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Presented by : EsraaAlkhusheiny

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Cognitive radio Overview Spectrum sensing

Spectrum management Spectrum sharing Spectrum mobility

Remaining challenges

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CRtechnologies provide an opportunistic

spectrum sharing capability by enabling users toperform functionalities of spectrum sensing,spectrum management, spectrum sharing, andspectrum mobility.

CRis regarded as promising technology toincrease the utilized portion of spectrum by

adaptive it is parameter depending on thesurrounding environment

Atypical CR network environment consistsof a number of primary radio networks thatare licensed to operate over spectrum bandsand one or more (secondary) CRN .

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Spectrum sensing techniques usually can be classified intoprimary transmitter detectionDetection of signal from primary transmitter through

the observations of CR usersprimary receiver detectionMore efficient way to detect spectrum holes byidentifying the primary users that are receiving data

within the communication range of a CR userinterference based detectionMeasures interference using interferencetemperature model, allows CR users to use thespectrum band as long as those users dont exceed theinterference limit.

enables the unlicensed users to adapt to the dynamic environment bydetecting and opportunistically using spectrum holes without causing

interference to the primary network

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spectrum analysisEnables the characterization of differentspectrum bands with various parameters

(operating frequency, interference, bandwidth,path loss etc) being considered .

spectrum decisionCRNs decide which the best spectrum band

among the available bands according to theapplication requirement

required to decide the best available spectrum,spectrum management functions are :

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Spectrum mobility

Unlicensed users vacate the channel when a licenseduser is detected and continue its communication inanother vacant portion of the spectrum

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Spectrum sharing can be classified by : thearchitecture, spectrum allocation, and spectrum access technique.

1. The architecture Centralized:

a centralized entity, controls the spectrumallocation and access procedures

Distributed :each CR user being responsible for spectrumallocation/access based on its localmeasurements

since there may be multiple unlicensed users trying to access

the spectrum, CRN access should be coordinated to avoidcollision between unlicensed users

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2. Spectrum allocation

the available spectrum can be allocated to CR usereither in cooperative or in non-cooperative manner

Cooperative:

local measurements of each CR user are sharedwith the other users to improve spectrumutilization

Non-cooperative:

selfish spectrum allocation scheme, performsspectrum sharing by considering only the user athand

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3. Spectrum access technique

multiple CR users trying to access the same spectrumsimultaneously, both overlay and underlay spectrumaccess techniques enabled in CRNs Overlay:

a CR user access the network using spectrumband that are not used by the licensed users.

Underlay:CR users may access the spectrum that is used

by licensed users, CR users regarded as noise

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Primary user sensing challenges

it is difficult for a CR user to have a direct

measurement of a channel between a primaryreceiver and transmitter .

Spectrum mobility challenges

switching from one channel to another, introducesadditional delay to CRNs, is called switching delay .

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Thank you