LEACH is the base for various algorithms being developed with the purpose of achieving energy efficiency in WSNs.

1. LEACH
Cluster-based Routing Protocol
for
Wireless Sensor Networks
By
AKANKSHA UPADHYAY
Research Student, SATI, Vidisha

2. Need
• Cheap and energy-efficient as possible and rely on their large
numbers to obtain high quality results.
• Fault tolerance while minimizing energy consumption.
• Since the limited wireless channel bandwidth must be shared
among all the sensors in the network, routing protocols for
these networks should be able to perform local collaboration to
reduce bandwidth requirements.
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

3. Network routing protocols for WSNs
(Energy Analysis)
• Direct communication with BS
• Minimum energy multi-hop routing using sensor networks and
radio models
• Clustering
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

4. Direct communication with BS
• Each sensor sends its data directly to the base station.
• Possibly optimal if either the base station is close to the nodes,
or the energy required to receive data is large.
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

5. Minimum energy multi-hop routing
• Nodes route data destined ultimately for the base station
through intermediate nodes.
• The intermediate nodes are chosen such that the transmit
amplifier energy is minimized.
• Rather than just one (high-energy) transmit of the data, each
data message must go through n (low-energy) transmits and n
receives
• Shorten system lifetime as the nodes closest to the base station
are the ones to die out first since they are the ones most used
as “routers” for other sensors’ data.
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

6. Clustering
• Nodes are organized into clusters that communicate with a
local base station, and these local base stations transmit the
data to the global base station, where it is accessed by the end-
user.
• If the base station is an energy-constrained node, it would die
quickly, as it is being heavily utilized.
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

7. LEACH
• Low-Energy Adaptive Clustering Hierarchy
• Clustering-based protocol
• Select sensor nodes as CHs by rotation, so the high energy
dissipation in communicating with the BS is distributed evenly
to all sensor nodes in the network.
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

8. Assumption
• The base station is fixed and located far from the sensors.
• All nodes in the network are homogeneous and energy
constrained.
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

9. Key Features
• 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.
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

10. LEACH
• The nodes organize themselves into local clusters, with one
node acting as the local base station or cluster-head.
• Cluster-head nodes broadcast their status to the other sensors
in the network.
• Each sensor node determines to which cluster it wants to
belong by choosing the cluster-head.
• Each cluster-head creates a schedule for the nodes in its
cluster.
• Once the cluster-head has all the data from the nodes in its
cluster, the cluster-head node aggregates the data and then
transmits the compressed data to the base station.
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

11. Comparative Analysis
System lifetime using direct transmission,
MTE routing, static clustering, and
LEACH with 0.5 J/node
Total system energy dissipated using
direct communication, MTE routing
and LEACH for the 100node random
network,
Eelec=50nJ/bit, εamp=100pJ/bit/m2 and
the messages are 2000 bits
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

12. Algorithm
• The operation of LEACH is broken up into rounds.
• Each round comprises 2 phases
1. Set-up phase: when the clusters are organized,
2. Steady-state phase: when data transfers to the base
station.
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

13. Set-up Phase
• Decision of nodes to become cluster head
• Node n selects random number between 0 and 1
• If number is less than threshold T(n), node become cluster head for
current round. [T(n)]
• Cluster head nodes uses CSMA MAC protocol to broadcast
advertisement message to the rest of the nodes with same transmit
energy.
• According to the received signal strength nodes decides the cluster to
which it will belong in the round.
• Each node transmit information of its cluster head selection to
the cluster head again using CSMA MAC protocol.
• Cluster head creates a TDMA schedule telling the nodes when
to transmit.
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

14. Set-up Phase
Threshold Computation
[BACK]
)
1
mod(*1
P
rP
P

T(n) =
if n ϵ G
0 otherwise
n = node
P = the desired percentage of cluster
heads
r = the current round
G = set of nodes that have not been
cluster-heads in the last 1/P
rounds
During round 0, each node has a
probability P of becoming a
cluster-head. The nodes that are
cluster-heads in round 0 cannot
be cluster-heads for the next 1/P
rounds.
After 1/P-1 rounds, T=1for any
nodes that have not yet been
cluster-heads.
And after 1/P rounds, all nodes
are once again eligible to become
cluster-heads.
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

15. Steady-state Phase
• The radio of each non-cluster-head node can be turned off
until the node’s allocated transmission time ( according to
TDMA schedule).
• The cluster-head node must keep its receiver on to receive all
the data from the nodes in the cluster.
• When all the data has been received, then cluster head node
performs signal processing functions to compress the data into
a single signal.
• This composite signal is sent to the base station.
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

16. Conclusion
• LEACH distributes the energy among the nodes in the network
and is effective in reducing energy dissipation from a global
perspective.
• LEACH effectively enhances the system lifetime.
• LEACH is completely distributed, requiring no control
information from the base station, and the nodes do not require
knowledge of the global network in order for LEACH to
operate.
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

17. Reference
W.R. Heinzelman, A. Chandrakasan, H. Balakrishnan, “Energy-Efficient
Communication Protocol for Wireless Microsensor Networks”, Proceedings of the
33rd Annual Hawaii International Conference on System Sciences, Maui, HI, USA,
pp. 10–19, 4–7 January 2000.
AKANKSHA UPADHYAY, Research Student, SATI, Vidisha

18. THANK YOU