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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&