A study of the vehicular ad hoc network Speaker: Chih-Sheng Chen

A study of the vehicular ad hoc network

Speaker: Chih-Sheng Chen

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Outline• Overview• Applications Issues• Network Issues

• ITS• Radiolocation• Dissemination of alarm messages

• Routing scheme Issues• Conclusion• Reference

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Overview( 1/6)

Disproportionate increase in car ownership relative to population growth in China, India

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Overview( 2/6)• Safety: 6 Million crashes, 41,000 fatalities in

U.S. per year ($150 Billion)• Congestion: 3.5 B hours delay, 5.7 B gal.

wasted fuel per year in U.S. ($65 Billion)• Pollution: > 50% hazardous air pollutants in

U.S., up to 90% of the carbon monoxide in urban air

Source: 2005 Annual Urban Mobility Report (http://mobility.tamu.edu)

Texas Natural Resource Conservation Commission (http://www.tnrcc.state.tx.us/air)

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Overview( 3/6)

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Overview( 4/6)• Over the last

decades passive safety systems have helped to reduce the number of fatalities.

• The further reduction of severe accidents will be achieved by adding active safety systems to vehicle.

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Overview( 5/6)

• Vehicular Ad-hoc NETworks( VANET) are special cases of MANET.• Inter-vehicular communication( IVC) network.• Road-Vehicle Communications( RVC).

• The difference between VANET and MANET:• VANET nodes are highly mobile, so network

topology is changing very fast.• VANET nodes are vehicles, so there are less

power and storage constraints.• VANET nodes move non-randomly along specific

paths( roads).

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Overview( 6/6)

• New applications of wireless ad hoc networks with vehicular traffic

• Infrastructure based systems are not sufficient• Infrastructure may not be present• Signs may not be visible

• Mobility is constrained and directional• Links between peers will be dynamic and

unstable • Manual systems too slow

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Applications Issues( 1/8)

• Many recent incidents• Fog• Vehicular road accident in a busy highway• Delays in emergency vehicle reaching the

accident point• Unseen vehicles

• Broadband connectivity to area hospitals to relay patient’s vital information

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• Use peer ad hoc networks to send messages (both upstream and downstream) to reserve highway lanes for emergency vehicles• Law enforcement• ambulance• fire truck• Overtaking

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• Internet access in cars( Cont.) • Information services

• Traffic/road monitoring• Traveler & Tourist Assistance

• Entertainment (distributed games)• Links with fixed and mobile

• Internet Conversation• Control Internet device

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• Internet access in cars

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• Classifying Applications( Cont.)1. Assistance for Safe Navigation( ASaN)

2. Traffic Regulation and Internet Connectivity( TRIC)

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• Classifying Applications( Cont.)

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• Classifying Applications( Cont.)• Assistance for Safe Navigation

• Collision avoidance applications through accident, sudden braking, or road maintenance notifications,

• Hazardous driving condition detection,• Emergency services call after an accident, and• Detection of a rogue driver going the wrong

way.

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Applications Issues( 8/8)• Classifying Applications

• Traffic Regulation and Internet Connectivity• Advanced Navigation Assistance (ANA) such as

passing assistance, car pool formation, real time congestion notification, expected weather driving conditions, etc.,

• Internet connection services for added travel comfort and improved productivity,

• Vehicular Relay Chat (VRC) between users of the same highway, and

• Custom Local Shopping Advertisement( CuLSA), which lets local businesses inform travelers of local shops, malls, etc. Local gas stations could also advertise their location to attract cars that may not see them from the highway.

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Network Issues( 1/16)

• ITS( Cont.)• Intelligent Transportation Systems( ITS) is

receiving increased emphasis due to its role in traffic safety and ensuring better quality travel.

• The successful deployment of ITS relies heavily upon inter-vehicle communication for effective dissemination of information.

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Network Issues( 2/16)

• ITS( Cont.)• Five basic types of messages that are

exchanged between vehicles are:• Basic safety messages( highest priority)• Warning messages( high priority)• Infotainment messages( normal priority)• Routing messages( low priority)• Inter-personal messages( lowest priority)

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Network Issues ( 3/16)

• ITS( Cont.)• Basic safety messages

• Contains data describing the sender characteristics and driving conditions( e.g. sender position, speed , vehicle brake and steering conditions).

• Warning messages• Contains critical warning on emergency

situations that has occurred or could possibly occur within the traffic.

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• ITS• Infotainment messages

• Contains data about services and resources available and offered by other vehicles and information of general interest( e.g. traffic conditions or meteorological data).

• Routing messages• Contains data used by routing protocols.

• Inter-personal messages• Contains different profiles of the drivers and of the

passengers situated in the vehicles. These data are used when employing interpersonal applications.

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• Radiolocation( Cont.)• In the case of an accident, vehicles without

GPS have to be informed in the right moment.

• Radio location is useful to the VANET uses position-based routing( PBR) when some vehicles without GPS.

• Most generally used ones are based on signal propagation duration.

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• Radiolocation( Cont.)• The main three different measurement

methods are used in cellular ad hoc networks today :

• Received-Signal-Strength Indicator( RSSI)• Time-of-arrival( TOA) and Time-Difference-of-

arrival( TDOA)• Angle-of-arrival( AOA)

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• Radiolocation( Cont.)• Received-Signal-Strength Indicator( RSSI)

• RSSI measures the power of the signal at the receiver. Based on the known transmit power, the effective propagation loss can be computed.

• TOA or time-difference of arrival( TDOA)• The propagation time can be directly translated into

distance, based on known signal propagation speed.• Angle-of-arrival( AOA)

• AOA techniques estimate the desired target by measuring the angle at which signals from several BSs through the use of directive antennas of antenna arrays.

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• Radiolocation( Cont.)• SPA( 1/2)

• Self-positioning algorithm( SPA) has been proposed for positioning mobile nodes in wireless ad hoc networks without relying on GPS.

• SPA uses the distance between the nodes to build a relative coordinate system in which the node positions are computed in two dimensions.

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• Radiolocation( Cont.)• SPA( 2/2)

• A node executing SPA algorithm fails in some situations to computes its coordinates since it is based on some conditions on its neighbors.

• SPA is not well suited for inter vehicle communication.

• Another method for Using SPA for GPS-free position in VANET.

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• Radiolocation( Cont.)• Using radiolocation on broadcast( 1/2)

• The way with which a node is designated as relay is based on distance defer time algorithm.

• The node that receives an alarm message does not rebroadcast it immediately but has to wait some time to take a decision about rebroadcast.

• When the defer time expires, if it does not receive the same alarm message from another node behind it, it deduces that there is no relay node behind it.

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• Radiolocation• Using radiolocation on broadcast( 2/2)

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• Dissemination of alarm messages( Cont.)• RBM( Role Based Multicast)

• Based on neighbor detection• TRADE( Track Detection)

• Based on neighbor maintenance• DDT( Distance Defer Time)

• Inserts distance-based defer time slots• ODAM( Optimized Dissemination of Alarm

Messages)• Based on geographical multicast

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Network Issues ( 13/16)• Dissemination of alarm messages( Cont.)

• RBM• Based on neighbor detection• Consumes more bandwidth• Presents longer delays• More packet loss

• TRADE• Based on neighbor maintenance• Consumes more bandwidth• Presents longer delays• The scalability in dense networks is limited.

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• DDT• GPS-unequipped vehicles Computing defer time fails in

some situations.• The lack of supporting fragmented ad hoc networks

makes DDT unsuitable for light-crowded highways.

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• ODAM• Using SPA for GPS-free position to Support

localization of GPS-unequipped vehicles in VANET.

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Network Issues ( 16/16)• Dissemination of alarm messages

• ODAM• Based on geographical multicast, which consists in determining the multicast group according to the driving direction and the positioning of the vehicles

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Routing scheme Issues( 1/27)

• Routing challenges for VANET• The network can frequently form partitions

preventing end-to-end communication strategies.

• Resource discovery and naming are problematic as the vehicles are in general unreliable and frequent arrivals and departures occur.

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• Existing routing protocols designed for MANET are not suitable for VANET.

• The VANET uses position-based routing( PBR), because it outperforms topology-based routing in highly dynamic vehicular environments.

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• PBR• PBR requires that each node determine its own

position through the use of Global Positioning System( GPS).

• PBR thus does not require the establishment or maintenance of routes but routing decisions at each node is based on the destination’s position contained in the packet header.

• With PBR, each node selects for each packet the next reachable forwarder that is geographically closest to the destination.

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• Partitioned network( Cont.)• Mobility can also create temporary network

partitions that interrupt end-to-end connectivity and cause packet loss.

• In order to reduce the number of network partitions, oncoming traffic is included when determining next hops.

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• Partitioned network( Cont.)• Forward mode

• Message forwarding within a partition

• Catch-up mode • Vehicle movement allows message

propagation between partitions

Dis

tanc

e

Time

Catch-up Mode

Forward Mode

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• Partitioned network• In order to bridge gaps in IVC networks and

improve multi-hop routing performance, an alternative would be to forward data packets to its destination via roadside infrastructures.

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• DDP( Cont.)• Directional Propagation Protocol( DPP) utilize

the directionality of data and vehicles for information propagation.

• DDP is comprised of three components:• Custody Transfer Protocol( CTP)• Inter-Cluster Routing Protocol• Intra-Cluster Routing Protocol

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• DDP( Cont.)• Each cluster has a header and a trailer,

located at the front and rear of each cluster, entrusted with the task of communicating with other clusters.

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Routing scheme Issues( 9/27)• DDP( Cont.)

• Inter-Cluster Routing & Intra-Cluster Routing• Immediately routed to header or trailer

depending upon the direction in which in which information needs to propagate.

• Any duplicate messages received at any of the nodes are dropped.

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• DDP( Cont.)• Custody Transfer Protocol( CTP)

• The custody is implicitly transferred to another cluster that is in front along the direction of propagation and is logically the next hop in terms of the message path.

• The traffic in opposing direction acts as a bridge but is never given custody of the message.

• The custody of the message may be accepted or denied by a cluster by virtue of it being unable to satisfy the requirements of the message.

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• DDP• algorithm

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• MOPR( Cont.)• Movement Prediction based

Routing( MOPR) algorithm predicts future positions of vehicles involved in each routing path based on their positions, speeds, and directions.

• So MOPR is able to estimate links lifetime.• MOPR predicts if an intermediate routing

node is likely to cause a rupture link during the transmission time or not.

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• MOPR( Cont.)• MOPR dynamically selects the most stable

route among the routes provided by classical multi-path routing algorithms.

• What is a stable route?• It is the one composed by( more) stable nodes.

• What is a stable node?• It should have a direction and a speed similar

to the ones of the destination node( and the source node).

• Note that intermediate nodes can be moving or static.

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• MOPR( Cont.)

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• MOPR

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• VHRP( Cont.)• To avoid link ruptures and to establish

reliable routes, the routing algorithm dynamically searches for the most stable route that includes only hops from the same group. The proposed scheme is dubbed Vehicle-Heading based Routing Protocol (VHRP).

• Reference to MOPR

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• VHRP( Cont.)• Problem formulation: a link rupture event is more

likely to occur between vehicles A, B, and D.

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• VHRP( Cont.)• Vehicles are

grouped into a number of sets according to their moving directions.

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• VHRP( Cont.)• Vehicles are assumed to be equipped with

Global Positioning Systems (GPSs) to detect their geographical location.

• Using the velocity vector and unit vectors, the group of vehicle A can be decided as follows.

• Vehicle A belongs to Group N, if the dot product of its velocity vector and the unit vector SN(VA · SN) takes the maximum value.

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• VHRP( Cont.)• When a vehicle X receives a control message

from another vehicle Y, it compares its group ID with that of the originating vehicle (Vehicle Y).

• If the two vehicles belong to the same group, routing metrics are not modified and routing is performed according to the number of traversed hops as in the basic distributed Bellman-Ford routing algorithm.

• If the two vehicles belong to two different groups, the link between the two vehicles is judged to be unstable.

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• VHRP( Cont.)• A penalty is then added to the routing

metric between the two vehicles and routes are updated. In such a manner, added penalties can reflect the information of groups on the routing procedure.

• If the route already exists, vehicle X has to update its route only if the sequence number and routing metric indicated in the control packet are smaller.

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• VHRP( Cont.)

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• VHRP( Cont.)• Performance evaluation(1 /5)

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• VHRP( Cont.)• Performance

evaluation( 2/5)• To enable vehicles to

travel a long enough distance, the simulation end time is varied in function of the speed of vehicles as shown in Table I.

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• VHRP( Cont.)• Performance evaluation( 3/5)

• Table II summarizes the parameters used for road traffic simulation.

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• VHRP( Cont.)• Performance evaluation( 4/5)

• where Np and Nt denotes the number of received packets in case of the proposed scheme and TBRPF (or DSDV), respectively.

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• VHRP• Performance evaluation( 5/5)

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Conclusion( 1/3)

• Routing in the VENET• Topology based routing protocols would

incur greater routing overhead if used in vehicular environments with much greater mobility rates rendering it inappropriate for usage in VANET.

• Position base routing requires that each node determine its own position( e.g., through GPS).

• PBR have some problem with changeful location.

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Conclusion( 2/3)

• Applications for GPS-free position in VANET are more flexible.

• Further work• The hybrid approach combines PBR and

TBR for GPS-free in VANET.• Process something when stop for traffic

signal• Use radar or radiolocation to avoid

obstacle in routing

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Conclusion( 3/3)

• Mobile distributed computing systems on the road are coming• Safety likely to be the initial primary application.• Enable wide variety of commercial applications.• V2V communication provides a means to

supplement infrastructure-based communications.

• WiMax

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Reference( 1/2)• [1]Benslimane, A. Localization in Vehicular Ad Hoc Networks.

Systems Communications, 2005. Proceedings 14-17 Aug. 2005 Page(s):19 - 25 Digital Object Identifier 10.1109/ICW.2005.54.

• [2] Taleb, T.; Ochi, M.; Jamalipour, A.; Nei Kato; Nemoto, Y. An efficient vehicle-heading based routing protocol for VANET networks. Wireless Communications and Networking Conference, 2006. WCNC 2006. IEEE Volume 4, 3-6 April 2006 Page(s):2199 – 2204.

• [3] Little, T.D.C.; Agarwal, A. An information propagation scheme for VANETs. Intelligent Transportation Systems, 2005. Proceedings. 2005 IEEE13-15 Sept. 2005 Page(s):155 - 160 Digital Object Identifier 10.1109/ITSC.2005.1520039.

• [4] Selvaretnam, B.; Wong, K.D. Handling the inter-vehicular communications challenge - a survey. Communications Systems, 2004. ICCS 2004. The Ninth International Conference on 6-8 Sept. 2004 Page(s):86 – 90.

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Reference( 2/2)• [5] Merlin, C.J.; Heinzelman, W.B. A study of safety applications in

vehicular networks. Mobile Adhoc and Sensor Systems Conference, 2005. IEEE International Conference on 7-10 Nov. 2005 Page(s):8 pp. Digital Object Identifier 10.1109/MAHSS.2005.1542781.

• [6] Schmitz, R.; Leiggener, A.; Festag, A.; Eggert, L.; Effelsberg, W. Analysis of Path Characteristics and Transport Protocol Design in Vehicular Ad Hoc Networks. Vehicular Technology Conference, 2006. VTC 2006-Spring. IEEE 63rd Volume 2, 2006 Page(s):528 - 532 Digital Object Identifier 10.1109/VETECS.2006.1682880.

• [7] Richard Fujimoto Hao Wu; Randall Guensler Michael Hunter, An Architecture Study of Ad-Hoc Vehicle Networks. Georgia Institute of Technology.

• [8] Mr. Hamid MENOUAR, Dr. Massimiliano Lenardi, and Dr. Fethi Filali, A Movement Prediction based Routing Protocal for Vehicle-to-Vehicle Communications. http://www.v2vcom.org/V2VCOM%202005/V2VCOM05_LENARDI.pdf

• [9] Dipak Ghosal, Vehicular Traffic Based Mobile Adhoc Networks: Applications and Challenges. Department of Computer Science University of California, Davis

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A study of the vehicular ad hoc network Speaker: Chih-Sheng Chen