CognitiveCognitive Radio: General Radio: General

ConceptsConcepts and 802.22and 802.22

Eero RikkonenEero Rikkonen

Jukka TalvitieJukka Talvitie

OutlineOutline

�� CognitiveCognitive Radio Radio ConceptConcept

�� TypesTypes of of CognitiveCognitive RadioRadio

�� Main Main FunctionsFunctions–– SpectrumSpectrum SensingSensing

–– SpectrumSpectrum ManagementManagement

–– SpectrumSpectrum MobilityMobility

–– SpectrumSpectrum SharingSharing

�� 802.22802.22–– IntroductionIntroduction

–– PHY PHY LayerLayer

–– MAC MAC LayerLayer

The ConceptThe Concept

�� wireless communication wireless communication in which the in which the transmission or transmission or

reception parameters reception parameters are changed to communicate are changed to communicate

efficiently without interfering with licensed usersefficiently without interfering with licensed users

�� parameter changes are based on the active monitoring parameter changes are based on the active monitoring

of several factors in the radio environment (of several factors in the radio environment (e.g. radio e.g. radio

frequency spectrum) frequency spectrum)

�� this approach is enabled by softwarethis approach is enabled by software--defined radiodefined radio

BackgroundBackground

�� most of the radio frequency spectrum inefficiently most of the radio frequency spectrum inefficiently utilizedutilized

–– cellular network bands vs. amateur radio bandscellular network bands vs. amateur radio bands

�� spectrum utilization depends strongly on time and placespectrum utilization depends strongly on time and place

�� fixed spectrum allocation wastes resourcesfixed spectrum allocation wastes resources

�� improved efficiency by allowing unlicensed users to improved efficiency by allowing unlicensed users to exploit spectrum whenever it would not cause exploit spectrum whenever it would not cause interference to licensed users interference to licensed users

Types of Cognitive RadioTypes of Cognitive Radio

�� Two main approachesTwo main approaches

–– Full Cognitive Radio (Full Cognitive Radio (““MitolaMitola RadioRadio””))

�� every possible parameter taken into accountevery possible parameter taken into account

–– Spectrum Sensing Cognitive RadioSpectrum Sensing Cognitive Radio

�� only radio frequency spectrum consideredonly radio frequency spectrum considered

�� Also division based on frequency spectrumAlso division based on frequency spectrum

–– Licensed Band Cognitive RadioLicensed Band Cognitive Radio

–– Unlicensed Band Cognitive RadioUnlicensed Band Cognitive Radio

Spectrum Sensing Cognitive Spectrum Sensing Cognitive

RadioRadio

�� most of the research work focused on this approachmost of the research work focused on this approach

�� the essential problem is in designing of high quality the essential problem is in designing of high quality

spectrum sensing devices and algorithms for exchanging spectrum sensing devices and algorithms for exchanging

spectrum sensing data between nodes spectrum sensing data between nodes

Main FunctionsMain Functions

�� Spectrum sensingSpectrum sensing

�� Spectrum managementSpectrum management

�� Spectrum mobilitySpectrum mobility

�� Spectrum sharingSpectrum sharing

Spectrum Sensing Spectrum Sensing 1/21/2

�� in order to avoid interference the spectrum in order to avoid interference the spectrum holes need to be sensedholes need to be sensed–– primary user detection the most efficient wayprimary user detection the most efficient way

�� spectrum sensing techniques are divided into spectrum sensing techniques are divided into three categoriesthree categories–– transmitter detectiontransmitter detection

–– cooperative detectioncooperative detection

–– interference based detection interference based detection

Spectrum Sensing Spectrum Sensing 2/22/2

�� Transmitter DetectionTransmitter Detection–– whether the signal from a primary transmitter is whether the signal from a primary transmitter is locally present in a certain spectrum or notlocally present in a certain spectrum or not�� three different approachesthree different approaches

–– matched filter detectionmatched filter detection

–– energy detectionenergy detection

–– cyclostationarycyclostationary detectiondetection

�� Cooperative DetectionCooperative Detection�� method where information from multiple users are method where information from multiple users are incorporated for primary user detectionincorporated for primary user detection

Spectrum ManagementSpectrum Management

�� needed to capture the best available spectrum to meet needed to capture the best available spectrum to meet user communication requirementsuser communication requirements

�� cognitive radios should decide on the best spectrum cognitive radios should decide on the best spectrum band to meet the band to meet the QoSQoS requirements over all available requirements over all available spectrum bandsspectrum bands

�� management functions classified asmanagement functions classified as–– spectrum analysisspectrum analysis

–– spectrum detection spectrum detection

Spectrum MobilitySpectrum Mobility

�� the process where a cognitive radio user exchanges its the process where a cognitive radio user exchanges its frequency of operation frequency of operation

�� target to use the spectrum in a dynamic manner by target to use the spectrum in a dynamic manner by allowing the radio terminals to operate in the best allowing the radio terminals to operate in the best available frequency band available frequency band

�� seamless communication requirements during the seamless communication requirements during the transition to better spectrum must be maintainedtransition to better spectrum must be maintained

Spectrum SharingSpectrum Sharing

�� providing the fair spectrum scheduling methodproviding the fair spectrum scheduling method

�� sharing is a major challenge in open spectrum sharing is a major challenge in open spectrum usageusage

�� corresponds to MAC problems in existing corresponds to MAC problems in existing systemssystems

802.22 802.22 -- IntroductionIntroduction

�� IEEE working group aiming at constructing Wireless IEEE working group aiming at constructing Wireless Regional Area Network (WRAN) working utilizing white Regional Area Network (WRAN) working utilizing white spaces in TV bands spaces in TV bands

�� the first standard based on cognitive radiosthe first standard based on cognitive radios

�� different approaches proposeddifferent approaches proposed–– centralized servers provide information on available channels incentralized servers provide information on available channels in

the area of Access Point (AP)the area of Access Point (AP)

–– local spectrum sensing only, where the AP would decide local spectrum sensing only, where the AP would decide independently which channels are availableindependently which channels are available

–– combination of the previous approachescombination of the previous approaches

802.22 802.22 -- IntroductionIntroduction

802.22 802.22 -- Topology Topology 1/21/2

�� fixed pointfixed point--toto--multipoint wireless air interfacemultipoint wireless air interface

�� Base Station (BS) manages its own cell and all Base Station (BS) manages its own cell and all associated Consumer Premise Equipment (associated Consumer Premise Equipment (CPEsCPEs))

�� BS is responsible ofBS is responsible of–– medium access controlmedium access control

–– managing distributed sensing by instructing the managing distributed sensing by instructing the CPEsCPEs to perform to perform measurements of different channelsmeasurements of different channels

–– deciding which steps to take (based on feedback) deciding which steps to take (based on feedback)

802.22 802.22 -- Topology Topology 2/22/2

802.22 802.22 -- PHY Layer PHY Layer 1/31/3

�� PHY layer must be able to PHY layer must be able to –– adapt to the different conditionsadapt to the different conditions

–– be flexible for jumping from channel to channel be flexible for jumping from channel to channel without errors in transmission or loosing clients without errors in transmission or loosing clients ((CPEsCPEs))

–– dynamically adjust the bandwidth, modulation and dynamically adjust the bandwidth, modulation and coding schemes coding schemes

�� OFDMA will be the modulation scheme for OFDMA will be the modulation scheme for transmission in UL and DL transmission in UL and DL –– possible to achieve fast adaptationpossible to achieve fast adaptation

802.22 802.22 -- PHY Layer PHY Layer 2/32/3

�� The approximate throughput by using just one The approximate throughput by using just one TV channel is 19 TV channel is 19 Mbit/sMbit/s at a 30 km distanceat a 30 km distance

�� this is not adequate to fulfill the requirements of this is not adequate to fulfill the requirements of the standardthe standard

�� Channel BondingChannel Bonding utilizes more than one channel utilizes more than one channel allowing the system to have a larger bandwidth allowing the system to have a larger bandwidth and higher throughputand higher throughput

802.22 802.22 -- PHY Layer PHY Layer 3/33/3

�� Channel Channel BondingBonding

802.22 802.22 -- MAC Layer MAC Layer 1/31/3

�� based on cognitive radio technologybased on cognitive radio technology

�� consists of two structures: Frame and Superframeconsists of two structures: Frame and Superframe

�� Superframes are sent through every vacant TV channelSuperframes are sent through every vacant TV channel

802.22 802.22 -- MAC Layer MAC Layer 2/32/3

�� no preno pre--determined channel (frequency, time, determined channel (frequency, time, code) for CPE to look for BScode) for CPE to look for BS

�� at startat start--up CPE scans the TV channels and up CPE scans the TV channels and builds a spectrum occupancy mapbuilds a spectrum occupancy map

�� this information may be later sent to BS and is this information may be later sent to BS and is also used by the CPE to determine where to also used by the CPE to determine where to look for BS look for BS

802.22 802.22 -- MAC Layer MAC Layer 3/33/3

�� MAC layer will perform sensing in either inMAC layer will perform sensing in either in--band or outband or out--ofof--band band

measurementsmeasurements

�� Both of these are further divided intoBoth of these are further divided into

–– fast sensing (under 1ms per channel)fast sensing (under 1ms per channel)

–– fine sensing (about 25 ms per channel) is done if the BS feels tfine sensing (about 25 ms per channel) is done if the BS feels that hat

more detailed sensing is neededmore detailed sensing is needed

ReferencesReferences

�� MitolaMitola, J. , J. Cognitive Radio - An Integrated Agent Architecture for Software Defined Radio. Dissertation. Stockholm 2000. Royal Institute of Technology (KTH), Teleinformatics. ISSN 1403 ISSN 1403 –– 5286. 5286.

� Akyildiz, I.F., Won-Yeol Lee, Vuran, M.C. & Mohanty, S. NeXt generation/dynamic spectrum access/cognitive radio wireless networks: A survey. Computer Networks 50 (2006) pp. 2127–2159. Available at http://www.sciencedirect.com.

� Hoven, N., Tandra, R. & Sahai, A. Some Fundamental Limits on Cognitive Radio. University of California at Berkeley 2005. Wireless Foundations, EECS.

�� CabricCabric, D., , D., MishraMishra, S.M. & , S.M. & BrodersenBrodersen, R.W. , R.W. ImplementationImplementation issuesissues in in spectrumspectrumsensingsensing for for cognitivecognitive radiosradios. . SignalsSignals, Systems and Computers, 2004. , Systems and Computers, 2004. ConferenceConferenceRecordRecord of the of the ThirtyThirty--EighthEighth AsilomarAsilomar ConferenceConference ononVolumeVolume 1, 1, IssueIssue 77--10 10 NovNov. 2004 . 2004 Page(sPage(s): 772 ): 772 -- 776 Vol.1. 776 Vol.1.

�� HillenbrandHillenbrand, J., , J., WeissWeiss, T.A. & , T.A. & JondralJondral, F.K. , F.K. CalculationCalculation of of detectiondetection and and falsefalse alarmalarmprobabilitiesprobabilities in in spectrumspectrum poolingpooling systems. systems. CommunicationsCommunications LettersLetters, IEEE , IEEE VolumeVolume 9, 9, IssueIssue 4, 4, AprilApril 2005 2005 Page(sPage(s): 349 ): 349 -- 351.351.

�� CordeiroCordeiro, C., , C., ChallapaliChallapali, K., , K., BirruBirru, D., , D., ShankarShankar, S.N. IEEE 802.22: An Introduction to , S.N. IEEE 802.22: An Introduction to the First Wireless Standard based on Cognitive Radios. Journal Othe First Wireless Standard based on Cognitive Radios. Journal Of Communications f Communications Vol. 1, No. 1, April 2006Vol. 1, No. 1, April 2006