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– Outdated neighbor positions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