Relay Based Cooperative Spectrum Sensing in Cognitive
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Transcript Relay Based Cooperative Spectrum Sensing in Cognitive
Performance of Energy Detection:
A Complementary AUC Approach
Saman Atapattu, Chintha Tellambura & Hai Jiang
Electrical and Computer Engineering
University of Alberta
CANADA
GLOBECOM 2010
Outline
Introduction
Spectrum
sensing
Energy detection
Research work
Cooperative
Analysis
Results
spectrum sensing
2
Spectrum Sensing
Cognitive radio: environment awareness & spectrum intelligence [1].
Dynamic spectrum access
Spectrum sensing
busy
Idle
(spectrum hole)
Spectrum sensing: to identify the spectrum holes.
Cooperative spectrum sensing: to mitigate multipath fading,
shadowing/hidden terminal problem.
3
Spectrum Sensing
Primary user has two states, idle or busy.
Noise
Noise + signal
Binary Hypothesis:
Performance metrics:
False alarm (Pf): efficiency
Missed-detection (Pm): reliability
Detection (Pd): 1-Pm
Higher Pd (lower Pm) and lower Pf are preferred.
4
Spectrum Sensing Techniques
Matched Filter
Perfect knowledge
Dedicated receiver structure
Eigenvalue Detection
Max-Min eigenvalues
Computational complexity
Difficulty of threshold selection
Accuracy
MF
Eigenvalue
Cyclo
ED
Cyclostationary Detection
Cyclostationary property
High sampling rate
Complex processing algorithm
Complexity
Energy Detection [2]
5
Energy Detection
Energy of the received signal.
Digital implementation:
Y(t)
Noise pre-filter
ADC
( )2
∑
Analog-to-digital converter
Squaring device
Integrator
Test
statistics
Test statistic:
Noise (AWGN), Signal (deterministic/random), Channel.
Compared with threshold.
6
Performance Measurements
Average Pd:
(1, 1)
(0, 0)
n
tio
0
et
ec
ld
ho
es
Th
r
ROC (receiver operating
characteristic) curve:
Pd vs. Pf
8
Pd vs. SNR
D
Detection probability
ca
pa
bi
lit
y
False alarm probability
AUC (area under ROC curve) [3]: probability that choosing correct
decision is more likely than choosing incorrect decision.
AUC vs. SNR
7
Research Work
Complementary AUC (CAUC)
Area under the complementary ROC (Pm vs Pf)
CAUC = 1-AUC, varies from 0.5 to 0
Good representation for diversity order
r1
System Model
hr1 d
hpr1
Data fusion strategy
AF relaying
Square-law combining (SLC)
Rayleigh fading
hpr2
r2
hpd
hr i d
hpri
ri
p
hprn
ROC analysis in [4].
hr 2 d
relay link
direct link
d
hrn d
rn
p: primary user
ri: i-th cognitive relay
d: fusion center
8
Analysis
AUC for instantaneous SNR in [3].
CAUC:
Average CAUC:
where
9
Results
Average CAUC for relay based-cooperative spectrum
sensing network.
easy to extend for diversity techniques.
Sensing Diversity Order:
For high SNR
Without direct path:
With direct path:
Nakagami-m fading:
Diversity techniques:
10
Results
ROC curves
1
0.8
0.6
n = 1, 2, 3, 4, 5
Pd
0.4
0.2
Simulation
Analytical
0
0
0.2
0.4
0.6
0.8
1
Pf
(SNR=5dB)
11
Results
CAUC curves
semi-log scale
log-log scale
0.5
Without direct path (n = 1)
Only direct path
With direct path (n = 1)
With direct path (n = 2)
With direct path (n = 3)
With direct path (n = 4)
With direct path (n = 5)
0.45
0.4
0.35
-5
Log [Average CAUC]
Average CAUC
10
0.3
0.25
0.2
n = 1, 2, 3, 4, 5
-10
10
0.15
Without direct path n = 1
Only direct path
With direct path n = 1
With direct path n = 2
With direct path n = 3
With direct path n = 4
With direct path n = 5
n = 1, 2, 3, 4, 5
0.1
0.05
0
-20
-10
0
10
Average SNR (dB)
20
30
-20
-10
0
10
Average SNR (dB)
20
30
(SNR=5dB)
12
Results
CAUC curves
Nakagami-m
Diversity techniques
-1
-1
10
10
-2
-2
10
10
-3
10
-3
10
Log[Average CAUC]
Log[Average CAUC]
L=1
-4
10
m = 1, 2, 3, 4, 5
-5
10
-6
10
-4
10
L=2
-5
10
L=5
-6
10
-7
10
m
m
m
m
m
-8
10
-9
10
-10
-5
=
=
=
=
=
-7
1
2
3
4
5
10
-8
10
0
(SNR=5dB)
5
10
15
Average SNR (dB)
20
25
30
-10
SC
SLC
MRC
-5
0
5
10
Average SNR (dB)
15
20
13
Contribution
Introduced Complementary Area under ROC Curve
(CAUC)
Derived CAUC for relay-based cooperative spectrum
sensing network.
Showed that Diversity order:
Cooperative network: n or (n+1)
Nakagami fading: m
Diversity techniques: L
Proposed methodology and results can be useful for
other wireless research topics.
14
Reference
1.
S. Haykin, “Cognitive radio: brain-empowered wireless communications,”
IEEE JSAC, vol. 23, no. 2, pp. 201–220, Feb. 2005.
2.
F. F. Digham, M. S. Alouini, and M. K. Simon, “On the energy detection of
unknown signals over fading channels,” IEEE Trans. Commun., vol. 55, no.
1, pp. 21–24, Jan. 2007.
3.
S. Atapattu, C. Tellambura, and H. Jiang, “Analysis of area under the ROC
curve of energy detection,” IEEE Trans. Wireless Commun., vol. 9, no. 3,
pp. 1216–1225, Mar. 2010.
4.
S. Atapattu, C. Tellambura, and H. Jiang, “Relay based cooperative
spectrum sensing in cognitive radio networks,” in IEEE Global Telecommn.
Conf. (GLOBECOM), Dec. 2009.
15
Thank You !
16