International Journal of Advanced Computer Engineering and Communication Technology (IJACECT)
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Efficient Hierarchical Based Routing Protocol Enhancement for
Energy Balancing and Prolonging the Lifetime of the WSNs
1
Surekha K B, 2T. G. Basavaraju
1
Research Scholar, Dept of CSE, Prof & HOD: Dept. of Computer Sciences & Engg
JNTUH Hyderabad, Government SKSJ Technological Institute, Bangalore-560 001
E-Mail: 1prashanth.surekha@gmail.com, 2tgbraju@gmail.com
2
Abstract— A Wireless Sensor Network (WSN) is a wireless
network consisting of spatially distributed autonomous tiny
computing devices, each equipped with sensors, a wireless
radio, a processor, and a power source. Sensor networks
are envisioned to be deployed in the physical environment
in order to monitor a wide range of environmental
phenomena. Efficient usage of energy is one of the most
important concerns in wireless sensor networks, especially
while designing a routing protocol. LEACH is a promising
protocol that combines medium access with routing and
application-specific data aggregation to achieve good
performance in terms of network lifetime, energy and
throughput. The paper aims at evaluating the performance
of the LEACH protocol for Wireless Sensor Network
under varying network models. Thus, an extensive
comparison of energy, throughput and lifetime of the
sensor network under different network scenarios is
carried out and result analysis is done in detail. Through
NS2 simulation, it is clearly shows that LEACH works well
for a network with the Base Station placed at the position
(50,175) and when the numbers of clusters or clusters
heads are 5 percentages of the total sensor nodes.
Keywords— Wireless Sensor Networks, Base Station,
Energy Efficiency, LEACH protocol, performance,
analysis, lifetime
I. INTRODUCTION
Wireless Sensor Networks (WSNs) nodes are powered
by non-rechargeable batteries and thus energy is a scarce
resource. It is imperative that energy conservation is
considered across all layers of the protocol stack in order
to minimizing the total network energy consumption and
prolong the operational lifetime of the network. WSNs
have extensive potential applications. Nodes of a WSN
are generally deployed to collect the interested data
(temperature, chemicals, etc.) or just sense the presence
or the absence of a phenomenon of interest in an
information field. The amount of data collected by nodes
varies with the application requirement of the WSN. The
application requirement can be simply embodied by
source rates of nodes.
communication of nodes in WSNs. Therefore, the
energy efficient approaches for the low rate setup should
be explored for WSNs. Among arts of energy efficiency
in WSNs, joint cross-layer design stands as the most
alternative to inefficient traditional layered protocol
architectures. There has been some cross-layer work
aiming to optimize the network energy consumption and
prolong the lifetime of the network. In [1], authors
characterize an inherent trade-off in simultaneously
maximizing the network lifetime and the application
performance (characterized as network utility) by
considering a cross-layer design problem in a wireless
sensor network with orthogonal link transmissions.
The lifetime of the wireless sensor network is highly
dependent on the lifetime of the sensors battery,
preserving energy in sensors will increase the lifetime of
the network. Most of the energy is consumed by the
nodes for making efficient routing and sensing
operations [2]. In this paper the performance evaluation
of LEACH routing protocol for Wireless Sensor
Networks is carried out. LEACH is a promising protocol
which combines the best characteristics of medium
access with routing and application specific data
aggregation to achieve good performance in terms of
network lifetime, information latency and collecting
application dependent quality [3]. Wireless sensor
networks are emerging network technology with
innumerable applications. But the energy constraints
reduce its successful deployment. This paper evaluate
the performance of existing LEACH protocol in terms of
throughput (data received at the base station), total
energy consumed, total number of nodes alive, when the
network is subject to various traffic scenarios. The
remainder of the paper is organized as follows: In
Section 2 related work carried out is discussed. The
LEACH protocol and its working is discussed in Section
3. In section 4, protocol design is described. We provide
simulation and analysis of or LEACH protocol and
finally, the paper is concluded in Section 5.
II. RELATED WORK
Typically, the data generation and transmission rates of
nodes are low by reason of the scarce of power and the
limitation of capacity of storage, processing and
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International Journal of Advanced Computer Engineering and Communication Technology (IJACECT)
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A sensor network is defined as being composed of a
large number of nodes which are deployed densely in
close proximity to the phenomenon to be monitored.
Each of these nodes collects data and its purpose is to
route this information back to a sink. The network must
possess self-organizing capabilities since the positions
of individual nodes are not predetermined. Cooperation
among nodes is the dominant feature of this type of
network, where groups of nodes cooperate to
disseminate the information gathered in their vicinity to
the user.
LEACH is energy efficient hierarchical based protocol
that balances the energy expense, saves the node energy
and hence prolongs the lifetime of the network [4]. The
efficient utilization of energy source in a sensor node is
very important criteria to prolong the life time of
wireless sensor network. Wireless sensor networks have
explored many new protocols specifically designed for
sensor network where energy consideration is very
crucial.
Most of importance, given to hierarchical routing
protocols based on clustering which has better
scalability. As sensor nodes are generally battery
powered devices, the critical aspects to face concern
how to reduce the energy consumption of nodes, so that
the network lifetime can be extended to reasonable times,
LEACH protocol is analysed in terms of energy,
throughput and lifetime [5].
Low Energy Adaptive Clustering Hierarchy (LEACH) is
the first energy efficient routing protocol for hierarchical
clustering. It reduces the energy significantly. The
LEACH protocol forms clusters in the sensor networks
and randomly selects the cluster heads for each cluster.
The basic principle is that it assigns overall energy
consumption of the network uniformly to each sensor
node through periodically selecting different nodes as
cluster-head. This makes the survival time of nodes
close to the lifetime of network. Thus, the energy
consumption can be reduced and lifetime of the entire
network can be pro-longed [6].
Clustering is an efficient technique used to achieve the
specific performance requirements of large scale
wireless sensor networks. The simulation results based
on the LEACH protocol identify some important factors
that induce unbalanced energy consumption among
sensor nodes and hence affect the network lifetime. This
highlights the need for an adaptive clustering protocol
that can increase the network lifetime by further
balancing the energy consumption among sensor nodes
[7].
Different traffic models are introduced to LEACH
protocol for wireless sensor network. Network
performance of LEACH with these traffic models is
analysed. The results provide design guidelines for
LEACH implementation under a realistic traffic model
in which each node has a range of transmission
probabilities and for a range of network sizes [8].
The resource constrained nature of WSN implies various
challenges in its design and operations, which degrades
its performance. However, the major fact that sensor
nodes run out of energy quickly, has been an issue.
Many routing, power management, and data
dissemination protocols have been specifically designed
for WSNs, where energy consumption is an essential
design issue, which preserves longevity of the network.
Out of these, clustering algorithms have gained more
importance, in increasing the lifetime of WSN, because
of their approach in cluster-head selection and data
aggregation [9].
III.
LEACH PROTOCOL
LEACH protocol is one of the renowned hierarchical
routing approaches for wireless sensor networks. It is
novel energy efficient clustering hierarchy which
focuses on the equalize energy distribution and area
distribution for the clusters. This method improves the
lifespan of the network and also the data throughput of
the network [10].
LEACH uses a TDMA based MAC protocol, and in
order to maintain balanced energy consumption. The
TDMA adds feature to leach to reduce the consumption
of the network resource in each round. The protocol
shows a significant reduction in network energy
consumption [11].
LEACH [12] is a hierarchical protocol in which most
nodes transmit to cluster heads, and the cluster heads
aggregate and compress the data and forward it to the
base station (sink). Each node uses a stochastic
algorithm at each round to determine whether it will
become a cluster head in this round. LEACH assumes
that each node has a radio powerful enough to directly
reach the base station or the nearest cluster head, but that
using this radio at full power all the time would waste
energy [13].
Nodes that have been cluster heads cannot become
cluster heads again for P rounds, where P is the desired
percentage of cluster heads. Thereafter, each node has a
1/P probability of becoming a cluster head in each round
[14]. At the end of each round, each node that is not a
cluster head selects the closest cluster head and joins
that cluster. The cluster head then creates a schedule for
each node in its cluster to transmit its data [15].
IV.
PROTOCOL DESIGN
A. Mathematical Model
The mathematical model of [16] is used to compute the
total energy dissipation in the sensor network for the
transmission of a frame. The derivative of the total
energy is taken to find the optimum number of clusters
Hopt is given by
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International Journal of Advanced Computer Engineering and Communication Technology (IJACECT)
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H opt
N

2
Ef
D
2
Em d CHBS
Where N is the total number of sensor nodes, D is the
dimension of the sensor area, dCHBS is the distance
between cluster head and base station, Ef and Em are the
amplifier energies.
In [17], a mathematical model is proposed to compute
the total energy consumption in the sensor network
during a single round. By taking the derivative of the
total energy, it also finds the optimum number of
clusters,
correlated values. Finally it transmits the aggregated
data directly to BS. The function of LEACH is divided
into rounds which are further organized in two phases.
The setup phase consists of CH selection and cluster
formation followed by steady-state phase in which
selected CH does data collection, aggregation, and
delivery to BS.
B. Setup Phase
It starts with the self-election of nodes to become CHs.
The self-election algorithm ensures that CH role rotates
among nodes to distribute energy consumption evenly
across all nodes.
CH selection and rotation algorithm
N
H opt 

Ef
Em d
D
2
CHBS
In [18], a mathematical model is proposed to calculate
the total energy consumption in the sensor network
during a single round. It also finds the desired optimum
cluster head probability, Popt as—
Popt  1
Ef
2  E d4  E  E
m CHBS
efec
DA


where, λ is the intensity of homogeneous spatial Poisson
process that indicates the sensor node density, Eelec is
the electronic energy required for coding, modulation,
filtering etc. and EDA is the energy required for data
aggregation.
All nodes that are not cluster heads only communicate
with the cluster head in a TDMA fashion, according to
the schedule created by the cluster head. They do so
using the minimum energy needed to reach the cluster
head, and only need to keep their radios on during their
time slot. LEACH also uses CDMA so that each cluster
uses a different set of CDMA codes, to minimize
interference between clusters.
LEACH is a cross layered protocol architecture that
combines medium access with routing to collect and
deliver data to BS.
The main goals of LEACH are:
•
Increasing network lifetime.
•
Decreasing network energy consumption.
The CH selection algorithm is simple and lightweight
using random choice for CH selection. This reduces the
overhead for determining optimal CH. To decide if it is
its turn to become a CH, a node, n, generates a random
number, v, between 0 and 1. It then compares it with CH
selection threshold, T (n) which is designed to ensure
with high probability that a pre-determined fraction of
nodes, P, is elected as CH for each round. Threshold
also ensures that nodes which served in past 1/P rounds
are not selected as CH
in the current round. To meet up these necessities, the
threshold of a contending node n is articulated as
follows:
P
1- P*(r mod 1/P)
T (n) =
0
if n € G
otherwise
C. Steady State Phase
During this phase, NCH nodes periodically collect
sensor data and transmit it to CH in their allocated slots.
The entire steady-state operation is broken into frames
which are further broken into slots of constant duration.
NCH nodes send collected sensor data to their respective
CH at most once per frame during their allocated
transmission slot and enter the sleep mode otherwise.
Data transmissions are scheduled to avoid collisions and
increase sleep time of each NCH node.
With slots of constant duration, time to send a frame of
data depends on the number of nodes in the cluster.
•
Reducing number of communication messages
by data aggregation.
In order to achieve these goals, LEACH uses
hierarchical approach and organizes the network into a
set of clusters. Each cluster is administered by a selected
CH. The CH does the task of creating TDMA-based
schedule to assigns a time slot to each Cluster Member
(CM) for periodic data transmission to CH. CH then
aggregates the data to remove redundancy among
V. SIMULATION RESULTS AND
ANALYSIS
A. Simulation Environment
NS2 is written in the C++ programming language with
the Object Tool Common Language (OTCL) as the
front-end interpreter. A class of hierarchy supported in
C++ is the compiled hierarchy and the interpreter
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International Journal of Advanced Computer Engineering and Communication Technology (IJACECT)
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hierarchy for OTCL. The complete simulations are
carried out using Network Simulation NS2 [19]. The
Table I show the simulation parameters used in the
simulation.
TABLE I
SIMULATION PARAMETERS
Parameter
Description
Node Density
25, 50, 75and 100
Simulation Area
1000m x 1000m
Fig 1. Simulation Snap Shot
Base Station
Location
(50, 100), (50,125),
(50,150) and (50, 175)
Packet Size
512 bytes and 1024 bytes
Initial Energy
40J
Processing Delay
50 µs
Graphs are plotted for the extracted values like Position
of BS versus Data received at the BS, Total energy
consumed versus Number of Clusters, Number of Nodes
versus Data received at the BS, Network Lifetime versus
Number of Clusters, Total data received at the BS versus
Number of Clusters, Node Density, Packet size versus
Energy consumed.
Signal Wavelength
0.325 m
For every event created by the network component, the
event will be placed onto an event queue linked to the
scheduler. The data structure is ordered to be
synchronized with the executing events invoked by the
event handler. As the simulation progresses, the first
event in the queue is assigned with the appropriate
network component and executed. The scenarios are
implemented with scripts written in TCL that comprise
commands and parameters for simulator initialization,
node creation and configuration. The trace file will
contain information on the various events which
occurred, details of node behaviour, packet
transmissions and receptions, communication layer,
packet drops, etc.
Simulation is carried out for scenarios containing 25, 50,
75 and 100 nodes with the simulation time of 3600
seconds and each node having an initial energy of 2
joules. Simulation is done by considering the channel as
wireless, propagation as two-ray ground, antenna type is
Omni-directional where it can receive and transmit in all
directions.
A.
Position of Base Station versus Total Energy
Consumed
Fig. 2. Position of BS vs. Total energy
consumed
When the position of the Base Station is changed, we
observe that the total energy consumed increases.
Therefore the optimal position of the Base Station in the
LEACH protocol is (50,175), where less energy is
consumed, than the other positions as shown in figure 2.
B. Position of Base Station versus Data received at the
Base Station
B. Simulation Results
The simulation is carried out in NS2 simulation
environment for LEACH protocol to obtain certain
parameters for comparison. The required values are
extracted from simulation output of the LEACH
protocol that is subject to various traffic conditions.
Simulation snap shot for initial network condition is
shown in figure 1. The red colour nodes depicts that
node energy depletion
Fig 3: Position of BS vs. Data received at BS
As shown in figure 3, when we change the position of
the Base Station, we observe that the total data received
at the Base Station goes on increasing. Therefore the
optimal position of the Base Station in the LEACH
protocol is considered to be (50,175) where the amount
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International Journal of Advanced Computer Engineering and Communication Technology (IJACECT)
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of data received is comparatively better that other
positions.
heads are 5 percentages of the sensor nodes then the
performance is good.
C. Total Energy Consumed versus Number of Clusters
F. Throughput versus Number of Nodes
In this scenario, the numbers of nodes in the network are
varied.
Fig 4: Number of Clusters Vs Energy dissipation of the
network
From the figure 4 results, we observe that if the clusters
in the network or cluster heads in the network are below
or above 5 percentage of the total number of nodes, the
performance of the network is degraded.
D. Network Lifetime versus Number of Clusters
Fig 7: No. of Nodes Vs Throughput
The base station are set to different values such as 25,
50, 75 and 101, by replacing the existing one at (50,
175) and by keeping the number of cluster heads in the
network to 5 percentage of the total sensor nodes, and
observe the total data received at the base station.
From the figure 7 results, we observe that the
performance of the network is better when the number
of clusters is set to 5 percentages of the total sensor
nodes in the network and when the position of the Base
Station is at (50, 175).
G. Node Density versus Packet Size
Fig 5: Number of Clusters Vs Energy dissipation of the
network
The figure 5 results shows that if the clusters in the
network or cluster heads in the network are below or
above 5 percentage of the total number of nodes, the
performance of the network is degraded in terms of
lifetime.
E. Throughput versus Number of Clusters
Fig 8: Energy Level for Different Packet Size and Node
Density
From the figure 8 results, we observe that as we increase
the packet size for different nodes, the energy
consumption at the Base Station also increases.
Therefore the packet size must be kept optimal so that
the performance of the network is enhanced in terms of
energy and throughput.
VI.
Fig 6: No. of Clusters Vs Throughput of the network
CONCLUSIONS
Efficient usage of energy is one of the most important
concerns in wireless sensor networks, especially while
designing a routing protocol. The project works aims at
evaluating the performance of the LEACH protocol for
Wireless Sensor Network under varying network models.
Through our simulation, we show that LEACH works
From the figure 6 results, we observe that by varying the
different number of cluster head/clusters in the network
below or above 5 percentage of the total number of
nodes, the performance of the network is degraded in
terms of throughput, so when the numbers of cluster
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International Journal of Advanced Computer Engineering and Communication Technology (IJACECT)
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well for a network with the Base Station placed at the
position (50,175) and when the numbers of clusters/
clusters heads are 5 percentages of the total sensor nodes.
We compare the energy, throughput and lifetime of the
network under different network scenarios. LEACH is a
promising protocol that combines medium access with
routing and application-specific data aggregation to
achieve good performance in terms of network lifetime,
energy and throughput. The simulations results are
limited in scope and hence more thorough experiments
are required by changing many parameters.
Implementing the protocol in real life scenario is straight
forward but may require little modifications. More wide
research is necessary to further increase the efficient
usage of energy in wireless sensor network.
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,

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