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EBAS: An Energy-Efficient Event Boundary Approximated
Suppression Algorithm in Wireless Sensor Networks
Longjiang GuoHeilongjiang University [email protected]
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Outline
Introduction
EBAS Algorithm
Experiment And Result Analysis
Conclusion
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Introduction
Event Boundary Approximated
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Example
Forest fire alarm system
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Challenge
Sink has to collect information from all the nodes that lie in field boundaries.
Therefore:A lot of the number of sending messagesMuch more energy consuming The higher the message packets collision rate
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Resolving
Based on the above challenge, we propose a novel energy-efficient algorithm (EBAS).
In EBAS, sink do not need all the information from the nodes in field boundaries.
EBAS supports a suppression scheme that conservers energy by reducing the number of sending message.
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Outline
Introduction
EBAS Algorithm
Experiment And Result Analysis
Conclusion
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EBAS algorithm
EBAS is composed of three parts
Key node automatically selection in-network
Transportation
Event boundary rebuilt
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Key node selection
Definition 1 :[Slope] We define the slope of a sensor node i which lies in an event boundary as following:
Given the coordination of sensor node i as (Xi, Yi) and the coordination of the neighbor j of sensor node i as (Xj, Yj), we calculate the slope of sensor node i with its neighbor j as following:
ij
ijij
ij
ji
XXwhen
XXwhenXX
YY
K ,
,,
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Key node selection
Definition 2. [Verge Node] A node is called verge node if it has only one neighbor on an event boundary.
Definition 3. [Key Node] A sensor node m is called Key node if and only if it satisfies one of the following 2 conditions:
(1) Difference of slopes with its two neighbor nodes i and j outrages the predefined threshold, ε. i.e.
(2) It is a verge node in an event boundary. || ,, jmim KK
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Slope: K23, 24=-2, K23, 22=0.5. Node 1 and node 27 is Verge Node.When ε=0.5 , | K23, 24 -K23, 22|>0.5 ,so node 23 is a Key Node
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1 0 1 1 1 2
1 3
1 4
1 5 1 6 1 7
1 8
1 9
2 0
2 1
2 2
2 3
2 4
2 52 6
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( 0 ,0 )
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Key node selection
Initialization Phase:Individual behavior :Each node lies in an event
boundary broadcasts its node ID and coordination (ID, X, Y) to its neighbors. If a node just gets one message. Definition 2 If a node just gets two messages. Definition 3 if a node receives more than 2 messages, for each received
node id, calculate the distance between the two nodes using Euclidean distance, then sort these distances, pick out the 2 nodes with least distances. Then apply Definition 3.
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EBAS algorithm
EBAS is composed of three parts
Key node automatically selection in-network
Transportation
Event boundary rebuilt
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Transportation
Building aggregation tree Transportation key node information Suppression Strategy
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Building aggregation tree
There are two types of message package in building aggregation tree: one is Tree-building package: (PackageType=1, NodeID, level) (PackageType=2, ParentNode, NodeID).
Initialization sink node broadcasts the Tree-building package (1, sink’s NodeID, 0) and set the local level with 0.
Individual Behavior Each node in senor networks maintains three variables: parent, child and level which are initialized with null, null, and . parent, child and level indicate the parent, children and level of sensor node in aggregation tree respectively.
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Example
s ink
(null,0 ,0)
(null,1 ,+ )
(nu ll,3 ,+ )(nu ll,4 ,+ )
(nu ll,2 ,+ )
s ink(null,0 ,0)
(0 ,1 ,+ )
(1 ,3 ,+ )(2 ,4 ,+ )
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Transportation key node information
Given a set of key nodes Mi={di1, di2, di3, …} located on sensor node i. Sensor node i will send Mi to his parent node. Suppose j is a parent node in aggregation tree. i1, i2 …ik are j’s children. When sensor node j receives Mi1, Mi2 …Mik, sensor node j will unite Mi1, Mi2 …Mik as following operation:
(1) MjMi1Mi2 …Mik..
(2) Sensor node j sends Mj to his parent.
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Suppression Strategy
Given a set of key nodes M= {di1, di2, di3 …}, the FM sketch of M, denoted S (M), is a bitmap of length k. The entries of S (M), denoted S (M) [0… k-1], are initialized to zero and are set to one using a random binary hash function h applied to the elements of M. Formally,
.}1),(|min{ s.t. 1])[( ijdhjMdiffiMS
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EBAS algorithm
EBAS is composed of three parts
Key node automatically selection in-network
Transportation
Event boundary rebuilt
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Event Boundary Rebuilt
Transportation over,Since we know exactly all key node ID, we can put event boundary rebuilt easy.
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Outline
Introduction
EBAS Algorithm
Experiment And Result Analysis
Conclusion
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Experiment and result analysis
We have completed EBAS implementation in the TinyOS2.x TOSSIM simulator.
The accuracy error is defined as follows: 22 )ˆ()ˆ(
1Error iiii yyxx
n
0 1 2 3 4
0
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8
10
Err
or
Slop threshlod
Centralized EBAS
This Figure shows that the accuracy of EBAS mainly depends on the predefined threshold, ε. The smaller the predefined threshold is, the smaller the accuracy error of the recovered event boundaries is.
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Message quantity with slope threshold varying
0 1 2 3 4
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35
Network size is 30
Me
ssa
ge
Slope threshlod
Centralized EBAS
0 1 2 3 4
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Network size is 40:
Me
ssa
ge
Slope threshold:
Centralized EBAS
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Outline
Introduction
EBAS Algorithm
Experiment And Result Analysis
Conclusion
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Conclusion
In this paper, we present a novel energy-efficient algorithm EBAS to solve event boundaries transportation problems.
The entire idea can be divided into 4 parts: Key node generation;Key nodes set suppression;Transportation; Decompression.
Our experiment results confirmed the correctness and effectiveness of our algorithm.
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Thanks