The LEACH & PEGASIS are the Protocols.

1. LEACH & PEGASIS
PROTOCOL
By:
Reena Shekar
III MCA
Mangalore University

2. LEACH
 Is a clustering based protocol to collect
data from wireless network.
 In the network, hundreds and thousands of
wireless sensors are dispersed that collects and
transmit data.
 Also in these networks cluster heads are elected
out of the sensors to transmit the data collected
to base station.

3.  LEACH includes distributed cluster formation, local
processing to reduce global communication, and
randomized rotation of the cluster -heads.
 LEACH performs local data fusion to “compress” the
amount of data being sent from the clusters to the
base station.
 further reducing energy dissipation and enhancing
system lifetime.

4. LEACH Network

5. The Cluster Head
 The LEACH Network is made up of nodes, some
of which are called cluster-heads
 The job of the cluster-head is to collect data
from their surrounding nodes and pass it on to
the base station
 LEACH is dynamic because the job of cluster-
head rotates

6. Existing Routing Protocols
 LEACH is compared against three other routing
protocols:
 Direct-Transmission
 Single-hop
 Minimum-Transmission Energy
 Multi-hop
 Static Clustering
 Multi-hop

7. Direct-Transmission
 Each sensor node transmits directly to the sink,
regardless of distance.
 Most efficient when there is a small coverage
area and/or high receive cost.

8. Minimum Transmission Energy (MTE)
 Traffic is routed through intermediate nodes
 Node chosen by transmit amplifier cost
 Receive cost often ignored
 Most efficient when the average transmission
distance is large.

9. Static Clustering
 Indirect upstream traffic routing
 Cluster members transmit to a cluster head
 TDMA
 Cluster head transmits to the sink
 Not energy-limited
 Does not apply to homogenous environments

10. Network Diameter
 LEACH vs. Direct Transmission
 7x-8x energy reduction
 LEACH vs. MTE
 4x-8x energy reduction

11. Energy and Diameter

12. LEACH’s Two Phases
 The LEACH network has two phases: the set-up
phase and the steady-state
 The Set-Up Phase
 Where cluster-heads are chosen
 The Steady-State
 The cluster-head is maintained
 When data is transmitted between nodes

13. The key featuresof LEACH are:
 Localized coordination and control for cluster set-
up and operation.
 Randomized rotation of the cluster “base stations”
or “cluster-heads” and the corresponding clusters.
 Local compression to reduce global
communication.

14. An Example for LEACH Network
While neither of these diagrams is the
optimum scenario, the second is better
because the cluster-heads are spaced out
and the network is more properly
sectioned

15. Future Work
 Extend ns to simulate LEACH, MTE, and Direct
Transmission
 Include energy levels in self-election
 Implement hierarchical clustering

16. PEGASIS
 PEGASIS is the improved protocol where only one node is
chosen a head node which sends the fused data to the BS
per round. This achieves factor of 2 improvement
compared to LEACH protocol
 It a near optimal chain-based protocol that is an
improvement over LEACH.
 In PEGASIS, each node communicates only with a close
neighbor and takes turns transmitting to the base station.

17.  PEGASIS performs better than LEACH.
 In sensor networks, data fusion helps to reduce
the amount of data transmitted between sensor
nodes and the BS.
 Data fusion combines one or more data packets
from different sensor measurements to produce
a single packet.
 The key idea in PEGASIS is to form a chain
among the sensor nodes so that each node will
receive from and transmit to a close neighbor.

18.  Gathered data moves from node to node, get fused,
and eventually a designated node transmits to the
BS.
 The PEGASIS protocol achieves between 100 to
300% improvement when 1%, 20%,50% and 100%
of nodes node die compared to the LEACH
protocol.

19. Step one in PEGASIS Protocol
 Chain construction: To construct the chain we
start from the furthest node from the Base Station
(BS), and then greedy approach is used
to construct the chain.

20. Step two in PEGASIS Protocol
 Gathering data: Leader of each round is selected
randomly. If N is number of nodes i mod N node
is selected as head node for i round. Randomly
selecting head node also provides benefit as it is
more likely for nodes to die at random locations
thus providing robust network.
 When a node dies chain is reconstructed to
bypass the dead node.
 Head node receives all the fused data and
sends to the BS.

21. PAGASIS Network

22. Advantages and Disadvantages
Advantages of PEGASIS over LEACH:
 Compare to LEACH transmitting distance for most of
the node reduces in PEGASIS.
 Messages received by each head node are at most 2
in PEGASIS is less compared to LEACH.
 Experimental results show that PEGASIS provides
improvement by factor 2 compared to LEACH protocol
for 50m * 50m network and improvement by factor 3
for 100m * 100m network.
 Since each node gets selected once, energy
dissipation is balanced among sensor nodes.

23. Drawbacks of the PEGASIS protocol:
 When a head node is selected, there is
consideration how far the BS is located
from the head node.
 When a head node is selected its energy level
is not considered.
 Since there is only one node head, it may be
the bottle neck of the network causing delay.
 Redundant transmission of data as only one
head node is selected.

24. Performance results for a 100m x 100m
network
with initial energy .5J/node

25. Performance results for a 50m x 50m
network
with initial energy .25J/node

26. Conclusions and Future Work
 PEGASIS, a greedy chain protocol that is near
optimal for a data-gathering problem in sensor
networks.
 PEGASIS outperforms LEACH by eliminating the
overhead of dynamic cluster formation, minimizing
the distance non leader-nodes must transmit,limiting
the number of transmissions and receives among all
nodes, and using only one transmission to the BS per
round.

27.  In order to verify our assumptions about
PEGASIS, we will extend the network simulator
ns-2 to simulate PEGASIS, LEACH, and direct
transmission protocols.
 Based on our C simulations, we expect that
PEGASIS will outperform the other two protocols
in terms of system lifetime and the quality of the
network.