SEEKER: An Adaptive and Scalable Location Service for Mobile Ad Hoc Networks

Jehn-Ruey Jiang and Wei-Jiun Ling

Presented byJehn-Ruey Jiang

National Central University

NCU ACN Lab. 2ICS 2006

Outline

• Introduction

• Related Work

• The SEEKER Location Service

• Simulation Result

• Conclusion

NCU ACN Lab. 3ICS 2006

Categories of Routing Protocols for MANETs

• Topology-Based routing protocols:– AODV, DSR …etc

• Position-Based routing protocols:– Each node knows its location via a GPS or the like– A source node knows the destination location– Routing via greedy forwarding or the like

More Scalable

NCU ACN Lab. 4ICS 2006

Greedy Forwarding

S

a

D

b c

e

NCU ACN Lab. 5ICS 2006

Location Service

• Position-Based routing requires a location service to support :– location registration– location update– location query

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Problem

• A good location service must have :– High scalability– High query accuracy and success rate– Low protocol overhead

• Update and maintenance overhead• Query overhead

• How to design a good location service?

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Outline

• Introduction

• Related work

• The SEEKER Location Service

• Simulation Result

• Conclusion

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The Classification of Rendezvous-Based Location Services

NCU ACN Lab. 9ICS 2006

Quorum-Based (XYLS)

[Stojmenovic 1999]

Updates

QueriesIntersection

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Hierarchical-Based (GLS)

[Li et al. @MobiCom 2000]

26, 31, 32, 74, 75, 79, 98

2

55

43

75

98

31

63

17

79

12

27

87

32

23

81

33

856

4

28

99

62

74

12

26

91

23

2323

23

23

23

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Hash-Based (SLURP)

[S.-C. M 2001]

A

A

Region

Home Region

B

NCU ACN Lab. 12ICS 2006

Outline

• Introduction

• Related Work

• The SEEKER Location Service

• Simulation Result

• Conclusion

NCU ACN Lab. 13ICS 2006

SEEKER - Overview

• Control overhead can be reduced by aggregate update

• Adapt to mobility by adjusting the frequency of location updates to further reduce overhead: adaptive update

• Goals: to achieve– High scalability– High query accuracy and success rate– Low protocol overhead

NCU ACN Lab. 14ICS 2006

SEEKER – Aggregate Update

• Initial nodes send LOC packet (location update packet) periodically.

• The initial node sets a virtual destination to deliver the LOC packet to.

• The LOC packet is relayed by greedy forwarding until it reaches the terminal node.

• The nodes in the path from the initial node to the terminal node serve as the location servers for all the nodes in the same row of regions.

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SEEKER – Location Update

Initial node

Initial node :

Self-selection by testing neighbors in the east and west

Ex. If no node is to the west of a node, it will be the initial node to send LOC to the east

Virtual destination

Terminal node

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SEEKER – Location Query

A

BC

Unicast Query-Reply

Unicast Query-Request

Broadcast Query Request

Broadcast Query Reply

NCU ACN Lab. 17ICS 2006

SEEKER - Adaptive Location Update

• Observation: there is a tradeoff between update interval and query accuracy

• Basic idea: let the terminal node calculate the average speed of nodes of each row

• Procedures:1. Calculate the average speed and transform it into

the new update interval by the terminal node2. Spread the new update interval to the terminal

node’s neighbors3. Spread the new update interval by LOC packets

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Transform Average Speed into Update Interval

• Define speed levels, – ex: 2.5 m/s, 5.0 m/s, 7.5 m/s, 10.0 m/s, and 12.5 m/s

• Adopt ½ difference (1.25 m/s) to be interval boundaries

• Next update interval = Transmission range / Speed level

Update interval Range of Speed levels

1.25 2.5 7.55.0 10.0 12.5

100 (s)50 (s)

30 (s)25 (s)

20 (s)

0

200 (s)

m/s

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Procedure of Adaptive Location Update

A LOC

Next update

Hello packet

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Outline

• Introduction

• Related Work

• The SEEKER Location Service

• Simulation Result

• Conclusion

NCU ACN Lab. 21ICS 2006

Simulation Result

• Simulation environment– Simulate by ns2– Node density within 100 nodes/km2

– Random waypoint with speed 0~10 m/s – 300 seconds per simulation

• Metrics– Control overhead (update + query)– QSR (Query Success Rate)– PDR (Packet Delivery Rate)

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Comparison

• Up to 600 nodes

• Compared with GLS and HIGH-GRADE

• Bandwidth is 2Mbps

• The performance of fixed update interval vs. adaptive update interval

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Update Overhead

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Query Overhead (reply excluded)

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Query Success Rate (QSR)

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Packet Delivery Rate (PDR)

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0 100 200 300 400 500 600

Number of nodes

Pack

et d

eliv

ery

rate

SEEKER GLS

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Outline

• Introduction

• Related Work

• The SEEKER Location Service

• Simulation Result

• Conclusion

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Conclusion

• SEEKER achieves comparably low control overhead by using aggregate update

• Control overhead (esp. update overhead) can be further reduced by adaptive update

• SEEKER achieves – comparably high scalability (2000 nodes)– comparably high query success rate– comparably high query accuracy– comparably low maintenance cost

NCU ACN Lab. 29ICS 2006

Thank you!Questions and Comments?