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On the Energy Hole Problem of Nonuniform Node Distribution in Wireless Sensor Networks

Xiaobing Wu, Guihai ChenState Key Laboratory for Novel Software Technology

Nanjing University

Sajal K. DasDepartment of Computer Science and Engineering

The University of Texas at Arlington

MASS 2006

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Outline

Introduction Theoretical Analysis of Nonuniform Node Dist

ribution Strategy Routing with A Nonuniform Node Distributio

n Strategy Simulation Results Conclusions

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Introduction

Nodes nearer the sink have to take heavier traffic load

A

Sink

Sensor

B

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Introduction

Sensor nodes that are closer to sink consume their energy rapidly (Energy Hole Problem) Network partition

A

Sink

Sensor

B

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Motivation and Goal

Motivation Explore the theoretical aspects of power balanc

e problem in wireless sensor networks with nonuniform node distribution

Goal Propose a node distribution strategy to achieve

a suboptimal balanced energy depletion

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Assumptions and Network Model

A circular area with a radius of R Transmission range of all the nodes is fixed Data can be transmitted to the next inner corona with

one hop

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Theoretical Analysis of Nonuniform Node Distribution Strategy

Ei : Energy consumed per unit time by the nodes in corona Ci

Ni : The number of nodes in the corona Ci

A node Send one bit : e1 units of energy

Receive one bit : e2 units of energy Generate and send L bits of data per unit time

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The Impossibility of Balanced Energy Depletion of The Network

Initial energy

A perfect and maximum energy efficiency is not achievableNodes in the corona CR only need to transmit their own data

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The Suboptimal Balanced Energy Depletion of The Network Find that a balanced energy depletion among t

he coronas except the outmost one is possible

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The Suboptimal Balanced Energy Depletion of The Network

The number of nodes in coronas varies with a geometric proportion from outer coronas to inner ones in the whole network

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Routing with A Nonuniform Node Distribution Strategy Assume the number of nodes in the coronas i

ncreases with geometric proportion Each node in Ci+1 can communicate directly w

ith q different nodes in Ci

48163264 q=2

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Routing with A Nonuniform Node Distribution Strategy In network initialization, nodes find their

upstream node and their q relay candidates The source node selects one relay node with

maximum energy resource

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Simulation Results

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Simulation Results

Most nodes have little energy wasted

C1 (128)C2(64)

C3(32)

C4(16)

C5(8)

C6(4)

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Simulation Results

Small variances in the fragments

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Simulation Results

Residual energy ratios of different values of network radius and q

Simulated value q=2

Theoretical value q=2

Simulated value q=3

Theoretical value q=3

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Conclusions

With the number of nodes in the coronas increasing from outer areas to inner ones with geometric proportion The network achieves a high energy efficiency