vanet routing
TRANSCRIPT
Vanet Routing on city roads using Real time
Vehicular traffic Information(ieee transactions on vehicular technology, vol. 58, no. 7, september 2009)
VANET A subclass of Mobile Ad hoc networks.
Uses vehicular traffic as its nodes.
Allows high node mobility.
Takes advantage of restricted paths
(Roads).
Limitations of MANET[1]:• Inefficient mobile node handling.• Leads to frequent makings and
breakings of path between source and destination.
Geographical Routing:May got failed in case of dead ends.
Inefficient Route Selection
RBVTEvery node is equipped with-
1) GPS Transceiver2) Digital Maps3) A Navigation System
RBVT Protocols:
1. RBVT-R – A reactive protocol
2. PBVT-P – A pro active protocol
– Road based using vehicular traffic Information protocols.
RBVT-R: A Reactive ProtocolCreates road based paths by using
connected road segments.Information about the route is
stored in the header of the packet.
Routing is done in 3 steps: 1) Route Discovery 2) Route Reply
3) Route Maintenance
1. Route DiscoverySource floods an RD packet.Uses improved flooding
mechanism.RD Packet gets updated with the identities [Ij] of
Intersections.
2. Route ReplyDestination node generates RR
packet.Data in RD is copied to RR.RR reaches source through the
same pathAfter receiving RR, source transmits data packets.
3. Route Maintenance
Route once generated cannot be the same forever.
RU packets are used to update routes.
RE packets are uni-casted back to source if any intersection
is unreachable. Only after few REs, RD packets are generated by source.
RBVT-P : A proactive protocolPeriodically computes real time graph of connected road segments.
Maintains consistent view of network connectivity at each node.
Source uses location based queries to find destination’s location.
Routing is done in 4 steps:1) Topology Discovery2) Topology Dissemination3) Route Computation4) Route Maintenance
1. Topology Discovery
CPs are unicasted in the network.A Node decides to transmit CP or
not - by itself independently.CP operates in a limited perimeter –
decided by its generatorEndpoints of traversed segments are stored in CPCP returns back to its generator with neteork topology info.
2. Topology DisseminationTopology info from CP is copied to
RU packets.Old routing table at nodes are
updated by new RU content.Routing tables areupdated in segment by segment basis.
3. Route Computation
Source node computes the shortest path.
Series of intersections representing path are stored in header.
Timestamp is also included for freshness comparison.
4. Route Maintenance
Header of data packets are updated with fresher information by intermediate nodes.
In case of any route break, auto transition to geographical routing takes place.
When packet reaches a node that has fresher information, then it switches back to RBVT-P.
Forwarding Optimization
Beaconing “Hello” messages in GR reduces overall end-end performance
But is important for maintaining accurate list of surrounding nodes
To overcome this IEEE 802.11 RTS/CTS mechanism is extended where next hop is self elected by receiver itself
Continue…
•RTS is sent
•CTS by n2
•DATA by nS
•ACK by n2
Conclusion:RBVT –R and RBVT-P are the two
efficient protocols to handle highly mobile vehicular nodes.
RBVT-R : best average delivery rate [2]
RBVT-P : Least average delay.
References:[1] Elizabeth M. R. and Chai-Keong
T.,,”A review of current routing protocols for ad hoc mobile wireless networks”, Technical report, University of California and eorgia Institute of Technology, USA, 1999
[2] Josiane Nzouonta, Neeraj Rajgure, Guiling Wang and Cristian Borcea, ” VANET Routing on City Roads Using Real-Time Vehicular Traffic Information”, IEEE Transactions on Vehicular Technology, Vol. 58, No. 7, pp. 3609-3626, September 2009.