The Wireless SessionSIGCOMM 2016

VamsiTallaUniversityofWashington

EvolutionofWirelessSystems

Firstwirelesstransmitter:Thesparkgaptransformer

1GMobilePhone

PagingSystems

MainstreamGenesis

Implantable&IoT

3G,4GCellular

5G:MassiveMIMO- Wi-Fi&MillimeterWave

Ubiquity

HotResearchinWireless

PowerEfficiency HighDataRates

0Mbps 1 Gbps

250Mbps

750Mbps

500Mbps

WhyisCommunicationExpensiveinPower?

KeyReason:GenerationofRFsignalrequirestremendousamountofpower

Solution:Don’tgeneratejustreflect!

TheFlashlightAnalogyEncodedatausingreflections

BackscatterinRF

Reflectionsconsume4-5ordersofmagnitudelowerpower

Encodedatausingreflections

EvolutionofBackscatter

AmbientBackscatter

• ReflectambientTVsignals

• Communicateb/wbattery-freedevices

• SIG’13:100bps-1kbps@upto 10feet

• SIG’14:10kbps-1Mbps@upto80feet

Wi-FiBackscatter

• CommunicatewithCOTSWi-Ficlients

• EncodedatausingvariationsintheWi-Fichannel

• SIG'14:100bps-10kbps@10feet

PassiveWi-Fi

• CommunicatewithunmodifiedWi-Ficlients

• Create802.11bWi-Fipacketsusingreflections

• NSDI'16:1-11Mbps@100feet

Backscatter@SIGCOMM2016

• UseCommoditydevicesØ RepurposeexistingBluetoothandWi-Firadios

Ø Easeofuseanddeployment

KeyideabehindusingCommodityDevices

ff1 f22.4

GHz2.5GHz

Physicallayer:shiftthesignalintoadifferentfrequencyband

UsingCommodityDevices

• FS-BackscatterØ ShiftsentireBLE/Wi-Fipacketstoadjacentband

Ø Requireslowlevelfirmwareaccess

Ø InterandIntrapacketencoding(upto50kbps)

• Interscatter (BestPaperAward)Ø TransformsBLEpacketintosingletonesignalinuserspace

Ø ConvertstheBLEpacketintoaWi-Fi/ZigBeepacket

Ø Encodesdatain802.11b2-11MbpsWi-Fipackets

Backscatter@SIGCOMM2016

• UseCommoditydevicesØ RepurposeexistingBluetoothandWi-Firadios

Ø Easeofuseanddeployment

• CombineradioswithbackscatterØ Radios->highpowerbutgiveslongrange

Ø Backscatter->Ridiculouslylowpowerbutshorterrange

Bradio:Switchbetweenradioandbackscatter

Achievinghighdatarates

• Cellular:2G->3G->4G

• 802.11Wi-Fi:b->g->n->ac

• Nextgeneration(5G)wirelessstandards

Ø MillimeterWave

Ø LargeMIMOSystems– Wi-Fi,Cellular,60GHz and

implementbeamforming,nulling,etc.

Challenge:Channelestimationbecomesharderandincurshugeoverhead inlargeMIMOsystems

MIMOrequiresperiodicestimationofchannel

MIMOinCellular(BestPaperAward)CellularSystemsuseFrequencyDivisionDuplexing

f

• Modelthechannel/wirelesspropagationwith

frequencyindependentparameters

• Thenusechannelreciprocity

fupfdn

MegaMIMO2.0

• Traditionalchannelreciprocitymethodsfailinlarge

MIMOsystems

• SoftwarehardwarearchitecturefordistributedMIMO

It’sgoingtobeanexcitingsession!

• BackscatterSystems

Ø Coolphysicallayertrick- brushuponbasic

modulationandtrig.identities

Ø BuildMACandnetworkinglayerontopofit

Ø RFhardwareexpertiseisrequiredtobuildthese

systems!

2ofthe3BestPapersareintheWirelessSession

It’sgoingtobeanexcitingsession!

• MIMOSystems

Ø It’sallaboutestimatingchannelparameters

Ø Brushuponbasicwavepropagationandmatrix

operations

Ø Beamforming,nullingandpowercontrol

techniquesinlargeantennasystem

Exponentialimprovementsincomingyearsinboth

backscatterandMIMOsystems