V2X on Phones:Enabling next-generation mobile ITS apps

Jason&H.&Gaojasongao@mit.edu

Next%gen(ITS(Apps(via(D2D

V2X(&(D2D(Radios(on(Phones

RoadRunner (Gao et. a l. , 2014) use sV2X commun ication s to r eali ze city4wide fin e4grained traffic management.Roads or ge ograph ic areas are d ivide dinto r egion s, and some can bedesignate da s congest ion contro lle d. Toenter such a region , a vehicle mustposses a d igital t oken. When it exit s, itpasse s the token to another vehic le v iaV2 V, or back to a fal lback server if the reare no nearby vehicles that need it.

Li,Shiuan&Pehpeh@csail.mit.edu

RoadRunner

Automotive connectivity standards promise to usher in new appsand services that utilize vehicle4to4vehicle communications, andmobile app trends point to the potential of direct device4to4deviceconnections. The convergence of the two, made possible by newhardware, system software, and programming abstractions,promises to realize next4generation mobile ITS apps. The city4scaleimpact of such convergence can now be projected using newevaluation infrastructure that captures interactions betweenhumans, vehicles, devices and networks.

Evaluation(&(Test(Infrastructure

V2X(&(D2D(System(Software

SignalGuru (Koukoum idiset. al. , 2011) runson windsh ield4m ounte d iPhones thatcollaborat ively sen se, share, and learntraffic signal trans itions. It prov ides GreenLight Opt imal Speed Advisory (GLOSA) todrivers ,re ducing fuel consumptionby 20%.The phone s comm unicated via ad4hocWiFi , wh ich has every short ra nge ,necessitat ing a r oad4s ide relay node.Longer4range V2V wou ld elim inate theneed for such infrastructure.

SignalGuru

Gao et. al. (2012) impleme nted a clone of Panoram io (a popular location4 based photosharing app) that leverages D2D. A geogra phical ar ea is divided into a gr id of reg ion s,and the phones wit hin each region col laborat ively host location4base d se rvices. Appscan access data in other regions via m ult i4hop netwo rking between reg ion s. The D2D4enabled app impr oved latency 10X versu sa 3G4on ly ba sel ine a nd2 X versus 4G4on ly,andoffloaded cel lular ne twork accesse s by 9 6%. A dep loyment with 20 device s was l imitedto re latively sma ll regions and d istance s betwee n phone s, again due to the l imitedrange of ad4hoc WiFi. Longer4range a nd faste r V2X wou ld a llow much larger reg ion s,and improve service responsiveness.

Panoramio0cloneDIPLOMA(DIstributed Pr ogramming LayerOver Mobi le Agen ts) i sa p rogramming layerand distributed share d memory sy stem that provide s cohere nt relaxed4con sistencyaccessto data re sid ing on different mobile phone sacrossa large geograph ic area that isdivide d into regions. It abstract s a col lection of unr elia ble mob ile nodes int o astationa ry reliab le “virtua l computer core”, wh ile a ddressing practical i ssue s arisingfrom unpre dictable mob il ity and unre liab le networking by jud iciou sly using the c loudfor occasional coordination.

DIPLOMA

MobiStream s is a Distributed Stream Process ing System (DSPS) that runs direct ly onsmartphones int erconnected by D2D via ad4 hoc WiFi , wherea s other DSPSsty pically runon cluster s of re lia ble se rvers interconnected by high4 spee dEt hernet. To overcome theunrel iabi lity of us ing smar tphones ,Wang et. al. (201 2) bu ild up a re liab le DSPS u singcheck4pointing, with two new approaches to reduce overhead:1) Token:tr iggered checkp oint ing: sour ce operator s can gener ate token s t hat f low

down and t rigger che ckpoint ing at ea ch downstream operator , avoid ing the red undantdata saves that occur in prior fault tolerance schemes.2) Bro adcast: based checkpo int ing: che ckpoint dat a tr ansm iss ion is spl it into mult iple

phases , and u ses un reliable UDP broa dca sts in the first p hase s t o avoid red undanttransmission.

MobiStreams

Bus Capacity Pred iction (BCP) (Wang et. al. , 2012) i san app that pre dicts the number ofpassenge rs on incoming buse s so t hat u sers at bus st ops canmake dec isions l ikewa itingfor a less crowded bus or boar ding a lternative buse s. Wang et. al. dep loyed it along acampus bu s route in Singapore , on 8 phones , and use s stat ist ical mode ls for(dis)embark ing passengers , collected via on4vehicle infrare d sen sors and camerasinstalled at bus stops.

Bus<Capacity<Prediction

RoadRunner( prototype( mounted( in(vehicle(

Screenshot( of(SignalGuru app

The(DSPS(for(each(bus(stop( in( the(BCP( app.Operators( with( the(same( color( run(on( the(same( node.(

802.11p is a standard for Vehicle% 2%Vehicle (V2V) and Vehicle%2%Anyt hing (V2X)wireless comm unications. It is sim ilar t o 802.11a , but t o real ize 8 02.11p rad ios wit hinthe power and size constra ints of phone s, Choi et. al. (2 014) leverage the LEES pr ocesstode sig na suita ble RF front4e nd wh ich can be integrated on phones to rea lize Dev ice%to%Device (D2D) radios.

Example(of(802.11p( front%end( integration( on(mobile( device

The app s de scribed have bee n l imited to small pi lot d eployments of several vehicle s.Large4scale s imulat ion infrastr ucture can enable eva luation of city4scale im plications ofV2X4enabled ITS apps.

SimMobilitySimMobility (Basak et. a l. , 2013) is an integrated s imulat ion p latform that enab lesdevelopmen t a nd evaluat ion of fut ure ITS scena rio s, with integrated models of humanandcommercia lactiv itie s, la nd use , transportat ion ,e nvironm ental im pacts, and energyuse.

As an example of t he potent ial of large4scale evaluat ion infrastr ucture l ike SimMob ili tyto measu re city4scale impact , we wer e ab le to s imulate 74 ,904 vehicle trips over 24hours of s imu lated t ime for RoadRunner, compare d to 10 veh icles fo r 2 hour s in thedeployment.

SimilitudeSimilit ude (Hetu et. a l. , 2 014) comb ine s SimMob ili ty w ith emulate d Andro id devicesand the n s43 network simu lator to allow sim ulat ion of m obi le ITS a pps at city4scale. TheAndr oid a pps requ ire some rudimenta ry mod ification s, but S imi litu de prov ides a Javalibrary, s immob ili ty4andro id ,t oea se integration and provide sh ims for f unctionality l ikelocation updates, timing, and message passing.