Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni
VANETs
VANETs
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.
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
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
Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni
PHY/MAC
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
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
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
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
Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni
DSRC/802.11p
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
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
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
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
Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni
Routing
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.
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
⇒
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
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
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
Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni
Classes of Applications
Classes of Applications
Assistance for Safe Navigation
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
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
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
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:
EuropeanEuropean 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
•
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,
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
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
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
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
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
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 -
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
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 -
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
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
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
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
•
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
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.. -
Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni
Drive-thru (3/5)
Drive-thru (3/5)
•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
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
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
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
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-roadsideUniversità 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
Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni
CarTorrent
CarTorrent
(5/11)
(5/11)
Inter-vehicle communicationInternet
Internet
Roadside base station
•
• Basic idea:Basic idea: •
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
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/downloaderUniversità 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
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.
Università degli Studi di Catania
Dipartimento di Ingegneria Informatica e delle Telecomunicazioni
CarTorrent
CarTorrent
(10/11)
(10/11)
•
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)
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
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
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
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
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
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
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
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 ofvehicular 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
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
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