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An Energy-Efficient Unequal Clustering Mechanismfor Wireless Sensor Networks
Chengfa Li, Mao Ye, Guihai ChenState Key Laboratory for Novel Software Technology
Nanjing UniversityJie Wu
Department of Computer Science and EngineeringFlorida Atlantic University
MASS 2005Speaker: Sheng-Wen Chang
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Outline
Introduction The EEUC Mechanism Simulation Conclusions
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Introduction --- Background
Clustering provides an effective way for prolong the lifetime of the WSNs
Using equal size of clusters to balance traffic overhead
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Introduction --- Background
Within a clustering organization Intra-cluster communication can be
single-hop or multi-hop
Inter-cluster communication Single-hop: LEACH Multi-hop: HEED (Infocom 2004)
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Introduction --- LEACH
CHs farther away from the BS must transmit packets over longdistances than those of CHs closer to the BS
Cluster Head
Cluster member
BS
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Introduction --- LEACH
M. Ye, C. Li, G. H. Chen, and J. Wu,"EECS: An Energy Efficient Clustering Scheme in Wireless Sensor Networks(International Journal of Ad Hoc & Sensor Wireless Networks, 2005)
Cluster header
BS
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Introduction --- HEED
The initial probability for each node to become a tentative CH depends on its residual energy
Final CHs are selected according to the cost
Cluster Head
Cluster member
BS
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Introduction --- HEED
The role of cluster head is usually periodically rotated among nodes
Not balance the energy consumption among CHs
Cluster Head
Cluster member
BS
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Introduction --- HEED
Hop spots problem In each round, CHs closer to the BS are burdened
with heavy relay traffic and tend to die early
Cluster Head
Cluster member
BS
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Introduction --- Motivations and Goals
Motivations Using unequal clustering mechanism to solve
hot spot problem among CHs in each round Clusters closer to the BS have smaller sizes
than those farther away form the BS
Goals Balances the energy consumption Prolong network lifetime
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EEUC --- Assumptions
Sensors uniformly deploy over a sensor field
Sensors and a BS are all stationary Sensors can use power control A node can compute the approximate
distance to another node Based on the received signal strength
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EEUC --- Overview
CHs closer to the BS support smaller cluster sizes More clusters are produced closer to the BS
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EEUC --- Overview
Unequal Clustering Algorithm CHs are selected by localized
competition
Inter-cluster Multi-hop Routing A CH chooses a relay CH
Adjacent CH’s residual energy Its distance to the BS
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EEUC --- Unequal Clustering Algorithm
The BS broadcasts a “hello” message to all nodes
Each node computes the distanceto the BS
Several tentative CHs are selected to compete for final CHs
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EEUC --- Unequal Clustering Algorithm
If Si becomes a tentative CH, Si has a competition range Rcomp
If Si becomes a CH at the end of the competition, there will not be another CH within Si ‘s competition diameter
S3
S4
R4
R3
S2S1
R2R1
S1and S2 can be CHs
S3 or S4 can be a CH
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EEUC --- Unequal Clustering Algorithm
The node’s Rcomp should be decrease as its distance to the BS decreases
is the maximum competition radius c is a constant coefficient between 0 and 1 and
controls Rcomp range
d (si, BS) dmax : si.Rcomp= dmin : si.Rcomp=
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EEUC --- Unequal Clustering Algorithm
The broadcast radius of every control message is
Each tentative CH broadcasts a COMPETE_HEAD_MSG Competition radius Residual energy
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EEUC --- Unequal Clustering Algorithm
Each tentative CH maintains a set SCH
of its “adjacent” tentative CH Tentative head sj is an “adjacent” n
ode of si
Si
Sj
RjRi
SjSi
Rj Ri
sj is in si’s competition diameter orsi is in sj’s competition diameter
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EEUC --- Unequal Clustering Algorithm
Each tentative CH checks its SCH and makes a decision whether it can the final CH
Si’s residual energy is more than all the nodes in its SCH It will win the competition Broadcast a FINAL_HEAD_MSG to inform its a
djacent tentative CHs
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EEUC --- Unequal Clustering Algorithm
A B
If A receives a FINAL_HEAD_MSG from B, A will give up the competition immediately
A informs all nodes in its SCH by broadcasting a QUIT_ELECTION_MSG
C
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EEUC --- Unequal Clustering Algorithm
A B
C receives a QUIT_ELECTION_MSG form A C will remove A from its SCH
C
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EEUC --- Unequal Clustering Algorithm
Each CH broadcasts a CH_ADV_MSG across the network area Node ID Residual energy Distance to the BS
Each ordinary node joins its closest CH
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EEUC --- Inter-cluster Multi-hop Routing
A threshold TD_MAX into our multi-hop forwarding model
If a CH’s distance to the BS is smaller than TD_MAX It transmits its data to the BS directly
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EEUC --- Inter-cluster Multi-hop Routing
A CH chooses a node to forwarding its data from its candidate set RCH More residual energy Smallest distance between the CH and the Relay
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Simulation
Network coverage: (0,0)~(200,200)m
BS location: (100,250)m Number of nodes: 400 : 90m c=0.5 TD_MAX=150m
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Simulation
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SimulationToo many clusters will be produced closer to the BS
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Simulation The first node dies
The last node dies
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Conclusions
Propose a novel energy-efficient clustering mechanism for WSNs
The hot spots problem between CHs is solved
The EEUC mechanism improves the lifetime over LEACH and HEED