low energy adaptive clustering hierarchy with deterministic cluster-head selection

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http://www-md.e-technik.uni-rostock.de/

University of Rostock

Applied Microelectronics and Computer Science

Dept. of Electrical Engineering and Information Technology

Low Energy Adaptive Clustering Hierarchy with Deterministic Cluster-Head Selection

M. J. Handy, M. Haase, D. Timmermann

Institute of Applied Microelectronics and Computer Science


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Outline

Introduction / Motivation

sensor networks, lifetime, communication models

Problem Formulation

cluster-head selection, LEACH algorithm

Contribution

improved CH-selection algorithm, definition of sensor network lifetime

Simulations

simulation tool, simulation set-up, results

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- Only the sandbags know

- Useful application of wireless microsensor networks

- Equip each sandbag with a moisture sensor

- Collect and evaluate data

How do sensors collaborate efficiently?

Introduction

Where is the spot of leakage?

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Efficient collaboration of sensors means:

- Ensure connectivity

- Efficient role assignment

- Collect only significant data

- Decrease latency

- Save energy

Our Goal: Extend network lifetime

Introduction

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Introduction

How to increase sensor lifetime?

Reduce energy consumption

- Hardware issue(e.g. circuit design)

- Software issue

•Applications / OS

•Algorithms

•Protocols

Increase energy supply

- Energy density is the problem

- Battery capacity increases only by 30-50 % in 5 years

- Compare with Moore‘s Law

- Micro-sensors vs. macro-batteries?

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N

iiiampielecdt dkkEE

ii1

- Direct transmission

- Multihop transmission

- Clustering

CHnonCHclusterct E

l

NEllEE

toBSTxTx

H

iTxRxmt EEEEE

gg _

1

21

Communication Models

[1]

[1]

[1] Heinzelman, Chandrakasan `01

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Cluster-Based Communication

A Simple Algorithm

The problem: Select j cluster-heads of N nodes without communication among the nodes

The simplest solution:

- Each node determines a random number x between 0 and 1

- If x < j / N node becomes cluster-head

...it‘s good, but:

Cluster-heads dissipate much more energy than non cluster-heads!

How to distribute energy consumption?

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LEACH Communication Protocol

Low-Energy Adaptive Clustering Hierarchy

- Cluster-based communication protocol for sensor networks, developed at MIT

- Adaptive, self-configuring cluster formation

- The operation of LEACH is divided into rounds

- During each round a different set of nodes are cluster-heads

- Each node n determines a random number x between 0 and 1

- If x < T(n) node becomes cluster-head for current round

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Cluster-Head Selection

LEACH Algorithm

Gn

PrP

PnT

1

mod1

GnnT 0P = cluster-head probability (j/N)

r = number of the current round

G = set of nodes not been cluster-heads in the last 1/P rounds

Every node becomes cluster-head exactly once within 1/P rounds

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Cluster-Head Selection

LEACH Algorithm

Gn

PrP

PnT

1

mod1

GnnT 0P = cluster-head probability (j/N)

r = number of the current round

G = set of nodes not been cluster-heads in the last 1/P rounds

Every node becomes cluster-head exactly once within 1/P rounds

Drawback: Selection of cluster-heads is completely stochastic!

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Cluster-Head Selection, Our Approach I

xman

currentn

E

E

PrP

PnT

_

_

1mod1

En_current = current energy of node n

En_max = initial energy of node n

Simulations showed:

+ longer network lifetime

- After a certain number of rounds the network is stuck, although there are still nodes alive

- The reason: T(n) is too low since the remaining nodes have very low energy level

Basic Idea: Include the remaining energy level

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Idea: Increase T(n) when network is stuck

max_

_

_

_ 11

1mod1 n

currentns

xman

currentn

E

E

Pdivr

E

E

PrP

PnT

rs = number of rounds a node has not been cluster-head

(reset to 0 when a node becomes cluster-head)

- T(n) is increased when the network is stuck

- Possible deadlock of the network is solved

Significant longer network lifetime

Cluster-Head Selection, Our Approach II

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Lifetime of Microsensor Networks

Introducing 3 New Metrics

First Node Dies (FND)

- Network quality decreases considerably as soon as one node dies

Half of the Nodes Alive (HNA)

- The loss of a single or few nodes does not diminish the QOS of the network

Last Node Dies (LND)

- Estimated value for overall lifetime of thenetwork

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Simulations

Simulation Tool

- YANASim (Yet Another Network Analyzing and Simulation Tool)

- Simulates energy consumption of microsensor networks

- Uses Clustering, Multihop and Direct Transmission

- Visualisation of simulation results

- Platform independent (Java)

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Simulations

Energy Model

TransmitElectronics

ReceiveElectronics

Tx Amplifierk bit packet

k bit packet

ETx(d)

ERx

Eelec* k eamp* k * d2

Eelec* k

d

kdkEdkE ampelecTx ,

kEkE elecRx

Transmit:

Receive:

k = message length

d = distance

λ = path-loss index

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Simulations

Simulation Results (1)

574

746

1104

1337

0

500

1000

1500

LEACH Improved CHS

Lif

etim

e (R

ou

nd

s)

FND

HNA

Simulation Setup:

Nodes: 200

Area: 200m*200m

Base Station Pos.: (100,300)m

Initial Energy / Node: 1 J

Message Length: 200 bit

CH-Probability: 0.05

Path-Loss (intra-cluster): 2

Path-Loss (to BS): 2.5

30 % longer lifetime for FND, 20 % for HNA

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Simulations

Simulation Results (2)

107134

251

297

0

100

200

300

400

LEACH Improved CHS

Lif

etim

e (R

ou

nd

s)

FND

HNA

Simulation Setup:

Nodes: 200

Area: 200m*200m

Base Station Pos.: (100,500)m

Initial Energy / Node: 1 J

Message Length: 200 bit

CH-Probability: 0.05

Path-Loss (intra-cluster): 2

Path-Loss (to BS): 2.5

25 % longer lifetime for FND, 18 % for HNA

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Contribution / Conclusions

- Improvement of LEACH‘s cluster-head selection algorithm

- 30 % increase of lifetime of sensor networks

- Only local information is necessary for cluster-head selection

- Communication with the base station or an arbiter node is not necessary

- Three new lifetime metrics FNA, HNA, and LND

- Use of metrics depends on application.

low energy adaptive clustering hierarchy with deterministic cluster-head selection

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