```Talha Naeem Qureshi
Joint work with
COMSATS, Institute of Information Technology,
www.comsats.edu.pk
www.njavaid.com
15th International Multi Topic Conference (INMIC), Islamabad, Pakistan
13th to 15th December 2012
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Wireless Sensor Networks (WSNs) are composed of
multiple unattended ultra-small, limited-power sensor
nodes
Sensor nodes are deployed randomly in the area of interest
Sensor nodes have limited processing, wireless
communication and power resource capabilities
Sensor nodes send sensed data to sink or Base Station (BS)
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Goal:
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Clustering is useful in reducing energy
consumption
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LEACH – Low Energy Adaptive Clustering Hierarchy [Heinzelman et
al., 2000]
SEP - Stable Election Protocol [G. Smaragdakis et al., 2004]
DEEC - Distributed Energy Efficient Clustering [Li Qing et al., 2006]
LEACH:
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where:
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◦ Unable to differentiate nodes in terms of energy (homogeneous)
◦ Node i chooses random number s between 0 and 1
◦ If s < T(si), node i becomes a Cluster Head (CH) for the current round where:
◦ T(si)=threshold
◦ Pi = desired percentage of CHs
◦ G = set of nodes that have not been a CH in the last 1/P rounds
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Each node is elected CH once every 1/P
rounds (epoch length)
On average, n x P nodes elected per round
◦ n = total number of nodes
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Differentiate nodes in terms of their energy
(heterogeneous)
Consider two types of nodes w.r.t energy: normal and
where:
◦ Energy of advanced nodes > Energy of normal nodes
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CH selection probability of advanced nodes is greater
than normal nodes
Use same threshold T(si) for CH selection as
described by LEACH
Each node is elected CH once every 1/P rounds
(epoch length)
Epoch of advanced nodes < epoch of normal nodes
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Differentiate nodes in terms of their energy
(heterogeneous)
Consider multiple energy levels of nodes
Use same threshold T(si) for CH selection as
described by LEACH
Epoch of high energy nodes < epoch of low
energy nodes
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Mostly sensor nodes overlaps each other or placed close to
each other during deployment
Overlapped and close nodes have same sensed data
There is no need to send same sensed data two times to BS
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Sending same data two times to BS cause
◦ Energy loss
◦ Stability period and life time of WSN decreases
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No previous protocol including LEACH, SEP
and DEEC is addressing this issue
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Our goal:
◦ To minimize energy consumption
◦ To enhance network stability period and network
Concept of pairing is introduced
Sensor nodes of same application and at
minimum distance between them will form a pair
for data sensing and communication
CHs selection technique is enhanced
CH selection on basis of remaining energy of
nodes
CH of current round will predict the CH for next
round
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Mechanism:
◦ Sensor nodes are supposed to be equipped with
Global Positioning System (GPS)
◦ Senor nodes measure their location through GPS
◦ Nodes transmit their location information to sink
◦ In first round clusters are formed by same
mechanism described by LEACH
◦ Nodes which are at minimum distance from each
other in their intra cluster transmission range and
of same application type are coupled in pair by BS
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Mechanism:
◦ Sink broadcast pairing information to all the nodes in
network
◦ Nodes become aware of their coupled node
According to the proposed scheme, The nodes switch
between ”Sleep” and ”Awake” mode during a single
communication Interval
Initially node in a pair, switch into Awake mode also
called Active-mode if its distance from the sink is
less then its coupled node
Node in Active-mode will gather data from
surroundings and transmit data to CHs
During this period transceiver of the coupled node
will remain off and switches into Sleep-mode
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In next round, nodes in Active-mode switch
into Sleep-mode and Sleep-mode nodes
switch into active-mode
Energy consumption is minimized because
nodes in Sleep-modes save their energy by
not communicating with the CHs
Unpaired nodes remain in Active-mode for
every round till their energy resources
depleted
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Green circles – coupled or paired nodes
Read circles – unpaired or isolated nodes
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CH selection mechanism:
◦ Initially, in first round CHs are selected by same
mechanism described by LEACH
◦ CHs selection after first round is based on
remaining energy of each node
◦ Nodes in Active-mode take participation in CH
election process
◦ During start of round, nodes also transmit their
energy information to CH
◦ CH computes the remaining energy of every node
in cluster and its distance from each node and
select CH for the next upcoming round
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Transmission phase:
◦ When node has been selected as CH, it broadcasts
◦ Only Active-mode nodes hear the broadcast
◦ They select their CHs on the basis of Received
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Nodes in Active-mode, transmit their sensed
data to CH during their assigned TDMA slots
Nodes in Sleep-mode do not take
participation in data transmission and save
their energy by turning their transceiver off
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Node mode setup algorithm
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Performance metrics:
◦ Stability period: It is duration of network operation
from start till first node dies
start till last node is alive
◦ Instability period: It is duration of network
operation from first node dies till the least node
dies
◦ Number of CHs: It indicates the number of clusters
generated per round
◦ Packet to BS: It is rate of successful data delivery
to BS from CHs
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In EESAA first node dies around 1800 round
Stability period of EESAA is almost 120% 50% and 35% greater
than LEACH, SEP and DEEC respectively
EESAA has 100% 102% and 50% network lifetime as compared
to LEACH, SEP and DEEC
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SEP, DEEC and LEACH has more uncertainties in CHs selection
Random number of CHs are selected in every round but ESSA
has controlled CHs selection.
EESAA efficient CHs selection algorithm helps it in better and
constant data rate transmission to BS
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EESAA has sleep-awake policy for nodes
Less number of data is transmitted to BS in starting rounds
due to sleep mode of some nodes
But after 4300 rounds, EESAA has highest data rate
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EESAA is location aware protocol
EESAA minimizes energy consumption by
sleep-awake mechanism
Simulation results show significant
improvement all performance metrics as
compared to existing routing protocols e.g.,
SEP, LEACH and DEEC
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