Energy Aware Dynamic Clustering and Hierarchical Route based on LEACH for WSN

Abstract

Optimization of resource utilization especially energy with higher Quality of Service (QoS) parameter such as packet delivery ratio etc, is an open and active research issue in wireless sensor networks (WSN). Existing methods such as direct transmission, multi-hop routing, minimum transmission energy and static clustering methods were not optimal for certain applications. LEACH protocol is built on the assumption of direct communication between cluster head and Sink nodes. Where as in many real time applications cluster head to cluster head communication is required. The Proposed work in this paper is an improvement in LEACH protocol by means of dynamic cluster head selection and routing from Cluster head to sink node through other cluster heads and their by increases the network life time. The proposed work gives better performance of network life time, low energy consumption compared to LEACH.

Full text

International Journal of Computer Networking,
Wireless and Mobile Communications (IJCNWMC)
ISSN 2250-1568
Vol. 3, Issue 3, Aug 2013, 79-86
© TJPRC Pvt. Ltd.
ENERGY AWARE DYNAMIC CLUSTERING AND HIERARCHICAL ROUTING BASED ON
LEACH FOR WSN
DAKSHAYINI M1, PRAVEEN KURER2 & GURUPRASAD H S3
1Professor, Department of Information Science and Engineering, BMSCE, Bangalore, Karnataka, India
2Research Scholar, Department of Information Science and Engineering, BMSCE, Bangalore, Karnataka, India
3Professor & HOD, Department of Information Science and Engineering, BMSCE, Bangalore, Karnataka, India
ABSTRACT
Optimization of resource utilization especially energy with higher Quality of Service (QoS) parameter such as
packet delivery ratio etc, is an open and active research issue in wireless sensor networks (WSN). Existing methods such as
direct transmission, multi-hop routing, minimum transmission energy and static clustering methods were not optimal for
certain applications. LEACH protocol is built on the assumption of direct communication between cluster head and Sink
nodes. Where as in many real time applications cluster head to cluster head communication is required. The Proposed work
in this paper is an improvement in LEACH protocol by means of dynamic cluster head selection and routing from Cluster
head to sink node through other cluster heads and their by increases the network life time. The proposed work gives better
performance of network life time, low energy consumption compared to LEACH.
KEYWORDS: Energy Optimization, LEACH, Packet Delivery Ratio, Routing, Wireless Sensor Network (WSN)
INTRODUCTION
Wireless sensor network is becoming most popular network technology to forward the sensed collected data to the
base station with restricted energy capacity. A Wireless Sensor Network (WSN) consists of a large number of tiny nodes
with sensing, computing, and wireless communications capabilities [1][5]. Each Sensor nodes are equipped with a radio
transceiver, a small microcontroller, energy source and sensors. The sensors attached to nodes measure surrounding
conditions related to the environment in which they are deployed, process the data and transmit them to base station. A
large number of sensor nodes are deployed in the area which is to be monitored. Usually the area under consideration will
be harsh or hostile environments. These sensor nodes once deployed organize themselves to form network. Each sensor has
limited battery and it is very necessary to efficiently use its energy [2][4].Because of its remote deployment manual battery
replacement is not possible. Hence primary design objective of wireless sensor network is to use energy efficiently. One
way of achieving energy efficiency is through optimized routing [8][11][10].
The routing protocols in WSNs can be divided into flat, hierarchical, and location based routing depending on the
network structure [3][9]. Hierarchical routing is also known as cluster based routing because in this type of routing sensor
nodes are grouped together and form clusters. In each cluster, a node is assigned as a head-node and known as cluster-head
(CH). The CH acts as the leader of their own cluster having the responsibilities like collection and aggregation the data
from their respective clusters and transmitting the aggregated data to the Base station (BS). LEACH is the most well
known hierarchical protocol in WSN whose main aim is to distribute the energy load equally among all sensor nodes in the
network and prolong network life time. LEACH assumes direct communication between cluster head and base station
which is not suitable for the applications where the base station is located far away from the sensor nodes and also
consumes more energy. Hence the proposed routing algorithm is an improvement in LEACH protocol which considers the

80 Dakshayini M, Praveen Kurer, & Guruprasad H S
cluster head to cluster head routing which minimizes energy consumption and their by increasing the network life time[7].
The rest of the paper is organized as follows in section 2 we discuss the detailed description of LEACH protocol
and its disadvantages. In section 3 we introduce our proposed protocol section 4 presents the implementation details,
section 5 results and discussion.
DISCRIPTION OF LEACH PROTOCOL
LEACH [2][6] stands for Low-Energy Adaptive Clustering Hierarchy and it is one of the popular cluster-based
hierarchical routing protocol. In this protocol, the sensor nodes are combined together and form a local cluster. Among all
sensor nodes one node acts as a CH inside from the local cluster. A randomize rotation technique of CH is used by this
protocol whose main aim is to distribute the energy load equally among all sensors in the network which ultimately gives
result of a longer life to the node‟s battery. The major role of CH is to collect data from their respective cluster and
aggregate those collected data and finally sent to the base station.
The Operation of LEACH is divided into two phases. Each LEACH round begins with a set-up phase and a
steady-state phase. In set-up phase cluster heads are randomly chosen and cluster are organized as shown in the following
Figure 1.
Figure 1: Cluster Organization in LEACH Protocol
In steady-state phase nodes transmit their data to their respective CHs, and after that the CHs transmit the whole
cluster data to the base station. The time line diagram that includes both two phases for single round of LEACH is shown
in Figure 2.
Figure 2: Time for a Single Round of LEACH
Phases Description
Set-up Phase
In set-up phase cluster heads are randomly chosen and clusters are organized. The selection of cluster head
depends on decision made by the node by generating random number between 0 and 1. If the generated random number is
less than threshold T(n) the node becomes a cluster head for current round. The threshold is set as

Energy Aware Dynamic Clustering and Hierarchical Routing Based on LEACH for WSN 81
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Where P is percentage of cluster heads for a given network consisting of „N‟ nodes, G is the number of nodes that
have not been cluster heads in the last 1/P rounds. During the first round (r=0) each node has a probability P of becoming a
cluster head. The nodes that are cluster heads in round 0 cannot be cluster be cluster heads for the next 1/P rounds. To
increase the probability of remaining nodes to become cluster heads. After 1/P-1 rounds the threshold is 1 for any nodes
that have not yet been cluster heads.
Once cluster heads have been chosen the cluster heads broadcast advertisement message to all the other nodes in
network using CSMA MAC protocol. The regular nodes must keep their receivers on during this phase to hear the
advertisement messages of all the cluster heads in the network. The regular nodes after receiving advertisement message
choose their cluster head for the current round based on the least communication energy to reach the cluster head. After
this each regular node transmits this information back to the cluster head again using a CSMA MAC protocol. The cluster
head receives all the messages for nodes that would like to join in the cluster. Once cluster head receives all messages it
allocates TDMA schedule for each node telling when it can transmit the sensed data.
Steady-State Phase
After set-up phase regular nodes will send data to their cluster heads during their allocated transmission time
according to the TDMA schedule. The cluster head will keep its receiver on to receive all the data from the nodes in the
cluster. When all the data is received the cluster head performs data fusion function to compress all the data into a single
signal. After that the cluster head sends the signal to the base station. If the base station is far away, this is a high energy
transmission.
Drawbacks of LEACH
LEACH is suitable for small size network because in LEACH it assumes that all nodes can communicate with
each other and are able to reach sink which is not suitable for applications where the sink is situated far from sensor nodes.
LEACH assumes that all cluster heads are able to communicate with the sink with one hop which consumes more energy.
PROPOSED ALGORITHM
A lot of simulation works /experiments are going on in the research field of WSN to make routing protocols more
and more energy efficient. In this paper, we propose a modified version of LEACH that can increase energy efficiency than
original LEACH. The basic concept involved in increasing energy efficiency is to keep radio communication distance as
possible as minimum. To keep communication distance minimum cluster head to cluster head routing is considered.
In proposed algorithm it is assumed that nodes in a network are equipped with global positioning system (GPS).At
the time of random deployment sensor nodes send location information to the base station before the set-up phase and
steady state phase. Once the base station receives location information it divides the deployment square area „A‟ into
groups A1, A2,A3,..etc. The groups are made depending upon the node location and cluster head election probability „p‟.
The groups are made only once by base station and hence it does not consume too much energy. In each group a cluster
head is randomly chosen for each round so that the elected cluster heads are evenly distributed in the network. After
electing cluster heads in each group they broadcast cluster head identity message so that all cluster heads know their
neighbor cluster heads before the steady state phase.

82 Dakshayini M, Praveen Kurer, & Guruprasad H S
In steady state phase the cluster heads collect the data from regular nodes as in LEACH but instead of directly
sending the data to the base station the proposed algorithm routes the data to the nearest cluster head if the base station is
far away. Hence it reduces radio communication distance. The radio communication model used in the proposed algorithm
is shown in Figure.3
Figure 3: Radio Communication Model
The node radio energy consumed in transmission is
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Where, k is the number of bits transmitted, d is the distance between transmitter and receiver, and do is the
constant referred as crossover distance. Depending on the transmission distance both the free space Efs and the multi-path
fading Emp channel models are used. For receiving the k bit message the node radio consumes.
ERX(k)= k x E(elec)
As communication cost is considered to be much larger than computational cost, so the contribution of
computations to the energy consumption is considered to be negligible in this analysis. The assumed energy required for
running the transmitter and receiver electronic circuitry E(elec) is 50nJ/bit and for acceptable SNR required energy for
transmitter amplifier for free space propagation Efs is 100pJ/bit/m2 and for two ray ground Emp is 0.0013pJ/bit/m4. The
crossover distance do is assumed to be 87m.The cluster head to cluster head routing is as shown in Figure 4.
Figure 4: Cluster-Head to Cluster-Head Routing

Energy Aware Dynamic Clustering and Hierarchical Routing Based on LEACH for WSN 83
IMPLIMENTATION DETAIL
The proposed routing algorithm has been simulated in MATLAB. These have been made assuming a network
having dimensions 100 x 100 meters. The number of nodes is assumed to be 100. The nodes are generated and placed
randomly. The energy-awareness and network life time of proposed routing protocol is evaluated with respect to the
following parameters.
 The energy consumption by nodes in each round.
 Number of alive and dead nodes in each round.
For each node in the protocol an initial energy is given say E0 and after the completion of each round, energy is
consumed by the protocol and E0 starts decreasing. For each round the energy consumed by the network in joules and the
number of alive and dead nodes are calculated.
Figure 5: Shows the Deployment of Sensor Nodes, All Nodes are Deployed Randomly in the 100 x 100 Area
The simulation parameters used in proposed algorithm are as shown in Table 1.
Table 1
Sl.
No
Simulation Parameters and Their Values
Parameters
Values
1
Environment size
100 x 100
2
Number of nodes
100
3
Initial energy of nodes
0.1 J
4
Eelec
50 nJ / bit
5
Efs
10 pJ / bit / m2
6
Emp
0.0013pJ/ bit/m4
7
EDA
5 nJ / bit
RESULTS AND DISCUSSIONS
The proposed routing algorithm is compared with original LEACH protocol. The network parameters such as
residual energy, Number of alive nodes and Number of dead nodes are calculated versus number of rounds. The graphs
show that the proposed algorithm outperforms the LEACH protocol.

84 Dakshayini M, Praveen Kurer, & Guruprasad H S
Figure 6: Rounds Vs Residual Energy
The Figure 6. Shows that the proposed algorithm residual energy lasts for 460 rounds compared to LEACH which
lasts only for 193 rounds. Hence the proposed algorithm distributes energy more equally among all nodes compared to
LEACH.
Figure 7: Rounds Vs Alive Nodes
Figure 7. Shows that in the proposed algorithm the first node dead at 240 rounds compared to LEACH in which
first node dead at 102 rounds. In proposed algorithm all nodes will dead at 462 round and in LEACH all nodes will dead at
only 194rounds. Hence proposed algorithm will significantly increases network life time compared to LEACH. Figure 8.
Shows the number of dead nodes
Figure 8: Rounds Vs Dead Nodes
CONCLUSIONS
In this paper we proposed routing algorithm is an improvement in LEACH which is suitable for the applications
where the base station is located far from the sensor nodes. The proposed algorithm minimizes the radio communication
distance by routing from cluster head to cluster head and hence consumes less energy. The proposed routing algorithm also
distributes energy load more equally among all nodes in network and hence increases the network life time significantly.

Energy Aware Dynamic Clustering and Hierarchical Routing Based on LEACH for WSN 85
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