CLUSTERING IN WIRELESS SENSOR NETWORKS B Y K ALYAN S ASIDHAR

R ESEARCH P ROBLEM 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 CLUSTERING 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

HEED[1]

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

L ITERATURE S URVEY O F C LUSTERING A LGORITHMS 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 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

HEED 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 CH prob =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

MRECA Assumptions: 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

EEDC 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.

LEACH Assumptions: Fixed and remote base station Nodes homogeneous and energy constrained Radio channel is symmetric  E A -E B =E B -E A 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 CLUSTER Energy efficiency distributed:  CH selection-both residual energy and P T  Number of nodes-network size and P T  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

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

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