Cognitive radio is a type of wireless communication that senses its operational environment and can change its transmission parameters accordingly. It allows unlicensed users to access portions of the radio spectrum normally reserved for licensed users, provided they do not cause harmful interference. Key functions of cognitive radio include spectrum sensing, analysis, management and sharing to efficiently utilize available spectrum. It provides benefits like optimal diversity, improved spectrum efficiency and quality of service. However, issues like spectrum management and ensuring co-existence with other systems need to be addressed for cognitive radio to be effectively implemented. Potential applications include use in emergency communications and wireless regional area networks.

1. PRESENTED BY
D.KAVYA SHREE
17304005

2. CONTENTS
 INTRODUCTION
 SDR
 COGNITIVE RADIO
 ARCHITECTURE OF CR
 FUNCTIONS
 BENEFITS
 ISSUES
 APPLICATIONS
 FUTURE SCOPE
 CONCLUSION

3. INTRODUCTION
COMMUNICATION
It refers to transmission of signals or
information ,reception and processing of information by
some methods.
RADIO COMMUNICATION
It can be defined as the process of sending
information from one place to another without using
connecting wires.

4. With the rapid development of wireless communication
technology, the contradiction between the limited
spectrum resources and the growing demand for wireless
communication is becoming more and more serious. In
order to alleviate the spectrum resource congestion for
more effective use, Dr.Mitola put forward the cognitive
radio technology in 1999, namely by perceiving the
external environment information, the available spectrum
holes are found in time and space, thus the second users
access to the available spectrum dynamically and achieve
efficient use of radio spectrum resources.

5. SDR
Software defined radio is a radio communication
system where the components that have been traditionally
implemented in hardware are instead implemented by
means of software on a pc or embedded system.
A basic SDR system may consist of a personal
computer equipped with a sound card, or other analog-to-
digital converter, preceded by some form of RF front end.
Significant amounts of signal processing are handed over
to the general-purpose processor, rather than being done in
special-purpose hardware (electronic circuits). Such a
design produces a radio which can receive and transmit
widely different radio protocols (sometimes referred to as
waveforms) based solely on the software used.

6. A software-defined radio can be flexible enough to
avoid the "limited spectrum" assumptions of designers
of previous kinds of radios, in one or more ways
including:
 Spread spectrum and ultrawideband techniques allow
several transmitters to transmit in the same place on the
same frequency with very little interference, typically
combined with one or more error detection and correction
techniques to fix all the errors caused by that interference.

7.  Software defined antennas adaptively "lock onto" a
directional signal, so that receivers can better reject
interference from other directions, allowing it to detect
fainter transmissions.
 Dynamic transmitter power adjustment, based on
information communicated from the receivers, lowering
transmit power to the minimum necessary, reducing the
near-far problem and reducing interference to others, and
extending battery life in portable equipment.
 Wireless mesh network where every added radio increases
total capacity and reduces the power required at any one
node.Each node only transmits loudly enough for the
message to hop to the nearest node in that direction,
reducing near-far problem and reducing interference to
others.

8.  Cognitive radio techniques: each radio measures the spectrum
in use and communicates that information to other cooperating
radios, so that transmitters can avoid mutual interference by
selecting unused frequencies. Alternatively, each radio connects
to a geo location database to obtain information about the
spectrum occupancy in its location and, flexibly, adjusts its
operating frequency and/or transmit power not to cause
interference to other wireless services.

9. COGNITIVE RADIO
Cognitive radio is a paradigm for wireless
communication in which either a network or a wireless
node changes its transmission or reception parameters
to communicate efficiently avoiding interference with
licensed or unlicensed users. This alteration of
parameters is based on the active monitoring of
several factors in the external and internal radio
environment, such as radio frequency spectrum, user
behavior and network state.

10. Cognitive Radio (CR) is an adaptive,
intelligent radio and network technology that can
automatically detect available channels in a wireless
spectrum and change transmission parameters
enabling more communications to run concurrently
and also improve radio operating behavior.

11. ARCHITECTURE OF CR

12. LINK LAYER FUNCTIONS
Group Management
It is assumed that any secondary station will belong to a SU
Group. A newly arriving user can either join one of the existing groups
or create a new one through the Universal Control Channel.
Link Management
covers the setup of a link in order to enable the communication
between two SUs and afterwards the maintenance of this SU Link for
the duration of the communication.
Medium Access Control
As long as it can be assured that all Sub-Channels are used
exclusively, i.e. all Sub-Channels used by one SU Link cannot be
used by any other SU Link this problem comes down to a simple
token-passing algorithm ensuring that only one of the two
communication peers is using the link.

13. SPECTRUM MANAGEMENT
• The immediate interest to regulators in fielding
cognitive radios is to provide new capabilities that support new
methods and mechanisms for spectrum access and utilization
now under consideration by international spectrum regulatory
bodies.
• These new methodologies recognize that fixed
assignment of a frequency to one purpose across huge
geographic regions (often across entire countries) is quite
inefficient.
• Today, this type of frequency assignment results in
severe underutilization of the precious and bounded spectrum
resource.

14. • The Federal Communications Commission (FCC; for
commercial applications) and the National Telecommunications and
Information Administration (NTIA; for federal applications) in the
United States, as well as corresponding regulatory bodies of many
other countries, are exploring the question of whether better
spectrum utilization could be achieved given some intelligence in the
radio and in the network infrastructure
• Many frequencies are allocated to more than one purpose. An
example of this is a frequency allocated for remote control
purposes—many garage door opener companies and automobile door
lock companies have developed and deployed large quantities of
products using these remote control frequencies.

15.  In addition, there are broad chunks of spectrum for which
NTIA has defined frequency and waveform usage, and how
the defense community will use spectrum in a process
similar to that used by the FCC for commercial purposes.
Finally, there are spectrum commons and unlicensed
blocks. In these frequencies, there is overlapping purpose
among multiple users, waveforms, and geography.

16. MANAGING UNLICENSED SPECTRUM
The 2.4 and 5GHz band are popularly used for wireless computer
networking. These bands, and others, are known as the industrial,
scientific, medical (ISM) bands. Energy from microwave ovens falls in
the 2.4GHz band. Consequently, it is impractical to license that band
for a particular purpose. However, WiFi® (802.11) and Bluetooth
applications are specifically designed to coexist with a variety of
interference waveforms commonly found in this band as well as with
each other. Various types of equipment utilize a protocol to determine
which frequencies or time slots to use and keep trying until they find a
usable channel. They also acknowledge correct receipt of
transmissions, retransmitting data packets when collisions cause
uncorrectable bit errors.

17. Although radio communication equipment and applications
defined in these bands may be unlicensed, they are restricted to
specific guidelines about what frequencies are used and what effective
isotropic radiated power (EIRP) is allowed. Furthermore, they must
accept any existing interference (such as that from microwave ovens
and diathermy machines), and they must not interfere with any
applications outside this band. Bluetooth and 802.11 both use
waveforms and carrier frequencies that keep their emissions inside the
2.4GHz band. Both use methods of hopping to frequencies that
successfully communicate and to error correct bits or packets that are
corrupted by interference.

18. FUNCTIONS OF CR
 Power Control: Power control is usually used for spectrum sharing CR
systems to maximize the capacity of secondary users with interference
power constraints to protect the primary users.
 Spectrum sensing: Detecting unused spectrum and sharing it, without
harmful interference to other users; an important requirement of the
cognitive-radio network is to sense empty spectrum. Detecting primary
users is the most efficient way to detect empty spectrum.
 Null-space based CR: With the aid of multiple antennas, CR detects the
null-space of the primary-user and then transmits within the null-
space, such that its subsequent transmission causes less interference to
the primary-user

19.  Wideband spectrum sensing: refers to spectrum sensing over large
spectral bandwidth, typically hundreds of MHz or even several GHz.
Since current ADC technology cannot afford the high sampling rate
with high resolution, it requires revolutional techniques, e.g.,
compressive sensing and sub-Nyquist sampling.

20. FOUR IMPORTANT ASPECTS OF
COGNITIVE RADIO
 Spectrum Sensing
 Spectrum Analysis
 Spectrum Management
 Spectrum Sharing

21. BENEFITS OF COGNITIVE RADIO
 Optimal Diversity
 Spectrum Efficiency
 Improved QoS
 Benefits to the Service Provider
 Benefits to the Regulator

22. SIMULATION OF CR NETWORKS
 At present, modeling & simulation is the only paradigm
which allows the simulation of complex behavior in a given
environment's cognitive radio networks. Network
simulators like OPNET, NetSim, MATLAB and NS2 can be
used to simulate a cognitive radio network. CogNS is an
open-source NS2-based simulation framework for cognitive
radio networks. Areas of research using network simulators
include:
 Spectrum sensing & incumbent detection
 Spectrum allocation
 Measurement and/or modeling of spectrum usage
 Efficiency of spectrum utilization

23. ISSUES IN CR
 Spectrum management
 presence of white spaces
 Spectral co-existence

24. APPLICATIONS
 The application of CR networks to emergency and public safety
communications by utilizing white space
 The potential of CR networks for executing dynamic spectrum access
(DSA)
 Application of CR networks to military action such as chemical
biological radiological and nuclear attack detection and investigation,
command control, obtaining information of battle damage evaluations,
battlefield surveillance, intelligence assistance, and targeting.
 Extending Mobile Network
 Over night Back up system
 Outside Broad Casting
 Open air Events
 Multi Technology phone

25. FUTURE PLANS
The IEEE 802.22 working group, formed in November 2004, is tasked
with defining the air-interface standard for wireless regional area
networks (based on CR sensing) for the operation of unlicensed devices
in the spectrum allocated to TV service.To comply with later FCC
regulations on unlicensed utilization of TV spectrum, the IEEE 802.22
has defined interfaces to the mandatory TV White Space Database in
order to avoid interference to incumbent services.

26. CONCLUSION
Thus the cognitive radio is able to provide a wide variety of
intelligent behaviors. It can monitor the spectrum and choose
frequencies that minimize interference to existing communication
activity. It will follow a set of rules that define what frequencies may be
considered, what waveforms may be used, what power levels may be
used for transmission, and so forth. It may also be given rules about the
access protocols by which spectrum access is negotiated with spectrum
license holders, if any, and the etiquettes by which it must check with
other users of the spectrum to ensure that no user hidden from the
node wishing to transmit is already communicating.

27. THANK YOU