Transcript CLUSTERING IN WIRELESS SENSOR NETWORKS

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