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Collaborative Sensing To Enhance Cognitive
Radio Performance .
Presented by: Sara Elboutaybi.
Graduate Student, Computer science engineering
ENSEM Casablanca.
November 30th 2011
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Introduction to cognitive radio:
- The Need Of Cognitive Radio
- What Is Cognitive Radio
Motivation:
A Global view of collaborative Sensing
-Components of Collaborative Sensing
- The Dominating Factors Of Collaborative Sensing
Conclusion
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Outline:
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The Need of Cognitive Radio:
Introduction To Cognitive Radio:
The spectrum is scarce resource.
Multiple secondary access,
aggregate interference control and
agile modulation techniques
Actual measurements indicate
Underutilized bands.
Fig.1 USA frequency allocations and
Spectrum usage measurements.
http://e/Here%20u%20go/BiblioNet/Presentation_prep/illustration/frquency_use.PNGhttp://c/Users/Illusion/Desktop/2003-allochrt.pdf7/31/2019 Collaborative Sensing to Enhance Cognitive Radio Performance .
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Introduction To Cognitive Radio:
transforming radio nodes
from blind executors of
predefined protocols toradio-domain-aware
intelligent agents that
search out ways to deliver
the services that the userwants even if that user
does not know how to
obtain them
J. Mitola III and G. Q. Maguire :
Fig2. Cognitive radio cycle
Decide
ActSense
Analyse
What Is Cognitive Radio
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Enabling cognitive radio via Sensing:c
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What Is Cognitive Radio:
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Awareness of an opportunity ?
Fig.3 Multi-dimensional radio spectrum space and transmission opportunities
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Motivation:
Exploit the spatial diversity.
Multipath fading
Shadowing
Receiver uncertainty
issues
..
Improving Performance of detection
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Fig.4 Receiver uncertainty and multipath/shadow
fading.
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FCC: Cognitive devices shouldbe able to sense both
television signals and wireless
microphones down to
114 dBm.:A cognitive device with a 114 dBm
sensitivity level will identify all DTT channels as
occupied.
BT Response to Ofcom Consultation on Digital
Dividend:
SNR walls
Relaxing sensivity requirements:
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Fig.5 Cooperation allows us to reduce the sensitivity of the CR device.
Motivation:
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How cooperative CR share the data?
A Global view of collaborative Sensing:
Fig.6 Classification of cooperative sensing: (a) centralized, (b)
distributed and ( c) relay-assisted. 9
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Components Of Collaborative Sensing
How can
cognitive
radios
cooperate?
Fig.7 Framework of centralized
cooperative sensing. 10
A Global view of collaborative Sensing:
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Components Of Collaborative Sensing:
Cooperation models:
How CRs cooperate to perform
spectrum sensing?Models
Parallel FusionModel
GameTheoretical
Model
Fig. 9 Game theoretical model.
Fig. 8 Parallel fusion model.
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Sensing techniques:
A quick Compraison:
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Accuracy
Complexity
Waveform-
based Sensing
Match
Filtering
Radio Identi
-fication
Cyclostationary
Energy
Detector
Components Of Collaborative Sensing:
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Kullback-leibler distance: Motivation
In Akaiks paper we find:
Research results using AIC.
Fig. 10 Comparison with energy detection with
noise uncertainty .
Components Of Collaborative Sensing:
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Exploiting model selection tools through distribution comparisonto detect vacant holes in the spectrum band.
The probability distribution of
the received signal.
The probability distribution
of noise.
Estimating the kullback-leibler divergence from the sampled
signal?
Kullback-leibler distance:
Components Of Collaborative Sensing:
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-Probability of false detection.
- Probability of missed detection.
Hypothesis Testing
Fig. 11 Receiver Operating Characteristic
curve at SNR=-15db. [ ]
Components Of Collaborative Sensing:
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HypothesisTesting
Binary
HypothesisTesting
Composite
Hypothesis
Testing
SequentialTesting
The distributions under
both hypotheses f(y|Hi) are completely
known?
Unknown parameters in the
PDFs ?
The number of required samples
for testing :fixed or variable?
Hypothesis Testing
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Components Of Collaborative Sensing:
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Control Channel and Reporting:
A channel to report local sensing data.
A point to point link from a cooperating CR to the fusion center.
A MAC scheme for all the CRs to access the control channel.
Reporting sensing data:
Control Channel
Bandwidth
Reliability
Security
Requirements
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Components Of Collaborative Sensing:
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Data Fusion
CombiningData
SoftCombining
Quantized
SoftCombining
HardCombining
Transmit the entire local sensing
samples or the complete local test.
Quantize the local sensing results andsend only the quantized data .
Make a local decision and transmit the one-bit
decision
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(1)
(2)
(3)
Combining local sensing data for hypothesis testingwhile considering the control channel bandwidth
requirements.
(2)
(1)
(3)
Components Of Collaborative Sensing:
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UserSelection
Centralizedselection
Cluster-based
selection
User Selection
Correlated shadowing
Selecting a set of cooperating users satisfying
some conditions.
Grouping the cooperating users into clusters or
coalitions.
Malicious users..
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Components Of Collaborative Sensing:
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Knowledge
Base
Received Signal
Strength
Primary User
Activity & StatisticsPrimary User
Localization &
Tracking
Radio Environment
Map
Channel Gain Map
Power Spectral
Density Map
Knowledge Base:
All the knowledge of the RF environments.
To assist or even replace the cooperative sensing.
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Components Of Collaborative Sensing:
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Dominating factors of collaborative sensing:
Issues
Sensing Time& Delay.
ChannelImpairments
EnergyEfficiency
CooperationEfficiency
Mobility
Security
WidebandSensingStill other issues to
deal with !
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References:
I still have to right down myreferences,
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