1. A discussion on channel sensing techniques By James Xu Supervised by Dr. Fakhrul Alam

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

7. 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)

8. 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

9. What is channel sensing

10. Our research  Our research focus  Energy detection  Cyclostationary feature extraction

11. Our CR workbench

12. Energy detection  Easy to implement  Fast  Not effective under low SNR

13. What is energy detection?  All radio transmission have energy  Based on hypothesis testing

14. Energy detector

16. Problems with the detector  Misdetection on Narrowband signals

17. Problems with the detector  Misdetection on partial signals

18. Adaptive energy detection  We proposed an improvement  Introduced adaptive detection

19.  Improved detection

21. Adaptive ED characteristics

23. 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

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

25. Cyclostationary Features

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

29. 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

30. CRLibs  A library for cognitive radio research

33. 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)

34. Acknowledgement  Dr Fakhrul Alam  Dr James Chang  Dr Tom Moir  Everyone in our lab

35. 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?