1. LEACH protocol for
WIRELESS SENSOR NETWORK
CALCUTTA INSTITUTE OF ENGINEERING AND MANAGEMENT
24/1A, CHANDI GHOSH ROAD, KOLKATA-700040
2012-2013
Presented by: RAMESH VERMA
ANIL KUMAR
PRAVIND KUMAR
C.S.E.4th Year

2. Overview-LowEnergyAdaptiveClusteringHierarchy
(LEACH)
 Introduction to leach protocol
 Two phases of leach
 Set-up phase/ thresold algorithm
 Set-up phase/advertisement
 Set-up to steady state phase
 Weakness in leach
 DECSA(Distance Energy Cluster Structure Algorithm )
 Initialization stage
 Stable working stage
 comparision

3. IntroductiontoLEACHprotocol
 Falls under hierarchical networks
 Self-organizing, adaptive clustering protocol that
uses randomization to distribute energy load evenly
 Dense network of sensor nodes grouped into
clusters.
 All nodes are assumed to be homogenous + energy
constrained.
 Base station is fixed + away from sensors.
 Cluster member elect cluster head to avoid excessive
energy consumption.
 Incorporates data aggregation.

4. LEACH two phases
 It has two phases
 The set-up phase and the steady- state phase
 The set-up phase where cluster heads are chosen
 The steady state phase the cluster head is maintained
where data is transmitted between nodes

5. Set-up phase/ Thresold
algorithm
 Cluster-heads can be chosen stochastically
(randomly based) on this algorithm:
T(n) =P/1-P*(r mod/p) if n€G
0 , otherwise
Where n is a random no. between 0 and 1 and
P is cluster head probability and G is the set of
nodes that were not cluster head in the last round.
 If n <T(n), then that node becomes a cluster
head
 The algorithm is designed so that each node
becomes a cluster-head at least once

6. Algorithm - Setup Phase |
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 Each node that elected itself a cluster-head for
current round broadcasts advertisement
message to rest of nodes
 All cluster-heads transmit advertisement using
same transmit energy
 Non-cluster-head nodes must keep receivers on
during this phase to hear advertisements
 now they decide which cluster to belong to for
this round by choosing cluster-head that requires
minimum communication energy
 In case of ties, random cluster-head chosen

7. Algorithm - Setup to Steady
Phase
 After node picks cluster, must inform cluster-
head
 Cluster-head now knows number of members
 cluster-head then creates a TDMA schedule
telling each node when it can transmit
 allows radio components of each non-cluster-
head node to be turned off during its transmit
time, thus minimizing energy dissipated in
individual sensors
 cluster-head now has all data from the nodes in
its cluster, aggregates data & transmits to base

8. Weakness in LEACH
LEACH assumes that
 all nodes can communicate with each other and are able to
reach the sink (therefore, it is only suitable for small size
networks)
 all nodes have data to send and so assign a time slot for a
node even though some nodes might not have data to
transmit.
 all nearby nodes have correlated data which is not always true
 all nodes are continuously listening ( this is not realistic in a
random distribution of the sensor nodes, for example, where
cluster-heads would be located at the edge of the network),

9. DECSA (Distance Energy Cluster
Structure Algorithm)
 DECSA is improvement over LEACH.
 It considers both the distance and residual energy
information of nodes.
 Three level hierarchy structure of DECSA consists of
BS(Base Station), BCH(Base Station Cluster Head), CH(
ordinary Cluster head), SN(sensor nodes)

10. Initialization Stage
 The process of cluster head select consists of following 2
parts: election of ordinary cluster head node (CH) and election
of Base Station Cluster head (BCH)
 First round cluster head is called false-cluster-head
 All nodes compare their k(i) with the false cluster head.
 If k(i) < false cluster head’s k(i), then false cluster head
becomes CH otherwise the node.
k(i)=En(i)/do(i)
k(i)=thresold of elected CH
En(i)=residual energy of node i
do(i)=average distance of node I from all other nodes in the
network

11. Initialization Stage
Selection of BCH
1.TBCH of all CH is calculated and compared
with predefinedTBCH0
2. CH whoseTBCH are larger than the predefined
thresholdTBCH0 becomes the base-station cluster-
head( BCH).
TBCH(i)=(En(i)/Eo)+(En(i)/d(i))
En(i)=current residual energy of node I
Eo is the initial energy of node in the network
d(i)= distance between node I and the base station

12. Stable working Stage
 base station broadcasts the message to the entire
network forming a communication path.
 Common nodes (SN) in the cluster will transmit data
packet to their closest cluster-head
 luster-head will collect and fusion those data and
transmit them to the base-station cluster- head, rather
than transmit them to the base station directly
 then, base-station-cluster-head will communicate with
the base station

13. Comparison
 DECSA prolongs 31% of the lifetime, reduces 40% of the energy
consumption and has a better performance than the original LEACH
protocol.
 . Residual energy relationship of nodes between DECSA and LEACH

14. Conclusion
 DECSA considering both the distance and
residual energy of nodes
 It improved the process of cluster head
election and the process of data transmission
of network
 Reduces the adverse effect on the energy
consumption of the cluster head
 prolongs 31% of the lifetime, reduces 40% of
the energy consumption.

15. Bibiliography
 “Low Energy Adaptive Clustering Hierarchy with
Deterministic Cluster-Head Selection”; M.J.Handy,
M. Haas, D.Timmermann; 2002;
http://www.vs.inf.ethz.ch/publ/se/IEEE_MWCN2
002.pdf
 “Probabilistic Modeling of Leach Protocol and
Computing Sensor Energy Consumption Rate in
Sensor Networks”; Song, Dezhen; February
22,2005;
http://www.cs.tamu.edu/academics/tr/tamu-cstr-
2005-2-2