LLR-based Distributed Detection for Wireless Sensor Networks
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LLR-based Distributed Detection for Wireless Sensor Networks
後卓越進度報告
蔡育仁老師實驗室2008/01/07
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LLR: Log Likelihood Ratio The received signal
Observation noise: assumed to be
Binary Hypothesis Testing
2 2
1 0 1 01 12
0 0
2( | ) ( )ln ln
( | )
ii ii
i i n
yf y H f yDefine LLR Z
f y H f y
),(~)(
),(~)(2
00
211
ni
ni
Nyf
Nyf
0 1
Low LLR High LLR
0H 1H
0 0
1 1
:
:i i
i i
H y n
H y n
2~ (0, )i nn N
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Distributed Detection Depends on Likelihood Ratio
LLR can be treated as the reliability of a sample value Power allocation in WSNs
Power allocation in each sensor based on the instantaneous observed signal
Large absolute value of LLR High reliability Allocate more power; vice versa
Sequential detection in WSNs Can reduce the number of required transmission with t
he similar detection performance Ordering the message transmission based on the LLR
can further reduce the number of transmission Save more communication power
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0 0
1 1
( )
( )
P H
P H
2~ (0, )k nn N
k kp u
2 2p u
0 1/H H
1S
2S
……
NS
1y
2y
Ny
Fusion Center
1 1p u
= ,
1, 2,......k k k kr p u w
k N
2~ (0, )k ww N
Power Allocation Depends on Log Likelihood Ratio in WSNs
2
1 00 2 2
4Define the local observation quality SNR at each node as
n n
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Sequential Detection Depends on Log Likelihood Ratio in WSNs The thresholds ln(A) and ln(B) depend on the target false
alarm probability and miss detection probability
H1
NLLR
(N)
lnA
lnBH0
1 2 3 4 5 6 7 8
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Simulation – LLR-based Power Allocation
10-5
10-4
10-3
10-2
10-1
0
10
20
30
40
50
60
70
80
90
100
Detection error probability
Req
uire
d po
wer
in p
erce
ntag
e
Scheme 1,o=4
Scheme 1,o=6
Scheme 1,o=8
Scheme 1,o=10
Scheme 2,o=4
Scheme 2,o=6
Scheme 2,o=8
Scheme 2,o=10
Scheme1 g
Scheme2 g
k k
k k k
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Simulation – LLR-based Sequential Detection
FSSReal Value T-SPRTOrdered Real Value T-SPRT
Detection error probability
Req
uire
d nu
mbe
r of
tra
nsm
issi
on
10-4
10-3
10-2
10-1
15
20
25
30
35
40
45
50
55
60ConventionalReal Value T-SPRTOrdered Real Value T-SPRT
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Publications
Journal Paper Yuh-Ren Tsai, “Sensing Coverage for Randomly Distributed Wire
less Sensor Networks in Shadowed Environments,” IEEE Transactions on Vehicular Technology, vol. 57, no. 1, Jan. 2008. (SCI, EI)
Conference Paper Yuh-Ren Tsai, Kai-Jie Yang and Sz-Yi Yeh, “Non-uniform Node
Deployment for Lifetime Extension in Large-scale Randomly Distributed Wireless Sensor Networks,” in Proc. of IEEE International Conference on Advanced Information Networking and Applications (AINA2008), Okinawa, Japan, March 2008.
Yuh-Ren Tsai, and Jyun-Wei Syu, “Down-link CIR Spatial Correlation and CIR Prediction for CDMA Cellular Systems,” in Proc. of IEEE 2008 Vehicular Technology Conference (VTC-2008 Spring), Singapore, May 2008.