CLUSTERING IN WIRELESS SENSOR CLUSTERING IN WIRELESS SENSOR NETWORKSNETWORKS

BYKALYAN SASIDHAR

RESEARCH PROBLEMRESEARCH 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

INTRODUCTION TO CLUSTERINGINTRODUCTION 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

HEED[1]

ADVANTAGES OF CLUSTERINGADVANTAGES 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

LITERATURE SURVEY OF CLUSTERING LITERATURE SURVEY OF CLUSTERING ALGORITHMSALGORITHMS • HEED: A hybrid energy efficient distributed clustering approach for

ad-hoc sensor networks

• MRECA: Mobility resistant efficient clustering approach for ad-hoc sensor networks

• Energy efficient dynamic clustering algorithm for ad-hoc sensor networks

• LEACH-Energy efficient communication protocol for WSN

• EEDC-Dynamic clustering and energy efficient routing technique for WSN

Problem statementProblem 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

HEEDHEED

Assumptions Sensor quasi-stationary

Links are symmetric

Energy consumption non-uniform for all nodes

Nodes-location unaware

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:• 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 network

Future work:• Only two level hierarchy provided but can be extended to multilevel hierarchy

MRECAMRECAAssumptions:• 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

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’

Future work• Extensive simulations on large scale

networks with elaborate power models,

• Extensions to k-hop clusters and integration of clustering with network applications

EEDCEEDC

Assumption:• 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

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.

LEACHLEACHAssumptions:• Fixed and remote base station

• Nodes homogeneous and energy constrained

• Radio channel is symmetric

EA-EB=EB-EA

• Sensing rate for all sensors fixed

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

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

DYNAMIC CLUSTERDYNAMIC 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?

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

CONCLUSIONSCONCLUSIONS• 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

REFERENCESREFERENCES

[1]. A hybrid energy efficient distributed clustering approach for ad-hoc sensor networks