Maximizing Network Lifetime by Using Smart Cluster Head Selection

IOSR Journal of Electronics and Communication Engineering (IOSR-JECE)
e-ISSN: 2278-2834,p- ISSN: 2278-8735.Volume 10, Issue 6, Ver. III (Nov - Dec .2015), PP 95-100
www.iosrjournals.org
DOI: 10.9790/2834-106395100 www.iosrjournals.org 95 | Page
Maximizing Network Lifetime by Using Smart Cluster Head
Selection
Simimol.Surendran1
, Ajitsinh.N.Jadhav2
1
(Electronics & Telecommunication, D. Y. Patil college of Engg. & Tech. Kolhapur / Shivaji University ,India)
2
(Electronics & Telecommunication, D. Y. Patil college of Engg. & Tech. Kolhapur /India)
Abstract: In wireless sensor network, one of the major issues is how to optimize the network lifetime. The
network lifetime depends on the life of the nodes that are deployed on the field area where these sensor nodes
are left unattended and unmonitored. Most of the energy is consumed by the nodes during communication
amongst cluster members and the cluster head. More energy is dissipated while communication as compared to
sensing of the data done by sensor nodes. Hence to reduce the communication distance proper selection of
cluster head is necessary. Hence a simple technique of smart cluster head selection is implemented on the basic
LEACH protocol to enhance its performance by all aspects and sustain the network lifetime.
Keywords: Smart cluster head selection (SCHS), LEACH, energy efficiency, Network lifetime.
I. Introduction
Wireless sensor network is composed of a large number of tiny sensors that communicate with each
other and coordinate activities amongst themselves in a very orderly manner to achieve a particular purpose. The
applications of sensor networks range from environmental monitoring, military surveillance, health care, home
automation and so on. These sensors are made of very small battery with limited battery life and are deployed
uncertainly and in such regions or areas where humans cannot reach hence these sensor node batteries cannot be
replaced nor can they be charged [1]. Thus network lifetime of a wireless sensor network depends on the battery
life of the sensors. Hence energy efficient clustering protocols play a crucial role in enhancing the performance
of a Wireless sensor network.
II. Clustering
In clustering, the sensor nodes in a wireless sensor network are divided into different virtual groups,
and they are allocated geographically adjacent into the same cluster according to some set of rules defined.
These sensor nodes are assigned a different status or function, such as cluster head or cluster member [2].The
cluster head is elected for each round and the rest cluster members senses the data and communicates it to the
cluster head. The cluster head then aggregates the data and only informative data is forwarded to the base
station.
Figure: 1.Cluster
The communication between the cluster members and its head in known as intra cluster communication
whereas the communication between the cluster heads in a wireless sensor network is known as inter cluster
communication. More energy is consumed while transmitting as compared to sensing of the data [3].

Maximizing Network Lifetime by Using Smart Cluster Head Selection
Fig: 2 Data flow in a clustered network [4]
Hence the energy is consumed more during communication. More the distance between the members
and the associated cluster head for that round more will be the energy consumption. Thus placing the cluster
head at proper place will help to reduce the communication distance between themselves and so in this paper a
smart cluster head selection scheme is implemented on the LEACH protocol to increase its network lifetime by
reducing the energy consumption, node death rate and ultimately contributing more data to be received at the
base station
III. Low Energy Adaptive Clustering Hierarchy (Leach)
This is the first hierarchical cluster-based routing protocol for wireless sensor networks. LEACH
arranges the nodes into small clusters and chooses one of them as the cluster-head. The other member nodes of
that sensor network senses and send the information to its cluster head. The role of cluster head is to aggregate
the information received from all the member nodes and sends it to the base station. This protocol is divided into
rounds and each round consists of two phases. [5]
Set-up Phase
(1) Advertisement Phase
(2) Cluster Set-up Phase
Steady Phase
(1) Schedule Creation
(2) Data Transmission
3.1 Set-Up Phase:
Every member decides independently decides if it can become a cluster head for that particular round.
This decision is based depending upon the threshold value T(n). The threshold value depends upon the desired
percentage to become a cluster-head- p, the current round r, and the set of nodes that have not become the
cluster-head in the last 1/p rounds, which is denoted by G.
The equation is as
Based on all messages received within the cluster, the cluster head creates a TDMA (Time Division
Multiple Access) schedule, pick a CSMA code randomly, and broadcast the TDMA table to cluster members
every node wanting to be the cluster-head chooses a value, between 0 and 1. If this random number is less than
the threshold value, T (n), then the node becomes the cluster- head for the current round. Then each elected
cluster head broadcasts an advertisement message to the rest of the nodes in the network to invite them to join
their clusters. Based upon the strength of the advertisement signal, the non-cluster head nodes decide to join the
clusters. In the set-up phase, the cluster head nodes are randomly selected from all the sensor nodes and several
clusters are constructed dynamically.
3.2 Steady Phase
During the steady phase, the sensor nodes i.e. the cluster members starts sensing data and sends it to
their cluster-head according to the TDMA schedule. The cluster-head node, after receiving data from all the
member nodes, aggregates it and then sends it to the base-station. After a certain time, the network again goes

back into the setup phase and new cluster-heads are chosen. Each cluster communicates using unique CDMA
codes in order to reduce interference from nodes belonging to other clusters.
In the LEACH protocol, the cluster heads are not distributed uniformly hence there is a chance of cluster head
getting located at the edges of the cluster as shown in Fig3.a.
Figure: 3.a. Bad distribution of cluster head Figure: 3.b.Expected distribution of cluster head
To overcome this drawback of non-uniform distribution of cluster head, a scheme known as smart
cluster head selection is implemented on LEACH which almost allows having a good distribution as shown in
Fig.3.b.
IV. Smart Cluster Head Selection (SCHS)
In this scheme only the inner nodes are eligible to become the cluster head. Due to this the intra-cluster
communication distance is decreased and hence less energy is consumed in sending the data to the cluster head
which is located in the inner area. This protocol also works in the same manner as the LEACH does, the only
difference is that this scheme checks if the node is placed at the border area as shown in Fig.4.
Figure: 4.Partioning of network area [3]
In the set-up phase, each node is checked whether it belongs to border area or to inner area. If a node
belongs to inner area, it will participate for cluster head role and if it belongs to border area then it will be a
member node. Cluster heads announce their status message and wait for the response from nodes. Cluster head
constitute the TDMA schedule for the cluster members. In the steady phase, the nodes wake up as the time slot
allotted arrives and sends the data to cluster head. To conserve energy nodes go back to sleep state and wait for
the next wake up slot. Cluster head aggregates the data and sends the data to base station. The steady phase is
repeats itself till the round time is over. After completion of round time, set-up phase is executed again. [3]
V. Energy Model
In wireless sensor network, nodes are deployed randomly but we make an assumption that in the radio
channel the energy required to transmit and receive a message from one node to another node is same [6]. Thus
for sending l-bit data at a distance d, the total energy utilized by the node is given by,
(1)

Where do=sqrt (Efs/Emp) denotes the threshold distance
Eelec represents the energy consumption for transmitting and receiving data. Efs and Emp depends on
the transmitter amplifier model. And the energy consumption for receiving that message is given by:
(2)
The energy dissipation model is shown in Fig: 5.
Figure: 5. Energy Dissipation Model
VI. Simulation Results
In the simulation, distance of 10 m is considered as border area for the smart cluster head selection
scheme. The simulation parameters as well as the energy model parameters are kept similar for both LEACH
and SCHS and are as shown in Table1.
Table1.
Parameter Value
Network area 100m*100m
Base station 75m
Number of nodes 100
Number of clusters 10
Initial Energy 0.5J
Efs 10pJ/bit/m2
Emp 0.0013pJ/bit/m4
EDA 5nJ/bit/message
Eelec=ETx=ERx 50nJ/bit
Simulations helped to make a comparative study about the node death rate, energy consumption rate
network lifetime and data units send to base station.
Node Death Rate:
It is defined as number of alive nodes with respect to time and from the Fig.6, the node death rate of
SCHS is lower than LEACH.
0 200 400 600 800 1000 1200 1400 1600 1800
0
10
20
30
40
50
60
70
80
90
100
Node Death Rate Analysis for 100 Node Network
Round Number
AliveNodes
Leach
SCHS
Figure 6
Energy Consumption Rate:
It is defined as energy consumption by the whole network with respect to time and the comparative
graph from Fig.7 shows that the curve of SCHS is lower than the slope of LEACH which indicates that the
energy consumption rate in case of SCHS is always lesser than LEACH.

0 200 400 600 800 1000 1200 1400 1600 1800
0
10
20
30
40
50
60
Energy Consumption Rate Analysis for 100 Node Network
Round Number
EnergyConsumed(J)
Leach
SCHS
Figure 7
Data Units Received at Base Station:
This metric is important for data gathering networks. It states the data units received successfully at
base station
0 200 400 600 800 1000 1200 1400 1600 1800
0
1000
2000
3000
4000
5000
6000
7000
Data Units Received at Base Station Analysis for 100 Node Network
Round Number
ReceivedData(Bytes)
Leach
SCHS
Figure 8
Network Lifetime:
Network lifetime is the main measure for an energy efficient approach
1 50
0
100
200
300
400
500
600
700
800
1st and 100% Node Death Analysis for 100 Node Network
RoundNumber
Node Death
Leach
SCHS
Figure 9

VII. Conclusion
Clustering approach are energy efficient protocols used in wireless sensor networks. More over
reduction in the communication distances reduces the energy utilization. Proper cluster head selection places an
important factor for enhancing the network lifetime of a wireless sensor network. In this paper, smart cluster
head selection is implemented on the very first basic clustering protocol known as LEACH to analyze if there is
any enhancement in the performance of the network parameters and simulation results shows that SCHS
extended the lifetime of network since the node death rate and energy consumption rate of nodes is low for
SCHS when compared with LEACH. As well as more data units are received at the base station in SCHS as
compared to LEACH.
References
[1] Ning Xu, “A Survey of Sensor Network Applications," University of Southern California, Jan. 2004
[2] Asis Kumar Tripathy and Suchismita Chinara,” Comparison of Residual Energy-Based Clustering” International Scholarly
Research Network ISRN Sensor Networks Volume 2012, Article ID 375026, 10 pages doi:10.5402/2012/375026
[3] V.Pal,R .P.Yadav,“Cluster Head Selection Scheme For Data Centric Wireless Sensor Networks” , Volume 2, PP. 395 - 399, April
2013, Advance Computing Conference (IACC), 2013 IEEE 3rd International
[4] Ossama Younis,et.al.University of Arizona-“Node Clustering in Wireless Sensor Networks: Recent Developments and Deployment
Challenges”
[5] M. Bani Yassein, A. Al-zou'bi, Y. Khamayseh, W. Mardini,” Improvement on LEACH Protocol of Wireless Sensor Network
(VLEACH)”
[6] I. F. Akyildiz, W. Su, Y. Sankarasubramaniam and E. Cayirci, “Wireless Sensor Networks: A Survey,” Com-puter Networks, Vol.
38, No. 4, 2002, pp. 393-422. doi:10.1016/S1389-1286(01)00302-4

Maximizing Network Lifetime by Using Smart Cluster Head Selection

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