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Inter-Vehicle Ad-hoc Networks. By Shweta Shrivastava Manali Joglekar Gaurav Rajguru. Traditional Roadside Sensor Networks. An array of sensors are embedded in the roads and on roadsides.

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inter vehicle ad hoc networks

Inter-Vehicle Ad-hoc Networks


Shweta Shrivastava

Manali Joglekar

Gaurav Rajguru

traditional roadside sensor networks
Traditional Roadside Sensor Networks
  • An array of sensors are embedded in the roads and on roadsides.
  • These sensors collect traffic and incident data and report it to a centralized location called data center via a gateway.
  • The communication between sensors and the gateway is over a LAN technology like 802.11 or some wired LAN technology.
  • The communication between gateway and data center is over some high speed network like ATM.
  • The data center organizes all information and stores it in a database.
traditional roadside sensor networks contd
Traditional Roadside Sensor Networks (contd.)
  • The information can be accessed by users using a web interface. A web server is used in this case to query the database.
  • The information is also available by phone.
  • In some cases, the information is pushed to user’s mobile phone, other handhelds or certain special devices installed in cars.
  • Technology like GPS is used to convey information to user’s handheld and in-car devices.
data flow in roadside sensor networks
Data Flow in Roadside Sensor Networks








pems uc berkeley caltrans
PeMS (UC-Berkeley & Caltrans)

PeMS : Freeway Performance Measurement System

inter vehicle networks
Inter-Vehicle Networks
  • An emerging concept is that of inter-vehicle sensor networks, which incorporate the functionality of the traditional networks and also provide additional advantages.
  • Inter-Vehicle Networks are ad hoc networks in which moving vehicles can communicate with each other by using the built in sensors.
  • They can also communicate with the roadside sensors and roadside gateways (for internet connectivity).
modes of communication
Modes of Communication
  • IEEE 802.11
  • Ultra-Wide Band (UWB)
  • Bluetooth
  • The above protocols provide peer-to-peer communication.
  • Bandwidth – broadband, typically tens of Mbps.
  • Range – short, typically 50-500 m.
applications of inter vehicle networks
Applications of Inter-Vehicle Networks
  • Driver can know traffic conditions a few miles ahead and thus avoid congested routes and select alternative routes.
  • He can know the available parking spaces around the current location of the vehicle.
  • The system may assist drivers in avoiding collisions.
  • High-speed tolling
  • Mobile infotainment etc.
some specific applications
Some Specific Applications
  • Sudden breaking of a lead vehicle can be immediately transmitted to the following vehicles, which can prevent or mitigate rear-end collisions.
  • At a signalized intersection, the information on the start of a preceding vehicle can be transmitted to the followings, which prevents the starting delay and increases the throughput of the intersection.
  • An oncoming vehicle in the opposite lane can transmit information on congestion, weather or road conditions ahead.
  • At blind intersections, a vehicle can know about other approaching vehicles.
advantages of vehicular networks over traditional roadside sensor networks
Advantages of Vehicular Networks over Traditional Roadside Sensor Networks
  • The lag due to satellite or infrastructure based communication is reduced and users have instant access to information. Results in minimal delay for time-critical safety-related information. More accurate and reliable information.
  • Low transmission costs as compared to cellular. Such an ad-hoc network is free of charge, assuming that vehicles are willing to relay messages for free (in exchange for their messages being relayed).
  • A (relative) position based addressing scheme can be used, no need of global addressing.
comparison with other wireless ad hoc networks
Comparison with Other Wireless Ad-hoc Networks
  • Relatively larger computational resources.
  • Ample and recharging power sources; hence power efficiency not a concern.
  • Mobility patterns are not random, but are constrained by road paths and driving speed restrictions.
  • Nodes move with high velocity with respect to each other. On highways, high relative velocities of up to 400km/h may occur.
  • Due to high relative velocities, the radio contact period of two approaching vehicles may be very short.
requirements of an inter vehicle protocol
Requirements of an Inter-Vehicle Protocol
  • The protocol should be flexible enough to maintain a network among vehicles when a new vehicle joins the network or a vehicle in the network leaves it.
  • The protocol should be able to handle real-time data transmission, especially for vehicle control and safety information.
  • There might be a trade-off in the above two requirements for a particular application. If maintaining network topology is more important, then a contention based protocol like CSMA can be used. If real time data transmission is more important, a non-contention type protocol would be preferable.
current routing protocols for ad hoc mobile wireless networks
Current Routing Protocols for Ad-hoc Mobile Wireless Networks
  • Two types of routing protocols exist:
    • Proactive – These protocols maintain routing information about all the available paths in the network even if these paths are not currently being used. E.g. DSDV, WRP etc.
    • Reactive – These protocols maintain routing information only about the routes that are currently in use, thus reducing the burden on the network. E.g. AODV, DSR, TORA etc.
  • In both the above schemes, some topology information has to be maintained, which limits the amount of topological changes that can be tolerated within a given amount of time.
  • Position-based routing makes routing decisions based on the location or position of a node and hence does not need to maintain routing information on nodes.
position based routing
Position-based Routing
  • Requires information about the physical position of the nodes. This can be determined by a node by using GPS or a similar service.
  • Each node needs to know its own position, the destination’s position and the positions of its one hop neighbors in order to forward packets.
  • A location service is used by the sender of a packet to determine the position of the receiver and to include it in the packet’s destination address.
  • Information can also be delivered using geocast, which is actually a geographic multicast, i.e. delivery of packets to all nodes in a given geographic region.
  • The position of the neighbors is learnt by periodic broadcasts of beacons containing a node’s position.
position based routing contd
Position based Routing (contd.)
  • Every node is identified by an ID and its location (these are analogous to IP address and MAC address).
  • An ID can be obtained by a hash function of the node’s IP address.
  • A transmitting node has to find the location of the destination node from its ID to forward packets.
  • The mapping from ID to location can be performed in two ways:
    • By querying a location service
    • By broadcasting a request for the mapping. The destination node or one of its neighbors will respond.
  • Once the mapping is obtained, the sending node sends the packet to that neighbor which is closer to the destination than the sending node itself.
various position based routing algorithms
Various Position-based Routing Algorithms
  • Greedy Algorithm – In this, a packet is forwarded to one randomly chosen node in the direction of the destination.
  • Restricted Directional Flooding – Packets are broadcasted in the general direction of the destination.
  • Hierarchical Algorithms – In these, routing is done hierarchically by means of a position-independent protocol at the local level and a greedy variant at long-distance level.
various position based routing protocols
Various Position based Routing Protocols
  • DREAM – Position information is flooded in the network. Time between flooding depends on node mobility. Nearby nodes are updated more frequently than farther nodes.
  • Quorum-based position discovery requires identifying overlapping groups of participants. Updates are transmitted to one of those groups and position queries directed to another one. Since groups overlap, the required information is available in each group.
  • The GLS approach works by hashing the ID of a node on the IDs of so-called location servers. These location servers are updated by the destination node with regard to its own position and queried by the source nodes that want to contact the destination node.
  • The Homezone algorithms requires that the ID of a node be hashed on a position. All nodes close to this position are informed about the position of the node and provide this information to sources that want to contact it.
drawbacks of existing algorithms
Drawbacks of Existing Algorithms
  • Most algorithms require the use of infrastructure based systems to query the location of the destination. There should be an ad-hoc means to do that.
  • They do not properly address the issue that what happens when a packet reaches a node that has no other node that is closer to the destination than itself.
  • More robust strategy needed to determine the next hop for forwarding a packet.
  • Most algorithms are not very efficient when the network is very sparsely or densely populated.
our aim for the project
Our Aim for the Project
  • To study various existing routing algorithms/protocols for vehicular networks and compare their performance by ns-2 simulations.
  • If time permits, suggest a new and more efficient routing algorithm.
  • K. F. Petty, “Incidents on the Freeway: Detection and Management”, Department of Electrical Engineering and Computer Science, University of California, Berkeley, California. Committee: P. Varaiya, S. Sastry, C. Daganzo. Fall 1997.
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