Presentation: Energy Efficient
Communication Protocol for
Wireless Microsensor Networks
Wendi Rabiner Heinzelman, Anantha
Chandrakasan, and Hari Balakrishnan
Massachusetts Institute of Technology
Underlying Model
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Hundred to thousands of nodes
A fixed basestation
A distant basestation (from sensor patch)
Basestation is not energy constrained
Sensing nodes are heterogeneous
Sensing nodes are energy constrained
Sensing nodes can aggregate data
Radio Characteristics
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50 nano-Joules per bit to operate
transmitter and receiver = Eelec
0.1 nano-Joules per bit per m 2= E amp
2
Sending = ( Eelec * k )  ( Eamp * k * d )
Receiving = Eelec * k
Operating the radio, not counting
generating the signal, takes 2k * Eelec
power equal to the signal amplifier
transmitting 31m.
Direct Communication Protocol
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r
r
n
…
Givens: k bits, n
nodes, r meters
between each node
Direct
communication from
furthest node to
basestation =
( Eelec * k )  ( Eamp * k * (nr )2 )
r
Minimum-Energy Multi-Hop
Routing (MTE)
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(nk * Eelec )  (( n  1)k * Eelec )  (nkr 2 * Eamp ) 
k ((( 2n  1) * Eelec )  (nr 2 * Eamp ))
r
r
n
…
Assumption: each
node sends to
nearest neighbor.
Direct
communication from
furthest node to
basestation =
r
The Observation
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Directly sending to the
basestation takes less
global energy in certain
situations
Which for the numbers
2
given occurs when nr
exceeds 1000
Eelec nr

Eamp
2
2
Pattern of Sensor Node
Deaths
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Direct Routing:
nodes further from
basestation die first
MTE Routing: nodes
closer to base
station die first
Static Clusters:
cluster heads die
first.
The LEACH Protocol
(Summary)
Divided into rounds, made of up of turns
consisting of:
 Nodes decide to be a cluster heads this turn.
 Nodes picks the “closest” cluster head.
 Cluster heads broadcast transmit schedule.
 Nodes send data to their cluster head.
 Cluster head aggregate/compress data and
send it to the basestation.
LEACH Comparison
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Ignoring cluster
setup portion of
algorithm.
8 times longer for
first node to die.
3 times longer for
last node to die.
LEACH Comparison (cont.)
LEACH Comparison (cont.)
LEACH’s Death Pattern
Details of LEACH
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Deciding to be a cluster head uses a
statistic method, where P is the optimal
number of clusters (dependent on
network parameters (5% in test cases)).
Probability of being a cluster head =
P
1
1  ( P * (rnd %( ))
P
0
if haven’t been a cluster head this round
otherwise
Details of LEACH (continued)
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Each cluster head broadcasts a clusterhead-advertisement using CSMA MAC
protocol.
Nodes receiving the advertisement,
choose a cluster head based on signal
strength.
Nodes (using CSMA protocol) inform
chosen cluster head of their choice.
Details of LEACH (continued)
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Cluster heads generate a TDMA
schedule and broadcast to member
nodes (may also pick a spreading code
for members).
Nodes transmit data based on TDMA
schedule. Radio’s turned off when not in
use.
Details of LEACH (continued)
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After data has been received, cluster
head perform signal
processing/compression and send to
basestation.
After a certain time (determined a prior)
a new turn begins.
After 1/P turns, a new round begins.
LEACH Animated (P=33%)
1. Decide cluster heads
2. Broadcast advertisement
3. Nodes transmit membership
4. Heads broadcast schedule
5. Nodes transmit data
6. Heads compress data and
send to basestation
7. New turn begins
goto 1.
Future Work
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Hierarchical Clustering
Cluster size should be variable with
distance from basestation?
Other thoughts?
Issues (things to think about)
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Does random picking of cluster heads result
in occasional “bad” turns?
Their example was hokey, what would the
numbers be versus different network layouts?
Their MTE routing algorithm always sent to
nearest neighbor, how does it compare
without this restriction?
Is power consumption really “fair” (those far
away still seem to consume more power)?