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(1)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

VANETs

VANETs

(2)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

VANETs

VANETs

Vehicular Ad-hoc NETworks (VANETs) can be considered as a

subset of Mobile Ad hoc NETworks (MANETs) with unique

characteristics.

A typical VANET consists of vehicles and access points along the

road. Vehicles move on the roads sharing information between

themselves and with the Internet through the access points.

(3)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Vehicles communication

Vehicles communication

Vehicle-to-vehicle communication

Vehicle-to-infrastructure communication Multi-hop communication

(4)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

VANETs vs

VANETs vs

.

.

MANETs

MANETs

Vehicles mobility

Vehicles often move at high speed but their mobility is rather regular andVehicles often move at high speed but their mobility is rather regular and predictable

predictable

Network topology

High speed movement creates scenarios characterized by a veryHigh speed movement creates scenarios characterized by a very dynamic network topology

dynamic network topology

No significant power constraint

Vehicles can always rely on recharging batteriesVehicles can always rely on recharging batteries

Localization

AnAn accurate estimate of accurate estimate of vehiclesvehicles position can position can bebe mademade availableavailable through through GPS

(5)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

PHY/MAC

(6)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

DSRC/802.11p (1/2)

DSRC/802.11p (1/2)

Dedicated Short Range Communication (DSRC) was

released in 2002 by the American Society for Testing and

Materials (ASTM)

In 2003 the standardization moved to IEEE Forum and

changed the name from DSRC to WAVE (Wireless Ability in

Vehicular Environments) also known as 802.11p

(7)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

DSRC/802.11p (2/2)

DSRC/802.11p (2/2)

The standard is based on IEEE 802.11a PHY layer and

IEEE 802.11 MAC layer

Seven 10 MHz channels at 5.9GHz

(8)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

DSRC/802.11p

DSRC/802.11p

vs

vs

. 802.11a (1/3)

. 802.11a (1/3)

802.11a is designed for high data rate multimedia communications in indoor

environment with low user mobility

DSRC PHY uses a variation of OFDM modulation scheme to multiplex data

high spectral efficiency, simple transceiver design and avoids

(9)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

DSRC/802.11p

DSRC/802.11p

vs

vs

. 802.11a (2/3)

. 802.11a (2/3)

DSRC/802.11p reduces the signal bandwidth from 20MHz to 10MHz

all parameter values are doubled in time domain in order to increase

the robustness to ISI caused by the multi-path delay spread and Doppler spread effect

Data rates from 6 up to 27 Mbps

Transmit power level are changed to fit requirements of outdoor vehicular

communications

(10)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

DSRC/802.11p

(11)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

DSRC/802.11p MAC

DSRC/802.11p MAC

MAC layer of DSRC is very similar to the IEEE 802.11 MAC

based on CSMA/CA with some minor modifications

DSRC involves vehicle and

vehicle-to-infrastructure communications

(12)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

DSRC/802.11p scenarios

DSRC/802.11p scenarios

relative speed between vehicles is low despite high absolute

speed – the effect of mobility can be ignored and considered only multi-hop aspects

the key attribute necessary for

communications in this kind of scenario is the need for very high download rates over a short duration

(13)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

802.11 MAC problems

802.11 MAC problems

Scenario a)

Starvation due to hidden terminal – exposed terminal

Solutions:

limiting data transmission duration by using small maximum TCP window size

MAC layer approaches (MACAW)

Scenario b)

Low efficiency and instability due to shortened connection time

Solutions:

low overhead protocol (no RTS/CTS handshake)

no variable rates because this leads to overestimation or underestimation of the NAV used in future

(14)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

MAC issues

MAC issues

Priority, response time and reliability should be assured

because are basic requirements of safety applications

Approaches:

Different CWs and backoff increase parameters for different priority classes in data traffic (e.g., DFS)

Assigning shorter CWs to low-delay real-time service

Static slot assignment for high-priority traffic and dynamic assignment for the low-priority traffic

(15)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Routing

(16)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Routing Protocols for

Routing Protocols for

VANETs

VANETs

(1/3)

(1/3)

Proactive algorithms (table-driven)

better performance in terms of delay but they need abetter performance in terms of delay but they need a considerable amount of control traffic (e.g., OLSR)

considerable amount of control traffic (e.g., OLSR)

Reactive algorithms (on-demand)

minimize the number of broadcast packets by creating routesminimize the number of broadcast packets by creating routes only on demand (e.g., AODV)

only on demand (e.g., AODV)

Several studies demonstrate that neither of the two protocol

classes outperform the other in every vehicular scenarios.

(17)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Routing Protocols for

Routing Protocols for

VANETs

VANETs

(2/3)

(2/3)

Traditional MANETs routing protocols require an explicit

route establishment phase before the data transmission

begins

They are not adequate to low delivery-latency requirement for

safety applications

Routing protocols for VANETs

should rely on packet forwarding based on geographic locationshould rely on packet forwarding based on geographic location of sender and receiver

of sender and receiver

(18)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Routing Protocols for

Routing Protocols for

VANETs

VANETs

(3/3)

(3/3)

Position-based unicast routing (geographical forwarding)

these routing protocols exploit the availability of accuratethese routing protocols exploit the availability of accurate location information

location information

more suited to dense networks and to frequent networkmore suited to dense networks and to frequent network disconnections (e.g., GPSR)

disconnections (e.g., GPSR)

Geocast routing

a a kindkind of of multicastmulticast routingrouting wherewhere the the destinationdestination nodesnodes are are characterized

characterized byby theirtheir geographicalgeographical coordinatescoordinates

in in VANETsVANETs nodesnodes interestedinterested in in notificationsnotifications of of traffictraffic congestions

(19)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Broadcast (1/2)

Broadcast (1/2)

Majority of applications for VANETs rely on broadcast

dissemination of information in the applications area

Blind flooding is the first approach to achieve broadcasting

since it does not require local or global topology information

Broadcasting has a strong influence on network performance

Serious redundancy, contention and collision problems canSerious redundancy, contention and collision problems can occur as a result of flooding

occur as a result of flooding

An efficient broadcast protocol should minimize the total

number of packet retransmissions, while at the same time

preserving network connectivity

(20)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Broadcast (2/2)

Broadcast (2/2)

A trade-off between robustness and redundancy should be found

Different approaches:

probability-basedprobability-based

a node forwards the packet with a probability a node forwards the packet with a probability p p which dependswhich depends on network scenario

on network scenario

location-basedlocation-based

the idea is to select as relays those nodes that permit to coverthe idea is to select as relays those nodes that permit to cover the widest additional area

the widest additional area

neighbor-basedneighbor-based

the nodes decide whether broadcasting the message or not onthe nodes decide whether broadcasting the message or not on the status of their neighbors

the status of their neighbors

cluster-basedcluster-based

nodes are nodes are groupedgrouped intointo smallsmall clustersclusters eacheach one one managedmanaged byby a a particualr

particualr nodenode calledcalled cluster-headcluster-head whichwhich hashas the task of the task of retransmitting

(21)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Classes of Applications

Classes of Applications

Assistance for Safe Navigation

(22)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Assistance for Safe Navigation (1/4)

Assistance for Safe Navigation (1/4)

Traffic safety

It is possible to detect dangerous situations It is possible to detect dangerous situations through on-through on-board

board sensorssensors

Warning messages Warning messages propagate propagate to other vehicles to other vehicles through through ad- ad-hoc networking

hoc networking

Traffic management services

Access Access points along points along the road the road distribute information aboutdistribute information about traffic congestion

(23)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Assistance for Safe Navigation (2/4)

Assistance for Safe Navigation (2/4)

Forward radar

Computing platform Event data recorder (EDR)

Positioning system Rear radar Communication facility Display

Smart vehicle’s onboard instrumentation:

Newer cars Newer cars include include features as recordingfeatures as recording, processing,, processing,

positioning positioning and location and location capabilitiescapabilities..

Communication facility supports wireless Communication facility supports wireless data data exchangeexchange

with other vehicles

(24)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

A potential danger scenario :

The system

The system automatically triggers automatically triggers the the propagation propagation of of warning messageswarning messages by exploiting multi-hop ad-hoc communications

by exploiting multi-hop ad-hoc communications

Assistance for Safe Navigation (3/4)

Assistance for Safe Navigation (3/4)

Roadside base station

Emergency event Inter-vehicle

communication Vehicle-to-roadside

(25)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Assistance for Safe Navigation (4/4)

Assistance for Safe Navigation (4/4)

Overview of some vehicular safety and communication projects:

European

European Community Community has recently funded has recently funded a forum a forum to support to support the the developmentdevelopment of a network system

of a network system offering assistance to offering assistance to the the driversdrivers..

Many interesting features

Many interesting features are are presented presented in the in the following projectsfollowing projects::

CarTalk

CarTalk

2000

2000

(26)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTalk

CarTalk

2000 (1/5)

2000 (1/5)

ObjectivesObjectives:: -

- DevelopmentDevelopment of co-operative driver of co-operative driver assistanceassistance systemssystems

basedbaseduponupon inter-vehicleinter-vehiclecommunicationcommunication -

- DevelopmentDevelopment of a mobile of a mobile ad-hocad-hoc radio network radio network asas a a

communicationcommunicationplatformplatform withwith the the aimaim of of preparingpreparing a future a future standard

standard

PARTNERS: Centro Ricerche Fiat,

(27)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTalk

CarTalk

2000 (2/5)

2000 (2/5)

Applications:Applications:

- - InformationInformation and and WarningWarning FunctionsFunctions::

transmissiontransmission of of warningwarning messagesmessages duringduring breakdownbreakdown, high, high

traffictraffic density or density or congestioncongestion, or , or dangerousdangerous road road surfacesurface conditionsconditions..

ThisThisallowsallows anan earlyearly warningwarning of the driver of of the driver of followingfollowing vehiclesvehicles on on the

(28)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTalk

CarTalk

2000 (3/5)

2000 (3/5)

Applications:Applications:

- - Communication-basedCommunication-based LongitudinalLongitudinal Control System: Control System:

ExistingExistingAdaptiveAdaptive CruiseCruise Control Control systemssystems onlyonly reactreact on the on the vehiclevehicle

directlydirectly in front. in front. ByBy integratingintegrating communicationcommunication, , thesethese systemssystems maymay

adaptadapt longitudinallongitudinal control control toto the the traffictraffic in front and can in front and can allowallow

anticipatinganticipating toto anan earlyearly brakingbraking maneuvermaneuver whenwhen anan invisibleinvisible vehiclevehicle

beyondbeyond the direct the direct predecessorpredecessor in front in front isis brakingbraking. . ThisThis leadsleads toto a a more

(29)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTalk

CarTalk

2000 (4/5)

2000 (4/5)

Applications:Applications:

- Co-operative - Co-operative AssistanceAssistance SystemsSystems:: A

A typicaltypical scenario scenario forfor co-operationco-operation isis the highway entry and the highway entry and

mergingmerging scenario. scenario. TodayToday, , misunderstandingsmisunderstandings betweenbetween driversdrivers on on

the highway and on the entry-lane cause

the highway and on the entry-lane cause criticalcritical situationssituations..

ByBy exchangingexchanging informationinformation up up toto simplesimple trajectorytrajectory plansplans, , criticalcritical

(30)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTalk

CarTalk

2000 (5/5)

2000 (5/5)

Technologies:Technologies:

- - CommunicationCommunication System: System: A

A keykey technologytechnology forfor CarTALKCarTALK 2000 2000 isis the the developmentdevelopment of a of a mobile

mobile multi-hopmulti-hop ad-hocad-hoc radio radio communicationcommunication system system thatthat

meetsmeets the the requirementsrequirements set set byby the the applicationsapplications..

ItIt willwill bebe basedbased on a UMTS radio access on a UMTS radio access technologytechnology, , usingusing a a

(31)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

FleetNet

FleetNet

(1/6)

(1/6)

Objectives:Objectives: -

- DevelopmentDevelopment of a of a communicationcommunication platformplatform forfor inter-vehicleinter-vehicle

communicationscommunications -

- ImplementationImplementation of of demonstratordemonstratorapplicationsapplications -

- DevelopmentDevelopment and and standardizationstandardization of of promisingpromising strategiesstrategies and and

solutionssolutions in in orderorder toto improveimprove driversdrivers’’ and and passengerspassengers’’ safetysafety

and comfort

and comfort

PARTNERS:

PARTNERS: DaimlerChryslerDaimlerChrysler AG, AG, FraunhoferFraunhofer FOKUS, NEC FOKUS, NEC EuropeEuropeLtdLtd,,

RobertRobertBoschBoschGmbHGmbH, , SiemensSiemens AG, TEMIC AG, TEMIC TelefunkenTelefunken, , microelectronicmicroelectronic

(32)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

FleetNet

FleetNet

(2/6)

(2/6)

Applications:Applications:

- Cooperative driver - Cooperative driver assistanceassistance : : -

- EmergencyEmergencynotificationnotification -

- OvertakingOvertaking assistanceassistance -

(33)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

FleetNet

FleetNet

(3/6)

(3/6)

Applications:Applications:

- - DecentralizedDecentralized floatingfloating carcar data data ::

-

- TrafficTraffic jamjam monitor monitor

-

- DynamicDynamic navigationnavigation

- Route

(34)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

FleetNet

FleetNet

(4/6)

(4/6)

Applications:Applications:

- - UserUser communicationscommunications and and informationinformation servicesservices :: -

- Hot-spotHot-spot Internet access Internet access

-

- Inter-vehicleInter-vehicle chatchat -

(35)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

FleetNet

FleetNet

(5/6)

(5/6)

Key Key FeaturesFeatures:: -

- WirelessWireless multi-hopmulti-hop ad hoc ad hoc networkingnetworking -

- UnlicensedUnlicensed radio radio frequencyfrequencybandsbands -

- AllowsAllows forfor lowlow costcost data data transmissiontransmission -

- Position-basedPosition-based routingrouting and and location-basedlocation-based servicesservices - Internet access and

- Internet access and integrationintegration - Open

(36)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

FleetNet

FleetNet

(6/6)

(6/6)

Technologies:Technologies: -

- FleetNetFleetNet plansplans toto useuse a UTRA TDD radio hardware: a UTRA TDD radio hardware: UMTS

UMTS TerrestrialTerrestrial Radio Access system Radio Access system willwill bebe enhancedenhanced or

or replacedreplacedbyby FleetNetFleetNet protocolsprotocolsenablingenabling operationoperation ad ad

hoc mode.

hoc mode.

-

- Radar-basedRadar-based communicationcommunication currentlycurrently under under feasibilityfeasibility

studystudy willwill focusfocus on on safety-relatedsafety-related applicationsapplications..

-

- DuringDuring the the FleetNetFleetNet developmentdevelopment processprocess IEEE 802.11 IEEE 802.11

wirelesswireless LAN LAN componentscomponentswillwill bebe usedused intermediatelyintermediately forfor

(37)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Internet Connectivity (1/2)

Internet Connectivity (1/2)

Internet-based services

Access Access to emailto email, web , web browsingbrowsing, etc., etc.

Video and audio Video and audio applicationsapplications

P2P

ChattingChatting, , multiplayer gamesmultiplayer games

(38)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Internet Connectivity (2/2)

Internet Connectivity (2/2)

Some proposed systems :

Drive-thru

Drive-thru

Internet

Internet

(39)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Drive-thru (1/5)

Drive-thru (1/5)

Proposed Architecture :Proposed Architecture : One or more

One or more locally interconnected locally interconnected access access points form points form a so-a

called called connectivity-islandconnectivity-island, , several several of of them along them along a road or in thea road or in the

same same area area may be interconnected may be interconnected and cooperate and cooperate to provideto provide

network access network access with with intermittentintermittent connectivity to drivers connectivity to drivers inin a

(40)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Drive-thru (2/5)

Drive-thru (2/5)

Features:Features: -

- Investigation about Investigation about the the feasibility feasibility of of providing providing networknetwork

connectivity connectivity and, and, ultimatelyultimately, Internet access , Internet access to to mobilemobile

users users in in vehicles by testing vehicles by testing UDP and TCP performance inUDP and TCP performance in

a

a real vehicular real vehicular scenario scenario using using IEEE 802.11b and 802.11gIEEE 802.11b and 802.11g

hardware

hardware

- Hot

- Hot spots along spots along the road the road will provide will provide WLAN access WLAN access forfor

some (some (relatively relatively short) short) period period of time of time to vehicles drivingto vehicles driving by

by.. -

(41)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Drive-thru (3/5)

Drive-thru (3/5)

(42)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Drive-thru (4/5)

Drive-thru (4/5)

Findings from measurements:Findings from measurements: -

- Both Both UDP and TCP UDP and TCP tests performed tests performed over IEEE 802.11b andover IEEE 802.11b and

802.11g hardware

802.11g hardware suggest to subdivide suggest to subdivide a a connectivityconnectivity session into three distinct phases

session into three distinct phases::

Entry Entry phasephase

Production Production phasephase

Exit Exit phasephase Only

Only in the production in the production phase phase a a stable connectivity jointlystable connectivity jointly with

with a a maximum throughput value is possiblemaximum throughput value is possible, , while while in thein the entry and exit

entry and exit phases performances decrease phases performances decrease due due to to aa

(43)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Drive-thru (5/5)

Drive-thru (5/5)

Results and impact on Internet Results and impact on Internet applicationsapplications:: -

- Usability Usability of of exsisting exsisting IEEE 802.11 radio hardware IEEE 802.11 radio hardware toto transmit

transmit a a significant amount significant amount of data of data during during aa

connectivity sessionconnectivity session

- - Limited connectivity period Limited connectivity period and and variable transmissionvariable transmission characteristics limit

characteristics limit the the usage usage of the system of the system forfor continous communications such as

continous communications such as IP IP telefony whiletelefony while

transaction based application like sending an email

transaction based application like sending an email

could be performed exploiting

could be performed exploiting more more than than oneone

(44)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTorrent

CarTorrent

(1/11)

(1/11)

Key Key FeaturesFeatures::

- Cooperative P2P

- Cooperative P2P vehicularvehicular strategystrategy proposedproposedforfor contentcontent

delivery of

delivery of largelarge multimedia multimedia filesfiles -

- ““CommunicationCommunicationefficientefficient”” swarmingswarming protocolprotocol whichwhich

usesuses a gossip a gossip mechanismmechanism toto propagate propagate contentcontent

avalaibilityavalaibility informationsinformations thatthat leveragesleverages the the broadcastbroadcast nature of

nature of wirelesswireless medium medium -

- Piece-selectionPiece-selection strategystrategy whichwhich takestakes proximityproximity intointo account

(45)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTorrent

CarTorrent

(2/11)

(2/11)

Key Key factorsfactors forfor usingusing opportuninisticopportuninistic ad hoc ad hoc networkingnetworking modelsmodels::

- - ProblemsProblems::

SStopping at gas station for full download is a nuisancetopping at gas station for full download is a nuisance Downloading from GPRS/3G too slow and quite expensive

Downloading from GPRS/3G too slow and quite expensive

- - Observation:Observation:

Many other drivers are interested in download sharing (like

Many other drivers are interested in download sharing (like

in the Internet)

in the Internet)

- Solution:- Solution:

Co-operative P2P Downloading via Car-Torrent

(46)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTorrent

CarTorrent

(3/11)

(3/11)

InfostationInfostation model model : :

downloadsdownloads onlyonly at at infostationinfostation

Roadside base station Download pieces

Internet

Internet

Vehicle-to-roadside
(47)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTorrent

CarTorrent

(4/11)

(4/11)

Basic idea:Basic idea:

Co-operative downloadCo-operative download –– phasephase 1 1

Roadside base station Download pieces

Vehicle-to-roadside communication

Internet

Internet

(48)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTorrent

CarTorrent

(5/11)

(5/11)

Inter-vehicle communication

Internet

Internet

Roadside base station

Basic idea:Basic idea:

(49)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTorrent

CarTorrent

(6/11)

(6/11)

A Bit TorrentA Bit Torrent reviewreview::

-- SwarmingSwarming:: ParallelParallel downloadsdownloads amongamong a a meshmesh of of

cooperatingcooperating peerspeers

-- Scalable:Scalable: System capacity increases with increase in System capacity increases with increase in number of peers

number of peers

-- Tracker:Tracker: Handles peer discovery Handles peer discovery

Centralized Tracker:Centralized Tracker: single point of failure single point of failure

Observation:

Observation: Might not work for Wireless scenarios, because of Might not work for Wireless scenarios, because of intermittent connectivity

intermittent connectivity

Issue:

Issue: Mobility increases churn of nodes participating in Mobility increases churn of nodes participating in a download

(50)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTorrent

CarTorrent

(7/11)

(7/11)

A pictureA picture of Bit of Bit TorrentTorrent system: system:

Uploader/downloader Uploader/downloader Uploader/downloader Uploader/downloader

Tracker

Uploader/downloader
(51)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTorrent

CarTorrent

(8/11)

(8/11)

Gossip protocolGossip protocol : :

FIlesFIles are are divideddivided in in chunkschunks. . A Gossip message containing TorrentA Gossip message containing Torrent

ID, Chunk list and Timestamp is

(52)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTorrent

CarTorrent

(9/11)

(9/11)

Peer Peer SelectionSelection StrategiesStrategies:: Problem:

Problem: how to select the peer for downloading? how to select the peer for downloading?

Possible selections schemes:Possible selections schemes: 1) Rarest First:

1) Rarest First: BitTorrentBitTorrent-like policy of searching for the rarest -like policy of searching for the rarest bitfieldbitfield

in your

in your peerlistpeerlist and downloading it and downloading it

2) Closest Rarest: download closest missing piece (break ties on

2) Closest Rarest: download closest missing piece (break ties on

rarity)

rarity)

3) Rarer

3) Rarer vsvs Closer: weights the rare pieces based on the distance to Closer: weights the rare pieces based on the distance to the closest peer who has that piece.

(53)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTorrent

CarTorrent

(10/11)

(10/11)

(54)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

CarTorrent

CarTorrent

(11/11)

(11/11)

Attractive Attractive aspectsaspects of of CarTorrentCarTorrent solutionssolutions:: -

- Bandwidth at the Bandwidth at the infostationinfostation is limited and is limited and ““not convenientnot convenient”” - It can become congested if all vehicles stop

- It can become congested if all vehicles stop

- It is a nuisance as I must stop and waste time

- It is a nuisance as I must stop and waste time

- GPRS and 3G bandwidth is also limited and expensive

- GPRS and 3G bandwidth is also limited and expensive

- The car to car bandwidth on the freeway is huge and

- The car to car bandwidth on the freeway is huge and

practically unlimited!

practically unlimited!

- Car to car radios already paid for by safe navigation

- Car to car radios already paid for by safe navigation

requirement

requirement

-

- CarTorrentCarTorrent transmissions are reliable - they involve only transmissions are reliable - they involve only few hops (proximity routing)

(55)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Vehicular mobility models and simulators

Vehicular mobility models and simulators

Modeling vehicular traffic

(56)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Modeling vehicular traffic (1/5)

Modeling vehicular traffic (1/5)

Issues:

One One key problem key problem in the in the study study of of VANETs is VANETs is the the need toneed to characterize vehicular nodes mobility

characterize vehicular nodes mobility and and traffic patterns traffic patterns inin

order to

order to produce produce mobility models that reflect as close asmobility models that reflect as close as

possible

possible the the real behaviour real behaviour of mobile of mobile systemssystems

(57)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Modeling vehicular traffic (2/5)

Modeling vehicular traffic (2/5)

Approaches:

Based Based on a on a level-of- detaillevel-of- detail classification classification, , traditionallytraditionally, , three typesthree types

of of approaches have been usedapproaches have been used::

Microscopic modelsMicroscopic models

Kinetic modelsKinetic models

(58)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Modeling vehicular traffic (3/5)

Modeling vehicular traffic (3/5)

Microscopic models:

The The most most basic and basic and detailed approaches detailed approaches are are microscopic microscopic oror

car following models

car following models, , modeling modeling the the actual response actual response ofof individual vehicles to their predecessor

individual vehicles to their predecessor

Each vehicle is described Each vehicle is described on the on the ““microscopic microscopic scalescale”” by itsby its space

(59)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Modeling vehicular traffic (4/5)

Modeling vehicular traffic (4/5)

Kinetic models:

PresentPresent anan intermediate intermediate stepstepbetweenbetween the the otherother twotwo modelsmodels

PartiallyPartially derivedderived fromfrom microscopicmicroscopic modelsmodels and and usedused toto obtainobtain

fluidfluid dynamicdynamic equationsequations, so , so leadingleading toto macroscopicmacroscopic modelsmodels

EffectiveEffective approachapproach forfor the the derivationderivation of of validvalid vehicularvehicular traffictraffic

modelsmodels whichwhich takestakes alsoalso intointo account account forfor the the psycho-

physiologicalphysiological nature of driver interaction ( nature of driver interaction (microscopicmicroscopic levellevel))

A A distributiondistribution functionfunction f(x,v,t)f(x,v,t) describesdescribes the the numbernumber of of vehiclesvehicles

(60)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Modeling vehicular traffic (5/5)

Modeling vehicular traffic (5/5)

Macroscopic models:

Coarsest level Coarsest level of of descriptiondescription

In In most applications most applications one one is neither interested is neither interested in the in the exactexact evolution

evolution of the of the singles vehicle nor singles vehicle nor in the in the distribution function distribution function ff

Use fluid dynamic equationsUse fluid dynamic equations

Main quantities Main quantities are the densityare the density, the , the mean speed mean speed and and speedspeed

variance

(61)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Vehicular simulators (1/3)

Vehicular simulators (1/3)

Issues:

While it is crucial to While it is crucial to test and test and evaluate protocolevaluate protocol

implementations

implementations in a in a real testbed environmentreal testbed environment, , simulationssimulations are

are still commonly used as still commonly used as a first a first step step in in any protocolany protocol

development for VANETs research

development for VANETs research

VANETs imply specific motion patterns that make VANETs imply specific motion patterns that make thethe

common

common random mobility models used random mobility models used in in MANETsMANETs

unrealistic

(62)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Vehicular simulators (2/3)

Vehicular simulators (2/3)

A quick overview :

Recently

Recently new new open-source tools open-source tools are are available for available for generation ofgeneration of

vehicular mobility patternsvehicular mobility patterns. . Most Most of of them them are are capable capable ofof

producing traces for producing traces for network network simulators such as simulators such as ns-2ns-2 or or OpNetOpNet

STRAW: The Street STRAW: The Street Random Waypoint tool provides Random Waypoint tool provides roadroad topology extraction from

topology extraction from the the maps maps of the TIGER database of the TIGER database asas well as micromobility support

well as micromobility support. The . The main drawback is that itmain drawback is that it produces traces not usable by different well-known

produces traces not usable by different well-known networknetwork simulators but only by

simulators but only by the SWANS the SWANS platform platform on on which it iswhich it is based

(63)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Vehicular simulators (3/3)

Vehicular simulators (3/3)

A quick overview :

CanuMobiSimCanuMobiSim: : is is a a tool for tool for the generation of the generation of movement tracesmovement traces

in a

in a variety variety of of conditionsconditions. . Extrapolation Extrapolation of of real topologiesreal topologies

from detailed Geographical

from detailed Geographical Data Data Files Files (GDF) are (GDF) are possiblepossible,,

many different mobility models

many different mobility models are are implementedimplemented, a GUI , a GUI isis present

present, and the , and the tool tool can generate can generate mobility traces for mobility traces for ns-2ns-2 and and other simulators

other simulators..

Micromobility is Micromobility is consideratedconsiderated, , implementing several car-to-implementing several car-to-car models

(64)

Università degli Studi di Catania

Dipartimento di Ingegneria Informatica e delle Telecomunicazioni

Future research and challenges

Future research and challenges

Solutions proposed for VANETs are inspired to well-known paradigms

defined for ad hoc networks and they do not fully exploit the peculiar features

characterizing VANETs

Most current research on multi-hop networks assumes fixed or very slow

varying network topology

⇒ the effect the effect of high of high mobility mobility in ad hoc in ad hoc networks should be fully investigatednetworks should be fully investigated ⇒

⇒ new mobility models should be developednew mobility models should be developed

New algorithms should be designed taking into consideration severe

delay-constraints of safety applications and real-time applications

⇒ new MAC schemesnew MAC schemes ⇒

⇒ routing schemes should provide a routing schemes should provide a good tradeoff between reliability good tradeoff between reliability and and overheadoverhead

Location privacy schemes should be designed to prevent or mitigate tracking

of vehicles during their communication with other vehicles or the road-side

infrastructure

References

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