VANET Hybrid Vehicular Communication Systems (HVC) IVC RVC AP
IVC server router AP RVC IVC 28
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Summary RVCIVCHVC Mobility management Choosing Internet gateway
Unicast Routing Cluster- Based Routing Geocast Routing Broadcast
Routing VANET 29
Slide 30
Outline Part I VANET VANET Part II Geographic Routing in City
Scenarios Part III Conclusions and Future work 30
Slide 31
Christian Lochert, Martin Mauve, Holger FuBler, Hannes
Hartenstein ACM SIGMOBILE Mobile Computing and Communications
Review, 2005 31
Slide 32
Introduction It is related to the idea of position-based source
routing as proposed for terminode routing. The static street map is
need due to its algorithm. This paper provide a method without
assumption that Nodes have access to a static street map and
Without using source routing 32
Slide 33
Position-based Routing Greedy forwarding An intermediate nodes
forward a packet to the direct neighbor which is closest to the
geographic position of destination For this task, nodes has to be
aware of Its own position The position of its direct neighbors The
position of the final destination 33
Slide 34
Local maximum Problem 34
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Greedy Perimeter Coordinator Routing Without using any global
information such as static map. GPCR consists of two parts: A
restricted greedy forward A repair strategy based on the topology
of real-world streets and junctions Therefore, it doesnt require a
graph planarization algorithm. 35
Slide 36
Restricted Greedy Routing Junctions are only places where
actual decision are taken Packets should always be forwarded to a
node on a junction rather than across a junction If the forwarding
nodes are all not located on a junction, chose the node that
Approximates an extension of the line between forwarding nodes
predecessor and itself. 36
Slide 37
Restricted Greedy Routing (cont.) Greedy Routing vs. Restricted
Greedy Routing in the area of a junction. 37 Source : U Destination
: D
Slide 38
Restricted Greedy Routing (cont.) 38
Slide 39
Repair Strategy As a consequence the repair strategy of GPCR
consists of two parts: (1) On each junction it has to be decided
which street the packet should follow next. (2) In between
junctions greedy routing to the next junction, as described above,
can be used. 39
Slide 40
Example A packet with destination D reaches a local maximum at
node S. The forwarding of the packet is then switched to the repair
strategy and it is routed along the street until it hits the first
coordinator node. 40
Slide 41
Detecting junctions By observing the beacon messages a node has
the following information for each neighbor: its position and the
position and presence of the neighbors neighbors. x y z 41
Slide 42
Detecting junctions We dene x i and y i as the x-coordinate and
y- coordinate of a node i. The variables x and y subsume the
population of all these positions x i and y i respectively. The
mean of a population x is marked by x 42
Slide 43
Cont. A correlation coefcient close to 1 indicates a linear
coherence as it is found when the node is located in the middle of
a street A correlation coefcient close to 0 shows that there is no
linear relationship between the positions of the neighbors.
Consequentially we conclude that the node is located on a junction
43
Slide 44
Simulation Results For the simulations we used a real city
topology which is a part of Berlin,Germany. The scenario consists
of 955 cars (nodes)on 33 streets in an area of 6.25 km *3.45 km
IEEE 802.11 was used as MAC with a transmission rate of 2 Mbps. The
transmission range was set to 500 m. 44
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GPCR vs. GPSR. Delivery rate 45
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GPCR vs. GPSR. Delivery rate 46
Slide 47
Conclusions and Future work Our approach does not require
external information such as a static street map to avoid the
problems that existing position-based approaches face in this type
of environment Future improvement Currently the next street to be
taken is determined without considering whether there is a sufcient
number of nodes on the street to allow packet forwarding to the
next junction. 47
Slide 48
Outline Part I VANET VANET Part II Geographic Routing in City
Scenarios Part III Conclusions and Future work 48
