TV White Space Networking: Characteristics, Challenges, and ...

TVWhiteSpaceNetworking:Characteristics,Challenges,andOpportunities

MahbuburRahmanDepartmentofComputerScience

WayneStateUniversity,Detroit,MI

TVWhiteSpaces• Refertoallocated butlocallyunused TVchannels

• Between54MHzand698MHzintheUS• TVchannelindex:2- 51• VHF(54-216MHz) andlowerUHF(470-698MHz)

• FederalCommunicationCommission(FCC)intheUS• Allowedunlicensedusein2008• Butnottointerfereprimaryusers

• Inothercountries• UKbyOfficeofCommunication(Ofcom)• CanadabyIndustryCanadaConsultation• SouthAfricabyCommunicationAuthority• Singapore,Kenya,Namibia,Argentina,etc.

2

Occupied

Whitespaces

Frequency(MHz)SignalStren

gth(dBm

)

TVWhiteSpace:FCCRegulations• OperationalRegulations• LicensedOperation• UnlicensedOperation• HybridOperation

• FCCallowsunlicensedoperations

• Unlicenseddevicecategory• Fixed• Personal/portable

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TVWhiteSpace:FCCRegulations• FixedDevice• Generallyplacedinoutdoorfixedlocations• Canusehighertransmissionpower• Sendsautomaticperiodicmessages

• Personal/portableDevice• Canbemobileandchangelocations• Usuallyuseslowertransmissionpower• Twooperationalmodes• ModeI (dependent)andModeII (independent)

4

Fixeddevice

Personal/portabledevice

TVWhiteSpace:FCCRegulations• AccessRegulations• TellshowtodetermineunoccupiedandoccupiedTVchannels

• 3Methods• Geo-locationDatabaseApproach• ControlSignalApproach• SpectrumSensing/listeningApproach

5

InternetLocation

Available channels

White Space Database

TVWhiteSpace:FCCRegulations

Attributes FixedDevicePersonal/portable Device

ModeI(ClientMode) ModeII(Independent)

Database Access ✓ X ✓

SpectrumSensing X X X

SensingThreshold -84 dBm -114 dBm -114 dBm

Tx Power 1Watt(30 dBm) 100mWatt (20dBm) 100mWatt (20dBm)

Antenna Height <30Meters N/A N/A

6

TVWhiteSpace:Opportunities• TVwhitespacecanenableseveralapplications• Lowcostandcomplexity

• Sensing&MonitoringApplications• Urbansensing,Environmental/habitatmonitoring,Oilfiledmonitoring,etc.

7ASensing&Monitoringnetwork(source:GreenOrb)

TVWhiteSpace:Opportunities• AgriculturalIoT Applications• Needsdata-drivendecisions• Temperature,humidity,waterlevel,etc.• Microsoft,ClimateCorp.,AT&T,Monsantoaretakinginitiatives

8SmartAgriculture(Source:AgfunderNews)

TVWhiteSpace:Opportunities• SmartandConnectedCommunityApplications• Promisetoaddresstheneedsofthepast,present,andfuture• Wirelessbroadbandaccess,publicsafety,etc.• Microsoft,Googlearealreadyadoptingwhitespaces.

9WirelessBroadbandAccess(Source:ArsTechnica)

TVWhiteSpace:Opportunities

• Real-timeApplications• TVwhitespacehaspotentialtosupportlarge-scalereal-timeCPS(Cyber-physicalsystems)applications• Industrialprocesscontrol• Datacenterpowermanagement• Civilinfrastructurecontrol,etc.

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Industrialprocesscontrol(oiltankmonitoring)

Controller

Valve

TVWhiteSpace:Opportunities

• SmartUtilityNetwork(SUN)Applications• Promisesefficientmanagementofelectricity,naturalgas,water,andsewage.• AdvancedMeteringInfrastructure(AMI)

11SmartWaterManagement(source:AllianceofWaterUtility)

TVWhiteSpace:Characteristics• TraditionalWirelessNetworkTechnologies• IEEE802.15.4,Wi-Fi,Bluetooth

• TraditionalNetworks:shortrangeàmulti-hoptopology• Complexprotocols,energyandlatencyoverhead

12IEEE802.15.4basedmeshnetworktopology

TVWhiteSpace:Characteristics• TVwhitespaceshavelongercommunicationrange• 𝒅𝒊𝒔𝒕𝒂𝒏𝒄𝒆 ∝ 𝟏 𝒇𝒓𝒆𝒒𝒖𝒆𝒏𝒄𝒚1 [fromFriss’Equation]

13Singlehopnetworkarchitecture

Receivedpower

Transmitpower

Transmittergain

Receivergain Speedoflight

distancefrequency

TVWhiteSpace:Characteristics• TVwhitespacescanpenetrateobstacles• Lowerfrequencyà longerwavelength• TVfrequency:wavelengthbetween43-59cm• Caneasilypenetratebuildingwallsandtrees

14Singlehopnetworkarchitecture

TVWhiteSpace:Characteristics• SpectrumAvailability• Largeinnumbercomparedto2.4GHzand5GHzbands• 2.4– 2.5GHz(2.4GHzband),5.725-5.875GHz(5GHzband)• 47TVchannels(54-698MHz)

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Whitespaceavailabilityatdifferentnumberofcounties(inUS)basedondatafromSpectrumBridge

database

TVWhiteSpace:Characteristics• Higherbitrate• AsingleTVchannelcanprovideupto21Mbps[Bahl etal.,SIGCOMM‘09]• OperatingonN channelscanboostthebitrateN-times• IEEE802.15.4maximumallowablebitrateis250kbps• Someapplicationsdemandhigherbitrate• E.g.,VolcanoMonitoringrequirehighbitrate

• Samplingperiod:100kHz• Eachsample:24bitsresolution

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TVWhiteSpace:StandardizationEfforts

17

WorkGroup Focus Agenda

IEEE802.22 WirelessRegionalNetwork (WRAN) CognitiveMedium AccessControl(MAC)layerandPhysicallayer(PHY)

IEEE802.11af WirelessLocalAreaNetwork (WLAN) MAC layerandPHY layer

IEEE802.15.4m Low-RateWireless PersonalAreaNetwork(LR-PAN) MAClayerandPHY layer

IEEE 802.19.1 WirelessCoexistenceGroup Coexistence methodsinwhitespace

IEEE1900.4a,1900.4.1

Heterogeneous MobileWirelessNetworks

Enabledistributedheterogeneous wirelessmobileservices

IEEE1900.7 RadioInterface forDynamicTVWSAccess Developradiointerface withMACandPHYlayer

TVWhiteSpace:Protocols• IndustriesarealreadyadoptingTVwhitespaces• WirelessBroadbandAccess(bothMicrosoftandGoogleinAfrica)• AgriculturalIoT (MicrosoftFarmBeats project)

• Researchcommunityisalsodevelopingprotocols

• Protocolsforwhitespacenetwork• TVwhitespacedetectionprotocols• Networkingprotocols

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TVWhiteSpace:DetectionProtocols

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Protocols TVWSAccess Location Mobility Security Applications

KNOWS[Yuanetal.,DySPAN ‘07]

Sensing+Database

Indoor/Outdoor ✓ X Indoor/outdoorTVWS

detection

SenseLess[Murty etal., TMC’12] Database Outdoor ✓ X OutdoorTVWS detection

WISER[Yingetal., MobiCom

‘13]

Sensing+Database Indoor ✓ X IndoorTVWSdetection

WINET[Zhang etal.,INFOCOM

’15]

Sensing+Database Indoor ✓ X IndoorTVWSdetection

TVWhiteSpace:NetworkingProtocols

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Protocols TVWSAccess Location Mobility Security Applications

CR-S[Ahujaetal.,DySPAN

‘08]

Sensing+Database

Indoor/Outdoor ✓ ✓ Sensing&Monitoring,IoT

WhiteFI[Bhal etal.,SIGCOMM

‘09]

Sensing+Database

Indoor/Outdoor ✓ X Wireless broadbandaccess

WhiteNet[Fengetal.,DySPAN ‘11]

Sensing+Database

Indoor/Outdoor ✓ X Wirelessbroadband access

SNOW[Rahmanetal., SenSys

’16,17]Database Indoor/

Outdoor X X Sensing &Monitoring,IoT

TVWhiteSpace:Challenges&Directions• Newchallengesforwirelesssensornetworks (WSNs)• WSNsaremainlyfordatacollection(many-to-onecommunication)• Whitespaces:multi-hopà singlehopàmoreconflictatBS(basestation)• LongrangeàmorehiddenterminalsàmorecollisionsatBS• WSNsneedscalabilityandenergyefficiency

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AB

C D

E

F

• WhileAtransmits,B,C,andDcannottransmitandhavetoback-off.

• E,Fcanbehiddenterminalsandthuswillcollideiftransmitatthesametime

• Needefficientmediumaccesslayer(MAC)andphysicallayer(PHY)solutions

ConflictandcollisioninsinglehopWSN

TVWhiteSpace:Challenges&Directions• Whatwehavedonefor wirelesssensornetworks (WSNs)• SNOW[Rahmanetal.,SenSys ‘16,17]• D-OFDM(DistributedOrthogonalFrequencyDivisionMultiplexing)basedphysicallayerthatenablesparallelTx/Rx• HiddenterminalawareCSMA/CA(CarrierSenseMultipleAccess/CollisionAvoidance)mediumaccesscontrollayer• Scalableandenergyefficient

InternetLocation

Available channels

f1 f2 f3 fnf4 …

…

White SpaceDatabase

Nodes

BS

22SNOWarchitecture

TVWhiteSpace:Challenges&Directions• Newchallengesforwirelesssensornetworks (WSNs)• CoexistenceofhomogeneousWSNs• SpectrumsharingbetweenWSNs• HandlinginterferencebetweenWSNs

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Possiblecoexistencescenarioinhomogeneous(SNOW)networks

TVWhiteSpace:Challenges&Directions• Whatwehavedoneforcoexistenceisssue• SOP[Rahmanetal.,IoTDI ‘18]• Trade-offbetweenscalabilityandinterference• Enablesconcurrentinter-SNOWandintra-SNOWcommunications

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Possiblecoexistencescenarioinhomogeneous(SNOW)networks

TVWhiteSpace:OpenChallenges&Directions

•Manyotherchallengesthatneedtoaddressedingeneral

• Interferencebetweenprimaryandsecondaryusers• Longercommunicationrangeàmoreinterferencetoprimaryusers(Specially,ifoperatingneararestrictedarea)• ReduceTransmission(Tx)powerà Reducecommunicationrangeà reducedthroughput• Trade-offbetweenTx powerandQualityofservice(QoS)

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TVWhiteSpace:OpenChallenges&Directions• FragmentationofTVwhitespaces• Presentsdiscontinuityinspectrum• Existingnetworkingprotocolsmaynotbeabletousefragmentedspectrum• Needtobeverycarefulaboutincumbentsinbetween• Neednewphysicallayerandmediumaccesslayersolutions(likeSNOW?)

26Dataonfragmentedspectrum(source:WhiteFi [Bhal etal.,SIGCOMM’09])

TVWhiteSpace:OpenChallenges&Directions• TemporalandSpatialvariations• NeedtooperateondifferentTVwhitespacesatdifferenttimesandplaces• Willhurtseamlessoperation• Criticaltoreal-timeapplications• Needcognitiveradiosolutions

27TemporalandspatialvariationsofTVwhitespaces(source:WISER[Yingetal.,MobiCom ‘13]

TVWhiteSpace:OpenChallenges&Directions• Scarcityandfutureadaptation• Whitespaceavailabilitydiffersinurban,suburban,andruralareas.• WhoknowsaboutFCC’splan?• Maketheprotocolscompatibleforotherfrequencybands

• Antennadesign• Lowerfrequencyà largerantenna• Antennasizeà atleastone-tenthofwavelengthforefficientreception• BetterQualityofservice(QoS)àMultipleantennas• Antennasneedtobeapartbyhalfofwavelength• Reduceantennaformfactor

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TVWhiteSpace:OpenChallenges&Directions• VariableBandwidth

• Howtoenablemany-to-onecommunicationwithvariablebandwidthsupport?• Noprotocolsexist.

• Mobility• FCCrules:needtocheckwhitespacesevery100mmove• Vehicle-to-vehiclecommunication• HowtolookforTVwhitespaces?• HowtoaddressDopplereffect?

• Security• Longerrangeà highersecurityvulnerability• Sniffing,spoofing,man-in-the-middle attacksmaynotbeviableforshortrangeprotocols• Possibleisolationofnodesinlongcommunicationrange• Dotheexistingsecurityprotocolssuffice?

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Conclusion• We’velookedintoTVwhitespaces

• Devicetypes• Regulations

• OpportunitiesofTVwhitespaces• Canenablevariouslow-powerwide-areanetworkingapplications• Havebenefitingcharacteristics(longrange,availability,highbitrate)

• TVwhitespaceprotocols• Standardizationefforts• Detectionandnetworkingprotocols

• Challengesanddirections• Scalability• Coexistenceandinterference• Fragmentation,temporalvariation,andspatialvariation• Variablebandwidth• Mobility• Security.

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References

• Saifullah, A., Rahman, M., Ismail, D., Lu, C., Chandra, R. and Liu, J., 2016, November. SNOW:Sensor network over white spaces. In Proceedings of the 14th ACM Conference on EmbeddedNetwork Sensor Systems CD-ROM (pp. 272-285). ACM.

• Saifullah, A., Rahman, M., Ismail, D., Lu, C., Liu, J. and Chandra, R., 2017, November. Enablingreliable, asynchronous, and bidirectional communication in sensor networks over white spaces. InProceedings of the 15th ACM Conference on Embedded Network Sensor Systems. ACM.

• Rahman, M. and Saifullah, A., 2018, April. Integrating Low-Power Wide-Area Networks in WhiteSpaces. In Internet-of-Things Design and Implementation (IoTDI), 2018 IEEE/ACM ThirdInternational Conference on (pp. 255-260). IEEE.

• Saifullah, A., Rahman, M., Ismail, D., Lu, C., Liu, J. and Chandra, R., 2018. Low-Power Wide-AreaNetwork Over White Spaces. IEEE/ACM Transactions on Networking, 26(4), pp.1893-1906.

• Rahman, M. and Saifullah, A., 2018. A Comprehensive Survey on Networking over TV WhiteSpaces. arXiv preprint arXiv:1810.07120.