Cogntive Radio

7/29/2019 Cogntive Radio

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Presented by

Vibhor Aggarwal

Vibhuti Narain Singh

Cognitive Radio


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Outline

Today's wireless systems

Cognitive radio (CR) system Different types of cognitive radio

Characteristics of cognitive radio system

Spectrum hole concept

Levels of cognitive radio functionality

Cognitive radio operation

How is it different from simple radios

Applications of cognitive radio

Problems


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Todays Wireless System

Most of the spectrums (licensed bands) are already allocated

users for exclusive use.Few, Small, unlicensed bands are left open for unlicensed userbands 900MHz and 2.4 GHz)

Technological advancement has resulted in the huge developmpersonal wireless technologies like Wi-Fi/802.11, Bluetooth, dcordless phones, 3G, and so on which operate on unlicensed b

Licensed bands are under-utilized but unlicensed bands are crresulting on spectrum scarcity.

Solution is to let unlicensed users use the licensed frequenciesprovided they can guarantee interference perceived by the primlicense holders will be minimal (a concept of cognitive radio).


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Cognitive Radio(CR) Syste

Allows the unlicensed users to dynamically and opportunistica

the under-utilized" licensed bands

Cognitive Radio- Termed by Joseph Mitola in 1991:

- Radio that includes a transmitter in which operating para

such as frequency range, modulation type or maximum outpu

can be altered by software.

A software-defined radio with some artificial intelligence to ma

detection and wise decision according to its environment.


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Fig 1: An example of cognitive radio system components


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ContinueIn order to access under-utilized licensed bandsdynamically and opportunistically, Cognitive Radio h

to- identify the spectrum opportunities (idle frequen

bands) in spatial and frequency domain.

- or use the licensed spectrum with transmit

power constraint so that the interferencecreated by secondary users is below the

tolerable limit.


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Different types of Cognitive Radio

Full Cognitive Radio: every possible radio parameter is tak

account to make spectrum decision

Spectrum Sensing Cognitive Radio: only radio frequency (

spectrum is observed and used in decision making

Licensed Band Cognitive Radio: device is capable of using

spectrum in addition to unassigned spectrum

Unassigned Band Cognitive Radio: device is only allowed t

unassigned and/or license exempt spectrum


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Characteristics of Cognitive Ra

System

Cognitive capability

Ability to capture or sense the information from itsradio environment and allows to identify and select tportion of the spectrum that are unused at a specifictime or location.

Reconfiguration ability

Dynamically programmable capability according toradio environment to transmit and receive on a varieof frequencies.


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Spectrum management

Functions incorporated for adapting to the dynamic spectrenvironment:

Spectrum sensing

Spectrum decision

Spectrum sharing

Spectrum mobility


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Spectrum sensing

A function in CR networks to monitor the unused spectrum bands

Provides the spectrum availability information required for other It is achieved thorough:

PU detection

CR user observes and analyzes its local radio environmdetermines the presence of PU transmissions and accordinglythe current spectrum availability if exists.

Cooperation

Observed information by CR user is exchanged with itsneighbors to improve sensing accuracy

Sensing control

Coordinates the sensing operations of the CR users an

neighbors


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Spectrum Decision

A function to select the most appropriate band (after spectrum sens

according to the quality of service (QoS) requirement.

Spectrum selection decision is performed considering end-to-end

consisting of multiple hops.

Available spectrum bands in CR network may differ from one hop

It is achieved through:

Spectrum characterization

CR user observes the characteristics of each available

which may be varying over time and space due to PU

Spectrum Selection

CR user finds the best spectrum for each hope to sati

requirement for end-to-end route


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Spectrum Sharing

Enables CR users to perform channel selection and power

according to their QoS

It is achieved through:

Resource allocation

Based on QoS, CR users selects the proper channe

their transmission power.

Spectrum access

Enables multiple CR users to share the channel de

who will access the channel or when a user may a

channel.


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continue spectrum sharing

Medium access protocols for spectrum access

Random access

Channel may be opportunistically captured by any CR user fo

data exchanges

Time slotted

Control and data are assigned fixed durations and prevent sim

transmission by multiple users

Hybrid

Fixed time duration for control packets followed by random a

capturing the channel before data transfer.


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CR users are mobile and so called visitors to the spectrum

If the spectrum in use by a CR user is required for PU, the commu

the CR user needs to be continued in another vacant portion of t

Spectrum mobility is required when:

PU is detected

CR user loses its connection due to mobility of other users

Current spectrum band cannot provide the QoS requirement

Spectrum mobility


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continue spectrum mobility

Spectrum mobility is achieved through

Spectrum handoff

CR user switches the spectrum band physically and re

the communication parameters (e.g. operating frequen

modulation type)

Connection management

CR user sustains the QoS or minimizes quality degrada

spectrum switching by interacting with each layer.

l


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Spectrum Hole

Spectrum hole:Temporarily unused licensed

spectrum


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Levels of Cognitive Radio Function

Level Capability Comments

0 Pre-programmed A software radio

1 Goal Driven Chooses Waveform According to Goal. Requires

Environment Awareness.

2 Context Awareness Knowledge of What the User is Trying to Do

3 Radio Aware Knowledge of Radio and Network Components,

Environment Models

4 Capable of Planning Analyze Situation (Level 2& 3) to Determine Goapower), Follows Prescribed Plans

5 Conducts Negotiations Settle on a Plan with Another Radio

6 Learns Environment Autonomously Determines Structure of Environm

7 Adapts Plans Generates New Goals

8 Adapts Protocols Proposes and Negotiates New Protocols


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NormalUrgent

Allocate Resources

Initiate Processes

Parse Stimuli

Pre-process

Establish Priority

Normal

Negotiate

Immediate

LearnNew

StatesObserve

Outside

World

Act

User Driven(Buttons)

Autonomous

PlaStates

G

W

Cognitive

radio

operation


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What is SDR?A software-defined radio (SDR) system is a radio communication sy

can tune to any frequency band and receive any modulation across

frequency spectrum by means of a programmable hardware which

by software.

The ideal scheme would be to attach an analog to digital converte

antenna. A digital signal processor would read the converter, and th

would transform the stream of data from the converter to any othe

Relationship Between SDR and


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Relation

Cognitive radio is a revolut

evolution of software radio

Cognitive radio without SD

limited.

Spectrum

Deregula

-tion

Software

-defined

Radio

Cognitive

Radio

Drives

H i C iti R di Diff t f


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Cognitive Can create n

waveforms o

Can negotiatinterfaces

Adjusts oper

meet the Qorequired by application fsignal enviro

How is Cognitive Radio Different f

Other Radios? - ApplicationConventional

Radio

Supports a fixednumber of systems

Reconfigurabilitydecided at the

time of design May support

multiple services,but chosen at thetime of design

d ff f


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How is Cognitive Radio Different from O

Radios? -Design

Conventional

Radio

Traditional RF

Design

Traditional

Baseband Design

Cognitive R

SDR +

Intelligence

Awareness

Learning

Observations

H i C i i R di Diff f O


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How is Cognitive Radio Different from O

Radios?upgrade cycle

Conventional Radio Cannot be made

future proof

Typically radios are

not upgradeable

Cognitive

SDR upgradmechanism

upgrades

Collaboratiupgrades

Typical Cognitive Radio Applicati


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Typical Cognitive Radio Applicati

What doescognitive

radio

enable?

Bandwidth isnt scarce


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Measurements averagedover six locations:

1. Riverbend Park, Great Falls,VA,

2. Tysons Corner, VA,

3. NSF Roof, Arlington, VA,

4. New York City, NY

5. NRAO, Greenbank, WV,

6. SSC Roof, Vienna, VA

~25% occupancy at peak

Bandwidth isn t scarce,

its underutilized


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RF components are expensive

Cheaper analog implies more

spurs and out-of-band emissions

Processing is cheap and getting cheaper

Cognitive radios will adapt around spurs(just another interference source) orteach the radio to reduce the spurs

Better radios results in still more availablespectrum as the need arises.

Likely able to exploit SDR

Cognitive radio permits the deployment of ch

radios

Impro ed Link Reliabilit


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Improved Link Reliability

Cognitive radio is aware of areas with abad signal

Can learn the location of the bad signal Has insight

Radio takes action to compensate for lossof signal

Actions available:

Power, bandwidth, coding,

channel, form an ad-hoc network Radio learns best course of action

from situation

GoodSignal Quality Can aid cellular system Inform system & other radios of identified gaps


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Cognitive Radio and Military Networ

How is the military planning

on using cognitive radio?

Drivers in Commercial and Military Netw


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Drivers in Commercial and Military Netw Many of the same commercial applications also apply to military

networks

Opportunistic spectrum utilization

Improved link reliability

Cheaper radios Collaborative networks

Military has much greater need for advanced networking techniques

MANETs and infrastructure-less networks

Disruption tolerant

Dynamic distribution of services

Energy constrained devices

Goal is to intelligently adapt device, link, and network parameters to helpachieve mission objectives

Potential Problems with Networked Cog


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Potential Problems with Networked Cog

RadiosDistributed

Infinite recursions Instability (chaos)

Adaptation collisions

Equitable distribution of

resources

Byzantine failure

Information distribution

Centralized

Signaling Overhead

Complexity

Responsiveness

The future is


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The future is

Cognitive Radio


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QUESTIONS ARE WELCOM

Cogntive Radio

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