is a solution in areas
where cables are impossible to install (e.g. hazardous
areas, long distances etc.)
– Easier to maintain
• Disadvantages:
– Has security vulnerabilities
– Unlike wired comm., wireless comm. is influenced by
physical obstructions, climatic conditions, interference
from other wireless devices

11. “Learning” to Adopt is the only Solution

18. Introduction
The radio spectrum is divided into licensed and unlicensed
frequencies.
• The licensed spectrum is for the exclusive use of
designated users. For instance, it includes the UHF/VHF
TV frequency bands.
• The unlicensed spectrum can be freely accessed by any
user, following certain rules (e.g., not exceeding a
defined limit for transmission power). It includes, for
instance, the ISM (Industrial, Scientific and Medical)
and U-NII (Unlicensed National Information
Infrastructure) frequency bands. ISM is shared by
technologies such as IEEE 802.11 for wireless local area
networks (WLANs), Bluetooth.

21. Bodies work on Standards for Radio
Frequency Allocation

22. 3 Categories of Radio Frequency bands

23. Radio waves generation
• When a high-frequency alternating current (AC) passes through a
copper conductor it generates radio waves which are propagated
into the air using an antenna
• radio waves have frequencies between:
– 3 Hz – 300 KHz - low frequency
– 300 KHz – 30 MHz – high frequency
– 30 MHz – 300 MHz – very high frequency
– 300 MHz – 300 GHz – ultra high frequency