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Maintaining Connected Coverage for Wireless Sensor

Networks

Jehn-Ruey Jiang and Tzu-Ming SungDepartment of Computer Science and Information E

ngineering,National Central University, Taiwan

The 28th International Conference on Distributed Computing Systems Workshops

ICDCS 2008

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Outline

Introduction Problem Formulation The Density Control Algorithm Simulation Results Conclusion

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Introduction

The wireless sensor network consists of a large number of micro sensors for different application Battlefield surveillance Environment monitoring Animal tracking

The most of the sensors are supported battery distributed over a large area It is hard to recharge

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Introduction

How to extend the network lifetime is an important problem in WSNs. To deploy high density sensors To use power saving mechanism

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Problem Formulation

Sensors Asynchronous Position-less Density-high Sensing range

Rs Communication r

ange Rc

Rc ≥ 2Rs

The interesting area G

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Problem Formulation

In the high density sensor deployment How to connect the coverage with the least

umber of the sensor? To power saving in the asynchronous

system How to provide a mechanism for sensor to

aware of active sensors’ statuses by asynchronously beaconing

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R. Kershner, “The Number of Circles Covering a Set”,American Journal of Mathematics

The Optimal (Least) Number of Sensors

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The Density Control Algorithm

Two type of the beacon a beacon

:near beacon1/ <α<1

b beacon:far beacon

R3

Ｒ

3

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The Density Control Algorithm

The power saving in asynchronous system Monitor interval

Beacon window TI (traffic indication) window n beacon intervals

Non-monitor interval Beacon window TI (traffic indication) window

round

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The Density Control Algorithm

j node can receive the beacon and store to the two type set

A set j can hear i’s a-beacon i is older than j i is oldest among those whose

AB set J can hear I’s b-beacon but not hear a-beacon

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The Density Control Algorithm

(158,a,0) (143,b,0)

(158,a,-1)

(158,a,-2)

In the beacon interval the sensor will

broadcast the beacon with the vector

(time, root, level)

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Simulation Results

Language C Area : 100m x 100m Rc =20 meters Rs = 10 meters Beacon interval 100ms α= 0.7, 0.75, 0.8 and 0.85

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Simulation Results

Optimal hexagon-base deployment

: 42 sensors

The Algorithm : 51 sensors

The cover factor R = 51/42

= 1.21

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Simulation Results

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Simulation Results

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Conclusion

Under the assumption Rc ≥ 2Rs This paper propose the algorithm

Without location information Use two type beacons

Near beacon Far beacon

To approximate the optimal connected hexagonal deployment

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Thank you