kais t a bidding protocol for deploying mobile sensors 발표자 : 권 영 진 guiling wang, guohong...

KAIST

A Bidding Protocol for Deploying Mobile SensorsA Bidding Protocol for Deploying Mobile Sensors

발표자 : 권 영 진

Guiling Wang, Guohong Cao, Tom LaPorta

The Pennsylvania State UniversityIEEE, ICNP 03

ContentsContents

Introduction

Voronoi diagram

Bidding protocol(key concepts, remained issues)

Performance evaluations

Conclusion

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Introduction ( 1/2 )Introduction ( 1/2 )

Mobile sensor

Problems : How to deploy mobile sensors efficiently?“Three distributed self-deployment protocols”

(Movement-Assisted Sensor Deployment, IEEE infocom 04)

Use only mobile sensor

Not cost-effective

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Introduction ( 2/2 )Introduction ( 2/2 )

“Bidding protocol”Key idea : static sensor + mobile sensor

Coverage holes : the area that sensor cannot cover

Static sensor : detection of coverage holes

Mobile sensor : heal of coverage holes

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Sensor circle

Coverage holes

Static sensor

Mobile sensor

Hole healing

Terminologies of Voronoi diagramTerminologies of Voronoi diagram

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Voronoi cell

Voronoi diagram

Applying Voronoi diagram to Mobile Applying Voronoi diagram to Mobile sensorsensor

Put sensor on site points

Each sensor is responsible for the sensing task in Voronoi cells

Each sensor can examine the coverage hole locally

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sensor

Bidding protocol ( key concepts) ( Bidding protocol ( key concepts) ( 1/7 )1/7 )

Important questionsHow to estimate coverage hole?

Which mobile sensor should move to the place?

Where should the mobile sensor move?

Bid ( for static sensor ) estimated size of hole

Base price ( for mobile sensor ) estimate of generated coverage hole after it leaves

the current place

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Bid Estimation( in Static Sensor )Farthest Voronoi vertex is the target location of mobile sensor

Bid is the area of the inner circle

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Bidding protocol ( key concepts) ( Bidding protocol ( key concepts) ( 2/7 )2/7 )

Healing of most largest hole

d

Bid = π * ( d – sensing_range)2

relative size of coverage hole

Bidding protocol ( key concepts) ( Bidding protocol ( key concepts) ( 3/7 )3/7 )

Base price evaluation( in mobile sensor )Initial value is 0

The accepted bid is a new base price

Meaning of a bid and a base price

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Bid: estimate of healed hole

Base price : estimate of upcoming hole

Bidding protocol ( key concepts) Bidding protocol ( key concepts) ( 4/7 )( 4/7 )

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Let’s put it all together !

Bidding protocol flows( round by round )

Service advertisement

Initialization

Serving

Bidding

Termination

Construct Voronoi diagram

Bidding protocol ( key concepts) Bidding protocol ( key concepts) ( 5/7 )( 5/7 )

Service advertisementMobile sensor broadcasts their base price and location

Base price is set to zero initially

BiddingCalculate bids and target location for the mobile sensor

Send bids to closest mobile sensor

whose base price is lower than bids

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Bidding protocol ( key concepts)Bidding protocol ( key concepts) ( 6/7 ) ( 6/7 )

ServingMobile sensor choose the highest bids and heal coverage holes

Accepted bids becomes new base price

TerminationIf base price of all mobile sensor is higher than bids, then terminate

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Bidding protocol ( key concepts)Bidding protocol ( key concepts) ( 7/7 ) ( 7/7 )

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Mobile sensorStatic sensor

93% coverage at round 5

40 sensors, 12 mobile sensors

82% coverage

Performance evaluations ( 1/3 )Performance evaluations ( 1/3 )

Evaluation methodologyMain cost

Number of sensor

Number of round

EnvironmentNs-2 simulator

40 sensors and 10 independent experiments

Some considerationsTrade off between cost and coverage

Cost ratio between the mobile sensor and the static sensor

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Performance evaluations ( 2/3 )Performance evaluations ( 2/3 )

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Random deployment : just use static sensorBidding protocol : static sensor + mobile sensorVEC algorithm : mobile sensor

Random deployment

Bidding protocol

VEC algorithm

Trade off The more mobile sensor are used, The better coverage is obtained But the sensor cost will be increased

Performance evaluations ( 3/3 )Performance evaluations ( 3/3 )

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ConclusionsConclusions

Voronoi diagram can be applied to a sensor network

using a greedy heuristic method

Mixture of a static sensor and a mobile sensor can achieve

a good balance between coverage and cost

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Extra ( 1/4 ) Extra ( 1/4 )

Duplicate healing

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Extra ( 2/4 ) Extra ( 2/4 )

Duplicate healing detection

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A

B

Broadcast

Check if base price of A > base price of BIf yes, run detection algorithmIf detected, set base price of A to zero

Extra ( 3/4 ) Extra ( 3/4 )

Detection AlgorithmDetecting threshold = π * ( dmin – sensing_range)2

dmin : Distance to closest neighbor

IF ( detecting threshold < new base price ||

dmin < sensing_range )

THEN duplication occurs

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Extra ( 4/4 )Extra ( 4/4 )

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A,B is mobile sensor

Snapshot in the middle of round

Nf ’s base price is calculated without consideration of Ne

at Nf

Detecting threshold < New base price

New base price of B

dmin

Why Detecting threshold < New base price?