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CLUSTERING IN WIRELESS SENSOR
NETWORKS
BY
KALYAN SASIDHAR
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RESEARCH PROBLEM
Understanding existing clustering algorithms and finding the problems
stated and addressed
Compare the pros and cons of each algorithm
Simulate algorithms and compare performance with and without clustering
mechanism
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INTRODUCTION TO CLUSTERING Grouping of similar objects or sensors in our context
distance or proximity
Logical organizing
Topology control approach
Load balancing, network scalability
Types of clustering
Static: local topology control
Dynamic: changing network parameters
Single hop and multi hop
Homogeneous and heterogeneous
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HEED[1]
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ADVANTAGES OF CLUSTERING
Transmit aggregated data to the data sink
reducing number of nodes taking part in transmission
Useful energy consumption
Scalability for large number of nodes
Reduces communication overhead for both single and multi hop
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LITERATURE SURVEY OF CLUSTERING ALGORITHMS HEED: A hybrid energy efficient distributed clustering approach for ad-
hoc sensor networks
MRECA: Mobility resistant efficient clustering approach for ad-hocsensor networks
Energy efficient dynamic clustering algorithm for ad-hoc sensornetworks
LEACH-Energy efficient communication protocol for WSN
EEDC-Dynamic clustering and energy efficient routing technique forWSN
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Problem statement Set of nodes, identify set of CHs that cover the entire network
Protocol distributed
Local information
One node-one cluster
Node-cluster head: single hop
CH-CH: multi hop using routing protocol
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HEED
Assumptions
Sensor quasi-stationary
Links are symmetric
Energy consumption non-uniform for all nodes
Nodes-location unaware
Processing and communication capability-similar
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Algorithm:
Cluster head selection hybrid of residual energy (primary) and communication cost (secondary)
such as node proximity
Number of rounds of iterations
Tentative CHs formed
Final CH until CHprob=1
Same or different power levels used for intra cluster communication
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Pros:
Balanced clusters
Low message overhead
Uniform & non-uniform node distribution
Inter cluster communication explained
Out performs generic clustering protocols on various factors
Cons:
Repeated iterations complex algorithm
Decrease of residual energy smaller probability
number of iterations increased
Nodes with high residual energy one region of a networkFuture work:
Only two level hierarchy provided but can be extended to multilevel hierarchy
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MRECAAssumptions:
Sensor quasi-stationary
Nodes-location unaware
Every node as source and server
Algorithm:
Mobility resistant clustering approach
Deterministic time without iterations
Computed score value used to compute delay
Delay used CH announcement
Node mobility
Local maintenance performed instead of re-clustering
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Pros Clusters generated as node speed increased
Only one iteration against repeated iterations in HEED
Each node one message
saving on message transmission better energy efficiency
Robust against synchronization errors
Can be used for environmental monitoring and battlefield
applications
Cons
Inter cluster communication not explained
CH rotation mentioned but not explained how
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Future work Extensive simulations on large scale
networks with elaborate power models,
Extensions to k-hop clusters and integration
of clustering with network applications
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EEDCAssumption: Two tier hierarchy network
Routing limited to CHs route set up cost minimized
Sensors clustered
Algorithm: Active node estimation and optimum probability of becoming cluster head
Received Signal power
Cluster formation
CH with a certain probability by wining a competition with neighbors
Data collection
Node-CH using MAC protocol-p-persistent CSMA
Data delivery CH-BS-multi hop routing protocol
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Pros
Number of clusters and CH-Dynamic
Energy dissipation-even distribution
Prolong network lifetime
most efficient for large-scale sensor network
Intra and inter cluster communication explained
Future work
Further investigating the applicability of the proposed clustering
technique and routing algorithm to more general wireless sensor
networks.
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LEACHAssumptions:
Fixed and remote base station
Nodes homogeneous and energy constrained
Radio channel is symmetric
EA-EB=EB-EA
Sensing rate for all sensors fixed
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Algorithm
CH position rotated among the nodes
energy load distributed .
Number of active nodes in the network and the optimal number of clusters
assumed a priori
Nodes join a target number of CHs
Node-CH communication-TDMA
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Pros
Incorporates data fusion into routing protocols
Amount of information to base station reduced
4-8 times effective over direct communication in prolonging network
lifetime
Grid like area
Cons
Only single hop clusters formed
Might lead to large number of clusters
No discussion on optimal CH selection
All CHs should directly transmit to the data sink
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DYNAMIC CLUSTER
Energy efficiency distributed:
CH selection-both residual energy and PT
Number of nodes-network size and PT
CH -center of the cluster
Rotating CH to average power consumption
Breaking clusters and reforming
compensate for differences of power consumption in different areas
Unique route
Only CH with lowest ID and high residual energy
What is only one CH is present and that CH as low residual energy?
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Pros
Reduce flooding in route discovery
Avoid duplicate data transmission
Cons
Inter cluster communication not explained
Number of iterations needed for CH selection and cluster
formation not mentioned
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CONCLUSIONS
Problem statement seems to be unique
Reduce energy consumption
Prolong network lifetime
Form set of clusters from a set of nodes
Cluster the whole network with the selected CH
Rotate CHs for energy distribution
Algorithms differ in CH selection and cluster formation
Some address intra and inter cluster communication
Some address real world applications
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REFERENCES
[1]. A hybrid energy efficient distributed clusteringapproach for ad-hoc sensor networks