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Channel Sensing for Cognitive Radio

A discussion on channel sensing techniques. Channel Sensing for Cognitive Radio . By James Xu Supervised by Dr. Fakhrul Alam. Presentation overview. Introduction to wireless communications What is Cognitive Radio (CR)? Why do we need CR? What is channel sensing Our workbench setup

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Channel Sensing for Cognitive Radio

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  1. A discussion on channel sensing techniques Channel Sensingfor Cognitive Radio By James Xu Supervised by Dr. FakhrulAlam

  2. Presentation overview • Introduction to wireless communications • What is Cognitive Radio (CR)? • Why do we need CR? • What is channel sensing • Our workbench setup • Our research • Our major contributions • Conclusion

  3. Wireless communications

  4. What is Cognitive Radio (CR) • Able to sense spectral environment • Able to provide opportunistic access • Find gaps in the spectrum • Adjust system parameters to utilize it

  5. Why do we need CR? • Unlicensed spectrum is rare • Almost none available under 3GHz

  6. Why do we need CR? • Licensed to primary user only (Incumbent) • We are running out of space, and higher frequency has problems • We are under utilizing licensed space • CR is allowed usage (guarantee interference free)

  7. What is channel sensing • The first step of CR is to identify free spectrum • Channel sensing is one of the most fundamental part of CR

  8. What is channel sensing

  9. Our research • Our research focus • Energy detection • Cyclostationary feature extraction

  10. Our CR workbench

  11. Energy detection • Easy to implement • Fast • Not effective under low SNR

  12. What is energy detection? • All radio transmission have energy • Based on hypothesis testing

  13. Energy detector

  14. Energy detector

  15. Problems with the detector • Misdetection on Narrowband signals

  16. Problems with the detector • Misdetection on partial signals

  17. Adaptive energy detection • We proposed an improvement • Introduced adaptive detection

  18. Improved detection

  19. Adaptive ED characteristics

  20. Adaptive ED characteristics

  21. Cyclostationary Features • Another channel sensing strategy • Digital communication systems have built in periodicity • A signal is a first order cyclostationary if it’s mean is periodic • A signal is second order cyclostationary it it’s auto-correlation is periodic

  22. Cyclostationary Features • Auto-correlation how much a signal has in common with itself, against delay • Alpha = Cyclic frequency • S = Spectrum Correlation Function (SCF)

  23. Cyclostationary Features

  24. Work in Progress • This is preliminary, a proof of concept • Could be done in future research

  25. Our major contributions • Xu J. Y., Alam, F., Adaptive Energy Detection for Cognitive Radio: An Experimental Study, ICCIT, 2009 • IET PATW Competition, Regional winner • cr.jamesyxu.com • Svn://cr.jamesyxu.com/svn • CRLibs

  26. CRLibs • A library for cognitive radio research

  27. Conclusion • Workbench setup • Investigated various channel sensing techniques (ED, SCF, Spectral Entropy) • Proposed and implemented improvements (AED) • Consolidated library (CRLibs), examples and codebase (SVN) • Full progress documentation (SVN, CR)

  28. Acknowledgement • Dr FakhrulAlam • Dr James Chang • Dr Tom Moir • Everyone in our lab

  29. Thank you for listening • You are invited to visit our CR workbench at Building 80 • Much more details in the project report • Adaptive energy detection model will be on IEEEXplore end of December • Any questions?

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