1. A discussion on channel sensing techniques By James Xu

2. Presentation overview  Introduction to wireless communications  What is Cognitive Radio (CR)?  Why do we need CR?  What is energy detection  Our workbench  Standard energy detector  Problem with the detector  Our improved detection model

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 scarce  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. Energy detection  The first step in CR is to identify free spectrum  Energy detection is being used

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

10. Our CR workbench

11. Energy detector

13. Problems with the detector  Misdetection on Narrowband signals

14. Problems with the detector  Misdetection on partial signals

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

16.  Improved detection

18. Adaptive ED characteristics

20. Thank you for listening  Any questions?