Ari Enzo Cognitive Radio Jr c

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Workshop on Dynamic spectrum management and cognitive radio for the public safety June 29, 2009

Opportunities and Challenges of

Cognitive Radio Networks

Loredana ArienzoLoredana [email protected]

EC Joint Research Center,

Italy

Ispra - June 29, 2009


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Fixed Spectrum Assignment

300 GHz

3 kHz


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Fixed Spectrum Util ization

Amplitu

de

(dBm)

Heavy Use Heavy Use

Medium UseSparse Use

Frequency3 kHz300 GHz

Spectrum use is inefficient


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Cognitive Radio Networks

Dynamic Spectrum Allocation Networks

Dynamic SpectrumDynamic SpectrumAllocationAllocation


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Cognitive Radio

Key enabling technology for Dynamic Spectrum Access

A Cognitive Radio is a radio that can change its transmitter

parameters based on interaction with the environment in

which it operates (FCC2005)

Capability to use or share the spectrum in an opportunistic

manner -> BANDWIDTH HARVESTING


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Recent Standardization Activity - ETSI

ETSI created a Technical Committee for Reconfigurable Radio

Systems (RRS) in January 2008 to study the feasibility of

standardization related to Software Defined Radio (SDR) and

Cognitive Radio

Feasibi lity report expected by Jan 2010

Committee focus on systems aspects, equipment architecture,

functional architecture

Clear focus on Public Safety application, recognizing

requirement for SDR and CR from Defence and Public Safety

segments

TC RRS

Systems

Aspects

Equipment

Architecture

Functional

Architecture

and CPC

Public

Safety


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Some Concepts

Primary Network An existing network infrastructure which has an access right to a

certain spectrum band.

e.g., Common cellular systems and e.g., Common cellular systemsand TV broadcast networks.

Primary User (or Licensed User) Has a license to operate in a certain spectrum band.

Secondary Network (or Unlicensed Network) Does not have license to operate in a desired band.

Hence, the spectrum access is allowed only in an opportunisticmanner !

Secondary User (or Unlicensed User ) has no spectrum license

Hence, additional functionalities are required to share the licensedspectrum band !


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Cognitive Radio NetworkArchitecture

PrimaryBase-station

PrimaryUser

Primary Network

Licensed Band I

Unlicensed Band

Licensed Band II

Cognitive Radio Network

CRNetworkAccess

CRUser

Spectrum Band

Primary

NetworkAccess

CRBase-station

Other

CRNetworks


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PrimaryBase-station

PrimaryUser

Primary Network

Licensed Band I

Unlicensed Band

Licensed Band II

Cognitive Radio Network

CRAd Hoc

Access

CRUser

Spectrum Band

Primary

NetworkAccess

CR Ad Hoc Network Architecture


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Research Challanges

Spectrum Sensing:A CR user should monitor the available

spectrum bands and detect unused spectrum or spectrumholes avoiding harmful interference with other users.

Spectrum Decision:A CR user can select the best availablechannel to meet the communication requirements.

Spectrum Sharing: A CR user should coordinate theaccess to this channel to prevent collision of multiple users.

Spectrum Mobility:CR users should vacate the channel

when a licensed user is detected.


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Spectrum Holes

Time

FrequencySpectrum Holes

Power

Spectrum occupied

by Licensed usersSensing issue

PU Detection(Sensing issue)

Channel Switching

(Hardware issue)

Resume

Communication(Sharing issue)

Sharing issue


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Receiver Uncertainty Problem

Primary User(Transmitter)

Primary

TransmitterRange

Primary User

CRTransmitter

Range

Interference

CR User

Cannotdetect the

PU transmitter

Interference due to uncertainty of receiver location


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Shadowing Problem

Hidden Terminal Problem due to Shadowing

CR

TransmitterRange

Primary User(Transmitter)

CR User

PrimaryTransmitter

Range

Primary User

Interference

Cannotdetect the

PU transmitter

Primary User

CR User


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Solution: Cooperation

Primary

User

PU

Multi-pathfading

Weak signals

are received

due to themulti-path

fading maynot detect the

PU

Shadowing

Cannot detect

the PU due tothe obstacles

Detect theprimary usercorrectly

By exchanging theirsensing information,

CR users can detect

the PU under fading

and shadowing

environments

CR User 22

CR User 3

CR User 1

BUS

IDLE

IDLE

BUSYBUSY


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Cognitive Radio Research

Fundamental research and algorithms based on:

Information and Coding Theory

Relay cooperation, User Cooperation, Coding techniques for

cooperation, Collaborative MIMO techniques

Signal Processing

Collaborative signal processing, Signal design for spectrum

sharing, Interference avoidance, Distributed sensing algorithms Game Theory

Microeconomics and pricing based schemes for spectrum

sharing, negotiation and coexistence, Incentive mechanisms for

cooperation

MAC and Networking Algorithms

Discovery protocols, Etiquette protocols, Self-organization

protocols, Multihop routing


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Spectrum Sensing

Objectives:

Opportunity discovery with interference avoidance

PU Detection

Measures the received signal level and determines the

presence of transmissions

Our concerns:Asymptotic approximations are useful only when enough

data is available, which is not always possible due to

time constraints, the nature of the signal or the

measurement setting


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Spectrum Sensing

InterferenceTemperatureManagement

TransmitterDetection

Spectrum Sensing

ReceiverDetection

Matched FilterDetection

EnergyDetection

CyclostationaryFeature Detection

Classification of Spectrum Sensing TechniquesClassif ication of Spectrum Sensing Techniques


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Our Approach: Bootstrap Hypothesis Test

We assume both PU and CR users operating over a wideband channel.

We consider the IEEE 802.15.4a channel model 3, i.e. a LOS indooroffice. We have f =8GHz and f=500MHz (i.e. T=T=2ns).

2 3 4 5 6 7 8

x 109

0

0.5

1

1.5

2

2.5

x 104

Frequency (Hz)

|H|2

IEEE 802.15.4a Channel Frequency Response

L. Arienzo, Bootst rapping the Spectrum in Ultra Wide-Band Cogniti ve Radio Networks , 2nd Int. Workshop on Cognit ive Radioand Advanced Spectrum Management (CogArt09) in conjunct ion with Wireless VITAE 2009, Aalborg, May 18-20, 2009


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Our Approach: Bootstrap Hypothesis Test

probability of false alarm equal to 0.01;

noise power level is v = 1;

wild bootstrap with 1000 samples for the bootstrap simulation.

Density of the true statistic, its wild bootstrap approximation, and the

corresponding asymptotic normal density


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Cognitive radio networks require a large of amount of

network (and channel) state information to enable efficient

Discovery Self-organization

Cooperation Techniques

In addition to advances in cognitive radio technology, Network

Architectures and Information Aids that support these arerequired

Coordination mechanisms for coexistence and cooperation

Network architectures

Spectrum Servers to advise/mediate sharing

Information aids

Spectrum Coordination Mechanisms (Cognitive Control

Channel)

Concluding Remarks


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Cognit ive Radio Applications

Sensor Network

Mapping

Environment monitoring

Event tracking

Localization of Mobile Devices

Location not only allows people to find you, but also allowsyou to find people

Primary location applications: navigator surveyor, tracking

busses, taxis, fleets and people, emergency, mil itary,

industrial or business operators

Ari Enzo Cognitive Radio Jr c

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