Cognitive Radio: NextGeneration

Communication System

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 determined by 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 with licensed or licensed exempt users.

• Monitoring of several factors in the external and internal radio environment

-radio frequency spectrum, user behaviour and network state

• FCC –Federal Communication Commission

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

Cognitive Radio Means “Smart” and “Alert

•It knows where it is

•It knows what services are available, for example, it can identify then use empty spectrum to communicate more efficiently

•It knows what services interest the user, and knows how to find them

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

•Learns and recognizes usage patterns from the user

•Applies “Model Based Reasoning” about user needs, local content, environmental context

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 - operating

characteristics

- improve its performance or to minimize a loss in performance

How Does a Cognitive Radio Get So Smart?

External Intelligence Sources

Mitola, “Cognitive 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 Global States

Set DisplaySend a Message

ObserveReceive a Message

Read Buttons

OutsideWorld

NewStates

The Cognition Cycle

PriorStates

Pre-process

Parse

ImmediateUrgent

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 multiple

Cognitive 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 Mobility

• Spectrum Mobility- when a user exchanges its frequency of operation

- use the spectrum in a dynamic manner with the best available frequency band- maintaining seamless communication requirements with better spectrum.

Spectrum Sharing

• Spectrum Sharing – provides the fair spectrum scheduling method

• One of the major challenges is spectrum sharing.

• 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 for unlicensed 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.

Thank

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Thank

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