Novel Node Distribution Strategies in Corona

Novel Node Distribution Strategies in CoronaBased Wireless Sensor Networks
Speaker : Huei-Wen Ferng (馮輝⽂文) Ph.D.
Wireless Communication and Network Engineering (WCANE) Laboratory,
Department of Computer Science and Information Engineering,
National Taiwan University of Science and Technology
Outline
Introduction
§  Introduction of WSN and its issue
§  Research contributions
Related Work
§  Non-uniform initial energy distribution
§  Mobile sinks
§  Energy-aware routing protocols
§  Energy-aware node distributions
§  Etc.
Network Model and Definitions
Analysis on the Non-Uniform Node Distribution Strategy
§  Optimal sensor node placement
§  Lower bound on the number of sensor nodes deployed in a corona
§  Energy depletion analysis
§  Balanced energy depletion analysis
WCANE Lab., NTUST ú Page 2
Outline
Proposed Solutions
§  Strategy I (for the non-uniform model)
§  Strategy II (for the uniform model)
-  Sensor node arrangement
-  Switch scheduling
Performance Evaluation and Discussions
§  Reference scheme
§  Evaluation arrangement
§  Results and Discussions
-  Residual energy of each sensor node
-  Network lifetime
-  Total number of sensor nodes
Conclusions
WCANE Lab., NTUST ú Page 3
Introduction
WCANE Lab., NTUST ú Page 4
Introduction
Introduction of WSN and its issue
§  Wireless Sensor Network (WSN)
-  A wireless network formed by a large number of autonomous sensor
devices to monitor physical conditions of an area of interest.
§  Applications of WSNs
-  Disaster relief, environment control, bio-diversity mapping, security
system, etc.
§  WSN issues
-  Sensor nodes power source, e.g., battery-driven one, is limited.
-  Sensor nodes near the sink tend to die faster than sensor nodes farther
away. Hence, once sensor nodes around the sink die, residual energy
from sensor nodes farther away will be left unused. This problem is wellknown as energy-hole problem in WSNs.
Is it possible to let all sensor nodes die
simultaneously in a WSN?
WCANE Lab., NTUST ú Page 5
Introduction
Research contributions
§  Analyzed and solved the coverage problem in a corona-based WSN,
giving the optimal node position within a corona and a lower bound for the
number of nodes that should be deployed within a corona,
§  Shown that completely balanced energy depletion in a corona-based
WSN is achievable under a specific sensor node distribution strategy,
§  Addressing corona-based WSN coverage, efficiency, and durability issues
to propose
-  Strategy I which can balance the energy depletion among sensor
nodes in a corona-based WSN,
-  Strategy II which efficiently uses sensor nodes with a simple node
scheduling, providing the longest lifetime as compared to the other
strategies in the literature.
WCANE Lab., NTUST ú Page 6
Related Work
WCANE Lab., NTUST ú Page 7
Related Work
Non-uniform initial energy distribution
Mobile sinks
Energy-aware routing protocols
Energy-aware node distributions
WCANE Lab., NTUST ú Page 8
Network Model and
Definitions
WCANE Lab., NTUST ú Page 9
Network Model and Definitions
Network Model
R
s s s s
R
so
su su su su su
A sensor node consumes
Eelec + eps ⋅ dist α and
Eelec to transmit and reNon-uniform 5-corona model
Uniform 5-corona model
§  Network assumptions:
ceive 1 bit of data, respectively.
-  Homogeneous initial energy for all sensor nodes ε > 0, but an unlimited amount of energy for the sink,
-  Each active node is required to generate and send L bits of data per unit time to the sink via multi-hop
communication (e.g., data logging application),
-  Ideal MAC layer with no collisions and retransmission is assumed,
-  No data aggregation is considered.
WCANE Lab., NTUST ú Page 10
Network Model and Definitions
Definitions
(1)  Corona lifetime (measured in unit time or rounds)
- 
The ratio of the total initial energy in corona Ci and the energy consumption per
unit time in corona Ci denoted by Ei.
(2)  Network lifetime (measured in unit time or rounds)
- 
The time interval from the very beginning of the network operation until the
instant that the first node depletes its energy. If the energy consumption within
the same corona is uniform, the network lifetime can then be determined by
the shortest corona lifetime.
(3)  Balanced energy depletion
- 
All sensor nodes in the network deplete their energy simultaneously. If the
energy consumption within the same corona is uniform, then balanced energy
depletion is achieved when all coronas have the same lifetime.
WCANE Lab., NTUST ú Page 11
Analysis on the non-uniform
node distribution strategy
WCANE Lab., NTUST ú Page 12
Analysis on the non-uniform node distribution strategy
Optimal sensor node placement
Theorem 1: Assuming a corona model ( k , w1 ,K , wi ,K , wk ) with si , i = 1,K , k ,
denoting the sensor node sensing range in corona Ci and
wi
2
≤ si ≤ 2
(∑
i
j =1
)
wj ,
the optimal position of a sensor node within corona Ci in order to have the maximum
corona coverage is the position with distance biopt measured from the center of the
corona, where biopt , i = 1,K , k satisfy the following conditions.
opt
1
b
opt
i
b
WCANE Lab., NTUST ú Page 13
⎧ w12 − s12 ,
⎪
3
= ⎨
⎪⎩ s12 − w12 ,
=
(∑
i −1
j =1
wj
2
) (∑
+
2
w1
2
≤ s1 ≤ w1
w1 < s1 ≤ 2 w1
i
j =1
wj
2
) −2 s
2
i
, i = 2,K , k
back
Analysis on the non-uniform node distribution strategy
Optimal sensor node placement
bi + si
y2 (bi )
( 0, bi )
b1 + s1
y1 ( bi )
bi − si
y1 ( b1 )
Ci
( 0, b1 )
C1
x1 (b1 ) w1
x1 (bi ) x2 ( bi )
(a) The innermost corona C1.
WCANE Lab., NTUST ú Page 14
i −1
∑ j =1 w j
∑
(b) Corona Ci , i = 2, K , k.
i
j =1
wj
Analysis on the non-uniform node distribution strategy
Lower bound on the number of sensor nodes deployed in a corona
Corollary 1: The minimum number of sensor nodes that should be deployed in
corona Ci in order to fully cover this corona is
Nimin
Ci
⎡
⎤
⎢
⎥
⎢
⎥
2π
= ⎢
2
⎥ ,
2
i
opt
2
⎢ 2 cos −1 ⎛⎜ (bi ) +(∑ j=1 w j ) − si ⎞⎟ ⎥
⎢
⎜ 2biopt ∑ ij=1 w j ⎟ ⎥
⎝
⎠ ⎥
⎢
i = 1, ..., k
∑
θi
i
j =1
θi 2
opt
i
b
si
(a) Maximum angle of two adjacent nodes in corona Ci .
WCANE Lab., NTUST ú Page 15
(1)
wj
si
biopt
(b) The representative triangle for Fig (a).
back
Analysis on the non-uniform node distribution strategy
Energy depletion analysis
Let N i , N ia and Ei denote the number of nodes, number of active nodes, and
the energy consumed per unit time in corona Ci , respectively. In
general, each corona energy consumption per unit time can be expressed
as.
⎧ L ⎡ N a ( E + eps ⋅ d α ) + k N a ( 2 E + eps ⋅ d α )⎤ , i = 1, K , k − 1
∑ j =i+1 j elec
i
elec
i
i
⎪
⎦
Ei = ⎨ ⎣
i=k
⎪⎩ N ka L ( Eelec + eps ⋅ d kα ) ,
(2)
The basic mode WSN operation sets all the nodes to be active; therefore,
(2) can be rewritten as follows:
⎧ L ⎡ N ( E + eps ⋅ d α ) + k N ( 2 E + eps ⋅ d α )⎤ , i = 1, K , k − 1
∑
i
j
elec
i
⎪ ⎣ i elec
j =i +1
B
⎦
Ei = ⎨
i=k
⎪⎩ N k L ( Eelec + eps ⋅ d kα ) ,
WCANE Lab., NTUST ú Page 16
(3)
Analysis on the non-uniform node distribution strategy
Energy depletion analysis
In the case where only minimum number of nodes should be active to
sense its surrounding area per round, then (2) can be rewritten as:
⎧ L ⎡ N min ( E + eps ⋅ d α ) + k N min ( 2 E + eps ⋅ d α )⎤ , i = 1, K , k − 1
∑
elec
i
j
elec
i
⎪ ⎣ i
j =i +1
M
⎦
(4)
Ei = ⎨
i=k
⎪⎩ N kmin L ( Eelec + eps ⋅ d kα ) ,
where Nimin is calculated from Corollary 1 (see Corollary 1)
WCANE Lab., NTUST ú Page 17
Analysis on the non-uniform node distribution strategy
Balanced energy depletion analysis
§  Non-uniform model
Theorem 2: If the number of active sensor nodes in coronas Ck −1 , K , C1
with transmission distance of d increases geometrically with a common ratio
q (> 1) and there are N ka = N ka−1 ( q − 1) active sensor nodes in corona Ck with
transmission distance of d o = ⎡
⎣
coronas is achievable.
2 Eelec + qε d α
( q −1)ε
1
α
⎤ , balanced energy depletion among all
⎦
N5
N4 = ( q − 1) N5
do
N3 = qN 4
d
N 2 = qN3
N1 = qN 2
d
d
d
Theorem 2 illustration.
WCANE Lab., NTUST ú Page 18
Proof
Analysis on the non-uniform node distribution strategy
Balanced energy depletion analysis
§  Uniform model
Corollary 2: The network can achieve balanced energy depletion if the
number of sensor nodes in corona Ci ( i = 1, 2,…, k ) is set to
i.e., Ni =
( )
Ei
Ek
( )N
Ei
Ek
min
k
N kmin , given Ei ( i = 1, 2, …, k ) and N kmin from (2) and (1),
( )N
=( )N
Ei
Ek
respectively, where
Proof: Since N i
Ei
Ek
min
k
min
k
is an integer.
, we have N k = N kmin and
i = 1, 2, K , k . Therefore, Ti =
ε Ni
Ei
ε Ni
Ei
= εENkk ,
= εENjj = T j , i, j ∈ {1, 2, K , k }.
With the homogeneous property operation for each sensor node in
the same corona, uniform energy consumption for each sensor node
in the same corona is obviously achievable. By Definition (3), the
proof is completed.
WCANE Lab., NTUST ú Page 19
,
Proposed Solutions
WCANE Lab., NTUST ú Page 20
Proposed Solutions
Strategy I (for the non-uniform model)
In order to meet the requirement of network radius R, the following equation
must hold:
( k −1) w + wo = R
d = cw, do = cwo
( k −1) d + do = cR
From Theorem 2, the above equation can be rewritten as
1
α
⎡ 2 Eelec + q ⋅ eps ⋅ d ⎤
( k − 1) d + ⎢
⎥ = cR
( q − 1) eps ⎦
⎣
α
The above equation can be solved heuristically using the Bisection Method.
After the value of d is determined, then the proposed strategy is used to
adjust the transmission range of sensor nodes and number of sensor nodes
to be deployed, respectively:
⎧ d , i = 1, 2,K , k − 1
di = ⎨
⎩d o , i = k
WCANE Lab., NTUST ú Page 21
⎧ qNi +1 ,
i = 1, 2,K , k - 2
⎪
Ni = ⎨( q − 1) N k , i = k − 1
⎪ N min ,
i=k
⎩ k
Proposed Solutions
Strategy I (for the non-uniform model)
Illustration
(5-corona model)
Calculate d and do
(for example, using Bisection Method)
Calculate N k = N
min
k
and Ni , i = 1,…, k -1
using the geometric ratio.
d = 94.09 and do =123.64
N5 = N5min = 19 and
N 4 = 19 → N3 = 38 → N 2 = 76 → N1 = 152
Deploy sensor nodes according to the optimal position or any scheme
constructing the q-ary tree.
WCANE Lab., NTUST ú Page 22
Proposed Solutions
Strategy I (for the non-uniform model)
N5 = 19
N 4 = 19
N3 = 38
N2 = 76
N1 = 152
C5
do
C4
d
C3
d
d
d
d
d
C2
C1
Non-uniform 5-corona model
WCANE Lab., NTUST ú Page 23
d
dd
d d
2-ary tree
dd
d
Proposed Solutions
Strategy II (for the uniform model)
§  Sensor node arrangement
-  Each sensor node is deployed according to Theorem 1, except for the
innermost corona, with the number of sensor nodes to be deployed follows:
)
(
⎧ ⎡ EiM N min ⎤ − ⎡ EiM N min ⎤ mod N min + N min I , i = 1, 2,K , k − 1
⎪ ⎢ EkM k ⎥ ⎢ EkM k ⎥
i
i
A
(5)
Ni = ⎨
i=k
⎪⎩ N kmin ,
where,
⎧0, if
⎪
I A = ⎨
⎪1, if
⎩
M
⎡ EiM N kmin ⎤ mod Nimin = 0
⎢ Ek
⎥
M
⎡ EiM N kmin ⎤ mod Nimin ≠ 0
⎢ Ek
⎥
back
WCANE Lab., NTUST ú Page 24
Proposed Solutions
Strategy II (for the uniform model)
§  Switch scheduling
-  To determine which sensor nodes
need to sense its surrounding area
WCANE Lab., NTUST ú Page 25
Proposed Solutions
Strategy II (for the uniform model)
§  Switch scheduling properties
• Within corona Ci ( i = 2, …, k ) , sensor nodes are deployed at the optimal positions
with uniform distance of 2π biopt N i to each other. For corona C1 , sensor nodes are
deployed at
w1
2
, with uniform distance of π w1 N1 . N1min are also calculated via
replacing biopt with
w1
2
. Each sensor node are grouped according to their counteri value
ranging from 1 to counteri max =
Ni
Nimin
.
• During the network operation, if counteri mod counteri max = 0, then the corresponding
sensor node will sense its surrounding area and forward data. In the next round, each
sensor node in the network increases its counter value by 1 in a cyclic manner (if the
current counter value is counteri max then the next counter value is 1) and the same
condition is checked again.
WCANE Lab., NTUST ú Page 26
Proposed Solutions
Strategy II (for the uniform model)
Illustration (5-corona model)
opt
i
Calculate b
Calculate N
min
i
using Theorem 1
b1opt = 50, b2opt = 122.47, b3opt = 234.52,
b4opt = 339.116, and b5opt = 441.59
using Corollary 1
Calculate EiM using Eq. (4)
N1min = 3, N 2min = 8, N3min = 11,
N 4min = 15, and N5min = 19
E1M = 0.0051, E2M = 0.0047, E3M = 0.0040,
E4M = 0.0029, and E5M = 0.0014
Calculate Ni using Eq. (5)
N5 = N5min = 19, N 4 = 45,
N3 = 66, N 2 = 72, N1 = 72
Deploy sensor nodes according to the optimal position, except for the innermost corona,
with their counter values pre-programmed prior to the deployment.
WCANE Lab., NTUST ú Page 27
Proposed Solutions
Strategy II (for the uniform model)
§  Switch scheduling illustration
3
2
2
1
2
1
2
1
Counter values
1
3
Sensing node
Not-sensing node
Sink node
counter2max = 3
counter1max = 2
WCANE Lab., NTUST ú Page 28
Performance Evaluation and
Discussions
WCANE Lab., NTUST ú Page 29
Performance Evaluation and Discussions
Reference schemes
§  Wu’s scheme: each sensor nodes are deployed on a uniform model, constructing
the q-ary tree with the number of sensor nodes follows:
⎧ qNi +1 ,
i = 1, 2,K , k - 2
⎪
Ni = ⎨( q − 1) N k , i = k − 1
⎪ N min ,
i=k
⎩ k
§  Uniform scheme: each sensor nodes are uniformly distributed over the uniform
corona model.
WCANE Lab., NTUST ú Page 30
Performance Evaluation and Discussions
Evaluation arrangement
WCANE Lab., NTUST ú Page 31
Performance Evaluation and Discussions
Network arrangement
500
500
sensor nodes
sink
400
400
300
300
200
200
100
100
0
0
-100
-100
-200
-200
-300
-300
-400
-400
-500
-500
-400
-300
-200
-100
0
100
200
300
400
sensor nodes
sink
500
(a) Wu’s scheme model
-500
-500
-400
-300
-200
-100
0
100
200
300
400
500
(b) Strategy I model
N5 = 19, N 4 = 19, N3 = 38, N 2 = 76, and N1 = 152
N5 = 15, N 4 = 15, N3 = 30, N 2 = 60, and N1 = 120
du = 100
d = 94.0904, do = 123.6383
WCANE Lab., NTUST ú Page 32
Performance Evaluation and Discussions
Network arrangement
500
500
sensor nodes
sink
400
400
300
300
200
200
100
100
0
0
-100
-100
-200
-200
-300
-300
-400
-400
-500
-500
-400
-300
-200
-100
0
100
200
300
400
sensor nodes
sink
500
(c) Strategy II model
-500
-500
-400
-300
-200
-100
0
100
200
300
400
500
(d) Uniform scheme model
N5 = 19, N 4 = 45, N3 = 66, N 2 = 72, and N1 = 72
N5 = 120, N 4 = 84, N3 = 64, N 2 = 36, and N1 = 12
du = 100
du = 100, grid length = 50
Go to formula
WCANE Lab., NTUST ú Page 33
Performance Evaluation and Discussions
Residual energy of each sensor node
0.5
Residual energy (in Joules)
Residual energy (in Joules)
0.5
0.4
0.3
0.2
0.1
0
0.4
0.3
All sensor nodes energy
level < 0.0005 J
0.2
0.1
50
100
150
Node ID
200
250
300
0
(a) Wu’s scheme
20
40
60
80
100
120 140
Node ID
160
180
200
220
240
(b) Strategy I
Wu’s scheme
Strategy I
Strategy II
Uniform scheme
Var (Eresidual)
0.0049
3.29 x 10-8
0.0031
0.2367
Residual energy ratio
3.56 %
0.06 %
9.20 %
86.24 %
WCANE Lab., NTUST ú Page 34
Performance Evaluation and Discussions
Residual energy of each sensor node
0.5
Residual energy (in Joules)
Residual energy (in Joules)
0.5
0.4
0.3
0.2
0.1
0
0.4
0.3
0.2
0.1
50
100
150
Node ID
200
250
0
(c) Strategy II
50
100
150
Node ID
200
250
300
(d) Uniform scheme
Wu’s scheme
Strategy I
Strategy II
Uniform scheme
Var (Eresidual)
0.0049
3.29 x 10-8
0.0031
0.2367
Residual energy ratio
3.56 %
0.06 %
9.20 %
86.24 %
WCANE Lab., NTUST ú Page 35
Performance Evaluation and Discussions
Residual energy of each sensor node
0.2
90
0.18
Residual energy ratio (in percentage)
80
Wu's scheme
Strategy I
Strategy II
Uniform scheme
70
60
50
40
30
20
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
10
0
Residual energy ratio (in percentage)
100
0
300
400
500
600
700
800
Network radius (in meters)
900
(a) Residual energy ratio for the four
strategies
1000
300
400
500
600
700
800
Network radius (in meters)
900
1000
(b) Residual energy ratio for Strategy I
§  As the network size grows larger, the cumulative sum of sensor nodes
residual energy can not be neglected and will become larger, explaining
the increasing trend of residual energy ratio for Strategy I.
WCANE Lab., NTUST ú Page 36
Performance Evaluation and Discussions
Network lifetime
8000
Network lifetime (in minutes)
7000
6000
§  Remark 1: Although Wu’s
scheme shows a stable network
lifetime over the various network
radii and the network lifetime of
Strategy I decreases as the
network radius increases,
Strategy I still always outperforms
Wu’s scheme.
Wu's scheme
Strategy I
Strategy II
Uniform scheme
5000
4000
3000
2000
1000
0
300
400
500
600
700
800
Network radius (in meters)
900
1000
(a) Network lifetime VS. network radius.
300
400
500
600
700
800
900
1000
Wu’s scheme
3048
3048
3047
3047
3046
3045
3045
3044
Strategy I
3902
3666
3532
3445
3384
3339
3305
3277
Strategy II
6944
6944
6944
6944
6943
6944
6944
6944
Uniform scheme
596
337
208
151
109
84
68
54
WCANE Lab., NTUST ú Page 37
Performance Evaluation and Discussions
Network lifetime
140
Improvement ratio (in percentage)
120
Strategy I
Strategy II
100
80
60
40
20
0
300
400
500
600
700
800
Network radius (in meters)
900
1000
(b) Network lifetime improvement ratio over Wu’s scheme.
300
400
500
600
700
800
900
1000
Strategy I
28.01 %
20.28 %
15.92 %
13.06 %
11.10 %
9.66 %
8.54 %
7.65 %
Strategy II
127.82 %
127.82 %
127.9 %
127.9 %
127.94 %
128.04 %
128.04 %
128.12 %
WCANE Lab., NTUST ú Page 38
Performance Evaluation and Discussions
Total number of sensor nodes
4
2
x 10
Wu's scheme
Strategy I
Strategy II
Uniform scheme
1.8
Total number of sensor nodes
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
300
400
500
600
700
800
Network radius (in meters)
900
1000
300
400
500
600
700
800
900
1000
Wu’s scheme
44
120
304
704
1664
3840
8448
18944
Strategy I
40
96
240
576
1344
3072
6656
14848
Strategy II
65
144
274
440
676
1008
1403
1878
Uniform scheme
112
196
316
440
612
796
1008
1256
WCANE Lab., NTUST ú Page 39
Conclusions
WCANE Lab., NTUST ú Page 40
Conclusions
§  The coverage problem for corona-based WSN is analyzed and solved, producing
the optimal sensor node position and lower bound on the number of sensor nodes
to be deployed.
§  Incorporating the coverage solutions, we propose two novel node distribution
strategies, namely Strategy I and Strategy II, which aim to provide full WSN
coverage, durable network lifetime, and efficient use of sensor nodes.
§  The impossibility of balanced energy depletion among sensor nodes in a coronabased WSN has been disproven by our Strategy I.
§  Addressing the efficiency use of sensor nodes and durability of network lifetime,
Strategy II has been shown to achieve the longest network lifetime using as few
sensor nodes as possible.
§  Strategy I is recommended to be used for small WSN area to achieve balanced
energy depletion among sensor nodes. However, for a large WSN area (over 600
meter of network radius), Strategy I is not recommended due to the enormous
number of sensor nodes to be used.
§  Strategy II is recommended to be used over any network radius, providing
competitive durable network lifetime although the energy depletion is not
completely balanced among sensor nodes.
WCANE Lab., NTUST ú Page 41
Thank you for listening!
WCANE Lab., NTUST ú Page 42
Proof of Theorem 1
Since Wu's scheme guarantees sub-balanced energy depletion among coronas C1 , K , Ck -1 ,
we only need to show the balanced energy depletion among coronas Ck −1 and Ck . With the
transmission distance of sensor nodes in the outermost corona d o = ⎡
⎣
( q − 1) eps ⋅ doα = 2 Eelec + q ⋅ eps ⋅ d α ,
2 Eelec + q⋅eps⋅d α
( q −1)eps
1
α
⎤ , we have
⎦
( q − 1) ( Eelec + eps ⋅ doα ) = ( 2 Eelec + eps ⋅ d α ) + ( q − 1) ( Eelec + eps ⋅ d α ) .
Multiplying both sides with N ka and N ka L, respectively, and noting that N ka−1 = ( q − 1) N ka ,
Ek = N ka ( Eelec + eps ⋅ d oα ) and L ⎡⎣ N ka−1 ( Eelec + eps ⋅ d α ) + N ka ( 2Eelec + eps ⋅ d α )⎤⎦ , we have
(
)
(
)
N ka−1 N ka L ( Eelec + eps ⋅ doα ) = N ka L N ka ( Eelec + eps ⋅ d α ) + N ka−1 ( Eelec + eps ⋅ d α ) ,
N ka−1 Ek = N ka Ek −1
Noting that the lifetime of corona Ci under the basic operation mode denoted by Ti
is equal to ε Ni EiB , we have the following equation by multiplying both sides by ε
and dividing it by Ek Ek −1 , and replacing Nia and Ei by Ni and EiB , respectively,
WCANE Lab., NTUST ú Page 43
Proof of Theorem 1
ε N k −1
E
B
k −1
=
ε Nk
E
B
k
,
Tk −1 = Tk ,
Further combining the sub-balanced energy depletion obtained by Wu's scheme and the
homogeneous property operation for each sensor node in the same corona, uniform
energy consumption for each sensor node in the same corona is obviously achievable.
By Definition (3), the proof of this theorem is completed.
back
WCANE Lab., NTUST ú Page 44
Reference
Huei-Wen Ferng, Mardianto Soebagio Hadiputro, and Arief Kurniawan “Design
of novel node distribution strategies in corona-based wireless sensor
networks,” IEEE Transactions on Mobile Computing, vol. 10, no. 9, pp.
1297-1311, Sept. 2011.
WCANE Lab., NTUST ú Page 45

Download Report