MODLEACH: A Variant of LEACH
for WSNs
Prepared by:
Danish Mahmood
Abstract
• Cluster Based Routing in Wireless Sensor
Networks
• We divided our work into two parts
• First phase:
– Modification in LEACH protocol
• Efficient Cluster Head Replacement scheme
• Dual Transmission power levels
• Second Phase
– Implement soft and hard thresholds in MODLEACH
– Performance analysis with respect to network
stability, throughput and cluster head formation.
MODLEACH: A Variant of LEACH for WSNs.
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Introduction: Routing in Wireless
Sensor Networks
• Major Limitations of Wireless Sensor
Networks.
– Energy
– Uncontrolled environment
• Role of routing protocol to cope with these
limitations
– Minimal usage of energy is key responsibility of
routing protocol running on WSN however,
environment can not be controlled fully.
MODLEACH: A Variant of LEACH for WSNs.
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Cluster Based Routing (1)
• In clustering, whole network is divided into fixed
or variable sized clusters containing sensor nodes
in it.
• Each cluster is represented by a cluster head that
is responsible for communication between base
station/ sink and other non cluster head nodes.
• Non cluster head nodes of cluster communicates
only with cluster head hence minimizing energy
utilization.
MODLEACH: A Variant of LEACH for WSNs.
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Cluster Based Routing (2)
BS
MODLEACH: A Variant of LEACH for WSNs.
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Cluster Based Routing (3)
• Here nodes are organized into clusters that
communicate with a local BS (CH) and these local Base
Stations transmit the data to the global BS, where it is
accessed by the end user.
• Reduced distance of data transmission as the local BS
(CH) is typically close to all nodes in the Cluster but BS
becomes energy constrained
• As soon as cluster -head node dies, all nodes from that
cluster effectively die since there is no way to get their
data to the base station.
• In Adaptive clustering, cluster heads change as nodes
move in order to keep the network fully connected
MODLEACH: A Variant of LEACH for WSNs.
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Cluster Based Routing (4)
• Cluster based routing has proven itself as
efficient routing strategy in WSNs.
• Many routing protocols are derived using
clustering mechanism that gives efficient
wireless sensor network.
• LEACH, being the parent routing protocol
receives many enhancements.
MODLEACH: A Variant of LEACH for WSNs.
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MODLEACH
• To understand the proposed modifications or
enhancements in LEACH,
• we initially have to understand
– Functionality
&
– operability
of LEACH protocol.
MODLEACH: A Variant of LEACH for WSNs.
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LEACH Routing Protocol
• LEACH (Low-Energy Adaptive Clustering
Hierarchy) is a routing protocol for wireless
sensor networks in which:
– The base station (sink) is fixed
– Sensor nodes are homogenous
• LEACH conserves energy through:
– Aggregation
– Adaptive Clustering
MODLEACH: A Variant of LEACH for WSNs.
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LEACH Properties
• Adaptive Clustering
– Distributed
• Randomized Rotation
– Biased to balance energy loss
• Heads perform compression
– aggregation
• In-cluster TDMA
MODLEACH: A Variant of LEACH for WSNs.
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LEACH Functioning (1)
• Cluster Head and Cluster Formation:
– Leach is based on adaptive Clustering.
– Every node has equal chances to be a cluster head
– Sensors elect themselves to be the local cluster
heads at any given time with a certain probability,
and broadcast their status to other sensors each
sensor node choosing the cluster-head with
strongest signal (can minimize transmission
power)
MODLEACH: A Variant of LEACH for WSNs.
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LEACH Functioning (2)
• Randomized Rotation
– The high energy cluster head position rotates among
the various sensors in order to not to drain the battery
of a single sensor. (currently just random)
– Sensors elect themselves to be the local cluster heads
at any given time with a certain probability, and
broadcast their status to other sensors each sensor
node choosing the cluster-head with strongest signal
(can minimize transmission power)
MODLEACH: A Variant of LEACH for WSNs.
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LEACH Operation
• The operation is broken up into rounds
– Advertisement phase
• use CSMA MAC protocol, and all cluster heads transmit
with same energy
– Set up phase : Cluster is organized
• each node transmits to which cluster head it wants to
belong to using a CSMA MAC
– Steady State Phase: Data Transfers to Base Station
occur
MODLEACH: A Variant of LEACH for WSNs.
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Problems and their solutions
• LEACH gives adaptive clustering mechanism
which very efficiently deals with energy
conservations.
• However, Leach doesn’t take account of residual
energy of a node.
– To address this, a novel technique as efficient Cluster
head Replacement is proposed.
• LEACH use same amplification energy for both
kinds of transmissions i.e. CH to BS and CM to CH.
– To address this, multi amplified power levels are
introduced.
MODLEACH: A Variant of LEACH for WSNs.
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Modifications in LEACH:
MODLEACH (1)
• For every round, protocol will check if energy
of Cluster Head has fallen a defined threshold
than it will undertake CH and cluster
formation process. Else same CH will continue
its operations.
• This is how much of energy that goes wasted
in cluster head formation process can be
saved. Moreover, control overhead is also
limitized.
MODLEACH: A Variant of LEACH for WSNs.
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Modifications in LEACH:
MODLEACH (2)
• In an adaptive clustering hierarchic, there can be
three kinds of communications w.r.t distances.
– Inter cluster communication.
– Intra cluster communication.
– Cluster head to base station/ sink communication.
• Using equal signal amplification energy for all of
above communications is also not needed. Hence
multi power levels are adjusted for all three kinds
of communication to preserve energy.
MODLEACH: A Variant of LEACH for WSNs.
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MODLEACH
• Basically, in MODLEACH, two modifications/
enhancements are made.
• These enhancements are (as discussed
earlier):
– Efficient cluster head replacement technique
– Dual amplification power levels
MODLEACH: A Variant of LEACH for WSNs.
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LEACH Vs MODLEACH
MODLEACH: A Variant of LEACH for WSNs.
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MODLEACH
with
Hard and Soft Threshold.
• Implementation of hard and soft threshold in
MODLEACH gives much better results
• Reactive nature of routing protocol not only
result in lower routing over head but also
better network life time.
• Applying thresholds in MODLEACH make the
protocol reactive in nature.
MODLEACH: A Variant of LEACH for WSNs.
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Simulations Tool and Parameters
• Simulations are conducted using MATLAB
(R2009a) and to get precise plots, confidence
interval is taken.
MODLEACH: A Variant of LEACH for WSNs.
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Simulation Results
• Simulations show that MODLEACH performs
better considering metrics of throughput,
network life time, and optimized cluster head
formation of network w.r.t LEACH.
• MODLEACH is further improved by using the
concept of soft and hard threshold as
introduced by TEEN. MODLEACHHT further
improve efficiency however, MODLEACHST
performs best amongst all.
MODLEACH: A Variant of LEACH for WSNs.
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Metrics under consideration
• LEACH, MODLEACH, MODLEACHHT and
MODLEACHST are simulated keeping
– Network life time
– Throughput
– Cluster head formation and scope
Under consideration
MODLEACH: A Variant of LEACH for WSNs.
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Network Life Time
• MODLEACHST gives
maximum network life time
amongst all protocols.
• Reasons are:
– Concept of soft threshold
– Efficient cluster head
replacement technique
– Dual amplification power
levels for inter and CH to Bs
communications.
MODLEACH: A Variant of LEACH for WSNs.
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Throughput
•
•
Maximum throughput is achieved by
MODLEACHST.
Comparing MODLEACH and LEACH,
MODLEACH gives better throughput
–
•
the mode of operation.
–
•
increased network life time due to dual
amplification power levels and better
cluster head replacement scheme.
LEACH and MODLEACH both are proactive
(periodical transmissions) in nature while
MODLEACHHT and MODLEACHST are
reactive (event driven).
This also depicts that
–
proactive routing protocols have lower
throughput than reactive routing
protocols.
MODLEACH: A Variant of LEACH for WSNs.
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Cluster head formation and scope
• Figure 6 (next slide) and Figure
7 show number of cluster
heads chosen at each round.
• All the techniques basically
used same algorithm hence no
major difference is there in
cluster head formation and
calculation manner
• However, MODLEACH differs
from LEACH in a sense that
initially its number of cluster
heads remain stable and then
cluster head formation
behavior goes similar to that
of LEACH.
MODLEACH: A Variant of LEACH for WSNs.
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Cluster head formation and scope
• Initially as modified in
LEACH, MODLEACH
executes same cluster
heads for next round/s if
they have energy greater
than defined threshold.
• This is the reason of stable
number of cluster heads
initially.
MODLEACH: A Variant of LEACH for WSNs.
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Conclusion
• In this work, we propose MODLEACH, a new variant of LEACH
• The two techniques utilized in MODLEACH can further be utilized in other
clustering routing protocols for better efficiency.
• MODLEACH tends to minimize network energy consumption by
– efficient cluster head replacement after very first round and
– dual transmitting power levels for intra cluster and cluster head to base
station communication.
• Further, soft and hard thresholds are implemented on MODLEACH to give
a comparison on performances of these protocols considering throughput
and energy utilization.
• In future, we will carry our work
– to calculate routing load of MODLEACH, MODLEACHST and MODLEACHHT
analytically
– And to apply efficient cluster head replacement mechanism along with dual
transmission power levels in other clustering routing protocols of wireless
sensor networks to study their impact in a broader sense.
MODLEACH: A Variant of LEACH for WSNs.
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