Connectivity-Aware Routing (CAR)
in Vehicular Ad Hoc Networks
Valery Naumov & Thomas R. Gross
ETH Zurich, Switzerland
IEEE INFOCOM 2007
Outline
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Introduction
Related Works
Connection-Aware Routing (CAR)
Simulation
Conclusion
Introduction
• Vehicular ad hoc networks (VANETs) using
802.11-based WLAN technology have recently
received considerable attention in many projects
• Several geographic routing (GR) protocols use an
idealized mechanism such that for every
originated data packet the true position of the
destination is known
– e.g. based on the simulator’s global view
Introduction
• Another problem is that, all of the GR protocols
do not take into account if a path between source
and destination is populated.
• This paper presents a novel position-based
routing scheme called Connectivity-Aware
Routing (CAR) to adress these kind of problems
Outline
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Introduction
Related Works
Connection-Aware Routing (CAR)
Simulation
Conclusion
Related Works
• GPSR (Greedy Perimeter Stateless Routing)
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A geographic routing protocol
Packets are marked with their destinations’locations.
Relay nodes make a local greedy routing.
Greedy mode & Perimeter mode
Related Works
Related Works
Outline
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Introduction
Related Works
Connection-Aware Routing (CAR)
Simulation
Conclusion
Connection-Aware Routing (CAR)
• Adaptive beaconing mechanism:
– Beacon interval is changed according to the
number of nearby neighbors.
• Beacons can be appended in the data packets.
Connection-Aware Routing (CAR)
• The CAR protocol consists of four main parts:
– (1) destination location and path discovery
– (2) data packet forwarding along the found path
– (3) path maintenance with the help of guards
– (4) error recovery
Connection-Aware Routing (CAR)
• Destination location discovery
• A source broadcast a path discovery (PD)
• Each node forwarding the PD updates some
entries of PD
• If two velocity vectors’angle > 18°, anchor is
set.
Connection-Aware Routing (CAR)
• If two velocity vectors’angle > 18°, anchor is set.
– Anchor contains coordinates and velocity vector of
current node and previous node.
Connection-Aware Routing (CAR)
• A route reply will send to the source with
unicast
• Advantages
– Finds the path that exist in reality
– Takes connectivity into account
– No try-and-error route test
– Only source-destination pairs keep anchor path to
each other
Connection-Aware Routing (CAR)
• Greedy forwarding over the anchored path
– A neighbor that is closer to the next anchor point
is chosen, instead of destination.
Connection-Aware Routing (CAR)
Connection-Aware Routing (CAR)
• Path maintenance
• If an end node (source or destination) changes
position or direction, standing guard will be
activated to maintain the path.
Connection-Aware Routing (CAR)
Connection-Aware Routing (CAR)
Connection-Aware Routing (CAR)
• Path maintenance
• If end node changes direction against the
direction of communication, traveling guard
will be activated.
– A traveling guard runs as end node’s old direction
and speed, and reroute the packets to the
destination.
– End node will send a notification to source
Connection-Aware Routing (CAR)
Connection-Aware Routing (CAR)
• Routing error recovery
• The reason for routing error
– A temporary gap between vehicles
– Long-term disconnection a suddenly closed road or big gap in traffic.
– The destination could not activate a guard due to lack of neighbors.
• Timeout algorithm with active waiting cycle
• Walk-around error recovery
Connection-Aware Routing (CAR)
• Timeout algorithm
• When a node detects a gap
– It tells other nodes and starts buffering packets.
– It tries to detest a next hop node, sends requests.
• A node receives the request will reply with a HELLO
beacon.
Connection-Aware Routing (CAR)
• Walk-around error recovery
• When fail to find the destination at its
estimate position
• When Timeout algorithm fail
– Start a location discovery
Connection-Aware Routing (CAR)
• If location discovery is unsuccessful
– Source starts a new path discovery.
• If successful, the new path will send to source
– Source analyzes the new path and current position,
Start a new path discovery if the source is closer then the
node to the destination.
Outline
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Introduction
Related Works
Connection-Aware Routing (CAR)
Simulation
Conclusion
Simulation
• Scenarios
– City
– Highway
• Traffic density
– Low – less than 15 vehicles/km
– Medium – 30-40 vehicles/km
– High – more then 50 vehicles/km
SimulationPacket Delivery Ratio
SimulationAverage data packet delay
SimulationRouting overhead
Outline
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Introduction
Related Works
Connection-Aware Routing (CAR)
Simulation
Conclusion
Conclusion
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Adaptive beaconing
PGB, AGF, and velocity vectors
Anchor points
Path maintenance with guards
Error recovery
Higher performance and lower routing
overhead than GPSR