Low Overhead With Speed Aware Routing (LOWSAR) in VANETs By Kannikar Siriwong Na Ayutaya
Mar 27, 2015
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– Outdated neighbor positions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