IMPROVEMENT OF LEACH AND ITS VARIANTS IN WIRELESS SENSOR NETWORK

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International Journal of Computer Engineering & Technology (IJCET)
Volume 7, Issue 3, May-June 2016, pp. 99–107, Article ID: IJCET_07_03_009
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IMPROVEMENT OF LEACH AND ITS
VARIANTS IN WIRELESS SENSOR
NETWORK
Chaudhari Komalben Kanjibhai
Dept. Computer Engineering,
Laljibhai Chaturbhai Institute of Technology,
Bhandu-384120, Mahesana, Gujarat, India
ABSTRACT
Sensor webs consisting of nodes with limited battery power and wireless
communications are deployed to collect useful information from the field.
Gathering sensed information in an energy efficient manner is critical to
operate the sensor network for a long period of time. A data collection
problem is defined where, in a round of communication, each sensor node has
a packet to be sent to the distant base station. If each node transmits its sensed
data directly to the base station then it will deplete its power quickly. Since
wireless communications consume significant amounts of battery power,
sensor nodes should spend as little energy as possible receiving and
transmitting data. It is necessary for communication protocols to maximize
nodes' lifetimes, reduce bandwidth consumption by using local collaboration
among the nodes, and tolerate node failures. Most of the work in energy
efficient data gathering application is motivated by LEACH by allowing
rotation of cluster head for load distribution. We have presented several
existing methods for energy efficient cluster head selection in wireless sensor
network. Our goal is to reducing the amount of cluster head selection and
replacement cost and ultimately to extend the lifetime of the entire networks
compared with the existing clustering protocols.
Key words: Clustering, Energy Efficiency, LEACH, Lifetime, Number of
Rounds, WSN
Cite this Article: Chaudhari Komalben Kanjibhai, Improvement of LEACH
and its Variants In Wireless Sensor Network, International Journal of
Computer Engineering and Technology, 7(3), 2016, pp. 99–107.
http://www.iaeme.com/IJCET/issues.asp?JType=IJCET&VType=7&IType=3

1. INTRODUCTION
Wireless sensor network is differ from other ad hoc networks likes mobile ad hoc
network and vehicular ad hoc network in the sense that they are resource limited, they
are prone to failure, their topology often changes, they use broadcast medium instead
of point to point, they are densely deployed etc. Wireless sensor networks are made
up of a large number of inexpensive devices. Sensor nodes are tiny devices that
comprises of battery, tiny processor, analog to digital converter and radio transceiver.
WSN consist of several nodes. Each node has computation capability like sensing,
control function and transmission/receiving. Every node sends their sensed data to
sink or Base Station (BS) using wireless communication. Sink receives sensed data;
aggregate that data and takes decision about action for particular application. So there
are various application based on WSN like disaster management, animal tracking and
monitoring, volcano monitoring etc. In these kind of application, sensor has require
energy for various operation; but at such place battery cannot be recharged or replace;
so taking care of energy consumption is issue now a days [16].
In an efficient wireless sensor network, we need efficient routing protocol that has
low routing overhead and well organized data aggregation mechanisms to increase
good put of network and to save limited power of sensor node
To solve problems of energy consumption hierarchical routing (clustering) is best
approach. In this approach cluster has been formed; each cluster has several nodes and
one cluster head. Every node sends their sensed data to CH; CH aggregates that data
and sends data to sink. This paper introduces various clustering protocols.
In this paper we clearly explain our work. In section II various protocol based on
clustering presented, in section III proposed protocol enlightened, in section IV results
were generated and analysed and in section V conclusion for proposed protocol.
2. REVIEW OF LITERATURE
LEACH Protocol
In past year many protocols developed for Clustering some of important are as
follows: Low Energy Adaptive Clustering Hierarchy (LEACH) was proposed by [1]
W. Heinzelman. It was first clustering approach introduce for WSN. It is for
homogeneous and dense sensor network. It is TDMA based MAC protocol integrated
with clustering and uses simple routing. It is working in 2 phase. 1) Set up phase:
Each node generates random number between 0 and 1. Node elected as CH by
calculating threshold using as in (1),
T (n) = p/ (1- p (r % (1/p))) if n belongs to G (1)
If (random number < T (n))
Current node becomes Cluster Head
Else
Current node becomes Cluster Member (normal node).
p = probability to become CH, r = round number, n = number of nodes
G= set of nodes which not become CH for last 1/p round.
Elected CH broadcast advertisement packet for nodes to join cluster. According to
receive signal strength nodes send joining packet to particular CH. CH send TDMA
schedule to nodes which want to join that particular cluster. 2) Steady state phase:
nodes transmit sensed data to CH in their time slot according to TDMA schedule; CH

Improvement of LEACH and its Variants In Wireless Sensor Network
aggregates that data and transmit to sink. In every round, this 2 phase are worked and
new CHs were elected.
LEACH-B Protocol
LEACH-B is a balanced LEACH. In which proposes an enhanced version of LEACH.
It finds the number of cluster heads which are near optimal. In LEACH-B, there is a
second stage for selecting cluster head. The second stage considers the residual
energy of candidate nodes to become the cluster head. This protocol can save energy
consumption by ensuring that the clusters are balanced. The optimal number of cluster
heads chosen is between 3 percentages to 5 percentage.
Figure 1 LEACH-B Protocol
Balanced LEACH guarantees the optimal number of cluster head. Network
lifetime increases significantly compared to LEACH.
In LEACH-B, we introduce another competition for cluster-heads after the first
selection of the cluster heads according to a random number as in LEACH to maintain
the constant cluster heads number of n×p Where p is the desired percentage of cluster
heads and n is the number of total nodes.
The first-selected number and the residual energy of cluster heads can be learned
by every node through the CHs' advertisement messages.
We should consider two different situations because of the uncertain number of
cluster heads created by LEACH algorithm.
If the number of cluster heads is less thann×p , some nodes should be elected from
the normal nodes into the cluster heads set. We set a timer for every normal nodes.
When the timer expires, and if the number is less thann×p , the normal node with
short time interval broadcast a CHs advertisement message (ADV_CH) to announce
its CH status by using a non-persistent carrier-sense multiple access (CSMA) MAC
protocol.

The value of time interval is set as
t =k/E (2)
Where k is the factor, E is the residual energy of each node. So the more energy
the node has, the shorter the time interval is generated, thus it has more probability to
become a cluster head.
If the number of cluster heads is more thann×p , we can eliminate some low
energy cluster head to modify the number of cluster number to n×p .
The cluster heads sort their residual energy by descend, if one cluster head’s
energy is ranked behind n×p , it is changed to normal node of course, this algorithm is
still a distributed algorithm, that is, nodes make autonomous decisions without any
centralized control.
Furthermore, this new protocol achieves the improvement of the balance of energy
consumption. Figure 2 shows the flow chart of the second selection of cluster head.
Improvement over LEACH
 Two phase of selection for cluster he
 Consider residual energy of nodes.
 Optimal number of cluster head.
Drawback
 Extra overhead of electing cluster head
 Each time new cluster head selection in LEACH-B Protocol.
3. PROPOSED APPROACH
In most of the energy efficient routing protocols, nodes selected as cluster heads must
broadcast to member nodes of the clusters to which they belong that they have
become cluster heads. As the frequency of rounding and of cluster head replacement
increases, energy consumption increases due to message transmission for
broadcasting
Our goal is to reducing the amount of cluster head selection and replacement cost
and ultimately to extend the lifetime of the entire networks compared with the
existing clustering protocols.
Cluster head does not directly sends data to the base station. But it sends the data
to the next cluster head that is near by the base station and finally data reaches to the
base station. (Multi-hop Approach).
Select cluster head having highest remaining energy. Replace the cluster head
based on the threshold value of residual energy on the sensor nodes. If the energy
value of a cluster head is higher than threshold value, then no need to replace the
cluster head.
The steps in order to setup clusters and then to elect cluster heads are the following:
1. Initially all nodes send their energy level to their neighbors, and ultimately the data
reaches to the base station. Base station has the global knowledge of the network. The
base station selects cluster head whose energy level is above the threshold.
2. 5% of the total no. of nodes are assigned to be cluster head. The BS broadcasts the
unique IDs of the newly selected cluster heads, and their cluster members and the
nodes use this information to form and enter a cluster.

3. Each cluster head creates a TDMA schedule and broadcast this schedule to all other
nodes in its cluster. The node sends data within its allocated time.
Figure 2 Proposed Methodology
4. Each cluster head aggregate the data and finally data reaches to the base station. A
round of data transmission has been completed. If the energy value of a cluster head
is higher than threshold value, then cluster head is not replaced.
The threshold value for the energy is calculated as per following equation:
Updated Threshold = Old Threshold – (0.15 * Old Threshold)
After completion of second round, node whose energy value greater or equal to
85% becomes Cluster Head.
The main features of our proposed method are as follow:
 Reduce the energy consumption
 Reduce cluster head selection and replacement cost.

4. SIMULATION SCENARIO
Table I Simulation parameter
Simulation Tool MATLAB
Area 100*100 m2
No. of Nodes 100
Initial energy of nodes 0.5 J
Energy required in sending or receiving 1 bit 50 nJ/bit
Data Aggregation Energy(EDA) 5 nJ/bit/signal
Energy consumed in amplifier(Eamp) 10 pJ/bit/m2
Base Station Location (50,50)
Above Table shows simulation Parameters.
Our aim is to prolong network life time.
Network life time: Network life time depends on the number of dying nodes. We
have measured no. of rounds for LEACH and LEACH B. We have measured no. of
rounds for the proposed method.
Simulation Results
The simulation by MATLAB shows that the improved protocol has balanced the
system energy consumption and has better performance of prolonging the network
lifetime than LEACH-B protocol.
The network performance is measured by its life time.
As shown in the figure, nodes in LEACH-B protocol shows that all nodes die after
about 1521 rounds. While proposed approach figure shows that all node dies after
1905 rounds.
Figure 3 Died nodes after 1521 rounds for LEACH-B
Figure 4 Died nodes after 1905 rounds for Proposed Approach

Figure 5 Number of alive nodes between LEACH-B and proposed method
Above Figure shows the system lifetime using the LEACH –B algorithm and
proposed method. It shows the number of alive nodes per rounds of LEACH-B and
proposed method.
Figure 6 Number of dead nodes between LEACH-B and proposed method
Above Figure 6 shows the number of died nodes per rounds of LEACH-B and
proposed method.
Comparison between LEACH, LEACH-B and proposed method
Table 4.2 Comparison between LEACH, LEACH-B and proposed method
Energy (J/node) Protocol Number of rounds when last node dies
0.5 LEACH 1312
0.5 LEACH-B 1521
0.5 Proposed method 1905

5. CONCLUSION
Energy Efficiency for prolonging the WSN has received much focused attention.
We have proposed a simple threshold based cluster head selection method in
which we reduce the amount of cluster head selection and replacement cost and
ultimately to extend the lifetime of the entire networks.
This enhanced algorithm has overcome the shortcoming of the original protocol
by taking the threshold value of nodes and minimize the cluster head selection
process.
6. FUTURE WORK
In future, we consider more parameters to increase the network life time like as
distance between cluster head to BS and or node to Cluster Head, packet delivery
ratio and network life time etc.
ACKNOWLEDGMENT
I would like to thank my parents, my guides Prof. S. V. Patel and all staff members of
LCIT, Bhandu for guidance throughout work period.
REFERENCES
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