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Low Overhead With Speed Aware Routing (LOWSAR) in VANETs
By Kannikar Siriwong Na Ayutaya
Outline• Problem• Routing Mechanism• Related Works• Objective• Contention-based Routing (CBR) Algorithm• Motivation• LOWSAR Algorithm• Results• Conclusion and Future works
Why need routing for VANETs?
• Reasons: High mobility and frequent network disconnection and merging
• Result: Topology-based routings in MANETs are NOT suitable for VANETs
• Solutions: Position-based routing and Contention-based routing
VANETs Routing Mechanism
• Beaconing: periodically exchange location message between vehicles
• Location service: process of searching for unknown destination location
• Forwarding: transmitting packets to destination (unicast, broadcast, anycast, scan)
Related Works
• Position-based Routing (PBR)– Neighbor positions
obtained by beaconing
– Routing decision is done locally by one node at a time
• Contention-based Routing (CBR)– Routing decision is
done in distributed manner without beaconing
Related Works
• Position-based Routing (PBR)
• Contention-based Routing (CBR)
1
2
43 1
2
43
Related Works (Pros & Cons)• PBR
– Outdated neighbor positions
– High routing decision computational complexity
– Increase message exchanging overhead
– Enhance packet collision
– Eliminate packet redundancy
• CBR– Eliminate beaconing
overhead during routing decision
– Create possibility of packet redundancy
Objective
• Extend contention-based routing (CBR) to account for speed of vehicles
• Propose LOWSAR algorithm to speed up data delivery delay
Basic CBR Algorithm (Terminology)
• T = constant bias clock delay• r = transmission range
• Dmn = distance from nodem to noden
• d = bias clock delay• W = ratio of difference of distance
and r
1
3
5
D15
D15
D35
r
D15 – D35
Basic CBR Algorithm
W = (D15 – D35)/r ≤ 1 d = T(1 – W)
D15Basic CBR Algorithm
d = T
1
3
45
6
2
d < Td > T
7
W = (D17 – Di7)r, i = 2,…,6 d = T(1 – W)
12
4
3
5
D15
D15
D35
r
D15 – D35
D25
D15 – D25 D45
D15 – D45 < 0
d = T(1-(D15 – D35)/r)
d = T(1-(D15 – D 15)/r) = T
d = T(1-(D15 – D25)/r)
d = T(1-(D15 – D45)/r) > T
Basic CBR Algorithm
B
VAt
VBt
VCt
Problem: Location Dominated Forwarding
C
A
A
BC
VA > 0
VC = 0
Problem: Speed Dominated Forwarding
LOWSAR Algorithm
• V = vicinity of a vehicle• D = distance from a node to destination
d = min{ T(1 – W), T(1 – W)/V, T( D/r - 1)}
Preliminary ResultsDelivery Delay Performance of LOWSAR and CBR
0
0.5
1
1.5
2
2.5
25 45 65
Speed Limits (mph)
End
-to-
End
Del
ays
(sec
)
LOWSAR
CBR
Conclusion and Future Works
• Under different speed limits, LOWSAR outperforms CBR in terms of delivery delay
• Explore effects of other parameters on delivery delay – Number of source nodes– Data rate– Number of vehicles (traffic density)
Conclusion and Future Works
• Investigate on other performance metrics– Average number of hops to a destination– Packet delivery ratio
• Compare these performance with other compatible routing algorithms
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