Prolonging the Lifetime of Wireless Sensor Networks via Unequal Clustering

Stanislava Soro Wendi B. Heinzelman

University of RochesterIPDPS 2005

Outline

• Introduction• Network Model• Theoretical Analysis• Simulations• Conclusions

Introduction

• Important issues in WSN• Energy• Network lifetime

• Cluster• Enables the efficient utilization of the

limited energy resources of the deployed sensor nodes

Introduction

• Equal Cluster Size• While in multi-hop communication, the nodes

closest to the base station are burdened with a heavy relay traffic load and die first

• Network partition

• Motivation• Maintain more uniform energy consumption

among the cluster heads, so that the total energy dissipated for every cluster head is similar

Environment

N sensor nodes

A smaller number of more powerfulNodes are deployed to serve as C.H.Nodes with pre-determined locations

Network Model

• Data aggregation• Perfect aggregation• Nonperfect aggregation

• The position of cluster heads• The energy consumed in each cluster of

each layer

Network Model --aggregation

• Perfect aggregation• Cluster head compresses all the data recei

ved from its cluster into one outgoing packet

• Nonperfect aggregation• Cluster head sends more than one outgoin

g packet toward the base station

Network Model --cluster header

• Overall energy consumption of nodes that belong the C.H.

• Keep the energy within in the C.H. as small as possible

Network Model --energy consumption

• P: p-bit packet• e1,e2 : Transmission/Amplifier• e3: aggregation consume• Ni: sensor in cluster i

Theoretical analysis

• Present the evaluation of the energy consumption for two clustered models• Equal Clustering Size (ECS)• Unequal Clustering Size (UCS)

• Compare the total energy consumed between ECS and UCS models, if the network is dimensioned to last at least T rounds

ECS

• For ECS, the radius of each layer is

• : Energy spent of C.H. in layer 1• : Energy spent of C.H. in layer 2

ECS

• The battery of sensor nodes• The furthest node from its cluster head

• Every node has to be equipped•

UCS

• Energy spent of cluster header•

• Sensor node has to be equipped•

Simulation

• Simulator : MATLAB• Ra: 200 m• Deploy node :400 nodes• R1: Ra[0.2, 0.9]

Simulation

Ratio of the total energy spent on batteries for the entire network for UCS and ECS

Every cluster head sends 1 aggregated packet.

Simulation

Ratio of the total energy spent on batteries for the entire network for UCS and ECS

The cluster heads perform aggregation with efficiency α = 0.1.

Simulation

Ratio of the total energy spent on batteries for the entire network for UCS and ECS

The cluster heads perform aggregation with efficiency α = 1.

Simulation

Maximum number of rounds for UCS and ECS.

Simulation

The ratio of average number of nodes in clusters in layer 1 and 2.

Simulation

• Consider 3 layers of clusters around the base station

• The ratio of the number of nodes in clusters of layer 1 and 2, and ratio of layer 2 and 3 is approximately equal to 1

Conclusions

• We analyze an approach for the hierarchical organization of wireless sensor networks where, in order to balance the energy consumption of cluster head nodes, unequal size clusters are formed