ProjectDetailsJiasi Chen

Lectures:Monday1:10-2pminSproul2343TA:RyanHolt

Lab:Tuesday7-10pminChung133

http://www.cs.ucr.edu/~rholt002/cs179i_winter17/1

Outline

• Virtualreality

• Videostreaming

• Downloadbooster

• Proposal

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VirtualReality

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AvailablePlatforms• GoogleCardboard

• $20cardboardviewertouseanyAndroidphoneasaVRdisplay

• SamsungGearVR• OnlycertainSamsungphones(GalaxyS7,GalaxyS6,Note5)• Bettermotion-tracking,higherresolutionscreens

• GoogleDaydream• Onlycertainphones(GooglePixel,MotoZ,ASUSZenfone,HuaweiMate,ZTEAxon)

• Bluetoothcontroller

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AvailablePlatforms

• HTCVive• Accuratemotiontrackingwithroomcameras

• OculusRift• Xboxcontroller• OculusTouchcontrollers

• 360cameras• 6GoPros onamount• AdobePremiereProandKolor Autopano

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HowtoProgram?

• Unity(GUI+C#)orAndroidStudio(Java)• NeedappropriateSDK(Oculus,Android,Daydream)

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MPEG-DASHVideoStreaming

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MPEG-DASHProtocol

• MPEG-DASH• APP-layerprotocolforadaptingvideoqualitytonetworkconditions• Client-driven:clientestimatesnetworkconditionsandrequestsappropriatevideoquality• Standarddoesn’tspecifyadaptationalgorithm,justthecommunicationprotocolbetweenclientandserver

• Whousesit?

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time

rate networkbandwidth

videorate

ProjectGoal

• Currentapproaches• Numerousapproachesproposedinresearchliteratureandinpractice• Needaapples-to-applescomparisonundercommonsetoftestconditions

• Resources• MPEG-DASHvideoplayer:https://github.com/Dash-Industry-Forum/dash.js/wiki

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Server

ManifestFile Multiplebit-rate/resolutionvideosdivided

intomulti-secondsegments

HowDASHWorks

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Clients

§ ClientsrequestanewvideosegmenteveryX seconds.§ Thebit-rateoftherequestedsegmentisbasedonthe

averageTCPthroughputoflastY segments.

HTTP

GET

VIDEOVIDEOVIDEO

GeneralVideoRateAdaptationAlgorithm

1. Estimatebandwidth1. Updatebandwidthestimateofith chunk,B[t]2. BasedonpreviousbandwidthestimatesB[1],B[2],...,B[t],predictnew

bandwidthB[t+1]

2. Makenewvideorateselection1. PickthenewvideorateR=f(videobitrate,networkbandwidth,buffersize)2. t++

3. Gotostep1

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CurrentApproach1:Bandwidth-based

• Defaultapproach:R[t+1]=max{r:r<B[t+1]}

• Problem:higherbitratesà higherbandwidthestimateà unfaircompetitionbetweenclients• Loweroverheadforhigherbitrates

• R[t+1]=f(previousvideobitrate,bandwidthestimate)=f(R[t],B[t+1])

• Compensatebyrampingupquicklyforlowerbitrates,rampingupslowlyforhigherbitrates

12Reference:http://conferences.sigcomm.org/co-next/2012/eproceedings/conext/p97.pdf

currentvideobitrate

rateofincrease

CurrentApproach2:Buffer-based

• Insteadystate,R=f(buffersize)

13Reference:http://yuba.stanford.edu/~nickm/papers/sigcomm2014-video.pdf

CurrentApproach3:Bandwidth+Buffer-based• Lookintothefuture:makebandwidthpredictionsforthenextNtimeslots

• R[t+1]=f(previousvideobitrate,bandwidthestimate,buffer)

=f(R[t],B[t],…,B[t+N],buffersize)

• Markovdecisionprocesswithonlinetablelookup• Multi-criterionobjective

14Reference:http://conferences.sigcomm.org/sigcomm/2015/pdf/papers/p325.pdf

DownloadBooster

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DownloadBooster• Wanttospeedupdownloadsoflargefilesbyusingmultipleinterfacessimultaneously(e.g.,WiFi,4G,Ethernet)

• SamsungintroducedDownloadBooster,butitgotblockedbymajorcarriers

• Multipath-TCPisanothermajorstandardizationefforttoenablemultiplenetworks

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ReviewofTCPThroughput

• Controltransmissionratebysettingwindowsize• Windowsize=min{cwnd,rwnd}• cwnd =congestionwindow(setbysender)• rwnd =receivewindow(setbyreceiver)

• Scheduler(multiplenetworksonly)• If#ofpkts tosend<windowsize,whichpipeshouldIsendthepkts on?

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time

cwnd

slowstart congestionavoidance

IfACKreceived:cwndß cwnd +1/cwnd

Ifloss:cwndß cwnd/2

TCPcongestionavoidance:

TransportandApplicationLayerApproaches

Transportlayer:multipath-TCP• MPTCPcongestioncontrol+(default,roundrobin)scheduler• Corse-grainedschedulercontrol(operateonpackets)

Applicationlayer:HTTPproxy• TCPcongestioncontrol+yourscheduler• Fine-grainedschedulercontrol(operateonbytes)

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Client

Internet

Application

Virtualinterface

Remoteserver

Multipath-TCP

• Congestioncontrol• Separatecongestionwindowforeachsubflow r

• Scheduler• Default:SendpacketsonthepipewiththelowestRTT• Round-robin:Mayleavespaceopenincongestionwindow

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[1]https://www.eecs.berkeley.edu/~sylvia/cs268-2014/papers/mptcp.pdf[2]http://conferences.sigcomm.org/co-next/2012/eproceedings/conext/p1.pdf

IfACKreceived:

cwndr ß cwndr +!"#%

&'()*+,,*

-

∑ /012*/�* 566*-

Ifloss:cwndß cwnd/2

MPTCPdefault[1] Pareto-optimal[2]

IfACKreceived:

cwndr ß cwndr +/0127/5667-

∑ /012*/�* 566*- +

9:/012:

Ifloss:cwndß cwnd/2

HTTPProxy

• Congestioncontrol• StandardTCPcongestioncontroloneachpipe

• Scheduler• Howtoschedulepacketsontoeachpipe?Yourdesign!• E.g.,schedulepacketsproportionaltoestimatedbandwidth

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IfACKreceived:cwndß cwnd +1/cwnd

Ifloss:cwndß cwnd/2

ExampleProjectsfromPreviousYears

• Convertfirst-person-shootervideogameonPCtodisplayinVR• “Zombietag”appusingNFConphones• WebsiteforsynchronizedvideowatchingonYouTube

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Proposal

• 1-pagesummaryandplanofyourproject• DuenextMonday• Worth10%ofyourgrade• FeelfreetocometoofficehoursonThursday2-4pm

• Sections• Executivesummary• Comparisonagainstwhatothershavedone

• e.g.,startups,researchpapers,commercialproducts• Targetfeatures

• Milestone0(oralprogressupdatemid-quarter)• Milestone1

• Methodology(e.g.,tools,programminglanguages)• Evaluation(e.g.,testbed,metrics)

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Proposal

• Makesuretoaddress• Whatmakesyourprojectinteresting?Doesitfulfilsomeunmetneed?Whoisitusefulfor?

• Atleastonefigureshowingsystemdesign/architecture

• Ifyou’rechoosinganexistingproject(MPEG-DASHorMPTCP)• Readthereferences,comparethem,anddiscusswhatyouexpecttofind/improve

• Ifyou’rechoosingyourownproject• Whyshouldsomeoneinvestinyour“startup”?

• Writtenfeedbackgiven1weeklater23

ComingUp…

• Labthisweek• Workonyourproposal

• TodobynextMonday(1/30)• SubmitproposalviaiLearn by1:10pm(onepergroup)

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