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Cognitive Radio: Next

Generation CommunicationSystem

ByV.ALAGU ABINAYA

11MCO02



Evolution of Communication

Systems



Software Defined Radio

Software Defined Radio as a basic platform on

which to build a Cognitive Radio

Cognitive Radio can provide the spectral

awareness technology to support FCC

initiatives in Spectral Use



Definition of SDR Software defined radios -evolutionary process from

purely hardware-based equipment to fully software-based equipment.

1. Hardware driven radios- Transmit frequencies, modulation type

and other radio frequency (RF) parameters are determinedby hardware and cannot be changed without hardware changes.

2. Digital radios - A digital radio performs part of the signal processing

or transmission digitally, but is not programmable in the field

3. Software Defined Radios- All functions, modes and applications

can be configured and reconfigured by software SDR Forum-

- waveform properties, cryptography and applications, is re-

programmable, and may be upgraded in the field with new

capabilities

- Importance of Standards (APIs)*Notice of Proposed Rule Making (NPRM) 8/12/00



Cognitive Radio



Spectrum Allocation



COGNITIVE RADIO

Two-way radio

Automatically changes its transmission or reception

parameters

communicates efficiently, avoiding interference withlicensed or licensed exempt users.

Monitoring of several factors in the external and internal

radio environment

-radio frequency spectrum, user behaviour andnetwork state

FCC ±Federal Communication Commission

³A software defined radio with a cognitive engine brain".



Cognitive Radio Means ´Smartµ

and ´AlertIt knows where it is

It knows what services areavailable, for example, it canidentify then use empty spectrumto communicate more efficiently

It knows what services interestthe user, and knows how to findthem

It knows the current degree of needs and future likelihood of needs of its user

Learns and recognizes usagepatterns from the user

Applies ³Model BasedReasoning´ about user needs,local content, environmentalcontext



Need for Cognitive Radio Radio spectrum is a scarce resource and is regulated

Spectrum usage is one of the key issues in

communication system challenges

The spectrum efficiency can be improved with idea of

dynamic spectrum allocation.

Cognitive radio network - on effective spectrum

utilization

-allocates to primary user or licensed user

-user is not utilizing ,secondary user can claim

without interfering to primary user



What is needed for a CR ?



Cognitive Radio Evolution



How Cognitive radio works?

Cognitive radio

-Spectrum sensing

-Spectrum management

-Spectrum mobility

-Spectrum sharing

awareness of changes in its environment

response to these changes adapts - operatingcharacteristics

- improve its performance or to minimize a loss in

performance



How Does a Cognitive Radio Get So Smart?

ExternalIntelligence

Sources

Mitola, ³Cognitive Radio for Flexible Mobile Multimedia Communications´, IEEE Mobile Multimedia Conference, 1999, pp3-10

OrientEstablish Priority

PlanNormal

Generate Alternatives(Program Generation)

Evaluate Alternatives

Register to Current Time

Decide

Alternate Resources

Initiate Process(es)(Isochronism Is Key)

Act

Learn

Save GlobalStates

Set DisplaySend a Message

ObserveReceive a Message

Read Buttons

Outside

World

New

States

The Cognition Cycle

Prior

States

Pre-process

Parse

Immediate

Urgent

Infer on Context Hierarchy



Spectrum Sensing Dynamic spectrum allocation

Cognitive radio networks

± scans the entire spectral band for the

presence/absence of primary users Performed either locally

- secondary user

- collectively by a group

Contd«



Spectrum Sensing

Transmitter detection- capability to determine if a signal

from a primary transmitter is locally present in a certain

spectrum.

There are several approaches-Matched filter detection

-Energy detection

-Cyclostationary feature detection

Cooperative detection- information from multipleCognitive radio users are incorporated for primary user

detection.

Interference based detection

Contd«



Spectrum Management Spectrum Management - capturing the best available

spectrum to meet user communication requirements

Decide on the best spectrum band -Quality of service

These management functions can be classified

± spectrum analysis

± spectrum decision

Practical implementation of functions

- very complex and multifaceted issue in itself.



Spectrum Mobilit y

Spectrum Mobility- when a user exchanges its

frequency of operation

- use the spectrum in a dynamic manner withthe best available frequency band

- maintaining seamless communication

requirements with better spectrum.



Spectrum Sharing

Spectrum Sharing provides the fair

spectrum scheduling method

O

ne of the major challenges is spectrumsharing.

It can be regarded to be similar to generic

media access control MAC problems in

existing systems



The future of CR

The unlicensed band in range of wireless

devices and services

FCC - consider opening further bands forunlicensed use.

Exploits the inefficiently utilized licensed

bands without causing interference to

incumbent users

Unlicensed radios to operate in the TV

broadcast bands and also TV services.

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