OmidAbariHaitham Hassanieh,MichaelRodriguez,MohammedAbdelghany,

DinaKatabi,andPiotrIndyk

FastMillimeterWaveBeamAlignment

EmergingApplications

VRstream7Gbps ofdatafromPCtoheadset

Oneautonomouscarwillgenerate4TB ofdataperday

5Gpromises1000timesfasterthan4GToday’swirelessnetworkscannotsupportfuture

applications

mmWave Technology

mmWave TechnologyMillimeterWaveBands

Currentlyweoperatehere

0 10GHz 20GHz 30GHz 40GHz 50GHz 60GHz 70GHz 80GHZ 90GHz 100GHz

FrequencySpectrum

Enablehigh-throughputwirelesslinks

mmWave changeshowwirelesssystemsoperateToday:Broadcast

mmWave changeshowwirelesssystemsoperate

mmWave:Pencil-beamAntennas

ProblemStatement:howcanwealignthebeamstoestablishalink?

mmWave radiosusephasedarraystocreateabeam

𝑁 :numberofpossibledirections

ClientAP𝑁directions

NaïveApproach:ExhaustiveScan

O 𝑁- measurementsà Tooslow

𝑁directions

802.11adScan

AP Client

Stage1:Clientusesomni-directional;APscansdirections

802.11adScanStage2:APusesomni-directional; clientscansdirections

AP Client

O 𝑁 measurementsàStillTooSlow[MOBICOM’14,SIGMETRICS’15,NSDI’16]

Canwefindthebestbeamalignmentwithoutscanningthespace?

Agile-Link

• Amillimeterwavesystemthatcanquicklyestablishalinkwithoutscanningthespace

• Workswithintheexisting802.11adstandard,andcansupportbothclientsandaccesspoints

• Implementedandevaluatedinpracticalsettings

30

210

60

240

90

270

120

300

150

330

180 0

AP

Client

60o

30

210

60

240

90

270

120

300

150

330

180 0

ConstructaMulti-ArmedBeam:Simultaneouslycollectssignalsfrommultipledirections.

30

210

60

240

90

270

120

300

150

330

180 0

Agile-LinkIdeaPotentialDirectionoftheClient:

0o,60o,90o or120o40o,60o,100o or150o

60oisdirectionofclient

30

210

60

240

90

270

120

300

150

330

180 0

1.Howdowecreatemulti-armedbeams?

2.Whatisthebestchoiceofmulti-armedbeamstominimizethenumberof

measurements?

CreatingMulti-ArmedBeams

ℎ/ℎ-

ℎ0

𝑎/

𝑎0

PhaseShifters

𝑦𝑖

ForanAntennaArray:𝒉 = 𝑭7𝒙, 𝑭′ isInverseFourierMatrix𝒚𝒊 = 𝒂𝒊𝒉 = 𝒂𝒊𝑭7𝒙

0

90

180

𝑭

Divide 𝒂𝒊intosegments

𝑭

𝒂𝒊

0

90

180

𝒂𝒊 =

1.Howdowecreatemulti-armedbeams?

2.Whatisthebestchoiceofmulti-armedbeamstominimizethenumberof

measurements?

Signalstravelingalongdifferentpathscancanceleachother

Whydoweneedtochoosethebeamscarefully?

AP Client

30

210

60

240

90270

120

300

150

330

1800

AP

Client

60o

Hashing

30

210

60

240

90270

120

300

150

330

1800

BestChoiceofMulti-ArmedBeams

0o 30o 60o 90o 120o 150o 180o

Bins: 1 2 3 4

SpatialDirections

• Pickmulti-armedbeamstocreaterandomhashfunctions

• EstimatethetruedirectionusingvotingVoting

Theorem

(Informal)- Assuming:

- Npossibledirections- Ksignalpaths

- Ouralgorithmfindstheoptimalbeamalignmentin 𝑂 𝐾log𝑁 measurements.

ExperimentalResults

ImplementationandEvaluation

BuiltaMillimeterWaveRadiowithaPhasedArray.

1

10

100

1000

10000

0 50 100 150 200 250

Red

uctio

n in

Sea

rch

Tim

e

Phased Array Size

Agile-Link vs Exhaustive SearchAgile-Link vs 802.11adOursystemvs.ExhaustiveOursystemvs.802.11ad

NumberofMeasurements

NumberofPotentialDirections(N)

Redu

ctioninth

eNum

ber

ofM

easuremen

ts

Oursystemrequiresordersofmagnitudefewermeasurements

BeamAlignmentLatency

NumberofDirections

802.11ad 802.11adwithouralgorithm

16 1ms 0.5ms

64 4ms 0.8ms

128 106ms 0.9ms

256 310ms 1.0ms

Achievedfastbeamalignment(lessthan1ms)

BeamAlignmentAccuracy

Agile-LinkperformsmuchbetterthanExhaustivesearchand802.11ad

0

0.2

0.4

0.6

0.8

1

0 1 2 3 4 5 6 7 8

CD

F

SNR Loss (dB)

Agile-Link802.11adExhaustive Search

RelatedWork• PastWorkonBeamAlignment:[D.AraujoEUSIPCO’14,J.KimJour.Communications’14,B.LiTrans.Wireless’13,Y.M.TsangGlobecom’11,J.WangCommunications’09,W.YuanPIMR’15,L.ZhouPIMRC’12,D.Ramasamy Allerton’12,A.AlkhateebIEEESP’14,B.Gao.IET’14,B.Li Trans.Wireless’13,T.Nitsche ENET’15,T.Nitsche Infocom’15,etc]

• PastWorkonmmWave ChannelStudies:[C.R.AndersonTrans.Wireless’04,S.Collonge Trans.Wireless’04,S.RanganIEEE’14,M.SmuldersTransonAnt.’09,J.VioletteNASAreport,J.Comm.’02,S.SurSIGMETRIC’15,A.SaeedVTC’16,X.Tie PAM’11,etc]

• PastWorkonusingSparsity:[E.Eltayeb GLOBESIP’15,A.Alkhateeb J.IEEE’14,B.Gao’IET14,D.Ramasamy,IEEE’14,etc]

Conclusion

• Establishingcommunicationlinksinmillimeterwavenetworksischallengingduetodirectionality.

• Agile-Link:millimeterwavesystemthatcanquicklyestablishalinkwithouthavingtoscanthespace.

• Excitingtimeformillimeterwavenetworks!

OmidAbariHaitham Hassanieh,MichaelRodriguez,MohammedAbdelghany,

DinaKatabi,andPiotrIndyk

FastMillimeterWaveBeamAlignment