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Channel Sensingfor Cognitive Radio
A discussion on channel sensing techniques
By James Xu
Supervised by Dr. Fakhrul Alam
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Presentation overview
Introduction to ireless communications
!hat is "ognitive #adio $"#%&
!hy do e need "#&
!hat is channel sensing
'ur orkbench setup
'ur research
'ur ma(or contributions
"onclusion
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Wirelesscommunications
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What is Cognitive Radio(CR) Able to sense spectral environment
Able to provide opportunistic accessFind gaps in the spectrum
Ad(ust system parameters to utili)e it
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Why do we need CR?
*nlicensed spectrum is rare
Almost none available under +,-)
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Why do we need CR?
icensed to primary user only $Incumbent% !e are running out o/ space0 and higher /requency
has problems
!e are under utili)ing licensed space
"# is alloed usage $guarantee
inter/erence /ree%
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What is channel sensing
1he /irst step o/ "# is to identi/y /ree
spectrum
"hannel sensing is one o/ the most
/undamental part o/ "#
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What is channel sensing
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Our research
'ur research /ocus
2nergy detection
"yclostationary /eature e3traction
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Our CR workbench
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Energy detection
2asy to implement
Fast
4ot e//ective under lo S4#
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What is energydetection? All radio transmission have energy
Based on hypothesis testing
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Energy detector
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Energy detector
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Problems with thedetector 5isdetection on 4arroband signals
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Problems with thedetector 5isdetection on partial signals
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Adative energydetection !e proposed an
improvement
Introduced adaptive
detection
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Improved detection
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Adative E!characteristics
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Adative E!characteristics
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Cyclostationary "eatures
Another channel sensing strategy
Digital communication systems have
built in periodicity
A signal is a /irst order cyclostationary i/
it6s mean is periodic
A signal is second order cyclostationary
it it6s auto7correlation is periodic
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Cyclostationary "eatures
Auto7correlation ho much a signal has in
common ith itsel/0 against delay
Alpha 8 "yclic /requency
S 8 Spectrum "orrelation Function $S"F%
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Cyclostationary "eatures
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Work in Progress
1his is preliminary0 a proo/ o/ concept
"ould be done in /uture research
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Our ma#or contributions
Xu J. 9.0 Alam0 F.0 Adaptive 2nergy
Detection /or "ognitive #adio: An
23perimental Study0 ICCIT, ;
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CR$ibs
A library /or cognitive radio research
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Conclusion
!orkbench setup
Investigated various channel sensing
techniques $2D0 S"F0 Spectral 2ntropy%
>roposed and implemented
improvements $A2D%
"onsolidated library $"#ibs%0 e3amples
and codebase $S@4% Full progress documentation $S@40 "#%
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Acknowledgement
Dr Fakhrul Alam
Dr James "hang
Dr 1om 5oir
2veryone in our lab
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%hank you &or listening
9ou are invited to visit our "#
orkbench at Building <
5uch more details in the pro(ect report
Adaptive energy detection model ill be
on I222Xplore end o/ December
Any questions&